IPv6
Network Working Group                                     Salman                                       S. Asadullah
INTERNET DRAFT                                              Adeel
Internet-Draft                                                  A. Ahmed
April
Expires: November 20, 2005                                            Ciprian                                  C. Popoviciu
                                                           Cisco Systems
                                                            Jordi
                                                                J. Palet
                                                             Consulintel
                                                            May 19, 2005

       ISP IPv6 Deployment Scenarios in Broadband Access Networks
           <draft-ietf-v6ops-bb-deployment-scenarios-01.txt>
           <draft-ietf-v6ops-bb-deployment-scenarios-02.txt>

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Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   This document provides detailed description of IPv6 deployment and
   integration methods and scenarios in today's Service Provider (SP)
   Broadband (BB) networks in coexistence with deployed IPv4 services.
   Cable/HFC, BB Ethernet, xDSL and WLAN are the main BB technologies
   that are currently deployed, and discussed in this document.  The
   emerging PLC/BPL access technology is also discussed for completion
   purposes.  In this document we will discuss main components of IPv6
   BB networks and their differences from IPv4 BB networks and how IPv6
   is deployed and integrated in each of these BB technologies using
   tunneling mechanisms and native IPv6.

Table of Contents: Contents

   1.  Introduction..................................................3   Introduction . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.   IPv6 Based BB Services........................................4 Services . . . . . . . . . . . . . . . . . . .   4
   3.   Scope of the Document.........................................5 Document  . . . . . . . . . . . . . . . . . . .   5
   4.  Core Backbone Network.........................................5   Core/Backbone Network  . . . . . . . . . . . . . . . . . . .   6
     4.1  Layer 2 Access Provider...................................6 Provider Network  . . . . . . . . . . . . .   7
     4.2  Layer3 Access Provider....................................6 Provider Network . . . . . . . . . . . . . .   7
   5.   Tunneling Options.............................................7 Overview . . . . . . . . . . . . . . . . . . . . .   8
     5.1  Access over Tunnels-customers Tunnels-Customers with public Public IPv4 address....7 Address . .   9
     5.2  Access over Tunnels-customers Tunnels-Customers with private Private IPv4 address...8 Address  .   9
     5.3  Transition a portion Portion of the IPv4 infrastructure...........8 Infrastructure  . . . . .  10
   6.   Broadband Cable Networks .....................................9 . . . . . . . . . . . . . . . . . .  10
     6.1  Broadband Cable Network Elements .........................9 . . . . . . . . . . . . .  11
     6.2  Deploying IPv6 in Cable Networks.........................10 Networks . . . . . . . . . . . . .  12
       6.2.1  Deploying IPv6 in a Bridged CMTS Network .............................11 . . . . . . .  13
       6.2.2  Deploying IPv6 in a Routed CMTS Network ..............................14
        6.3  . . . . . . .  16
       6.2.3  IPv6 Multicast ..........................................22
        6.4 . . . . . . . . . . . . . . . . . . . .  25
       6.2.4  IPv6 QoS ................................................22
        6.5 . . . . . . . . . . . . . . . . . . . . . . .  26
       6.2.5  IPv6 Security Considerations.............................23
        6.6 Considerations . . . . . . . . . . . . .  27
       6.2.6  IPv6 Network Management .................................24
            6.6.1  Using IPv6 for Management in Cable Networks ......24
            6.6.2  Updates to MIBs/Standards to support IPv6 ........25  . . . . . . . . . . . . . . .  28
   7.   Broadband DSL Networks.......................................25 Networks . . . . . . . . . . . . . . . . . . .  29
     7.1  DSL Network Elements ....................................25 . . . . . . . . . . . . . . . . . . .  29
     7.2  Deploying IPv6 in IPv4 DSL Networks......................26 Networks  . . . . . . . . . . .  30
       7.2.1  Point-to-Point Model..............................27 Model . . . . . . . . . . . . . . . . .  31
       7.2.2  PPP Terminated Aggregation (PTA) Model............29 Model . . . . . . . .  33
       7.2.3  L2TP  L2TPv2 Access Aggregation (LAA) Model...............31 Model  . . . . . . . .  36
       7.2.4  Hybrid Model for IPv4 and IPv6 Service ...........34 . . . . . . . .  38
     7.3  IPv6 Multicast...........................................36 Multicast . . . . . . . . . . . . . . . . . . . . . .  41
       7.3.1  ASM Based Deployments..............................36
            7.3.1 Deployments  . . . . . . . . . . . . . . . .  41
       7.3.2  SSM Based Deployments..............................37 Deployments  . . . . . . . . . . . . . . . .  42
     7.4  IPv6 QoS.................................................38 QoS . . . . . . . . . . . . . . . . . . . . . . . . .  43
     7.5  IPv6 Security Considerations.............................38 Considerations . . . . . . . . . . . . . . .  43
     7.6  IPv6 Network Management..................................39 management  . . . . . . . . . . . . . . . . .  44
   8.   Broadband Ethernet Networks..................................39 Networks  . . . . . . . . . . . . . . . .  45
     8.1  Ethernet Access Network Elements .......................39 . . . . . . . . . . . . .  45
     8.2  Deploying IPv6 in IPv4 BB Broadband Ethernet Networks.............40 Networks . . . .  46
       8.2.1  Point-to-Point Model.............................41 Model . . . . . . . . . . . . . . . . .  47
       8.2.2  PPP Terminated Aggregation (PTA) Model...........43 Model . . . . . . . .  49
       8.2.3  L2TP  L2TPv2 Access Aggregation (LAA) Model..............45 Model  . . . . . . . .  51
       8.2.4  Hybrid Model for IPv4 and IPv6 Service...........46 Service . . . . . . . .  53
     8.3  IPv6 Multicast..........................................47 Multicast . . . . . . . . . . . . . . . . . . . . . .  55
     8.4  IPv6 QoS................................................49 QoS . . . . . . . . . . . . . . . . . . . . . . . . .  56
     8.5  IPv6 Security Considerations............................50 Considerations . . . . . . . . . . . . . . .  56
     8.6  IPv6 Network Management.................................50 Management  . . . . . . . . . . . . . . . . .  57
   9. Broadband   Wireless LAN Networks..............................51 . . . . . . . . . . . . . . . . . . . . . . . .  58
     9.1  WLAN Deployment Scenarios...............................51 Scenarios  . . . . . . . . . . . . . . . .  58
       9.1.1  Layer 2 Switch Between AP and SP Edge Router.....52 Router  . . . . . .  59
       9.1.2  Access Router Between AP and SP Edge Router......54 Router  . . . . .  62
       9.1.3  PPP Based Model..................................56 Model  . . . . . . . . . . . . . . . . . . .  64
     9.2  IPv6 Multicast..........................................58 Multicast . . . . . . . . . . . . . . . . . . . . . .  66
     9.3  IPv6 QoS................................................60 QoS . . . . . . . . . . . . . . . . . . . . . . . . .  68
     9.4  IPv6 Security Considerations............................60 Considerations . . . . . . . . . . . . . . .  68
     9.5  IPv6 Network Management.................................61 Management  . . . . . . . . . . . . . . . . .  69
   10.  Broadband Power Line Communications (PLC)...................61 (PLC)  . . . . . . . . .  70
     10.1   PLC/BPL Access Network Elements.........................62 Elements  . . . . . . . . . . . .  70
     10.2   Deploying IPv6 in IPv4 PLC/BPL..........................63 PLC/BPL . . . . . . . . . . . . .  71
       10.2.1   IPv6 Related Infrastructure Changes..............63 Changes  . . . . . . . .  72
       10.2.2 Addressing.......................................63   Addressing . . . . . . . . . . . . . . . . . . . . .  72
       10.2.3 Routing..........................................64   Routing  . . . . . . . . . . . . . . . . . . . . . .  73
     10.3   IPv6 Multicast..........................................65 Multicast . . . . . . . . . . . . . . . . . . . . .  73
     10.4   IPv6 QoS................................................65 QoS . . . . . . . . . . . . . . . . . . . . . . . .  73
     10.5   IPv6 Security Considerations............................65 Considerations . . . . . . . . . . . . . .  73
     10.6   IPv6 Network Management.................................65 Management  . . . . . . . . . . . . . . . .  74
   11.  Gap Analysis................................................65 Analysis . . . . . . . . . . . . . . . . . . . . . . . .  74
   12. Contributors................................................67  IANA Considerations  . . . . . . . . . . . . . . . . . . . .  76
   13. Acknowledgments.............................................67  Security Considerations  . . . . . . . . . . . . . . . . . .  76
   14. References..................................................67
     Authors Addresses...............................................70  References . . . . . . . . . . . . . . . . . . . . . . . . .  76
     14.1   Normative References . . . . . . . . . . . . . . . . . .  76
     14.2   Informative References . . . . . . . . . . . . . . . . .  78
        Authors' Addresses . . . . . . . . . . . . . . . . . . . . .  79
        Intellectual Property and Copyright Statements . . . . . . .  80

1.  Introduction

   With the exponential growth of the Internet and increasing number of
   end users, SPs are looking for new ways to evolve their current
   network architecture to meet the needs of Internet ready appliances,
   new applications and services.  IPv6 is designed to enable SPs to
   meet these challenges and provide new services to their customers.

   As the number of devices per BB user increase exponentially
   worldwide, Cable, DSL, Ethernet to the Home, Wireless, PLC/BPL and
   other always-on access technologies can benefit from the huge address
   range [RFC3513] [9] of IPv6.  Other benefits of IPv6 include the capability to
   enhance end-to-end security, mobile communications, and ease system
   management burdens.  Some examples include peer-to-peer communication
   without NAT traversal problems, being able to access securely devices
   at home from work, enhanced IP Mobility [RFC3775] [24] and so on.

   Therefore SPs are aggressively evaluating the capabilities of IPv6 to
   meet these needs.  Some countries have taken a lead role in this race
   and moved from testing and evaluation to real deployments of IPv6 in
   the BB arena.  Japan is a prime example along with other countries
   that are looking at moving towards large scale production deployments
   of IPv6.

   The SPs are deploying tunneling mechanisms to transport IPv6 over
   their existing IPv4 networks as a start as well as deploying native
   IPv6 where possible.  Deployment of tunneling solutions is simpler,
   easier and more economical to start the IPv6 services, as they
   require minimal investments and network infrastructure changes in
   current SP model.  Depending on customer needs and requirements a
   native IPv6 deployment option might be more scalable and provide
   required service performance.

2.  IPv6 Based BB Services

   At this point IPv6 based services are seen as a differentiator that
   enables SPs to take advantage of the large IPv6 address space to the
   extent that subscribers get up to fixed /48 prefixes versus the
   single, temporary IPv4 addresses.  Such resources allow the SPs to
   better position themselves against the competition.  The IPv6
   deployments can be seen as a driver for lower service support costs
   by eliminating NAT with its negative impact on applications and its
   complex behavior.  Another reason of IPv6 being popular in some
   countries might be the government driven financial incentives and
   favorable legislation towards the IPs who are deploying IPv6.

   NTT East, Japan started a commercial dual-stack (devices capable of
   forwarding IPv4 and IPv6 packets) IPv6 unicast service option early
   this year for its ADSL and FTTH subscribers, under the name of
   FLETS.Net [Dual Stack Access]. [26].  For these users the IPv6 addresses are dedicated
   (/64 per user) and are used when needed.  However, this IPv6 service
   is available only to the NTT-East ADSL and FTTH subscribers who are
   part of FLETS.NET network and at this point does not provide
   connectivity to the IPv6 Internet.

   Some ISPs that are currently providing IPv4 based Multicast and VoIP
   services are evaluating IPv6 to take advantage of the huge
   address space improve and other useful features. expand their service.
   The Multicast services consist of video and audio streaming of
   several programs (streams).  The content provider will have certain content (which is of user
   interest) and they would send delivers these multicast
   streams to BB subscribers. Today,  One of today's challenges is the fact
   that when done through IPv4, there is generally a single device
   directly attached to the CPE that receives the Multicast stream.  By
   moving to IPv6, ISP should be capable to provide multiple streams to
   multiple devices on the customer site.

   For instance in Japan, Cable TV and dish services are not very
   popular,  the users expect everything content mostly through the broadcasted,
   free programs (traditional TV).  In case of BB users however, they
   can get
   some  extra additional content through the their SP, which is very reasonably can be delivered
   at a reasonable priced for 20 Mbps or 10/100 Mbps of bandwidth.
   Users sign up with a content provider that is multicasting several
   channels of video and audio.  A subscriber would join the multicast
   group of interest (after authentication) and will start receiving the
   stream(s).  An example of a video stream could be Disney movies and
   an example of an audio stream could be Karaoke (part of same *,G
   group).  Similar to Cable TV, where customers sign up and pay for
   single programs or packages of programs.

   SPs are also offering IPv6 services over wireless links using 802.11
   compliant WiFi Hot Spots.  This enables users to take notebook PCs
   and PDAs (Windows 2003 supports IPv6 capable Internet Explorer and
   Media Player 9) along with them and connect to the Internet from
   various locations without the restriction of staying indoors.

3.  Scope of the Document

   The focus of this

   This document is to present presents the options available in deploying IPv6
   services in the access portion of a BB Service Provider network
   namely Cable/HFC, BB Ethernet, xDSL, WLAN and PLC/BPL.

   This document briefly discusses the other elements of a provider
   network as well.  It provides different viable IPv6 deployment and
   integration techniques and models for each of the above mentioned BB
   technologies separately. individually.  The example list is not exhaustive but it
   tries to be representative.

   This document analyzes, how all the important parts of current IPv4
   based Cable/HFC, BB Ethernet, xDSL, WLAN and PLC/BPL networks will
   behave when IPv6 is integrated and deployed.

   The following important pieces are discussed:

   A. Available tunneling options

   B. Devices that would require to be upgraded to support IPv6

   C. Available IPv6 address assignment techniques and their use

   D. Possible IPv6 Routing options and their use

   E. IPv6 unicast and multicast packet transmission

   F. Required IPv6 QoS parameters

   G. Required IPv6 Security parameters

   H. Required IPv6 Network Management parameters

   It is important to note that the addressing rules provided throughout
   this document represent an example that follows the current
   assignment policies and recommendations of the registries.  They can
   be however adapted to the network and business model needs of the
   ISPs.

   The scope of the document is to advise on the ways of upgrading an
   existing infrastructure to support IPv6 services.  The recommendation
   to upgrade a device to dual-stack does not stop an SP from adding a
   new device to its network to perform the neccessary IPv6 functions
   discussed.  The costs involved could be offset by lower impact on the
   existing IPv4 services.

4.  Core/Backbone Network

   This section intends to briefly discuss the some important elements of a
   provider network tied to the deployment of IPv6.  A more detailed
   description of the core network is provided in other documents [ISP Networks IPv6 Scenarios]. [25].

   There are two networks identified in the Broadband deployments:

   A. Access Provider Network: This network provides the broadband
   access and aggregates the subscribers.  The subscriber traffic is
   handed over to the Service Provider at Layer 2 or 3.

   B. Service Provider Network: This network provides Intranet and
   Internet IP connectivity for the subscribers.

   The Service Provider network structure beyond the Edge routers that
   interface with the Access provider is beyond the scope of this
   document.

4.1  Layer 2 Access Provider Network

   The Access Provider can deploy a Layer 2 network and perform no
   routing of the subscriber traffic to the SP.  The devices that
   support each specific access technology are aggregated into a highly
   redundant, resilient and scalable layer two core.  The network core
   can involve various technologies such as Ethernet, ATM etc.  The
   Service Provider Edge Router connects to the Access Provider core.

   In this type of a network the impact of deploying IPv6 is minimal.
   The network is transparent to the Layer 3 protocol.  The only
   possible changes would come with the intent of filtering and
   monitoring IPv6 traffic based on layer 2 information such as IPv6
   Ether Type Protocol ID (0x86DD) or IPv6 multicast specific MAC
   addresses (3333.xxxx.xxxx).

4.2  Layer3 Access Provider Network

   The Access Provider can choose to terminate the Layer 2 domain and
   route the IP traffic to the Service Provider network.  Access Routers
   are used to aggregate the subscriber traffic and route it over a
   Layer3 core to the SP Edge Routers.  In this case the impact of the
   IPv6 deployment is significant.

   The case studies in this document only present the significant
   network elements of such a network: Customer Premises Equipment,
   Access Router and Edge Router.  In real networks the link between the
   Access Router and the Edge Router involves other routers that are
   part of the aggregation and the core layer of the Access Provider
   network.

   The Access Provider can forward the IPv6 traffic through its layer3
   core in three possible ways:

   A. IPv6 Tunneling: As a temporary solution, the Access Providers can
   choose to use a tunneling mechanism to forward the subscriber IPv6
   traffic to the Service Provider Edge Router.  This approach has the
   least impact on the Access Provider network however, as the number of
   users increase and the amount of IPv6 traffic grows, the ISP will
   have to evolve to one of the scenarios listed below.

   B. Native IPv6 Deployment: The Access Provider routers are upgraded
   to support IPv6 and can become dual-stack.  In a dual-stack network
   an IPv6 IGP such as OSPFv3 or IS-IS is enabled.  RFC4029 discusses
   the IGP selection options with their benefits and drawbacks.

   C. MPLS 6PE Deployment [6PE]: [27]: If the Access Provider is running MPLS
   in its IPv4 core it could use 6PE to forward IPv6 traffic over it.
   In this case only a subset of routers close to the edge of the
   network need to be IPv6 aware.  With this approach BGP becomes
   important in order to support 6PE.

   The 6PE approach has the advantage of having minimal impact on the
   Access Provider network.  Fewer devices need to be upgraded and
   configured while the MPLS core continues to switch the traffic
   un-aware un-
   aware of the fact that it transports both IPv4 and IPv6 traffic. 6PE
   should be leveraged only if MPLS is already deployed in the network.
   At the time of writing this document, a major disadvantage of the 6PE
   solution is the fact that it does not support multicast IPv6 traffic.

   The native approach has the advantage of supporting IPv6 multicast
   traffic but it may imply a significant impact on the IPv4 operational
   network from software, configuration and possibly hardware upgrade
   perspective.

   More detailed Core Network deployment recommendations are discussed
   in other documents [ISP Networks IPv6 Scenarios]. RFC4029.  The handling of IPv6 traffic in the Core
   of the Access Provider Network will not be discussed for the
   remainder of this document.

5.  Tunneling Overview

   Service Providers might not be able to deploy native IPv6 today due
   to the cost associated with HW and SW upgrades, the infrastructure
   changes needed to their current network and the current demand for
   the service.  For these reasons, some SPs might choose tunneling
   based transition mechanisms to start an IPv6 service offering and
   move to native IPv6 deployment at a later time.

   Several tunneling mechanisms were developed specifically to transport
   IPv6 over existing IPv4 infrastructures.  Several of them have been
   standardized and their use depends on the existing SP IPv4 network
   and the structure of the IPv6 service.  The requirements for the most
   appropriate mechanisms are described in
   [Assisted Tunneling] and [v6tc] [35] with more updates to
   follow.  Deploying IPv6 using tunneling techniques can imply as
   little changes to the network as upgrading SW on tunnel end points
   (TEP).  A Service Provider could use tunneling to deploy IPv6 in the
   following scenarios:

5.1  Access over Tunnels-customers Tunnels-Customers with Public IPv4 Address

   If the customer is a residential user, it can initiate the tunnel
   directly from the IPv6 capable host to a tunnel termination router
   located in the NAP or ISP network.  The tunnel type used should be
   decided by the SP but it should take into consideration its
   availability on commonly used software running on the host machine.
   Out of the many tunneling mechanisms developed [RFC3053, RFC3056,
   RFC2473, ISATAP, RFC2893, RFC2529] [[2], [3], [4], [28],
   [5], [6]] some are more popular than the others.

   If the end customer has a GWR installed, then it could be used to
   originate the tunnel and thus offer native IPv6 access to multiple
   hosts on the customer network.  In this case the GWR would need to be
   upgraded to dual-stack in order to support IPv6.  The GWR can be
   owned by the customer or by the SP. SP

5.2  Access over Tunnels-Customers with Private IPv4 Address

   If the end customer receives a private IPv4 address and needs to
   initiate a tunnel through NAT, techniques like 6to4 will may not work
   since they rely on Public IPv4 address.  In this case case, unless the
   existing CPE supports protocol-41-forwarding, the end user might have
   to use tunnels that can operate through NATs (such as Teredo tunnel [OPS]).
   [30]).

   The customer has the option to initiate the tunnel from the device
   (GWR) that performs the NAT functionality, similar to the GWR
   scenario discussed in section 5.1.  This will imply HW replacement or
   SW upgrade and a native IPv6 environment behind the GWR.

   It is important to note  Most GWRs
   support protocol-41-forwarding which means that the customers of a Service Provider hosts can initiate
   the tunnels in which case the GWR is not affected by the IPv6
   service.

   It is important to note that the customers of a Service Provider can
   choose to establish tunnels to publicly available and free tunnel
   services.  Even though the quality of such services might not be
   high, they provide free IPv6 access.  In designing their IPv6
   services, the SPs should take into considerations such options
   available to their potential customers.  The IPv6 deployment should
   support services (like multicast, VoIPv6 etc) and a level of quality
   that would make the access through the SP worthwhile to potential
   subscribers.

   It is also worth observing that initiating an IPv6 tunnel over IPv4
   through already established IPv4 IPsec sessions would provide a
   certain level of security to the IPv6 traffic [Tunnel through IPsec].

5.3  Transition a Portion of the IPv4 Infrastructure

   Tunnels can be used to transport the IPv6 traffic across a defined
   segment of the network.  As an example, the customer might connect
   natively to the Network Access Provider and a tunnel is used to
   transit the traffic over IPv4 to the ISP.  In this case the tunnel
   choice depends on its capabilities (for example, whether it supports
   multicast or not), routing protocols used (there are several types
   that can transport layer 2 messages such as GRE, L2TPv3 or
   Pseudowire), manage-ability and scalability (dynamic versus static
   tunnels).

   This scenario implies that the access portion of the network has been
   upgraded to support dual stack so the savings provided by tunneling
   in this scenario are very small compared with the previous two. two
   scenarios.  Depending on the number of sites requiring the service
   and considering the expenses required to manage the tunnels (some
   tunnels are static while others are dynamic [Dynamic Tunnel]) [29]) in this case, the
   SPs might find the native approach worth the additional investments.

   In all the scenarios listed above the tunnel selection process should
   consider the IPv6 multicast forwarding capabilities if such service
   is planned.  As an example, 6to4 tunnels do not support IPv6
   multicast traffic.

   The operation, capabilities and deployment of various tunnel types
   has been discussed extensively in the documents referenced earlier as
   well as in [OPS, RFC3904]. [[30], [7]].  Details of a tunnel based deployment are
   offered in the next section of this document (section 6).  In the
   case of Cable Access where the current DOCSIS specifications do not
   provide support for native IPv6 access.  Although sections 7, 8, 9
   and 10 focus on a native IPv6 deployments over DSL, FTTH, Wireless
   and PLC/BPL because this approach is fully supported today, tunnel
   based solutions are also possible in these cases based on the
   guidelines of this section and some of the recommendations provided
   in section 6.

6.  Broadband Cable Networks

   This section describes the infrastructure that exists today in cable
   networks providing BB services to the home.  It also describes IPv6
   deployment options in these cable networks.

   DOCSIS standardizes and documents the operation of data over Cable
   Networks.  The current version of DOCSIS has limitations that do not
   allow for a smooth implementation of native IPv6 transport.  Some of
   these limitations are discussed in this section.  For this reason,
   the IPv6 deployment scenarios discussed in this section for the
   existent Cable Networks are tunnel based.  The tunneling examples
   presented here could also be applied to the other BB technologies
   described in sections 7, 8, 9 and 10.

6.1  Broadband Cable Network Elements

   Broadband cable networks are capable of transporting IP traffic to/
   from users to provide high speed Internet access and VOIP services.
   The mechanism of transporting IP traffic over cable networks is
   outlined in the DOCSIS specification [RF Interface]. [33].

   Here are some of the key elements of a Cable network:

   Cable (HFC) Plant: Hybrid Fiber Coaxial plant, used as the underlying
   transport

   CMTS: Cable Modem Termination System (can be a Layer 2 bridging or
   Layer 3 routing CMTS)

   GWR: Residential Gateway Router (provides Layer 3 services to hosts)

   Host: PC, notebook etc. which is connected to the CM or GWR

   CM: Cable Modem

   ER: Edge Router

   MSO: Multiple Service Operator

   Data Over Cable Service Interface Specification (DOCSIS): The
   standards defining how data should be carried over cable networks.

   Figure 6.1 illustrates the key elements of a Cable Network

<---

   |--- ACCESS  ---><------  ---||------ HFC ------><----- ------||----- Aggregation / Core -----> -----|

   +-----+  +------+
   |Host |--| GWR  |
   +-----+  +--+---+
               |        _ _ _ _ _ _
            +------+   |           |
            |  CM  |---|           |
            +------+   |           |
                       |    HFC    |   +------+   +--------+
                       |           |   |      |   | Edge   |
   +-----+  +------+   |  Network  |---| CMTS |---|        |===> ISP
   |Host |--|  CM  |---|           |   |      |   | Router |   Network
   +-----+  +--+---+   |           |   +------+   +--------+
                       |_ _ _ _ _ _|
            +------+         |
   +-----+  | GWR/ |         |
   |Host |--| CM   |---------+
   +-----+  |      |
            +------+      Figure 6.1

6.2  Deploying IPv6 in Cable Networks

   One of the motivators for an MSO to deploy IPv6 over their Cable
   Network is to ease management burdens.  IPv6 can be enabled on the
   CM, CMTS and ER for management purposes.  Currently portions of the
   cable infrastructure use RFC1918 [1] IPv4 addresses; however, there are a
   finite number of those.  Thus, IPv6 could have utility in the cable
   space implemented on the management plane initially and later on
   focused on the data plane for end user services.  For more details on
   using IPv6 for management in Cable Networks please refer to section
   6.6.1.

   There are two different deployment modes in current cable networks: a
   bridged CMTS environment and a routed CMTS environment.  IPv6 can be
   deployed in both of these environments.

   1.  Bridged CMTS Network

   In this scenario, both the CM and CMTS bridge all data traffic.
   Traffic to/from host devices is forwarded through the cable network
   to the ER.  The ER then routes traffic through the ISP network to the
   Internet.  The CM and CMTS support a certain degree of Layer 3
   functionality for management purposes.

   2.  Routed CMTS Network

   In a routed network, the CMTS forwards IP traffic to/from hosts based
   on Layer 3 information using the IP source/destination address.  The
   CM acts as a Layer-2 bridge for forwarding data traffic and supports
   some Layer 3 functionality for management purposes.

   Some of the factors that hinder deployment of native IPv6 in current
   routed and bridged cable networks include:

   A. Problems with IPv6 Neighbor Discovery (ND) on CM and CMTS.  These
   devices rely on IGMP join messages to track membership of hosts that
   are part of a particular IP Multicast group.  In order to support ND
   the CM and CMTS will need to support IGMPv3/MLDv2 or v1 snooping.

   B. Classification of IPv6 traffic in the upstream and downstream
   direction.  The CM and CMTS will need to support classification of
   IPv6 packets in order to give them the appropriate priority and QoS.
   Without proper classification all IPv6 traffic will need to be sent
   best effort (BE) which can cause problems when deploying services
   like VOIP and IP Multicast video.

   C. Changes need to be made to the DOCSIS specification to include
   support for IPv6 on the CM and CMTS.  This is imperative for
   deploying native IPv6 over cable networks.

   Due to the above mentioned limitations in deployed cable networks,
   the only available option to cable operators is to use tunneling
   techniques in order to transport IPv6 traffic over their current IPv4
   infrastructure.  The following sections will cover these deployment
   scenarios in more detail.

6.2.1  Deploying IPv6 in a Bridged CMTS Network

   In IPv4 the CM and CMTS act as Layer 2 bridges and forward all data
   traffic to/from the hosts and the ER.  The hosts use the ER as their
   Layer 3 next hop.  If there is a GWR behind the CM it can act as a
   next hop for all hosts and forward data traffic to/from the ER.

   When deploying IPv6 in this environment, the CM and CMTS will
   continue to be bridging devices in order to keep the transition
   smooth and reduce operational complexity.  The CM and CMTS will need
   to bridge IPv6 unicast and multicast packets to/from the ER and the
   hosts.  If there is a GWR connected to the CM, it will need to
   forward IPv6 unicast and multicast traffic to/from the ER.

   IPv6 can be deployed in a bridged CMTS network either natively or via
   tunneling.  This section discusses the native deployment model.  The
   tunneling model is similar to ones described in sections 6.2.2.1 and
   6.2.2.2.

   Figure 6.2.1 illustrate the IPv6 deployment scenario

   +-----+  +-----+
   |Host |--| GWR |
   +-----+  +--+--+
               |              _ _ _ _ _ _
               |  +------+   |           |
               +--|  CM  |---|           |
                  +------+   |           |
                             |   HFC     |  +------+  +--------+
                             |           |  |      |  | Edge   |
         +-----+  +------+   |  Network  |---|  |--| CMTS |---| |--|        |===> ISP
         |Host |--|  CM  |---|           |  |      |  | Router | Network
         +-----+  +------+   |           |  +------+  +--------+
                             |_ _ _ _ _ _|

<-------------><---------------------------------><--------------->
   |-------------||---------------------------------||---------------|
       L3 Routed              L2 Bridged                 L3 Routed

                             Figure 6.2.1

6.2.1.1  IPv6 Related Infrastructure Changes

   In this scenario the CM and the CMTS bridge all data traffic so they
   will need to support bridging of native IPv6 unicast and multicast
   traffic.  The following devices have to be upgraded to dual stack:
   Host, GWR and ER.

6.2.1.2  Addressing

   The proposed architecture for IPv6 deployment includes two components
   that must be provisioned: the CM and the host.  Additionally if there
   is a GWR connected to the CM, it will also need to be provisioned.
   The host or the GWR use the ER as their Layer 3 next hop.

6.2.1.2.1  IP Addressing for CM

   The CM will be provisioned in the same way as in currently deployed
   cable networks, using an IPv4 address on the cable interface
   connected to the MSO network for management functions.  During the
   initialization phase, it will obtain its IPv4 address using DHCPv4,
   and download a DOCSIS configuration file identified by the DHCPv4
   server.

6.2.1.2.2  IP Addressing for Hosts

   If there is no GWR connected to the CM, the host behind the CM will
   get a /64 prefix assigned to it via stateless autoconfiguration or
   DHCPv6.

   If using stateless auto-configuration, the host listens for routing
   advertisements (RA) from the ER.  The RAs contain the /64 prefix
   assigned to the segment.  Upon receipt of an RA, the host constructs
   its IPv6 address by combining the prefix in the RA (/64) and a unique
   identifier (e.g., its modified EUI-64 format interface ID).

   If DHCPv6 is used to obtain an IPv6 address, it will work in much the
   same way as DHCPv4 works today.  The DHCPv6 messages exchanged
   between the host and the DHCPv6 server are bridged by the CM and the
   CMTS.

6.2.1.2.3  IP Addressing for GWR

   The GWR can use stateless auto-configuration (RA) to obtain an
   address for its upstream interface, the link between itself and the
   ER.  This step is followed by a request via DHCP-PD (Prefix
   Delegation) for a prefix shorter than /64, typically /48, /48 [8], which
   in turn is divided into /64s and assigned to its downstream
   interfaces connecting to the hosts.

6.2.1.3  Data Forwarding

   The CM and CMTS must be able to bridge native IPv6 unicast and
   multicast traffic.  The CMTS must provide IP connectivity between
   hosts attached to CMs and must do so in a way that meets the
   expectation of Ethernet attached customer equipment.  In order to do
   that, the CM and CMTS must forward Neighbor Discovery (ND) packets
   between ER and the hosts attached to the CM.

   Communication between hosts behind different CMs is always forwarded
   through the CMTS.  IPv6 communication between the different sites
   relies on multicast IPv6 ND [RFC2461] [18] frames being forwarded correctly by
   the CM and the CMTS.  As with the CM, a bridged CMTS that selectively
   forwards multicast datagrams on the basis of IGMPv2 MLD will potentially
   break IPv6 ND.

   In order to support IPv6 multicast applications across DOCSIS cable
   networks, the CM and bridging CMTS need to support IGMPv3/MLDv2 or v1
   snooping.  MLD is almost identical to IGMP in IPv4, only the name and
   numbers are changed.  MLDv2 is identical to IGMPv3 and also supports
   ASM (Any Source Multicast) and SSM (Single Source Multicast) service
   models.  Implementation work on CM/CMTS should be minimal because the
   only significant difference between IPv4 IGMPv3 and IPv6 MLDv2 is the
   longer addresses in the protocol.

6.2.1.4  Routing

   The hosts install a default route that points to the ER or the GWR.
   No routing protocols are needed on these devices which generally have
   limited resources.  If there is a GWR present it will also use static
   default route to the ER.

   The ER runs an IGP such as OSPFv3 or IS-IS.  The connected prefixes
   have to be redistributed.  If DHCP-PD is used, with every delegated
   prefix a static route is installed by the ER.  For this reason the
   static routes must also be redistributed.  Prefix summarization
   should be done at the ER.

   its IPv6 address by combining the prefix in the RA (/64) and a unique
   identifier (e.g., its modified EUI-64 format interface ID).

   If DHCPv6 is used to obtain an IPv6 address, it will work in much

6.2.2  Deploying IPv6 in a Routed CMTS Network

   In an IPv4 routed CMTS network the CM still acts as a Layer-2 device
   and bridges all data traffic between its Ethernet interface and cable
   interface connected to the cable operator network.  The CMTS acts as
   a Layer 3 router and may also include the ER functionality.  The
   hosts and the GWR use the CMTS as their Layer 3 next hop.

   When deploying IPv6 in a routed CMTS network, the CM still acts as a
   Layer-2 device and will need to bridge IPv6 unicast as well as
   multicast traffic.  The CMTS/ER will need to either tunnel IPv6
   traffic or natively support IPv6.  The host and GWR will use the
   CMTS/ER as their Layer 3 next hop.

   There could be five possible deployment scenarios for IPv6 in a
   routed CMTS network:

   1.  IPv4 Cable (HFC) Network

   In this scenario the cable network, including the CM and CMTS remain
   IPv4 devices.  The host and ER are upgraded to dual-stack.  This is
   the easiest way for a Cable Operator to provide IPv6 service as no
   changes are made to the cable network.

   2.  IPv4 Cable (HFC) Network, GWR at Customer Site

   In this case the cable network, including the CM and CMTS remain IPv4
   devices.  The host, GWR and ER are upgraded to dual-stack.  This
   scenario is also easy to deploy since the cable operator just needs
   to add GWR at the customer site.

   3.  Dual-stacked Cable (HFC) Network, CM and CMTS Support IPv6

   In this scenario the CMTS is upgraded to dual-stack to support IPv4
   and IPv6.  Since the CMTS supports IPv6 it can acts as an ER as well.
   The CM will act as a Layer-2 bridge but will need to bridge IPv6
   unicast and multicast traffic.  This scenario is not easy to deploy
   since it requires changes to the DOCSIS specification.  The CM and
   CMTS may require HW and SW upgrades to support IPv6.

   4.  Dual-stacked Cable (HFC) Network, Standalone GWR and CMTS Support
   IPv6

   In this scenario there is a standalone GWR connected to the CM.
   Since the IPv6 functionality exists on the GWR the CM does not need
   to be dual-stack.  The  CMTS is upgraded to dual-stack and it can
   incorporate the ER functionality.  This scenario may also require HW
   and SW changes on the GWR and CMTS.

   5.  Dual-stacked Cable (HFC) Network, Embedded GWR/CM and CMTS
   Support IPv6

   In this scenario the CM and GWR functionality exists on a single
   device which needs to be upgraded to dual-stack.  The CMTS will also
   need to be upgraded to a dual-stack device.  This scenario is also
   difficult to deploy in existent cable network since it requires
   changes on the Embedded GWR/CM and the CMTS.

   The DOCSIS specification will also need to be modified to allow
   native IPv6 support on the Embedded GWR/CM.

6.2.2.1  IPv4 Cable Network, Host and ER Upgraded to Dual-Stack

   This is one of the most cost effective ways for a Cable Operator to
   offer IPv6 services to its customers.  Since the cable network
   remains IPv4 there is relatively minimal cost involved in turning up
   IPv6 service.  All IPv6 traffic is exchanged between the hosts and
   the ER.

   Figure 6.2.2.1 illustrates this deployment scenario

                           +-----------+   +------+   +--------+
     +-----+  +-------+    |   Cable   |   |      |   |  Edge  |
     |Host |--|  CM   |----|  (HFC)    |----|    |---| CMTS |----| |---|        |=>ISP
     +-----+  +-------+    |  Network  |   |      |   | Router | Network
                           +-----------+   +------+   +--------+
             _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
           ()_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _()
                          IPv6-in-IPv4 tunnel

<---------><----------------------------------------><------------>

   |---------||----------------------------------------||------------|
     IPv4/v6                 IPv4 only                    IPv4/v6

                              Figure 6.2.2.1

6.2.2.1.1  IPv6 Related Infrastructure Changes

   In this scenario the CM and the CMTS will only need to support IPv4
   so no changes need to be made to them or the cable network.  The
   following devices have to be upgraded to dual stack: Host and ER.

6.2.2.1.2  Addressing

   The only device that needs to be assigned an IPv6 address at customer
   site is the host.  Host address assignment can be done in multiple
   ways.  Depending on the tunneling mechanism used it could be
   automatic or might require manual configuration.

   The host still receives an IPv4 address using DHCPv4, which works the
   same way in currently deployed cable networks.  In order to get IPv6
   connectivity, host devices will also need an IPv6 address and a means
   to communicate with the ER.

6.2.2.1.3  Data Forwarding

   All IPv6 traffic will be sent to/from the ER and the host device.  In
   order to transport IPv6 packets over the cable operator IPv4 network,
   the host and the ER will need to use one of the available IPv6 in
   IPv4 tunneling mechanisms.

   The host will use its IPv4 address to source the tunnel to the ER.
   All IPv6 traffic will be forwarded to the ER, encapsulated in IPv4
   packets.  The intermediate IPv4 nodes will forward this traffic as
   regular IPv4 packets.  The ER will need to terminate the tunnel
   and/or provide other IPv6 services.

6.2.2.1.4  Routing

   Routing configuration on the host will vary depending on the
   tunneling technique used, in some cases a default or static route
   might be needed to forward traffic to the next hop.

   The ER runs an IGP such as OSPFv3 or ISIS.

6.2.2.2  IPv4 Cable Network, Host, GWR and ER Upgraded to Dual-Stack

   The cable operator can provide IPv6 services to its customers, in
   this scenario, by adding a GWR behind the CM.  Since the GWR will
   facilitate all IPv6 traffic to/from the host and the ER, the cable
   network including the CM and CMTS do not need to support IPv6 and can
   remain as IPv4 devices.

   Figure 6.2.2.2 illustrates this deployment scenario

    +-----+
    |Host |
    +--+--+
       |                   +-----------+   +------+   +--------+
   +---+---+  +-------+    |   Cable   |   |      |   |  Edge  |
   |  GWR  |--|  CM   |----|  (HFC)    |----|    |---| CMTS |----| |---|        |=>ISP
   +-------+  +-------+    |  Network  |   |      |   | Router | Network
                           +-----------+   +------+   +--------+
             _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
           ()_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _()
                          IPv6-in-IPv4 tunnel

<---------><---------------------------------------><------------->

   |---------||---------------------------------------||-------------|
     IPv4/v6                 IPv4 only                    IPv4/v6

                              Figure 6.2.2.2

6.2.2.2.1  IPv6 Related Infrastructure Changes

   In this scenario the CM and the CMTS will only need to support IPv4
   so no changes need to be made to them or the cable network.  The
   following devices have to be upgraded to dual stack: Host, GWR and
   ER.

6.2.2.2.2  Addressing

   The only devices that needs to be assigned an IPv6 address at
   customer site are the host and GWR.  IPv6 address assignment can be
   done statically at the GWR downstream interface.  The GWR will send
   out RA messages on its downstream interface which will be used by the
   hosts to auto-configure themselves with an IPv6 address.  The GWR can
   also configure its upstream interface using RA messages from the ER
   and use DHCP-PD for requesting a /48 [8] prefix from the ER.  This
   /48 prefix will be used to configure /64s on hosts connected to the
   GWR downstream interfaces.  Currently the DHCP-PD functionality
   cannot be implemented if the DHCP-PD server is not the Edge Router.
   If the DHCP-PD messages are relayed, the Edge Router does not have a
   mechanism to learn the assigned prefixes and thus install the proper
   routes to make that prefix reachable.  Work is being done to address
   this issue, one idea being to provide the Edge Router with a snooping
   mechanism.  The uplink to the ISP network is configured with a /64
   prefix as well.

   The GWR still receives a global IPv4 address on its upstream
   interface using DHCPv4, which works the same way in currently
   deployed cable networks.  In order to get IPv6 connectivity to the
   Internet the GWR will need to communicate with the ER.

6.2.2.2.3  Data Forwarding

   All IPv6 traffic will be sent to/from the ER and the GWR, which will
   forward IPv6 traffic to/from the host.  In order to transport IPv6
   packets over the cable operator IPv4 network, the GWR and the ER will
   need to use one of the available IPv6 in IPv4 tunneling mechanisms.
   All IPv6 traffic will need to go through the tunnel, once it comes
   up.

   The GWR will use its IPv4 address to source the tunnel to the ER.
   The tunnel endpoint will be the IPv4 address of the ER.  All IPv6
   traffic will be forwarded to the ER, encapsulated in IPv4 packets.
   The intermediate IPv4 nodes will forward this traffic as regular IPv4
   packets.  In case of 6to4 tunneling, the ER will need to support 6to4
   relay functionality in order to provide IPv6 Internet connectivity to
   the GWR and hence the hosts connected to the GWR.

6.2.2.2.4  Routing

   Depending on the tunneling technique used there might some
   configuration needed on the GWR and the ER.  If the ER is also
   providing a 6to4 relay service then a default route will need to be
   added to the GWR pointing to the ER, for all non-6to4 traffic.

   If using manual tunneling, the GWR and ER can use static routing or
   they can also configure RIPng.  The RIPng updates can be transported
   over a manual tunnel, which does not work when using 6to4 tunneling.

   Customer routes can be carried to the ER using RIPng updates.  The ER
   can advertise these routes in its IGP.  Prefix summarization should
   be done at the ER.

   If DHCP-PD is used for address assignment a static route is
   automatically installed on the CMTS/ER for each delegated /48 prefix.
   The static routes need to be redistributed into the IGP at the
   CMTS/ER, so there is no need for a routing protocol between the
   CMTS/ER and the GWR.

   The ER runs an IGP such as OSPFv3 or ISIS.

6.2.2.3  Dual-stacked Cable (HFC) Network, CM and CMTS Support IPv6

   In this scenario the Cable Operator can offer native IPv6 services to
   its customers since the cable network including the CMTS supports
   IPv6.  The ER functionality can be included in the CMTS or it can
   exist on a separate router connected to the CMTS upstream interface.
   The CM will need to bridge IPv6 unicast and multicast traffic.

   Figure 6.2.2.3 illustrates this deployment scenario

                           +-----------+    +-------------+
     +-----+  +-------+    |   Cable   |    | CMTS / Edge |
     |Host |--|  CM   |----|  (HFC)    |----|             |=>ISP
     +-----+  +-------+    |  Network  |    |   Router    |  Network
                           +-----------+    +-------------+

  <-------><----------------------------><---------------->

     |-------||----------------------------||----------------|
      IPv4/v6              IPv4/v6              IPv4/v6

                             Figure 6.2.2.3

6.2.2.3.1  IPv6 Related Infrastructure Changes

   Since the CM still acts as a Layer-2 bridge, it does not need to be
   dual-stack.  The CM will need to support bridging of IPv6 unicast and
   multicast traffic and IGMPv3/MLDv2 or v1 snooping which requires
   changes in the DOCSIS specification.  In this scenario the following
   devices have to be upgraded to dual stack: Host and CMTS/ER.

6.2.2.3.2  Addressing

   In today's cable networks the CM receives a private IPv4 address
   using DHCPv4 for management purposes.  In an IPv6 environment, the CM
   will continue to use an IPv4 address for management purposes.  The
   cable operator can also choose to assign an IPv6 address to the CM
   for management, but the CM will have to be upgraded to support this
   functionality.

   IPv6 address assignment for the CM and host can be done via DHCP or
   stateless autoconfiguration.  If the CM uses an IPv4 address for
   management, it will use DHCPv4 for its address assignment and the
   CMTS will need to act as a DHCPv4 relay agent.  If the CM uses an
   IPv6 address for management, it can use DHCPv6 with the CMTS acting
   as a DHCPv6 relay agent or the CMTS can be statically configured with
   a /64 prefix and it can send out RA messages out the cable interface.
   The CMs connected to the cable interface can use the RA messages to
   auto-configure themselves with an IPv6 address.  All CMs connected to
   the cable interface will be in the same subnet.

   The hosts can receive their IPv6 address via DHCPv6 or stateless
   autoconfiguration.  With DHCPv6, the CMTS may need to act as a DHCPv6
   relay agent and forward DHCP messages between the hosts and the DHCP
   server.  With stateless autoconfiguration, the CMTS will be
   configured with multiple /64 prefixes and send out RA messages to the
   hosts.  If the CMTS is not also acting as an ER, the RA messages will
   come from the ER connected to the CMTS upstream interface.  The CMTS
   will need to forward the RA messages downstream or act as an ND
   proxy.

6.2.2.3.3  Data Forwarding

   All IPv6 traffic will be sent to/from the CMTS and hosts.  Data
   forwarding will work the same way it works in currently deployed
   cable networks.  The CMTS will forward IPv6 traffic to/from hosts
   based on the IP source/destination address.

6.2.2.3.4  Routing

   No routing protocols are needed between the CMTS and the host since
   the CM and host are directly connected to the CMTS cable interface.
   Since the CMTS supports IPv6, hosts will use the CMTS as their Layer
   3 next hop.

   If the CMTS is also acting as an ER, it runs an IGP such as OSPFv3 or
   ISIS.

6.2.2.4  Dual-Stacked Cable (HFC) Network, Standalone GWR and CMTS
         Support IPv6

   In this case the cable operator can offer IPv6 services to its
   customers by adding a GWR between the CM and the host.  The GWR will
   facilitate IPv6 communication between the host and the CMTS/ER.  The
   CMTS will be upgraded to dual-stack to support IPv6 and can acts as
   an ER as well.  The CM will act as a bridge for forwarding data
   traffic and does not need to support IPv6.

   This scenario is similar to the case described in section 6.2.2.2.
   The only difference in this case is the ER functionality exists on
   the CMTS instead of a separate router in the cable operator network.

   Figure 6.2.2.4 illustrates this deployment scenario

                                    +-----------+  +------------+
   +------+   +-------+  +-------+  |   Cable   |  |CMTS / Edge |
   | Host |---| GWR   |--|  CM   |---|   |--|  (HFC)    |----|    |--|            |=>ISP
   +------+   +-------+  +-------+  |  Network  |  |   Router   |Network
                                    +-----------+  +------------+
                      _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
                     ()_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _()
                             IPv6-in-IPv4 tunnel
<-----------------><--------------------------------><-------------->
   |-----------------||--------------------------------||--------------|
         IPv4/v6                      IPv4                  IPv4/v6

                               Figure 6.2.2.4

6.2.2.4.1  IPv6 Related Infrastructure Changes

   Since the CM still acts as a Layer-2 bridge, it does not need to be
   dual-stack nor does it need to support IPv6.  In this scenario the
   following devices have to be upgraded to dual stack: Host, GWR and
   CMTS/ER.

6.2.2.4.2  Addressing

   The CM will still receive a private IPv4 address using DHCPv4 which
   works the same way in existent cable networks.  The CMTS will act as
   DHCPv4 relay agent.

   The address assignment for the host and GWR happens in a similar
   manner as described in section 6.2.2.2.2.

6.2.2.4.3  Data Forwarding

   Data forwarding between the host and CMTS/ER is facilitated by the
   GWR and happens in a similar manner as described in section
   6.2.2.2.3.

6.2.2.4.4  Routing

   In this case routing is very similar to the case described in section
   6.2.2.2.4.  Since the CMTS now incorporates the ER functionality, it
   will need to run an IGP such as OSPFv3 or ISIS.

6.2.2.5  Dual-Stacked Cable (HFC) Network, Embedded GWR/CM and CMTS
         Support IPv6

   In this scenario the Cable Operator can offer native IPv6 services to
   its customers since the cable network including the CM/Embedded GWR
   and CMTS support IPv6.  The ER functionality can be included in the
   CMTS or it can exist on a separate router connected to the CMTS
   upstream interface.  The CM/Embedded GWR acts as a Layer 3 device.

   Figure 6.2.2.5 illustrates this deployment scenario

                               +-----------+    +-------------+
    +-----+   +-----------+    |   Cable   |    | CMTS / Edge |
    |Host |---| CM / GWR  |----|  (HFC)    |----|             |=> ISP
    +-----+   +-----------+    |  Network  |    |   Router    | Network
                               +-----------+    +-------------+

 <---------------------------------------------------------->

    |----------------------------------------------------------|
                              IPv4/v6

                             Figure 6.2.2.5

6.2.2.5.1  IPv6 Related Infrastructure Changes

   Since the CM/GWR acts as a Layer 3 device, IPv6 can be deployed
   end-to-end. end-
   to-end.  In this scenario the following devices have to be upgraded
   to dual-stack: Host, CM/GWR and CMTS/ER.

6.2.2.5.2  Addressing

   Since the CM/GWR is dual-stack, it can receive an IPv4 or IPv6
   address using DHCP for management purposes.  As the GWR functionality
   is Embedded in the CM, it will need an IPv6 address for forwarding
   data traffic.  IPv6 address assignment for the CM/GWR and host can be
   done via DHCPv6 or DHCP-PD.

   If using DHCPv6 the CMTS will need to act as DHCPv6 relay agent.  The
   host and CM/GWR will receive IPv6 addresses from pools of /64
   prefixes configured on the DHCPv6 server.  The CMTS will need to
   glean pertinent information from the DHCP Offer messages, sent from
   the DHCP server to the DHCP clients (host and CM/GWR), much like it
   does today in DHCPv4.  All CM/GWR connected to the same cable
   interface on the CMTS belong to same management /64 prefix.  The
   hosts connected to the same cable interface on the CMTS may belong to
   different /64 customer prefixes as the CMTS may have multiple /64
   prefixes configured under its cable interfaces.

   It is also possible to use DHCP-PD for IPv6 address assignment.  In
   this case the CM/GWR will use stateless auto-configuration to assign
   an IPv6 address to its upstream interface using the /64 prefix sent
   by the CMTS/ER in RA message.  Once the CM/GWR assigns an IPv6
   address to its upstream interface it will request a /48 [8] prefix
   from the CMTS/ER and chop this /48 prefix into /64s for assigning
   IPv6 addresses to hosts.  Currently the DHCP-PD functionality cannot
   be implemented if the DHCP-PD server is not the Edge Router.  If the
   DHCP-PD messages are relayed, the Edge Router does not have a
   mechanism to learn the assigned prefixes and thus install the proper
   routes to make that prefix reachable.  Work is being done to address
   this issue, one idea being to provide the Edge Router with a snooping
   mechanism.  The uplink to the ISP network is configured with a /64
   prefix as well.

6.2.2.5.3  Data Forwarding

   The host will use the CM/GWR as the Layer 3 next hop.  The CM/GWR
   will forward all IPv6 traffic to/from the CMTS/ER and hosts.  The
   CMTS/ER will forward IPv6 traffic to/from hosts based on the IP
   source/destination address.

6.2.2.5.4  Routing

   The CM/GWR can use a static default route pointing to the CMTS/ER or
   it can run a routing protocol such as RIP-ng or OSPFv3 between itself
   and the CMTS.  Customer routes from behind the CM/GWR can be carried
   to the CMTS using routing updates.

   If DHCP-PD is used for address assignment a static route is
   automatically installed on the CMTS/ER for each delegated /48 prefix.
   The static routes need to be redistributed into the IGP at the
   CMTS/ER so there is no need for a routing protocol between the
   CMTS/ER and the GWR.

   If the CMTS is also acting as an ER, it runs an IGP such as OSPFv3 or
   ISIS.

6.3

6.2.3  IPv6 Multicast

   In order to support IPv6 multicast applications across DOCSIS cable
   networks, the CM and bridging CMTS will need to support IGMPv3/MLDv2
   or v1 snooping.  MLD is almost identical to IGMP in IPv4, only the
   name and numbers are changed.  MLDv2 is almost identical to IGMPv3
   and also supports ASM (Any Source Multicast) and SSM (Single Source
   Multicast) service models.

   SSM is more suited for deployments where the SP intends to provide
   paid content to the users (Video or Audio).  This type of services
   are expected to be of primary interest.  Moreover, the simplicity of
   the SSM model often times override the scalability issues that would
   be resolved in an ASM model.  ASM is however an option that is
   discussed in section 7.3.1.  The Layer 3 CM, GWR and Layer 3 routed
   CMTS/ER will need to be enabled with PIM-SSM, which requires the
   definition and support for IGMPv3/MLDv1 or v2 snooping, in order to
   track join/leave messages from the hosts.  Another option would be
   for the Layer 3 CM or GWR to support MLD proxy routing.  The Layer 3
   next hop for the hosts needs to support MLD.

   Please refer to section 7.3 for more IPv6 multicast details.

6.4

6.2.4  IPv6 QoS

   IPv6 will not change or add any queuing/scheduling functionality
   already existing in DOCSIS specifications.  But the QoS mechanisms on
   the CMTS and CM would need to be IPv6 capable.  This includes support
   for IPv6 classifiers, so that data traffic to/from host devices can
   be classified appropriately into different service flows and be
   assigned appropriate priority.  Appropriate classification criteria
   would need to be implemented for unicast and multicast traffic.

   In order to classify IPv6 traffic the following classifiers would
   need to be modified in the DOCSIS specification to support the
   128-bit 128-
   bit IPv6 address:

   A. IP source address

   B. IP source mask

   C. IP destination address

   D. IP destination mask

   E. IP traffic class (DSCP)

   The following classifiers would be new for IPv6:

   A. IP version
   B. Flow label (optional)

   Traffic classification and marking should be done at the CM for
   upstream traffic and the CMTS/ER for downstream traffic in order to
   support the various types of services: data, voice, video.  The same
   IPv4 QoS concepts and methodologies should be applied for IPv6 as
   well.

   It is important to note that when traffic is encrypted end-to-end,
   the traversed network devices will not have access to many of the
   packet fields used for classification purposes.  In these cases
   routers will most likely place the packets in the default classes.
   The QoS design should take into consideration this scenario and try
   to use mainly IP header fields for classification purposes.

6.5

6.2.5  IPv6 Security Considerations

   Security in a DOCSIS cable network is provided using Baseline Privacy
   Plus (BPI+).  The only part that is dependent on IP addresses is
   encrypted multicast.  Semantically, multicast encryption would work
   the same way in an IPv6 environment as in the IPv4 network.  However,
   appropriate enhancements will be needed in the DOCSIS specification
   to support encrypted IPv6 multicast.

   The other aspect of security enhancement is mandated IPSec support in
   IPv6.  The IPv6 specifications mandate implementation of IPSec, but
   they do not mandate its use.  The IPv4 specifications do not mandate
   IPSec.  IPSec is the same for both IPv4 and IPv6, but it still
   requires a key distribution mechanism.  Cable operators may consider
   deploying it end-to-end on IPv6 as there is not an intermediate
   device(i.e.  NAT).

   There are limited changes that have to be done for hosts in order to
   enhance security.  The Privacy extensions [RFC3041] [14] for autoconfiguration
   should be used by the hosts.  IPv6 firewall functions could be
   enabled, if available on the host or GWR.

   The ISP provides security against attacks that come form its own
   subscribers but it could also implement security services that
   protect its subscribers from attacks sourced from the outside of its
   network.  Such services do not apply at the access level of the
   network discussed here.

   The CMTS/ER should protect the ISP network and the other subscribers
   against attacks by one of its own customers.  For this reason Unicast
   Reverse Path Forwarding (uRPF) [RFC3704] [23] and ACLs should be used on all
   interfaces facing subscribers.  Filtering should be implemented with
   regard for the operational requirements of IPv6 [Security
   considerations for IPv6].

   The CMTS/ER should protect its processing resources against floods of
   valid customer control traffic such as: Router and Neighbor
   Solicitations, MLD Requests.

   All other security features used with the IPv4 service should be
   similarly applied to IPv6 as well.

6.6

6.2.6  IPv6 Network Management

   IPv6 can have many applications in Cable Networks.  MSOs can
   initially implement IPv6 on the control plane and use it to manage
   the thousands of devices connected to the CMTS.  This would be a good
   way to introduce IPv6 in a Cable Network.  Later on the MSO can
   extend IPv6 to the data plane and use it to carry customer as well as
   management traffic.

6.6.1

6.2.6.1  Using IPv6 for Management in Cable Networks

   IPv6 can be enabled in a Cable Network for management of devices like
   CM, CMTS and ER.  With the roll out of advanced services like VoIP
   and Video-over-IP, MSOs are looking for ways to manage the large
   number of devices connected to the CMTS.  In IPv4, an RFC1918 address
   is assigned to these devices like CM for management purposes.  Since
   there is a finite number of RFC1918 addresses available, it is
   becoming difficult for MSOs to manage these devices.

   By using IPv6 for management purposes, MSOs can scale their network
   management systems to meet their needs.  The CMTS/ER can be
   configured with a /64 management prefix which is shared among all CMs
   connected to the CMTS cable interface.  Addressing for the CMs can be
   done via stateless autoconfiguration.  Once the CMs receive the /64
   prefix from the CMTS/ER via RA they can configure themselves with an
   IPv6 address.

   If there are devices behind the CM which need to be managed by the
   MSO, another /64 prefix can be defined on the CMTS/ER.  These devices
   can also use stateless autoconfiguration to assign themselves an IPv6
   address.

   Traffic sourced from or destined to the management prefix should not
   cross the MSO's network boundaries.

   In this scenario IPv6 will only be used for managing these devices on
   the Cable Network, all data traffic will still be forwarded by the CM
   and CMTS/ER using IPv4.

6.6.2

6.2.6.2  Updates to MIBs/Standards to support IPv6

   The current DOCSIS, PacketCable, and CableHome MIBs are already
   designed to support IPv6 objects.  In this case, IPv6 will neither
   add, nor change any of the functionality of these MIBs.  An object to
   identify the IP version, InetAddressType has been added to all the
   appropriate SNMP objects related to IP address.

   There are some exceptions, the following MIBs might need to add IPv6
   support:

   On the CMTS

   A. DOCS-QOS-MIB

   B. DOCS-SUBMGT-MIB (Subscriber Management Interface Specification
   ANNEX B)

   On the CM

   A. DOCS-QOS-MIB

   B. DOCS-CABLE-DEVICE-MIB (or RFC2669) [20])

7.  Broadband DSL Networks

   This section describes the IPv6 deployment options in today's High
   Speed DSL Networks.

7.1  DSL Network Elements

   Digital Subscriber Line (DSL) broadband services provide users with
   IP connectivity over the existing twisted-pair telephone lines called
   the local-loop.  A wide range of bandwidth offerings are available
   depending on the quality of the line and the distance between the
   Customer Premises Equipment and the DSLAM.

   The following network elements are typical of a DSL network [ISP
   Transition Scenarios]:

   DSL Modem: It can be a stand alone device, it can be incorporated in
   the host, it can incorporate router functionalities and also have the
   capabilities to act as a CPE router.

   Customer Premises Router: It is used to provide Layer 3 services for
   customer premises networks.  It is usually used to provide
   firewalling functions and segment broadcast domains for a Small
   business.

   DSL Access Multiplexer (DSLAM): It terminates multiple twisted pair
   telephone lines and provides aggregation to BRAS.

   Broadband Remote Access Server (BRAS): It aggregates or terminates
   multiple PVC corresponding to the subscriber DSL circuits.

   Edge Router (ER): It provides the Layer 3 interface to the ISP
   network.

   Figure 7.1 depicts all the network elements mentioned. mentioned

   Customer Premises | Network Access Provider | Network |Network Service Provider
          CP                     NAP                        NSP
   +-----+  +------+                 +------+   +--------+
   |Hosts|--|Router|              +--+ BRAS +---+ Edge   |       ISP
   +-----+  +--+---+              |  |      |   | Router +===> Network
               |                  |  +------+   +--------+
            +--+---+              |
            | DSL  +--+           |
            |Modem |  |           |
            +------+  |  +-----+  |
                      +--+     |  |
            +------+     |DSLAM+--+
   +-----+  | DSL  |  +--+     |
   |Hosts|--+Modem +--+  +-----+
   +-----+  +--+---+
                                   Figure 7.1

7.2  Deploying IPv6 in IPv4 DSL Networks

   There are three main design approaches to providing IPv4 connectivity
   over a DSL infrastructure:

   1.  Point-to-Point Model: Each subscriber connects to the DSLAM over
   a twisted pair and is provided with a unique PVC that links it to the
   service provider.  The PVCs can be terminated at the BRAS or at the
   Edge Router.  This type of design is not very scalable if the PVCs
   are not terminated as close as possible to the DSLAM (at the BRAS).
   In this case a large number of layer two circuits has to be
   maintained over a significant portion of the network.  The layer two
   domains can be terminated at the ER in three ways:

   A. In a common bridge group with a virtual interface that routes it
   out.

   B. Enable a Routed Bridged Encapsulation feature, all users could be
   part of the same subnet.  This is the most common deployment type of
   IPv4 over DSL but it might not be the best choice in IPv6 where
   address availability is not an issue.

   C. Terminate the PVC at Layer 3, each PVC has its own prefix.  This
   is the approach that seems more suitable for IPv6 and presented in
   7.2.1 In none of these cases the CPE (DSL Modem) has to be upgraded.

   2.  PPP Terminated Aggregation (PTA) Model: PPP sessions are opened
   between each subscriber and the BRAS.  The BRAS terminates the PPP
   sessions and provides Layer 3 connectivity between the subscriber and
   the ISP.  This model is presented in section 7.2.2.

   3.  L2TP Access Aggregation (LAA) Model: PPP sessions are opened
   between each subscriber and the ISP Edge Router.  The BRAS tunnels
   the subscriber PPP sessions to the ISP by encapsulating them into
   L2TPv2 tunnels.  This model is presented in section 7.2.3.

   In aggregation models the BRAS terminates the subscriber PVCs and
   aggregates their connections before providing access to the ISP.

   In order to maintain the deployment concepts and business models
   proven and used with existent revenue generating IPv4 services, the
   IPv6 deployment will match the IPv4 one.  This approach is presented
   in sections 7.2.1-3 that describe current IPv4 over DSL broadband
   access deployments.  Under certain circumstances where new service
   types or service needs justify it, IPv4 and IPv6 network logical
   architectures could be different as described in section 7.2.4.

7.2.1  Point-to-Point Model

   In this scenario the Ethernet frames from the Host or the Customer
   Premises Router are bridged over the PVC assigned to the subscriber.

   Figure 7.2.1 describes the protocol architecture of this model. model

        Customer Premises              NAP                 NSP
<------------------------->  <---------------> <-------------------->
   |-------------------------|  |---------------| |--------------------|

   +-----+  +-------+  +-----+  +--------+        +----------+
   |Hosts|--+Router +--+ DSL +--+ DSLAM  +--------+   Edge   |     ISP
   +-----+  +-------+  |Modem|  +--------+        |  Router  +==> Network  +==>Network
                       +-----+                    +----------+
                        <---------------------------->
                           |----------------------------|
                                       ATM
                                   Figure 7.2.1

7.2.1.1  IPv6 Related Infrastructure Changes

   In this scenario the DSL modem and the entire NAP is Layer 3 unaware,
   so no changes are needed to support IPv6.  The following devices have
   to be upgraded to dual stack: Host, Customer Router (if present) and
   Edge Router.

7.2.1.2  Addressing

   The Hosts or the Customer Routers have the Edge Router as their Layer
   3 next hop.

   If there is no Customer Router all the hosts on the subscriber site
   belong to the same /64 subnet that is statically configured on the
   Edge Router for that subscriber PVC.  The hosts can use stateless
   autoconfiguration or stateful DHCPv6 based configuration to acquire
   an address via the Edge Router.

   If a Customer Router is present:

   A. It is statically configured with an address on the /64 subnet
   between itself and the Edge Router, and with /64 prefixes on the
   interfaces connecting the hosts on the customer site.  This is not a
   desired provisioning method being expensive and difficult to manage.

   B. It can use its link-local address to communicate with the ER.  It
   can also dynamically acquire through stateless autoconfiguration the
   prefix for the link between itself and the ER.  The later option
   allows it to contact a remote DHCPv6 server if needed.  This step is
   followed by a request via DHCP-PD for a prefix shorter than /64 that
   in turn is divided in /64s and assigned to its downstream interfaces.

   The Edge Router has a /64 prefix configured for each subscriber VLAN.
   Each VLAN should be enabled to relay DHCPv6 requests from the
   subscribers to DHCPv6 servers in the ISP network.  The VLANs
   providing access for subscribers that use DHCP-PD as well, have to be
   enabled to support the feature.  Currently the DHCP-PD functionality
   cannot be implemented if the DHCP-PD server is not the Edge Router.
   If the DHCP-PD messages are relayed, the Edge Router does not have a
   mechanism to learn the assigned prefixes and thus install the proper
   routes to make that prefix reachable.  Work is being done to address
   this issue, one idea being to provide the Edge Router with a snooping
   mechanism.  The uplink to the ISP network is configured with a /64
   prefix as well.

   The prefixes used for subscriber links and the ones delegated via
   DHCP-PD should be planned in a manner that allows as much
   summarization as possible at the Edge Router.

   Other information of interest to the host, such as DNS, is provided
   through stateful DHCPv6 [RFC3315] [11] and stateless DHCPv6 [RFC3736]. [10].

7.2.1.3  Routing

   The CPE devices are configured with a default route that points to
   the Edge router.  No routing protocols are needed on these devices
   which generally have limited resources.

   The Edge Router runs the IPv6 IGP used in the NSP: OSPFv3 or IS-IS.
   The connected prefixes have to be redistributed.  If DHCP-PD is used,
   with every delegated prefix a static route is installed by the Edge
   Router.  For this reason the static routes must also be
   redistributed.  Prefix summarization should be done at the Edge
   Router.

7.2.2  PPP Terminated Aggregation (PTA) Model

   The PTA architecture relies on PPP-based protocols (PPPoA [RFC2364] [16] and
   PPPoE [RFC2516]). [15]).  The PPP sessions are initiated by Customer Premise
   Equipment and are terminated at the BRAS.  The BRAS authorizes the
   session, authenticates the subscriber, and provides an IP address on
   behalf of the ISP.  The BRAS then does Layer 3 routing of the
   subscriber traffic to the NSP Edge Router.  This model is often used
   when the NSP is also the NAP.

   There are two types of PPP encapsulations that can be leveraged with
   this model:

   A. Connection using PPPoA

     Customer Premises              NAP                   NSP
<--------------------> <----------------------> <----------------->
   |--------------------| |----------------------| |-----------------|
                                                   +-----------+
                                                   |    AAA    |
                                           +-------+   Radius  |
                                           |       |   TACACS  |
                                           |       +-----------+
                                           |
   +-----+  +-------+      +--------+ +----+-----+ +-----------+
   |Hosts|--+Router +------+ DSLAM  +-+   BRAS   +-+    Edge   |
   +-----+  +-------+      +--------+ +----------+ |   Router  +=>Core
                                                   +-----------+
             <-------------------------->
                |--------------------------|
                            PPP
                                  Figure 7.2.2.1
   The PPP sessions are initiated by the Customer Premise Equipment.
   The BRAS authenticates the subscriber against a local or a remote
   database.  Once the session is established, the BRAS provides an
   address and maybe a DNS server to the user, information acquired from
   the subscriber profile or from a DHCP server.

   This solution scales better then the Point-to-Point but since there
   is only one PPP session per ATM PVC the subscriber can choose a
   single ISP service at a time.

   B. Connection using PPPoE

        Customer Premises                NAP                 NSP
<----------------------------> <-------------------> <----------------->
   |--------------------------| |-------------------| |--------------|
                                                       +-----------+
                                                       |    AAA    |
                                               +-------+   Radius  |
                                               |       |   TACACS  |
                                               |       +-----------+
                                               |
   +-----+  +-------+          +--------+ +----+-----+ +-----------+
   |Hosts|--+Router +------------+ +----------+ DSLAM  +-+   BRAS   +-+    Edge   |  C
   +-----+  +-------+          +--------+ +----------+ |   Router  +=>O
                                                       |           |  R
                                                       +-----------+  E
            <-------------------------------->
               |-------------------------------|
                            PPP
                                  Figure 7.2.2.2

   The operation of PPPoE is similar to PPPoA with the exception that
   with PPPoE multiple sessions can be supported over the same PVC thus
   allowing the subscriber to connect to multiple services at the same
   time.  The hosts can initiate the PPPoE sessions as well.  It is
   important to remember that the PPPoE encapsulation reduces the IP MTU
   available for the customer traffic due to additional headers.

   The network design and operation of the PTA model is the same
   regardless of the PPP encapsulation type used.

7.2.2.1  IPv6 Related Infrastructure Changes

   In this scenario the BRAS is Layer 3 aware and it has to be upgraded
   to support IPv6.  Since the BRAS terminates the PPP sessions it has
   to support the implementation of these PPP protocols with IPv6.  The
   following devices have to be upgraded to dual stack: Host, Customer
   Router (if present), BRAS and Edge Router.

7.2.2.2  Addressing

   The BRAS terminates the PPP sessions and provides the subscriber with
   an IPv6 address from the defined pool for that profile.  The
   subscriber profile for authorization and authentication can be
   located on the BRAS or on a AAA server.  The Hosts or the Customer
   Routers have the BRAS as their Layer 3 next hop.

   The PPP session can be initiated by a host or by a Customer Router.
   In the latter case, once the session is established with the BRAS and
   an address is negotiated for the uplink to the BRAS, DHCP-PD can be
   used to acquire prefixes for the Customer Router other interfaces.

   The BRAS has to be enabled to support DHCP-PD and to relay the DHCPv6
   requests of the hosts on the subscriber sites.

   The BRAS has a /64 prefixes configured on the link to the Edge
   router.  The Edge router links are also configured with /64 prefixes
   to provide connectivity to the rest of the ISP network.

   The prefixes used for subscriber and the ones delegated via DHCP-PD
   should be planned in a manner that allows maximum summarization at
   the BRAS.

   Other information of interest to the host, such as DNS, is provided
   through stateful [RFC3315] [11] and stateless [RFC3736] [10] DHCPv6.

7.2.2.3  Routing

   The CPE devices are configured with a default route that points to
   the BRAS router.  No routing protocols are needed on these devices
   which generally have limited resources.

   The BRAS runs an IGP to the Edge Router: OSPFv3 or IS-IS.  Since the
   addresses assigned to the PPP sessions are represented as connected
   host routes, connected prefixes have to be redistributed.  If DHCP-PD
   is used, with every delegated prefix a static route is installed by
   the Edge Router.  For this reason the static routes must also be
   redistributed.  Prefix summarization should be done at the BRAS.

   The Edge Router is running the IGP used in the ISP network: OSPFv3 or
   IS-IS.

   A separation between the routing domains of the ISP and the Access
   Provider is recommended if they are managed independently.
   Controlled redistribution will be needed between the Access Provider
   IGP and the ISP IGP.

7.2.3  L2TPv2 Access Aggregation (LAA) Model

   In the LAA model the BRAS forwards the CPE initiated session to the
   ISP over an L2TPv2 tunnel established between the BRAS and the Edge
   Router.  In this case the authentication, authorization and
   subscriber configuration are performed by the ISP itself.  There are
   two types of PPP encapsulations that can be leveraged with this
   model:

   A. Connection via PPPoA

     Customer Premises              NAP                   NSP
<--------------------> <----------------------> <----------------->
   |--------------------| |----------------------| |-----------------|
                                                   +-----------+
                                                   |    AAA    |
                                           +-------+   Radius  |
                                           |       |   TACACS  |
                                           |       +-----+-----+
                                           |             |
   +-----+  +-------+      +--------+ +----+-----+ +-----+-----+
   |Hosts|--+Router +------+ DSLAM  +-+  BRAS    +-+   Edge    |
   +-----+  +-------+      +--------+ +----------+ |  Router   +=>Core
                                                   +-----------+
             <---------------------------------------->
                |----------------------------------------|
                                   PPP
                                         <------------>
                                            |------------|
                                                 L2TPv2
                           Figure 7.2.3.1
   B. Connection via PPPoE

       Customer Premises                NAP                   NSP
<---------------------------> <--------------------> <----------------->
   |-------------------------| |--------------------| |--------------|
                                                      +-----------+
                                                      |    AAA    |
                                               +------+   Radius  |
                                               |      |   TACACS  |
                                               |      +-----+-----+
                                               |            |
   +-----+  +-------+          +--------+ +----+-----+ +----+------+
   |Hosts|--+Router +------------+ +----------+ DSLAM  +-+  BRAS    +-+    Edge   |  C
   +-----+  +-------+          +--------+ +----------+ |   Router  +=>O
                                                       |           |  R
                                                       +-----------+  E
            <----------------------------------------------->
               |---------------------------------------------|
                                     PPP
                                             <-------------->
                                                |------------|
                                                    L2TPv2
                             Figure 7.2.3.2

   The network design and operation of the PTA model is the same
   regardless of the PPP encapsulation type used.

7.2.3.1  IPv6 Related Infrastructure Changes

   In this scenario the BRAS is forwarding the PPP sessions initiated by
   the subscriber over the L2TPv2 tunnel established to the LNS, the
   aggregation point in the ISP network.  The L2TPv2 tunnel between the
   LAC and LNS could run over IPv6 or IPv4.  These capabilities have to
   be supported on the BRAS.  The following devices have to be upgraded
   to dual stack: Host, Customer Router and Edge Router.  If the tunnel
   is set up over IPv6 then the BRAS must be upgraded to dual stack.

7.2.3.2  Addressing

   The Edge router terminates the PPP sessions and provides the
   subscriber with an IPv6 address from the defined pool for that
   profile.  The subscriber profile for authorization and authentication
   can be located on the Edge Router or on a AAA server.  The Hosts or
   the Customer Routers have the Edge Router as their Layer 3 next hop.

   The PPP session can be initiated by a host or by a Customer Router.
   In the latter case, once the session is established with the Edge
   Router, DHCP-PD can be used to acquire prefixes for the Customer
   Router interfaces.  The Edge Router has to be enabled to support
   DHCP-PD and to relay the DHCPv6 requests generated by the hosts on
   the subscriber sites.

   The BRAS has a /64 prefix configured on the link to the Edge router.
   The Edge router links are also configured with /64 prefixes to
   provide connectivity to the rest of the ISP network.  Other
   information of interest to the host, such as DNS, is provided through
   stateful [RFC3315] [11] and stateless [RFC3736] [10] DHCPv6.

   It is important to note here a significant difference between this
   deployment for IPv6 versus IPv4.  In the case of IPv4 the customer
   router or CPE can end up on any Edge Router (acting as LNS) where the
   assumption is that there are at least two of them for redundancy
   purposes.  Once authenticated, the customer will be given an address
   from the IP pool of the ER (LNS) it connected to.  This allows the
   ERs (LNSs) to aggregate the addresses handed out to the customers.
   In the case of IPv6, an important constraint that likely will be
   enforced is that the customer should keep its own address regardless
   of the ER (LNS) it connects to.  This could significantly reduce the
   prefix aggregation capabilities of the ER (LNS).  This is different
   than the current IPv4 deployment where addressing is dynamic in
   nature and the same user can get different addresses depending on the
   LNS it ends up connecting to.

   One possible solution is to ensure that a given BRAS will always
   connect to the same ER (LNS) unless that LNS is down.  This means
   that customers from a given prefix range will always be connected to
   the same ER (primary if up or secondary if not).  Each ER (LNS) can
   carry summary statements in their routing protocol configuration for
   the prefixes they are the primary ER (LNS) as well as for the ones
   for which they are the secondary.  This way the prefixes will be
   summarized any time they become "active" on the ER (LNS).

7.2.3.3  Routing

   The CPE devices are configured with a default route that points to
   the Edge router that terminates the PPP sessions.  No routing
   protocols are needed on these devices which have generally limited
   resources.

   The BRAS runs an IPv6 IGP to the Edge Router: OSPFv3 or IS-IS.
   Different processes should be used if the NAP and the NSP are managed
   by different organizations.  In this case, controlled redistribution
   should be enabled between the two domains.

   The Edge Router is running the IPv6 IGP used in the ISP network:
   OSPFv3 or IS-IS.

7.2.4  Hybrid Model for IPv4 and IPv6 Service

   It was recommended throughout this section that the IPv6 service
   implementation should map the existent IPv4 one.  This approach
   simplifies manageability and minimizes training needed for personnel
   operating the network.  In certain circumstances such mapping is not
   feasible.  This typically becomes the case when a Service Provider
   plans to expand its service offering with the new IPv6 deployed
   infrastructure.  If this new service is not well supported in a
   network design such as the one used for IPv4 then a different design
   might be used for IPv6.

   An example of such circumstances is that of a provider using an LAA
   design for its IPv4 services.  In this case all the PPP sessions are
   bundled and tunneled across the entire NAP infrastructure which is
   made of multiple BRAS routers, aggregation routers etc.  The end
   point of these tunnels is the ISP Edge Router.  If the provider
   decides to offer multicast services over such a design, it will face
   the problem of NAP resources being over utilized.  The multicast
   traffic can be replicated only at the end of the tunnels by the Edge
   router and the copies for all the subscribers are carried over the
   entire NAP.

   A Modified Point-to-Point (as described in 7.2.4.2) or PTA model are
   more suitable to support multicast services because the packet
   replication can be done closer to the destination at the BRAS.  Such
   topology saves NAP resources.

   In this sense IPv6 deployment can be viewed as an opportunity to
   build an infrastructure that might better support the expansion of
   services.  In this case, an SP using the LAA design for its IPv4
   services might choose a modified Point-to-Point or PTA design for
   IPv6.

7.2.4.1  IPv4 in LAA Model and IPv6 in PTA Model

   The coexistence of the two PPP based models, PTA and LAA, is
   relatively straight forward.  The PPP sessions are terminated on
   different network devices for the IPv4 and IPv6 services.  The PPP
   sessions for the existent IPv4 service deployed in an LAA model are
   terminated on the Edge Router.  The PPP sessions for the new IPv6
   service deployed in a PTA model are terminated on the BRAS.

   The logical design for IPv6 and IPv4 in this hybrid model is
   presented in Figure 7.2.4.1.

   IPv6          <-------------------------->          |--------------------------|
                            PPP                    +-----------+
                                                   |    AAA    |
                                           +-------+   Radius  |
                                           |       |   TACACS  |
                                           |       +-----+-----+
                                           |             |
   +-----+  +-------+      +--------+ +----+-----+ +-----+-----+
   |Hosts|--+Router +------+ DSLAM  +-+  BRAS    +-+   Edge    |
   +-----+  +-------+      +--------+ +----------+ |  Router   +=>Core
                                                   +-----------+
   IPv4          <---------------------------------------->          |----------------------------------------|
                                   PPP
                                         <------------>
                                            |------------|
                                                 L2TPv2
                                 Figure 7.2.4.1

7.2.4.2  IPv4 in LAA Model and IPv6 in Modified Point-to-Point Model

   In this particular scenario the Point-to-Point model used for the
   IPv6 service is a modified version of the model described in section
   7.2.1.

   For the IPv4 service in LAA model, the VLANs are terminated on the
   BRAS and PPP sessions are terminated on the Edge Router (LNS).  For
   IPv6 service in Point-to-Point model, the VLANs are terminated at the
   Edge Router as described in section 7.2.1.  In this hybrid model, the
   Point-to-Point link could be terminated on the BRAS, a NAP owned
   device.  The IPv6 traffic is then routed through the NAP network to
   the NSP.  In order to have this hybrid model, the BRAS has to be
   upgraded to a dual-stack router.  The functionalities of the Edge
   Router as described in section 7.2.1 are now implemented on the BRAS.

   The other aspect of this deployment model is the fact that the BRAS
   has to be capable of distinguishing between the IPv4 PPP traffic that
   has to be bridged across the L2TPv2 tunnel and the IPv6 packets that
   have to be routed to the NSP.  The IPv6 Routing and Bridging
   Encapsulation (RBE) has to be enabled on all interfaces with VLANs
   supporting both IPv4 and IPv6 services in this hybrid design.

   The logical design for IPv6 and IPv4 in this hybrid model is
   presented in Figure 7.2.4.2.

   IPv6              <---------------->              |----------------|
                            ATM                    +-----------+
                                                   |    AAA    |
                                           +-------+   Radius  |
                                           |       |   TACACS  |
                                           |       +-----+-----+
                                           |             |
   +-----+  +-------+      +--------+ +----+-----+ +-----+-----+
   |Hosts|--+Router +------+ DSLAM  +-+  BRAS    +-+   Edge    |
   +-----+  +-------+      +--------+ +----------+ |  Router   +=>Core
                                                   +-----------+
   IPv4          <---------------------------------------->          |----------------------------------------|
                                   PPP
                                         <------------>
                                            |------------|
                                                 L2TPv2
                                 Figure 7.2.4.2

7.3  IPv6 Multicast

   The deployment of IPv6 multicast services relies on MLD, identical to
   IGMP in IPv4 and on PIM for routing.  ASM (Any Source Multicast) and
   SSM (Single Source Multicast) service models operate almost the same
   as in IPv4.  Both have the same benefits and disadvantages as in
   IPv4.  Nevertheless, the larger address space and the scoped address
   architecture provide major benefits for multicast IPv6.  Through
   RFC3306 the large address space provides the means to assign global
   multicast group addresses to organizations or users that were
   assigned unicast prefixes.  It is a significant improvement with
   respect to the IPv4 GLOP mechanism [RFC2770]. [19].

   This facilitates the deployment of multicast services.  The
   discussion of this section applies to all the multicast sections in
   the document.

7.3.1  ASM Based Deployments

   Any Source Multicast (ASM) is useful for Service Providers that
   intend to support the forwarding of multicast traffic of their
   customers.  It is based on the PIM-SM protocol and it is more complex
   to manage because of the use of Rendezvous Points (RPs).  With IPv6,
   static RP and BSR [BSR] [34] can be used for RP-to-group mapping similar to
   IPv4.  Additionally, the larger IPv6 address space allows for
   building up of group addresses that incorporate the address of the
   RP.  This RP-to-group mapping mechanism is called Embedded RP and is
   specific to IPv6.

   In inter-domain deployments, Multicast Source Discovery Protocol
   (MSDP) [RFC3618] [22] is an important element of IPv4 PIM-SM deployments.  MSDP
   is meant to be a solution for the exchange of source registration
   information between RPs in different domains.  This solution was
   intended to be temporary.  This is one of the reasons why it was
   decided not to implement MSDP in IPv6 [IPv6 Multicast]. [32].

   For multicast reachability across domains, Embedded RP could be used.
   Despite its shortcomings, MSDP provides additional flexibility in
   managing the domains that may not be matched with the protocols
   available in IPv6 today.  The value of such flexibility is still
   under evaluation.

7.3.2  SSM Based Deployments

   Based on PIM-SSM, the Source Specific Multicast deployments do not
   need an RP and the related protocols (such as BSR or MSDP) but rely
   on the listeners to know the source of the multicast traffic they
   plan to receive.  The lack of RP makes SSM not only simpler to
   operate but also robust, it is not impacted by RP failures or inter
   domain constraints.  It is also has a higher level of security (No RP
   to be targeted by attacks).  For more discussions on the topic of
   IPv6 multicast see [IPv6 Multicast]. [32].

   The typical multicast services offered for residential and very small
   businesses is video/audio streaming where the subscriber joins a
   multicast group and receives the content.  This type of service model
   is well supported through PIM-SSM which is very simple and easy to
   manage.  PIM-SSM has to be enabled throughout the SP network.  MLDv2
   is required for PIM-SSM support.  Vendors can choose to implement
   features that allow routers to map MLDv1 group joins to predefined
   sources.

   Subscribers might use a set-top box that is responsible for the
   control piece of the multicast service (does group joins/leaves).
   The subscriber hosts can also join desired multicast groups as long
   as they are enabled to support MLDv1 or MLDv2.  If a customer premise
   router is used then it has to be enabled to support MLDv1 and MLDv2
   in order to process the requests of the hosts.  It has to be enabled
   to support PIM-SSM in order to send PIM joins/leaves up to its Layer
   3 next hop whether it is the BRAS or the Edge router.  When enabling
   this functionality on a customer premises router, its limited
   resources should be taken into consideration.  Another option would
   be for the customer premises router to support MLD proxy routing.

   The router that is the Layer 3 next hop for the subscriber (BRAS in
   the PTA model or the Edge router in the LAA and Point-to-Point model)
   has to be enabled to support MLDv1 and MLDv2 in order to process the
   requests coming from subscribers without customer premises routers.

   It has to be enabled for PIM-SSM in order to receive joins/leaves
   from customer routers and send joins/leaves to the next hop towards
   the multicast source (Edge router or the NSP core).

   MLD authentication, authorization and accounting is usually
   configured on the edge router in order to enable the ISP to do
   control the subscriber access of the service and do billing for the
   content provided.  Alternative mechanisms that would support these
   functions should be investigated further.

7.4  IPv6 QoS

   The QoS configuration is particularly relevant on the router that
   represents the Layer 3 next hop for the subscriber (BRAS in the PTA
   model or the Edge router in the LAA and Point-to-Point model) in
   order to manage resources shared amongst multiple subscribers
   possibly with various service level agreements.

   In the DSL infrastructure it is expected that there is already a
   level of traffic policing and shaping implemented for IPv4
   connectivity.  This is implemented throughout the NAP and it is
   beyond the scope of this document.

   On the BRAS or the Edge Router the subscriber facing interfaces have
   to be configure to police the inbound customer traffic and shape the
   traffic outbound to the customer based on the SLAs.  Traffic
   classification and marking should also be done on the router closest
   (at Layer 3) to the subscriber in order to support the various types
   of customer traffic: data, voice, video and to optimally use the
   infrastructure resources.  Each provider (NAP, NSP) could implement
   their own QoS policies and services so reclassification and marking
   might be performed at the boundary between the NAP and the NSP in
   order to make sure the traffic is properly handled by the ISP.  The
   same IPv4 QoS concepts and methodologies should be applied with IPv6
   as well.

   It is important to note that when traffic is encrypted end-to-end,
   the traversed network devices will not have access to many of the
   packet fields used for classification purposes.  In these cases
   routers will most likely place the packets in the default classes.
   The QoS design should take into consideration this scenario and try
   to use mainly IP header fields for classification purposes.

7.5  IPv6 Security Considerations

   There are limited changes that have to be done for CPEs in order to
   enhance security.  The Privacy extensions for auto-configuration
   [RFC3041] [14]
   should be used by the hosts.  ISPs can track the prefixes it assigns
   to subscribers relatively easily.  If however the ISPs are required
   by regulations to track their users at /128 address level, the
   Privacy Extensions can be implemented only in parallel with network
   management tools that could provide traceability of the hosts.  IPv6
   firewall functions should be enabled on the hosts or customer
   premises router if present.

   The ISP provides security against attacks that come form its own
   subscribers but it could also implement security services that
   protect its subscribers from attacks sourced from the outside of its
   network.  Such services do not apply at the access level of the
   network discussed here.

   The device that is the Layer 3 next hop for the subscribers (BRAS or
   Edge router) should protect the network and the other subscribers
   against attacks by one of the provider customers.  For this reason
   uRPF and ACLs should be used on all interfaces facing subscribers.
   Filtering should be implemented with regard for the operational
   requirements of IPv6 [Security considerations for IPv6]. [36].  Authentication and authorization should
   be used wherever possible.

   The BRAS and the Edge Router should protect their processing
   resources against floods of valid customer control traffic such as:
   Router and Neighbor Solicitations, MLD Requests.  Rate limiting
   should be implemented on all subscriber facing interfaces.  The
   emphasis should be placed on multicast type traffic as it is most
   often used by the IPv6 control plane.

   All other security features used with the IPv4 service should be
   similarly applied to IPv6 as well.

7.6  IPv6 Network management

   The necessary instrumentation (such as MIBs, NetFlow Records etc)
   should be available for IPv6.

   Usually, NSPs manage the edge routers by SNMP.  The SNMP transport
   can be done over IPv4 if all managed devices have connectivity over
   both IPv4 and IPv6.  This would imply the smallest changes to the
   existent network management practices and processes.  Transport over
   IPv6 could also be implemented and it might become necessary if IPv6
   only islands are present in the network.  The management stations are
   located on the core network.  Network Management Applications should
   handle IPv6 in a similar fashion to IPv4, however, they should also
   support features specific to IPv6 (such as Neighbor monitoring).

   In some cases service providers manage equipment located on customers
   LANs.  The management of equipment at customers' LANs is out of scope
   of this memo.

8.  Broadband Ethernet Networks

   This section describes the IPv6 deployment options in currently
   deployed Broadband Ethernet Access Networks.

8.1  Ethernet Access Network Elements

   In environments that support the infrastructure deploying RJ-45 or
   fiber (Fiber to the Home (FTTH) service) to subscribers, 10/100 Mbps
   Ethernet broadband services can be provided.  Such services are
   generally available in metropolitan areas, in multi tenant buildings
   where an Ethernet infrastructure can be deployed in a cost effective
   manner.  In such environments Metro-Ethernet services can be used to
   provide aggregation and uplink to a Service Provider.

   The following network elements are typical of an Ethernet network:

   Access Switch: It is used as a Layer 2 access device for subscribers.

   Customer Premises Router: It is used to provide Layer 3 services for
   customer premises networks.

   Aggregation Ethernet Switches: Aggregates multiple subscribers.

   Broadband Remote Access Server (BRAS)

   Edge Router (ER)

   Figure 8.1 depicts all the network elements mentioned.

   Customer Premises | Network Access Provider | Network |Network Service Provider
          CP                     NAP                        NSP

   +-----+  +------+                 +------+   +--------+
   |Hosts|--|Router|               +-+ BRAS +---+ Edge   |       ISP
   +-----+  +--+---+               | |      |   | Router +===> Network
               |                   | +------+   +--------+
            +--+-----+             |
            |Access  +-+           |
            |Switch  | |           |
            +--------+ |  +------+ |
                       +--+Agg E | |
            +--------+    |Switch+-+
   +-----+  |Access  | +--+      |
   |Hosts|--+Switch  +-+  +------+
   +-----+  +--------+
                                    Figure 8.1

   The logical topology and design of Broadband Ethernet Networks is
   very similar to DSL Broadband Networks discussed in section 7.

   It is worth noting that the general operation, concepts and
   recommendations described in this section apply similarly to a
   HomePNA based network environment.  In such an environment some of
   the network elements might be differently named.

8.2  Deploying IPv6 in IPv4 Broadband Ethernet Networks

   There are three main design approaches to providing IPv4 connectivity
   over an Ethernet infrastructure:

   A. Point-to-Point Model: Each subscriber connects to the network
   Access switch over RJ-45 or fiber links.  Each subscriber is assigned
   a unique VLAN on the access switch.  The VLAN can be terminated at
   the BRAS or at the Edge Router.  The VLANs are 802.1q trunked to the
   Layer 3 device (BRAS or Edge Router).

   This model is presented in section 8.2.1.

   B. PPP Terminated Aggregation (PTA) Model: PPP sessions are opened
   between each subscriber and the BRAS.  The BRAS terminates the PPP
   sessions and provides Layer 3 connectivity between the subscriber and
   the ISP.

   This model is presented in section 8.2.2.

   C. L2TPv2 Access Aggregation (LAA) Model: PPP sessions are opened
   between each subscriber and the ISP termination devices.  The BRAS
   tunnels the subscriber PPP sessions to the ISP by encapsulating them
   into L2TPv2 tunnels.

   This model is presented in section 8.2.3.

   In aggregation models the BRAS terminates the subscriber VLANs and
   aggregates their connections before providing access to the ISP.

   In order to maintain the deployment concepts and business models
   proven and used with existent revenue generating IPv4 services, the
   IPv6 deployment will match the IPv4 one.  This approach is presented
   in sections 8.2.1-3 that describes describe currently deployed IPv4 over
   Ethernet broadband access deployments.  Under certain circumstances
   where new service types or service needs justify it, IPv4 and IPv6
   network architectures could be different as described in section
   8.2.4.

8.2.1  Point-to-Point Model

   In this scenario the Ethernet frames from the Host or the Customer
   Premises Router are bridged over the VLAN assigned to the subscriber.

   Figure 8.2.1 describes the protocol architecture of this model.

   |   Customer Premises     |  |       NAP       |        NSP
<------------------------->  <---------------> <-------------------->        |

   +-----+  +------+  +------+  +--------+        +----------+
   |Hosts|--+Router+--+Access+--+ Switch +--------+   Edge   |     ISP
   +-----+  +------+  |Switch|  +--------+ 802.1q |  Router  +==> Network  +==>Network
                      +------+                    +----------+

                       <---------------------------->

                          |----------------------------|
                                  Ethernet/VLANs

                                   Figure 8.2.1

8.2.1.1  IPv6 Related Infrastructure Changes

   In this scenario the Access Switch on the customer site and the
   entire NAP is Layer 3 unaware so no changes are needed to support
   IPv6.  The following devices have to be upgraded to dual stack: Host,
   Customer Router and Edge Router.

   The Access switches might need upgrades to support certain IPv6
   related features such as MLD Snooping.

8.2.1.2  Addressing

   The Hosts or the Customer Routers have the Edge Router as their Layer
   3 next hop.  If there is no Customer Router all the hosts on the
   subscriber site belong to the same /64 subnet that is statically
   configured on the Edge Router for that subscriber VLAN.  The hosts
   can use stateless autoconfiguration or stateful DHCPv6 based
   configuration to acquire an address via the Edge Router.

   If a Customer Router is present:

   A. It is statically configured with an address on the /64 subnet
   between itself and the Edge Router, and with /64 prefixes on the
   interfaces connecting the hosts on the customer site.  This is not a
   desired provisioning method being expensive and difficult to manage.

   B. It can use its link-local address to communicate with the ER.  It
   can also dynamically acquire through stateless autoconfiguration the
   address for the link between itself and the ER.  This step is
   followed by a request via DHCP-PD for a prefix shorter than /64 that
   in turn is divided in /64s and assigned to its interfaces connecting
   the hosts on the customer site.

   The Edge Router has a /64 prefix configured for each subscriber VLAN.
   Each VLAN should be enabled to relay DHCPv6 requests from the
   subscribers to DHCPv6 servers in the ISP network.  The VLANs
   providing access for subscribers that use DHCP-PD as well, have to be
   enabled to support the feature.  Currently the DHCP-PD functionality
   cannot be implemented if the DHCP-PD server is not the Edge Router.
   If the DHCP-PD messages are relayed, the Edge Router does not have a
   mechanism to learn the assigned prefixes and thus install the proper
   routes to make that prefix reachable.  Work is being done to address
   this issue, one idea being to provide the Edge Router with a snooping
   mechanism.  The uplink to the ISP network is configured with a /64
   prefix as well.  The uplink to the ISP network is configured with a
   /64 prefix as well.

   The prefixes used for subscriber links and the ones delegated via
   DHCP-PD should be planned in a manner that allows as much
   summarization as possible at the Edge Router.

   Other information of interest to the host, such as DNS, is provided
   through stateful [RFC3315] [11] and stateless [RFC3736] [10] DHCPv6.

8.2.1.3  Routing

   The CPE devices are configured with a default route that points to
   the Edge router.  No routing protocols are needed on these devices
   which generally have limited resources.

   The Edge Router runs the IPv6 IGP used in the NSP: OSPFv3 or IS-IS.
   The connected prefixes have to be redistributed.  If DHCP-PD is used,
   with every delegated prefix a static route is installed by the Edge
   Router.  For this reason the static routes must also be
   redistributed.  Prefix summarization should be done at the Edge
   Router.

8.2.2  PPP Terminated Aggregation (PTA) Model

   The PTA architecture relies on PPP-based protocols (PPPoE).  The PPP
   sessions are initiated by Customer Premise Equipment and it is
   terminated at the BRAS.  The BRAS authorizes the session,
   authenticates the subscriber, and provides an IP address on behalf of
   the ISP.  The BRAS then does Layer 3 routing of the subscriber
   traffic to the NSP Edge Router.  This model is often used when the
   NSP is also the NAP.  The PPPoE logical diagram in an Ethernet
   Broadband Network is shown in Fig 8.2.2.1.

   |     Customer Premises     | |       NAP       | |     NSP
<---------------------------> <-----------------> <----------------->       |

                                                       +-----------+
                                                       |    AAA    |
                                              +-------+
                                                 +-----+   Radius  |
                                                 |     |   TACACS  |
                                                 |     +-----------+
   +-----+  +-------+ +--------+ +--------+ +----+-----+ +----+---+ +-----------+
   |Hosts|--+Router +-+A Switch+-+ Switch +-+  BRAS  +-+    Edge   |  C
   +-----+  +-------+ +--------+ +--------+ +----------+ +--------+ |   Router  +=>O
     <----------------
        |----------------  PPP ----------------> ----------------|       |           |  R
                                                       +-----------+  E
                               Figure 8.2.2.1

   The PPP sessions are initiated by the Customer Premise Equipment
   (Host or Router).  The BRAS authenticates the subscriber against a
   local or a remote database.  Once the session is established, the
   BRAS provides an address and maybe a DNS server to the user,
   information acquired from the subscriber profile or from a DHCP
   server.

   This model allows for multiple PPPoE session sessions to be supported over
   the same VLAN thus allowing the subscriber to connect to multiple
   services at the same time.  The hosts can initiate the PPPoE sessions
   as well.  It is important to remember that the PPPoE encapsulation
   reduces the IP MTU available for the customer traffic.

8.2.2.1  IPv6 Related Infrastructure Changes

   In this scenario the BRAS is Layer 3 aware and it has to be upgraded
   to support IPv6.  Since the BRAS terminates the PPP sessions it has
   to support PPPoE with IPv6.  The following devices have to be
   upgraded to dual stack: Host, Customer Router (if present), BRAS and
   Edge Router.

8.2.2.2  Addressing

   The BRAS terminates the PPP sessions and provides the subscriber with
   an IPv6 address from the defined pool for that profile.  The
   subscriber profile for authorization and authentication can be
   located on the BRAS or on a AAA server.  The Hosts or the Customer
   Routers have the BRAS as their Layer 3 next hop.

   The PPP session can be initiated by a host or by a Customer Router.
   In the latter case, once the session is established with the BRAS,
   DHCP-PD can be used to acquire prefixes for the Customer Router
   interfaces.  The BRAS has to be enabled to support DHCP-PD and to
   relay the DHCPv6 requests of the hosts on the subscriber sites.
   Currently the DHCP-PD functionality cannot be implemented if the
   DHCP-PD server is not the Edge Router.  If the DHCP-PD messages are
   relayed, the Edge Router does not have a mechanism to learn the
   assigned prefixes and thus install the proper routes to make that
   prefix reachable.  Work is being done to address this issue, one idea
   being to provide the Edge Router with a snooping mechanism.  The
   uplink to the ISP network is configured with a /64 prefix as well.

   The BRAS has a /64 prefix configured on the link facing the Edge
   router.  The Edge router links are also configured with /64 prefixes
   to provide connectivity to the rest of the ISP network.

   The prefixes used for subscriber and the ones delegated via DHCP-PD
   should be planned in a manner that allows maximum summarization at
   the BRAS.

   Other information of interest to the host, such as DNS, is provided
   through stateful [RFC3315] [11] and stateless [RFC3736] [10] DHCPv6.

8.2.2.3  Routing

   The CPE devices are configured with a default route that points to
   the BRAS router.  No routing protocols are needed on these devices
   which generally have limited resources.

   The BRAS runs an IGP to the Edge Router: OSPFv3 or IS-IS.  Since the
   addresses assigned to the PPP sessions are represented as connected
   host routes, connected prefixes have to be redistributed.  If DHCP-PD
   is used, with every delegated prefix a static route is installed by
   the BRAS.  For this reason the static routes must also be
   redistributed.  Prefix summarization should be done at the BRAS.

   The Edge Router is running the IGP used in the ISP network: OSPFv3 or
   IS-IS.  A separation between the routing domains of the ISP and the
   Access Provider is recommended if they are managed independently.
   Controlled redistribution will be needed between the Access Provider
   IGP and the ISP IGP.

8.2.3  L2TPv2 Access Aggregation (LAA) Model

   In the LAA model the BRAS forwards the CPE initiated session to the
   ISP over an L2TPv2 tunnel established between the BRAS and the Edge
   Router.  In this case the authentication, authorization and
   subscriber configuration are performed by the ISP itself.

   | Customer Premises  | |         NAP          | |       NSP
<--------------------> <----------------------> <----------------->

                                                     +-----------+       |

                                                       +----------+
                                                       |   AAA    |
                                              +------+
                                                 +-----+  Radius  |
                                                 |     |  TACACS  |
                                                 |      +-----+-----+     +----+-----+
                                                 |          |
   +-----+  +-------+ +--------+ +--------+ +----+-----+ +-----------+ +----+----+ +----------+
   |Hosts|--+Router +-+A Switch+-+ Switch +-+   BRAS  +-+   Edge   |  C
   +-----+  +-------+ +--------+ +--------+ +----------+ +---------+ |  Router  +=>O
                                                        |          |  R
                                                      +-----------+
                                                        +----------+  E
            <----------------------------------------------->
               |---------------------------------------------|
                                       PPP
                                             <-------------->
                                                |------------|
                                                    L2TPv2
                                   Figure 8.2.3.1

8.2.3.1  IPv6 Related Infrastructure Changes

   In this scenario the BRAS is Layer 3 aware and it has to be upgraded
   to support IPv6.  The PPP sessions initiated by the subscriber are
   forwarded over the L2TPv2 tunnel to the aggregation point in the ISP
   network.  The BRAS (LAC) can aggregate IPv6 PPP sessions and tunnel
   them to the LNS using L2TPv2.  The L2TPv2 tunnel between the LAC and
   LNS could run over IPv6 or IPv4.  These capabilities have to be
   supported on the BRAS.  The following devices have to be upgraded to
   dual stack: Host, Customer Router (if present), BRAS and Edge Router.

8.2.3.2  Addressing

   The Edge router terminates the PPP sessions and provides the
   subscriber with an IPv6 address from the defined pool for that
   profile.  The subscriber profile for authorization and authentication
   can be located on the Edge Router or on a AAA server.  The Hosts or
   the  Customer Routers have the Edge Router as their Layer 3 next hop.

   The PPP session can be initiated by a host or by a Customer Router.
   In the latter case, once the session is established with the Edge
   Router and an IPv6 address is assigned to the Customer Router by the
   Edge router, DHCP-PD can be used to acquire prefixes for the Customer
   Router other interfaces.  The Edge Router has to be enabled to
   support DHCP-PD and to relay the DHCPv6 requests of the hosts on the
   subscriber sites.  Currently the DHCP-PD functionality cannot be
   implemented if the DHCP-PD server is not the Edge Router.  If the
   DHCP-PD messages are relayed, the Edge Router does not have a
   mechanism to learn the assigned prefixes and thus install the proper
   routes to make that prefix reachable.  Work is being done to address
   this issue, one idea being to provide the Edge Router with a snooping
   mechanism.  The uplink to the ISP network is configured with a /64
   prefix as well.

   The BRAS has a /64 prefix configured on the link to the Edge router.
   The Edge router links are also configured with /64 prefixes to
   provide connectivity to the rest of the ISP network.

   Other information of interest to the host, such as DNS, is provided
   through stateful [RFC3315] [11] and stateless [RFC3736] [10] DHCPv6.

   The address assignment and prefix summarization issues discussed in
   section 7.2.3.2 are relevant in the same way for this media access
   type as well.

8.2.3.3  Routing

   The CPE devices are configured with a default route that points to
   the Edge router that terminates the PPP sessions.  No routing
   protocols are needed on these devices which have limited resources.

   The BRAS runs an IPv6 IGP to the Edge Router: OSPFv3 or IS-IS.
   Different processes should be used if the NAP and the NSP are managed
   by different organizations.  In this case controlled redistribution
   should be enabled between the two domains.

   The Edge Router is running the IPv6 IGP used in the ISP network:
   OSPFv3 or IS-IS.

8.2.4  Hybrid Model for IPv4 and IPv6 Service

   It was recommended throughout this section that the IPv6 service
   implementation should map the existent IPv4 one.  This approach
   simplifies manageability and minimizes training needed for personnel
   operating the network.  In certain circumstances such mapping is not
   feasible.  This typically becomes the case when a Service Provider
   plans to expand its service offering with the new IPv6 deployed
   infrastructure.  If this new service is not well supported in a
   network design such as the one used for IPv4 then a different design
   might be used for IPv6.

   An example of such circumstances is that of a provider using an LAA
   design for its IPv4 services.  In this case all the PPP sessions are
   bundled and tunneled across the entire NAP infrastructure which is
   made of multiple BRAS routers, aggregation routers etc.  The end
   point of these tunnels is the ISP Edge Router.  If the SP decides to
   offer multicast services over such a design, it will face the problem
   of NAP resources being over utilized.  The multicast traffic can be
   replicated only at the end of the tunnels by the Edge router and the
   copies for all the subscribers are carried over the entire NAP.

   A Modified Point-to-Point (see section 8.2.4.2) or a PTA model is
   more suitable to support multicast services because the packet
   replication can be done closer to the destination at the BRAS.  Such
   topology saves NAP resources.

   In this sense IPv6 deployments can be viewed as an opportunity to
   build an infrastructure that can better support the expansion of
   services.  In this case, an SP using the LAA design for its IPv4
   services might choose a modified Point-to-Point or PTA design for
   IPv6.

8.2.4.1  IPv4 in LAA Model and IPv6 in PTA Model

   The coexistence of the two PPP based models, PTA and LAA, is
   relatively straight forward.  It is a straight forward overlap of the
   two deployment models.  The PPP sessions are terminated on different
   network devices for the IPv4 and IPv6  services.  The PPP sessions
   for the existent IPv4 service deployed in an LAA model are terminated
   on the Edge Router.  The PPP sessions for the new IPv6 service
   deployed in a PTA model are terminated on the BRAS.

   The logical design for IPv6 and IPv4 in this hybrid model is
   presented in Figure 8.2.4.1.

   IPv6          <-------------------------->          |--------------------------|
                            PPP                    +-----------+
                                                   |    AAA    |
                                           +-------+   Radius  |
                                           |       |   TACACS  |
                                           |       +-----+-----+
                                           |             |
   +-----+  +-------+      +--------+ +----+-----+ +-----+-----+
   |Hosts|--+Router +------+ Switch +-+  BRAS    +-+   Edge    |
   +-----+  +-------+      +--------+ +----------+ |  Router   +=>Core
                                                   +-----------+

   IPv4          <---------------------------------------->          |----------------------------------------|
                                   PPP
                                         <------------>
                                            |------------|
                                                L2TPv2
                             Figure 8.2.4.1

8.2.4.2  IPv4 in LAA Model and IPv6 in Modified Point-to-Point Model

   The coexistence of the modified Point-to-Point and the LAA models
   implies a few specific changes.

   For the IPv4 service in LAA model, the VLANs are terminated on the
   BRAS and PPP sessions are terminated on the Edge Router (LNS).  For
   IPv6 service in Point-to-Point model, the VLANs are terminated at the
   Edge Router as described in section 7.2.1.  In this hybrid model, the
   Point-to-Point link could be terminated on the BRAS, a NAP owned
   device.  The IPv6 traffic is then routed through the NAP network to
   the NSP.  In order to have this hybrid model, the BRAS has to be
   upgraded to a dual-stack router.  The functionalities of the Edge
   Router as described in section 7.2.1 are now implemented on the BRAS.

   The logical design for IPv6 and IPv4 in this hybrid model is in
   Figure 8.2.4.2.

   IPv6              <---------------->              |----------------|
                           Ethernet
                                                   +-----------+
                                                   |    AAA    |
                                           +-------+   Radius  |
                                           |       |   TACACS  |
                                           |       +-----+-----+
                                           |             |
   +-----+  +-------+      +--------+ +----+-----+ +-----+-----+
   |Hosts|--+Router +------+ Switch +-+  BRAS    +-+   Edge    |
   +-----+  +-------+      +--------+ +----------+ |  Router   +=>Core
                                                   +-----------+
   IPv4          <---------------------------------------->          |----------------------------------------|
                                   PPP
                                          <------------>
                                             |------------|
                                                 L2TPv2
                                 Figure 8.2.4.2

8.3  IPv6 Multicast

   The typical multicast services offered for residential and very small
   businesses is video/audio streaming where the subscriber joins a
   multicast group and receives the content.  This type of service model
   is well supported through PIM-SSM which is very simple and easy to
   manage.  PIM-SSM has to be enabled throughout the ISP network.  MLDv2
   is required for PIM-SSM support.  Vendors can choose to implement
   features that allow routers to map MLDv1 group joins to predefined
   sources.

   Subscribers might use a set-top box that is responsible for the
   control piece of the multicast service (does group joins/leaves).
   The subscriber hosts can also join desired multicast groups as long
   as they are enabled to support MLDv1 or MLDv2.  If a customer premise
   router is used then it has to be enabled to support MLDv1 and MLDv2
   in order to process the requests of the hosts.  It has to be enabled
   to support PIM-SSM in order to send PIM joins/leaves up to its Layer
   3 next hop whether it is the BRAS or the Edge router.  When enabling
   this functionality on a customer premises router, its limited
   resources should be taken into consideration.  Another option would
   be for the customer premises router to support MLD proxy routing.
   MLD snooping or similar layer two multicast related protocols could
   be enabled on the NAP switches.

   The router that is the Layer 3 next hop for the subscriber (BRAS in
   the PTA model or the Edge router in the LAA and Point-to-Point model)
   has to be enabled to support MLDv1 and MLDv2 in order to process the
   requests coming from subscribers without customer premises routers.

   It has to be enabled for PIM-SSM in order to receive joins/leaves
   from customer routers and send joins/leaves to the next hop towards
   the multicast source (Edge router or the NSP core).

   MLD authentication, authorization and accounting is usually
   configured on the edge router in order to enable the ISP to do
   control the subscriber access of the service and do billing for the
   content provided.  Alternative mechanisms that would support these
   functions should be investigated further.

   Please refer to section 7.3 for more IPv6 multicast details.

8.4  IPv6 QoS

   The QoS configuration is particularly relevant on the router that
   represents the Layer 3 next hop for the subscriber (BRAS in the PTA
   model or the Edge router in the LAA and Point-to-Point model) in
   order to manage resources shared amongst multiple subscribers
   possibly with various service level agreements.

   On the BRAS or the Edge Router the subscriber facing interfaces have
   to be configured to police the inbound customer traffic and shape the
   traffic outbound to the customer based on the SLAs.  Traffic
   classification and marking should also be done on the router closest
   (at Layer 3) to the subscriber in order to support the various types
   of customer traffic: data, voice, video and to optimally use the
   network resources.  This infrastructure offers a very good
   opportunity to leverage the QoS capabilities of Layer two devices.
   DiffServ based QoS used for IPv4 should be expanded to IPv6.

   Each provider (NAP, NSP) could implement their own QoS policies and
   services so reclassification and marking might be performed at the
   boundary between the NAP and the NSP in order to make sure the
   traffic is properly handled by the ISP.  The same IPv4 QoS concepts
   and methodologies should be applied for the IPv6 as well.

   It is important to note that when traffic is encrypted end-to-end,
   the traversed network devices will not have access to many of the
   packet fields used for classification purposes.  In these cases
   routers will most likely place the packets in the default classes.
   The QoS design should take into consideration this scenario and try
   to use mainly IP header fields for classification purposes.

8.5  IPv6 Security Considerations

   There are limited changes that have to be done for CPEs in order to
   enhance security.  The Privacy extensions [RFC3041] [14] for autoconfiguration
   should be used by the hosts with the same considerations for host
   traceability as discussed in section 7.5.  IPv6 firewall functions
   should be enabled on the hosts or customer premises router if
   present.

   The ISP provides security against attacks that come form its own
   subscribers but it could also implement security services that
   protect its subscribers from attacks sourced from the outside of its
   network.  Such services do not apply at the access level of the
   network discussed here.

   If any layer two filters for Ethertypes are in place, the NAP must
   permit the IPv6 Ethertype (0X86DD).

   The device that is the Layer 3 next hop for the subscribers (BRAS
   Edge router) should protect the network and the other subscribers
   against attacks by one of the provider customers.  For this reason
   uRPF and ACLs should be used on all interfaces facing subscribers.
   Filtering should be implemented with regard for the operational
   requirements of IPv6 [Security considerations for IPv6]. [36].

   Authentication and authorization should be used wherever possible.

   The BRAS and the Edge Router should protect their processing
   resources against floods of valid customer control traffic such as:
   Router and Neighbor Solicitations, MLD Requests.  Rate limiting
   should be implemented on all subscriber facing interfaces.  The
   emphasis should be placed on multicast type traffic as it is most
   often used by the IPv6 control plane.

   All other security features used with the IPv4 service should be
   similarly applied to IPv6 as well.

8.6  IPv6 Network Management

   The necessary instrumentation (such as MIBs, NetFlow Records etc)
   should be available for IPv6.

   Usually, NSPs manage the edge routers by SNMP.  The SNMP transport
   can be done over IPv4 if all managed devices have connectivity over
   both IPv4 and IPv6.  This would imply the smallest changes to the
   existent network management practices and processes.  Transport over
   IPv6 could also be implemented and it might become necessary if IPv6
   only islands are present in the network.  The management stations are
   located on the core network.  Network Management Applications should
   handle IPv6 in a similar fashion to IPv4 however they should also
   support features specific to IPv6 such as Neighbor monitoring.

   In some cases service providers manage equipment located on customers
   LANs.

9.  Wireless LAN

   This section provides detailed description of IPv6 deployment and
   integration methods in currently deployed wireless LAN (WLAN)
   infrastructure.

9.1  WLAN Deployment Scenarios

   WLAN enables subscribers to connect to the Internet from various
   locations without the restriction of staying indoors.  WLAN is
   standardized by IEEE 802.11a/b/g.  Consideration should be also given
   to IEEE 802.16 WiMAX for similar deployment approaches.  IEEE 802.11
   offers maximum transmission speed from 1 or 2 Mbps, IEEE 802.11b
   offers 11 Mbps and IEEE 802.11a offers up to 54 Mbps.

   Figure 9.1 describes the current WLAN architecture.

       Customer Premises| |            Access Provider       |Service        | Service Provider
       Premise  |                                   |

     +------+        +--+ +--------------+ +----------+ +------+
     |WLAN  |  ----  |  | |Access Router/| |Underlying| |Edge  |
     |Host/ |-(WLAN)-|AP|-|Layer 2 Switch|-|Technology|-|Router|=>SP
     |Router|  ----  |  | |              | |          | |      |  Network      |Network
     +------+        +--+ +--------------+ +----------+ +------+
                                                           |
                                                        +------+
                                                        |AAA   |
                                                        |Server|
                                                        +------+
                                 Figure 9.1              +------+

   The host should have a wireless network interface card (NIC) in order
   to connect to a WLAN network.  WLAN is a flat broadcast network and
   works in a similar fashion as Ethernet.  When hosts initiate a
   connection, it is authenticated by the AAA server located at the SP
   network.  All the authentication parameters (username, password and
   etc.) are forwarded by the Access Point (AP) to the AAA server.  The
   AAA server authenticates the host, once authenticated successfully authenticated
   the host can send data packets.  The AP is located near the host and
   acts as a bridge.  The AP forwards all the packets coming to/from
   host to the Edge Router.  The underlying connection between the AP
   and Edge Router could be based on any access layer technology such as
   HFC/Cable, FTTH, xDSL or etc.

   WLANs are based in limited areas known as WiFi Hot Spots.  While
   users are present in the area covered by the WLAN range, they can be
   connected to the Internet given they have a wireless NIC and required
   configuration settings in their devices (notebook PCs, PDA or etc.).
   Once the user initiates the connection the IP address is assigned by
   the SP using DHCPv4.  In most of the cases SP assigns limited number
   of public IP addresses to the its customer.  When the user
   disconnects the connection and move moves to a new WiFi hot spot, the
   above mentioned process of authentication, address assignment and
   accessing the Internet is repeated.

   There are IPv4 deployments where customers can use WLAN routers to
   connect over wireless to their service provider.  These deployment
   types do not fit in the typical Hot Spot concept but they rather
   serve fixed customers.  For this reason this section discusses the
   WLAN router options as well.  In this case, the ISP provides a public
   IP address and the WLAN Router assigns private addresses [RFC1918] [1] to all
   WLAN users.  The WLAN Router provides NAT functionality while WLAN
   users access the Internet.

   While deploying IPv6 in the above mentioned WLAN architecture, there
   are three possible scenarios as discussed below.

   A. Layer 2 Switch Between AP and Edge Router

   B. Access Router Between AP and Edge Router

   C. PPP Based Model

9.1.1  Layer 2 Switch Between AP and Edge Router

   When a Layer 2 switch is present between AP and Edge Router, the AP
   and Layer 2 switch continues to work as a bridge, forwarding IPv4 and
   IPv6 packets from WLAN Host/Router to Edge Router and vice versa.

   When initiating the connection, the WLAN host is authenticated by the
   AAA server located at the SP network.  All the parameters related to
   authentication (username, password and etc.) are forwarded by the AP
   to the AAA server.  The AAA server authenticates the WLAN Hosts and
   once authenticated and associated successfully with WLAN AP, IPv6
   address will be acquired by the WLAN Host.  Note the initiation and
   authentication process is same as used in IPv4.

   Figure 9.1.1 describes the WLAN architecture when Layer 2 Switch is
   located between AP and Edge Router.

       Customer Premises| |            Access Provider       |Service        | Service Provider
       Premise  |                                   |

     +------+        +--+ +--------------+ +----------+ +------+
     |WLAN  |  ----  |  | |              | |Underlying| |Edge  |
     |Host/ |-(WLAN)-|AP|-|Layer 2 Switch|-|Technology|-|Router|=>SP
     |Router|  ----  |  | |              | |          | |      |  Network      |Network
     +------+        +--+ +--------------+ +----------+ +------+
                                                           |
                                                        +------+
                                                        |AAA   |
                                                        |Server|
                                                        +------+
                                 Figure 9.1.1

9.1.1.1  IPv6 Related Infrastructure Changes

   IPv6 will be deployed in this scenario by upgrading the following
   devices to dual-stack: WLAN Host, WLAN Router (if present) and Edge
   Router.

9.1.1.2  Addressing

   When customer WLAN Router is not present, the WLAN Host has two
   possible options to get an IPv6 address via the Edge Router.

   A. The WLAN host can get the IPv6 address from Edge router using
   stateless auto-configuration [RFC2462]. [12].  All the hosts on the WLAN belong to
   the same /64 subnet that is statically configured on the Edge Router.
   The IPv6 WLAN Host may use stateless DHCPv6 for obtaining other
   information of interest such as DNS and etc.

   B. IPv6 WLAN host can use DHCPv6 [RFC3315] [11] to get a IPv6 address from the
   DHCPv6 server.  In this case the DHCPv6 server would be located in
   the SP core network and Edge Router would act simply act as a DHCP Relay
   Agent.  This option is similar to what we do today in case of DHCPv4.
   It is important to note that host implementation of stateful auto-configuration auto-
   configuration is rather limited at this time and this should be
   considered if choosing this address assignment option.

   When a customer WLAN Router is present, the WLAN Host has two
   possible options as well for acquiring IPv6 address.

   A. The WLAN Router may be assigned a prefix between /48 and /64 [8]
   depending on the SP policy and customer requirements.  If the WLAN
   Router has multiple networks connected to its interfaces, the network
   administrator will have to configure the /64 prefixes to the WLAN
   Router interfaces connecting the WLAN Hosts on the customer site.
   The WLAN Hosts connected to these interfaces can automatically
   configure themselves using stateless auto-configuration with /64
   prefix.

   B. The WLAN Router can use its link-local address to communicate with
   the ER.  It can also dynamically acquire through stateless
   autoconfiguration the address for the link between itself and the ER.
   This step is followed by a request via DHCP-PD for a prefix shorter
   than /64 that in turn is divided in /64s and assigned to its
   interfaces connecting the hosts on the customer site.

   In this option, the WLAN Router would act as a requesting router and
   Edge Router would act as delegating router.  Once prefix is received
   by the WLAN Router, it assigns /64 prefixes to each of its interfaces
   connecting the WLAN Hosts on the customer site.  The WLAN Hosts
   connected to these interfaces can automatically configure themselves
   using stateless auto-configuration with /64 prefix.  Currently the
   DHCP-PD functionality cannot be implemented if the DHCP-PD server is
   not the ER.  If the DHCP-PD messages are relayed, the Edge Router
   does not have a mechanism to learn the assigned prefixes and thus
   install the proper routes to make that prefix reachable.  Work is
   being done to address this issue, one idea being to provide the Edge
   Router with a snooping mechanism.  The uplink to the ISP network is
   configured with a /64 prefix as well.

   Usually it is easier for the SPs to stay with the DHCP PD and
   stateless auto-configuration model and point the clients to a central
   server for DNS/domain information, proxy configurations and etc.
   Using this model the SP could change prefixes on the fly and the WLAN
   Router would simply pull the newest prefix based on the
   valid/preferred valid/
   preferred lifetime.

   The prefixes used for subscriber links and the ones delegated via
   DHCP-PD should be planned in a manner that allows maximum
   summarization as possible at the Edge Router.

   Other information of interest to the host, such as DNS, is provided
   through stateful [RFC3315] [11] and stateless [RFC3736] [10] DHCPv6.

9.1.1.3  Routing

   The WLAN Host/Router are configured with a default route that points
   to the Edge router.  No routing protocols are needed on these devices
   which generally have limited resources.

   The Edge Router runs the IGP used in the SP network such as OSPFv3 or
   IS-IS for IPv6.  The connected prefixes have to be redistributed.

   Prefix summarization should be done at the Edge Router.  When DHCP-PD
   is used, the IGP has to redistribute the static routes installed
   during the process of prefix delegation.

9.1.2  Access Router Between AP and SP Edge Router

   When a Access Router is present between AP and Edge Router, the AP
   continues to work as a bridge, bridging IPv4 and IPv6 packets from
   WLAN Host/Router to Access/Edge Router and vice versa.  The Access
   Router could be part of SP network or owned by a separate Access
   Provider.

   When WLAN Host initiates the connection, the AAA authentication and
   association process with WLAN AP will be similar as explained in
   section 9.1.1.

   Figure 9.1.2 describes the WLAN architecture when Access Router is
   located between AP and Edge Router.

       Customer Premises| |            Access Provider       |Service        | Service Provider
       Premise  |                                   |

     +------+        +--+ +--------------+ +----------+ +------+
     |WLAN  |  ----  |  | |              | |Underlying| |Edge  |
     |Host/ |-(WLAN)-|AP|-|Access Router |-|Technology|-|Router|=>SP
     |Router|  ----  |  | |              | |          | |      |  Network      |Network
     +------+        +--+ +--------------+ +----------+ +------+
                                                           |
                                                        +------+
                                                        |AAA   |
                                                        |Server|
                                                        +------+
                                  Figure 9.1.2

9.1.2.1  IPv6 Related Infrastructure Changes

   IPv6 is deployed in this scenario by upgrading the following devices
   to dual-stack: WLAN Host, WLAN Router (if present), Access Router and
   Edge Router.

9.1.2.2  Addressing

   There are three possible options in this scenario for IPv6 address
   assignment:

   A. The Edge Router interface facing towards the Access Router is
   statically configured with /64 prefix.  The Access Router receives/
   configures an /64 prefix on its interface facing towards Edge Router
   through stateless auto-configuration.  The network administrator will
   have to configure the /64 prefixes to the Access Router interface
   facing towards the customer premises.  The WLAN Host/Router connected
   to this interface can automatically configure themselves using
   stateless auto-configuration with /64 prefix.

   B. This option uses DHCPv6 [RFC3315] [11] for IPv6 prefix assignments to the
   WLAN Host/Router.  There is no use of DHCP PD or stateless
   auto-configuration auto-
   configuration in this option.  The DHCPv6 server can be located on
   the Access Router, on the Edge Router or somewhere in the SP network.
   In this case depending on where the DHCPv6 server is located, Access
   Router or the Edge Router would relay the DHCPv6 requests.

   C. It can use its link-local address to communicate with the ER.  It
   can also dynamically acquire through stateless autoconfiguration the
   address for the link between itself and the ER.  This step is
   followed by a request via DHCP-PD for a prefix shorter than /64 that
   in turn is divided in /64s and assigned to its interfaces connecting
   the hosts on the customer site.

   In this option, the Access Router would act as a requesting router
   and Edge Router would act as delegating router.  Once prefix is
   received by the Access Router, it assigns /64 prefixes to each of its
   interfaces connecting the WLAN Host/Router on customer site.  The
   WLAN Host/Router connected to these interfaces can automatically
   configure themselves using stateless auto-configuration with /64
   prefix.  Currently the DHCP-PD functionality cannot be implemented if
   the DHCP-PD server is not the Edge Router.  If the DHCP-PD messages
   are relayed, the Edge Router does not have a mechanism to learn the
   assigned prefixes and thus install the proper routes to make that
   prefix reachable.  Work is being done to address this issue, one idea
   being to provide the Edge Router with a snooping mechanism.  The
   uplink to the ISP network is configured with a /64 prefix as well.

   It is easier for the SPs to stay with the DHCP PD and stateless
   auto-configuration auto-
   configuration model and point the clients to a central server for
   DNS/domain information, proxy configurations and others.  Using this
   model the provider could change prefixes on the fly and the Access
   Router would simply pull the newest prefix based on the
   valid/preferred valid/
   preferred lifetime.

   As mentioned before the prefixes used for subscriber links and the
   ones delegated via DHCP-PD should be planned in a manner that allows
   maximum summarization possible at the Edge Router.  Other information
   of interest to the host, such as DNS, is provided through stateful [RFC3315]
   [11] and stateless [RFC3736] [10] DHCPv6.

9.1.2.3  Routing

   The WLAN Host/Router are configured with a default route that points
   to the Access Router.  No routing protocols are needed on these
   devices which generally have limited resources.

   If the Access Router is owned by an Access Provider, then the Access
   Router can have a default route, pointing towards the SP Edge Router.
   The Edge Router runs the IGP used in the SP network such as OSPFv3 or
   IS-IS for IPv6.  The connected prefixes have to be redistributed.  If
   DHCP-PD is used, with every delegated prefix a static route is
   installed by the Edge Router.  For this reason the static routes must
   be redistributed.  Prefix summarization should be done at the Edge
   Router.

   If the Access Router is owned by the SP, then Access Router will also
   run IPv6 IGP and will be part of SP IPv6 routing domain (OSPFv3 or
   IS-IS).  The connected prefixes have to be redistributed.  If DHCP-PD
   is used, with every delegated prefix a static route is installed by
   the Access Router.  For this reason the static routes must be
   redistributed.  Prefix summarization should be done at the Access
   Router.

9.1.3  PPP Based Model

   PPP TERMINATED AGGREGATION (PTA) and L2TPv2 ACCESS AGGREGATION (LAA)
   models as discussed in sections 7.2.2 and 7.2.3 respectively can also
   be deployed in IPv6 WLAN environment.

9.1.3.1  PTA Model in IPv6 WLAN Environment

   While deploying the PTA model in IPv6 WLAN environment the Access
   Router is Layer3 aware and it has to be upgraded to support IPv6.
   Since the Access Router terminates the PPP sessions initiated by WLAN
   Host/Router, it has to support PPPoE with IPv6.

   Figure 9.1.3.1 describes the PTA Model in IPv6 WLAN environment environment.

       Customer Premises| |            Access Provider       |Service        | Service Provider
       Premise  |                                   |

     +------+        +--+ +--------------+ +----------+ +------+
     |WLAN  |  ----  |  | |              | |Underlying| |Edge  |
     |Host/ |-(WLAN)-|AP|-|Access Router |-|Technology|-|Router|=>SP
     |Router|  ----  |  | |              | |          | |      |  Network      |Network
     +------+        +--+ +--------------+ +----------+ +------+
                                                           |
    <--------------------------->
       |---------------------------|                    +------+
                   PPP                                  |AAA   |
                                                        |Server|
                                                        +------+
                                Figure 9.1.3.1

9.1.3.1.1  IPv6 Related Infrastructure Changes

   IPv6 is deployed in this scenario by upgrading the following devices
   to dual-stack: WLAN Host, WLAN Router (if present), Access Router and
   Edge Router.

9.1.3.1.2  Addressing

   The addressing techniques described in section 7.2.2.2 applies to
   IPv6 WLAN PTA scenario as well.

9.1.3.1.3  Routing

   The routing techniques described in section 7.2.2.3 applies to IPv6
   WLAN PTA scenario as well.

9.1.3.2  LAA Model in IPv6 WLAN Environment

   While deploying the LAA model in IPv6 WLAN environment the Access
   Router is Layer3 aware and it has to be upgraded to support IPv6.
   The PPP sessions initiated by WLAN Host/Router are forwarded over the
   L2TPv2 tunnel to the aggregation point in the SP network.  The Access
   Router must have the capability to support L2TPv2 for IPv6.

   Figure 9.1.3.2 describes the LAA Model in IPv6 WLAN environment
       Customer Premises| |            Access Provider       |Service        | Service Provider
       Premise  |                                   |

     +------+        +--+ +--------------+ +----------+ +------+
     |WLAN  |  ----  |  | |              | |Underlying| |Edge  |
     |Host/ |-(WLAN)-|AP|-|Access Router |-|Technology|-|Router|=>SP
     |Router|  ----  |  | |              | |          | |      |  Network      |Network
     +------+        +--+ +--------------+ +----------+ +------+
                                                           |
    <-------------------------------------------------->|
       |-------------------------------------------------- |
                               PPP                         |
                                 <--------------------->|
                                    |--------------------- |
                                               L2TPv2      |
                                                        +------+
                                                        |AAA   |
                                                        |Server|
                                                        +------+
                                Figure 9.1.3.2

9.1.3.2.1  IPv6 Related Infrastructure Changes

   IPv6 is deployed in this scenario by upgrading the following devices
   to dual-stack: WLAN Host, WLAN Router (if present), Access Router and
   Edge Router.

9.1.3.2.2  Addressing

   The addressing techniques described in section 7.2.3.2 applies to
   IPv6 WLAN LAA scenario as well.

9.1.3.2.3  Routing

   The routing techniques described in section 7.2.3.3 applies to IPv6
   WLAN LAA scenario as well.

9.2  IPv6 Multicast

   The typical multicast services offered are video/audio streaming
   where the IPv6 WLAN Host joins a multicast group and receives the
   content.  This type of service model is well supported through
   PIM-SSM PIM-
   SSM which is enabled throughout the SP network.  MLDv2 is required
   for PIM-SSM support.  Vendors can choose to implement features that
   allow routers to map MLDv1 group joins to predefined sources.

   It is important to note that in the shared wireless environments
   multicast can have a significant bandwidth impact.  For this reason
   the bandwidth allocated to multicast traffic should be limited and
   fixed based on the overall capacity of the wireless specification
   used 802.11a, 802.11b or 802.11g.

   The IPv6 WLAN Hosts can also join desired multicast groups as long as
   they are enabled to support MLDv1 or MLDv2.  If a WLAN/Access Routers
   are used then they have to be enabled to support MLDv1 and MLDv2 in
   order to process the requests of the IPv6 WLAN Hosts.  The WLAN/Access WLAN/
   Access Router should also needs to be enabled to support PIM-SSM in
   order to send PIM joins up to the Edge Router.  When enabling this
   functionality on a WLAN/Access Router, its limited resources should
   be taken into consideration.  Another option would be for the WLAN/Access WLAN/
   Access Router to support MLD proxy routing.

   The Edge Router has to be enabled to support MLDv1 and MLDv2 in order
   to process the requests coming from IPv6 WLAN Host or WLAN/Access
   Router (if present).  The Edge Router has also needs to be enabled
   for PIM-SSM in order to receive joins from IPv6 WLAN Hosts or WLAN/Access WLAN/
   Access Router (if present) and send joins towards the SP core.

   MLD authentication, authorization and accounting is usually
   configured on the Edge Router in order to enable the SP to do billing
   for the content services provided.  Further investigation should be
   made in investigating finding alternative mechanisms that would support these
   functions.

   Concerns have been raised in the past related to running IPv6
   multicast over WLAN links.  Potentially these are same kind of issues
   when running any Layer3 protocol over a WLAN link that has a high
   loss-to-signal ratio, where certain frames that are multicast based
   are dropped when settings are not adjusted properly.  For instance
   this behavior is similar to IGMP host membership report, when done on
   a WLAN link with high loss-to-signal ratio and high interference.

   This problem is inherited to WLAN that can impact both IPv4 and IPv6
   multicast packets and not specific to IPv6 multicast.

   While deploying WLAN (IPv4 or IPv6), one should adjust their
   broadcast/multicast settings if they are in danger of dropping
   application dependent frames.  These problems are usually caused when
   AP are placed too far apart (not following the distance limitations),
   high interference and etc.  These issues may impact a real multicast
   application such as streaming video or basic operation of IPv6 if the
   frames were dropped.  Basic IPv6 communications uses functions such
   as Duplicate Address Detection (DAD), Router and Neighbor
   Solicitations (RS, NS), Router and Neighbor Advertisement (RA, NA)
   and etc. which could be impacted by the above mentioned issues as
   these frames are Layer 2 Ethernet multicast frames.

   Please refer to section 7.3 for more IPv6 multicast details.

9.3  IPv6 QoS

   Today, QoS is done outside of the WiFi domain but it is nevertheless
   important to the overall deployment.

   The QoS configuration is particularly relevant on the Edge Router in
   order to manage resources shared amongst multiple subscribers
   possibly with various service level agreements (SLA).  Although, the
   WLAN Host/Router and Access Router could also be configured for QoS.
   This includes support for IPv6 classifiers, so that data traffic
   to/from IPv6 WLAN Host/Router, Access Router and Edge Router can be
   classified appropriately into different service flows (SF) and be
   assigned appropriate priority. Appropriate classification criteria which
   would need to be implemented for IPv6 unicast and multicast traffic.

   On the Edge Router the subscriber facing interfaces have to be
   configure
   configured to police the inbound customer traffic and shape the
   traffic outbound to the customer, based on the SLA.  Traffic
   classification and marking should also be done on the Edge router in
   order to support the various types of customer traffic: data, voice,
   video.  The same IPv4 QoS concepts and methodologies should be
   applied for the IPv6 as well.

   It is important to note that when traffic is encrypted end-to-end,
   the traversed network devices will not have access to many of the
   packet fields used for classification purposes.  In these cases
   routers will most likely place the packets in the default classes.
   The QoS design should take into consideration this scenario and try
   to use mainly IP header fields for classification purposes.

9.4  IPv6 Security Considerations

   There are limited changes that have to be done for WLAN Host/Router
   in order to enhance security.  The Privacy extensions [RFC3041] [14] for
   autoconfiguration should be used by the hosts with the same
   consideration for host traceability as described in section 7.5.
   IPv6 firewall functions should be enabled on the WLAN Host/Router if
   present.

   The ISP provides security against attacks that come form its own
   subscribers but it could also implement security services that
   protect its subscribers from attacks sourced from the outside of its
   network.  Such services do not apply at the access level of the
   network discussed here.

   If the host authentication at hot spots is done using web based
   authentication system then the level of security would depend on the
   particular implementation.  User credential should never be sent as
   clear text via HTTP.  Secure HTTP (HTTPS) should be used between the
   web browser and authentication server.  The authentication server
   could use RADIUS and LDAP services at the back end.

   Authentication is an important aspect of securing WLAN networks prior
   to implementing Layer 3 security policies.  This would help for
   example avoid threats to the ND or stateless autoconfiguration
   processes. 802.1x provides the means to secure the network access
   however, the many types of EAP (PEAP, EAP-TLS, EAP-TTLS, EAP-FAST,
   LEAP) and the capabilities of the hosts to support some of the
   features might make it difficult to implement a comprehensive and
   consistent policy.

   If any layer two filters for Ethertypes are in place, the NAP must
   permit the IPv6 Ethertype (0X86DD).

   The device that is the Layer3 next hop for the subscribers (Access or
   Edge Router) should protect the network and the other subscribers
   against attacks by one of the provider customers.  For this reason
   uRPF and ACLs should be used on all interfaces facing subscribers.
   Filtering should be implemented with regard for the operational
   requirements of IPv6 [Security considerations for IPv6].
   Authentication and authorization should be used wherever possible.

   The Access and the Edge Router should protect their processing
   resources against floods of valid customer control traffic such as:
   RS, NS, MLD Requests.  Rate limiting should be implemented on all
   subscriber facing interfaces.  The emphasis should be placed on
   multicast type traffic as it is most often used by the IPv6 control
   plane.

9.5  IPv6 Network Management

   The necessary instrumentation (such as MIBs, NetFlow Records, etc)
   should be available for IPv6.

   Usually, NSPs manage the edge routers by SNMP.  The SNMP transport
   can be done over IPv4 if all managed devices have connectivity over
   both IPv4 and IPv6.  This would imply the smallest changes to the
   existent network management practices and processes.  Transport over
   IPv6 could also be implemented and it might become necessary if IPv6
   only islands are present in the network.  The management stations are
   located on the core network.  Network Management Applications should
   handle IPv6 in a similar fashion to IPv4 however they should also
   support features specific to IPv6 (such as Neighbor monitoring).

   In some cases service providers manage equipment located on customers
   LANs.

10.  Broadband Power Line Communications (PLC)

   This section describes the IPv6 deployment in Power Line
   Communications (PLC) Access Networks.  There may be other choices,
   but it seems that this is the best model to follow.  Lessons learnt
   from Cable, Ethernet and even WLAN access networks may be applicable
   also.

   Power Line Communications are also often called Broadband Power Line
   (BPL) and some times even Power Line Telecommunications (PLT).

   PLC/BPL can be used for providing, with todays technology, up to
   200Mbps (total, upstream+downstream) by means of the power grid.  The
   coverage is often the last half mile (typical distance from the
   Medium-to-Low Voltage transformer to the customer premise meter), and
   of course, as an in-home network (which is out of the scope of this
   document).

   The bandwidth in a given PLC/BPL segment is shared among all the
   customers connected to that segment (often the customers connected to
   the same medium-to-low voltage transformer).  The number of customers
   can vary depending on different factors, such as distances and even
   countries (from a few customers, just 5-6, up to 100-150).

   PLC/BPL could also be used in the Medium Voltage network (often
   configured as Metropolitan Area Networks), but this is also out of
   the scope of this document, as it will be part of the core network,
   not the access one.

   Just for information/clarification, often the PLC/BPL access networks
   use hybrid layer 2 combinations either with PLC/BPL in the medium
   voltage, point to point links, wireless links, satellite, etc., but
   once more, this seems to be out of the scope of this document, as
   those means are transparent, for the purpose of this document, to the
   last half mile access network deployed with PLC/BPL.

10.1  PLC/BPL Access Network Elements

   This section describes the different elements commonly used in
   PLC/BPL PLC/
   BPL access networks.

   Head End (HE): It is the router that connects the PLC/BPL access
   network (the power grid), located at the medium-to-low voltage
   transformer, to the core network.  The HE PLC/BPL interface appears
   to each customer as a single virtual interface, all of them sharing
   the same physical media.

   Repeater (RPT): It is the device which may be required in some
   circumstances to improve the signal on the PLC/BPL.  This may be the
   case if there are many customers in the same segment or building.
   Often is a bridge, but it could be also a router if for example there
   is a lot of peer-to-peer traffic in a building and due to the
   master-slave master-
   slave nature of the PLC/BPL technology, is required to improve the
   performance within that segment.  For simplicity, in this document,
   it will be considered that the RPT is always a transparent layer 2
   bridge, so it may be present or not (from the layer 3 point of view).

   Customer Premise Equipment (CPE): It is the modem (internal to the
   host), modem/bridge (BCPE), router (RCPE) or any combination among
   those (i.e. modem+bridge/router), located at the customer premise.

   Edge Router (ER)

   Figure 10.1 depicts all the network elements indicated above

     Customer Premises | Network Premises|Network Access Provider | Network Provider|Network Service Provider
            CP                     NAP                        NSP

     +-----+  +------+  +-----+        +------+   +--------+
     |Hosts|--| RCPE |--| RPT |--------+  HE  +---+ Edge   |      ISP
     +-----+  +------+  +-----+        |      |   | Router +===> Network +===>Network
                                       +--+---+   +--------+
     +-----+  +------+  +-----+           |
     |Hosts|--| BCPE |--| RPT |-----------+
     +-----+  +------+  +-----+
                                    Figure 10.1

   The logical topology and design of PLC/BPL is very similar to
   Ethernet Broadband Networks as discussed in section Section 8.

10.2  Deploying IPv6 in IPv4 PLC/BPL

   The most simplistic and efficient model, considering the nature of
   the PLC/BPL networks, is to see the network as a point-to-point one
   to each customer.  Even if several customers share the same physical
   media, the traffic is not visible among them because each one uses
   different channels, which are in addition encrypted by means of 3DES.

   Furthermore, if required, VLANs could also be used, as already
   described for the Ethernet case.

   In order to maintain the deployment concepts and business models
   proven and used with existing revenue generating IPv4 services, the
   IPv6 deployment will match the IPv4 one.  Under certain circumstances
   where new service types or service needs justify it, IPv4 and IPv6
   network architectures could be different.  Both approaches are very
   similar to those already described for the Ethernet case.

10.2.1  IPv6 Related Infrastructure Changes

   In this scenario the RPT is layer 3 unaware, but not the Head End,
   which should be upgraded to support IPv6.  Similarly other devices
   which have to be upgraded to dual stack: Hosts, RCPE and Edge Router.

10.2.2  Addressing

   The Hosts or the RCPEs have the HE as their Layer 3 next hop.

   If there is no RCPE, but instead a BCPE all the hosts on the
   subscriber site belong to the same /64 subnet that is statically
   configured on the HE.  The hosts can use stateless autoconfiguration
   or stateful DHCPv6 based configuration to acquire an address via the
   HE.

   If a RCPE is present:

   A. It is statically configured with an address on the /64 subnet
   between itself and the HE, and with /64 prefixes on the interfaces
   connecting the hosts on the customer site.  This is not a desired
   provisioning method being expensive and difficult to manage.

   B. It can use its link-local address to communicate with the HE.  It
   can also dynamically acquire through stateless autoconfiguration the
   address for the link between itself and the HE.  This step is
   followed by a request via DHCP-PD for a prefix shorter than /64
   (typically /48) /48 [8]) that in turn is divided in /64s and assigned to
   its interfaces connecting the hosts on the customer site.  This
   should be the preferred provisioning method, being cheaper and easier
   to manage.

   The Edge Router needs to have a prefix considering that each customer
   in general will receive a /48 prefix, and that each HE will
   accommodate customers.  Consequently each HE will require n x /48
   prefixes.

   It could be possible to use a kind of Hierarchical Prefix Delegation
   to automatically provision the required prefixes and fully auto-configure auto-
   configure the HEs, and consequently reduce the network setup,
   operation and maintenance cost.

   The prefixes used for subscriber links and the ones delegated via
   DHCP-PD should be planned in a manner that allows as much
   summarization as possible at the Edge Router.

   Other information of interest to the host, such as DNS, is provided
   through stateful [RFC3315] [11] and stateless [RFC3736] [10] DHCPv6.

10.2.3  Routing

   The HE

   If no routers are used on the custmer premises, the HE can simply be
   configured with a default route that points to the Edge Router. No routing protocols are needed  If a
   router is used on these devices
   which generally have limited resources.

   The Edge Router runs the IPv6 customer premises (RCPE) then the HE will run
   an IGP used in to the NSP: OSPFv3 ER such as OSPFv3, IS-IS or IS-IS. even RIPng.  The connected
   prefixes have to should be redistributed.  If DHCP-PD is used, with every
   delegated prefix a static route is installed by the HE HE.  For this
   reason the static routes must also be redistributed.  Prefix
   summarization should be done at the HE.

   The RCPE requires only a default route pointing to the HE.  No
   routing protocols are needed on these devices which generally have
   limited resources.

   The Edge Router runs the IPv6 IGP used in the NSP: OSPFv3 or IS-IS.
   The connected prefixes have to be redistributed as well as any RP
   other than the ones used on the ER that might be used between the HE
   and the ER.

10.3  IPv6 Multicast

   The considerations regarding IPv6 Multicast for Ethernet are also
   applicable here, in general, but assuming the nature of PLC/BPL being
   a shared media.  If a lot of Multicast is expected, it may be worth
   considering using RPT which are layer 3 aware.  In that case, one
   extra layer of Hierarchical DHCP-PD could be considered, in order to
   facilitate the deployment, operation and maintenance of the network.

10.4  IPv6 QoS

   The considerations introduced for QoS in Ethernet are also applicable
   here.  PLC/BPL networks support QoS, which basically are no different
   whether the transport is IPv4 or IPv6.  It is necessary to understand
   that the specific network characteristics, such as the variability
   that may be introduced by electrical noise, towards which the PLC/BPL
   network will automatically self-adapt.

10.5  IPv6 Security Considerations

   There are no differences in terms of security considerations if
   compared with the Ethernet case.

10.6  IPv6 Network Management

   There are no differences in terms of network management if compared
   with the already described Ethernet case.

11.  Gap Analysis

   Several aspects of deploying IPv6 over SP Broadband networks were
   highlighted in this document, aspects that require additional work in
   order to facilitate native deployments as summarized below:

   A. As mentioned in section 6, changes will need to be made to the
   DOCSIS specification in order for SPs to deploy native IPv6 over
   cable networks.  The CM and CMTS will both need to support IPv6
   natively in order to forward IPv6 unicast and multicast traffic.
   This is required for IPv6 Neighbor Discovery to work over DOCSIS
   cable networks.  Additional classifiers need to be added to the
   DOCSIS specification in order to classify IPv6 traffic at the CM and
   CMTS in order to provide QoS.  These issues are addressed in a recent
   proposal made to Cable Labs for DOCSIS 3.0 [31]

   B. Currently the DHCP-PD functionality cannot be implemented if the
   DHCP-PD server is not the Edge Router.  If the DHCP-PD messages are
   relayed, the Edge Router does not have a mechanism to learn the
   assigned prefixes and thus install the proper routes to make that
   prefix reachable.  Work needs to be done to address this issue, one
   idea being to provide the Edge Router with a snooping mechanism.  The
   uplink to the ISP network is configured with a /64 prefix as well.

   C. Section 7 stated that current RBE based IPv4 deployment might not
   be the best approach for IPv6 where the addressing space available
   gives the SP the opportunity to separate the users on different
   subnets.  The differences between IPv4 RBE and IPv6 RBE were
   highlighted in section 7.  If however, support and reason is found
   for a deployment similar to IPv4 RBE, then the environment becomes
   NBMA and the new feature should observe RFC2491 recommendations.

   D. Section 7 discussed the constraints imposed on a LAA based IPv6
   deployment by the fact that it is expected that the subscribers keep
   their assigned prefix regardless of LNS.  A deployment approach was
   proposed that would maintain the addressing schemes contiguous and
   offers prefix summarization opportunities.  The topic could be
   further investigated for other solutions or improvements.

   E. Sections 7 and 8 pointed out the limitations (previously
   documented in [IPv6 Multicast]) [32]) in deploying inter-domain ASM however, SSM based
   services seem more likely at this time.  For such SSM based services
   of content delivery (video or Audio), mechanisms are needed to
   facilitate the billing and management of listeners.  The currently
   available feature of MLD AAA is suggested however, other methods or
   mechanisms might be developed and proposed.

   F. In relation to section 9, concerns have been raised related to
   running IPv6 multicast over WLAN links.  Potentially these are same
   kind of issue issues when running any Layer3 protocol over a WLAN link that
   has a high loss-to-signal ratio, certain frames that are multicast
   based are dropped when settings are not adjusted properly.  For
   instance this behavior is similar to IGMP host membership report,
   when done on a WLAN link with high loss-to-signal ratio and high
   interference.  This problem is inherited to WLAN that can impact both
   IPv4 and IPv6 multicast packets and not specific to IPv6 multicast.

   G. The Privacy Extensions were mentioned as a popular means to
   provide some form of host security.  ISPs can track relatively easily
   the prefixes assigned to subscribers.  If however the ISPs are
   required by regulations to track their users at host address level,
   the Privacy Extensions [RFC3041] [14] can be implemented only in parallel with
   network management tools that could provide traceability of the
   hosts.  Mechanisms should be defined to implement this aspect of user
   management.

   H. Tunnels are an effective way to avoid deployment dependencies on
   the IPv6 support on platforms that are out of the SP control (GWRs or
   CPEs) or over technologies that did not standardize the IPv6 support
   yet (cable).  They can be used in the following ways:

   i.  Tunnels directly to the CPE or GWR with public or private IPv4
   addresses.

   ii.  Tunnels directly to hosts with public or private IPv4 addresses.
   Recommendations on the exact tunneling mechanisms that can/should be
   used for last mile access need to be investigated further and should
   be covered in a future IETF draft.

   I. Through its larger address space, IPv6 allows SPs to assign fixed,
   globally routable prefixes to the links connecting each subscriber.

   This approach changes the provisioning methodologies that were used
   for IPv4.  Static configuration of the IPv6 addresses for all these
   links on the Edge Routers or Access Routers might not be a scalable
   option.  New provisioning mechanisms or features might need to be
   developed in order to deal with this issue.

   J. New deployment models are emerging for the Layer 2 portion of the
   NAP where individual VLANs are not dedicated to each subscriber.
   This approach allows Layer 2 switches to aggregate more then 4096
   users.  MAC Forced Forwarding [MFF] is an example of such an
   implementation where a broadcast domain is turned into a NBMA like
   environment by forwarding the frames based on both Source and
   Destination MAC addresses.  Since these models are being adopted by
   the field, the implications of deploying IPv6 in such environments
   need to be further investigated.

   The outcome of solutions to some of these topics ranges from making a
   media access capable of supporting native IPv6 (cable) to improving
   operational aspects of native IPv6 deployments.

12. Contributors

   We would like to thank Pekka Savola for his contribution, guidance
   and feedback in order to improve this document.  IANA Considerations

   This document requests no action by IANA.

13. Acknowledgements

   We would like to thank Brian Carpenter, Patrick Grossetete, Toerless
   Eckert, Madhu Sudan, Shannon McFarland and Benoit Lourdelet for their
   valuable comments. The authors would like  Security Considerations

   Please refer to acknowledge the
   structure and information guidance provided by the work of Mickels et
   al on Transition Scenarios individual "IPv6 Security Considerations"
   technology sections for ISP Networks. details.

14.  References

14.1  Normative References

[RFC3053]
   Durand

   [1]   Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and E.
         Lear, "Address Allocation for Private Internets", BCP 5,
         RFC 1918, February 1996.

   [2]   Durand, A., Fasano Fasano, P., Guardini Guardini, I., Lento and D. Lento, "IPv6
         Tunnel Broker",
   RFC3053, RFC 3053, January 2001.

[RFC3056]
   Carpenter B., Moore K.,

   [3]   Carpenter, B. and K. Moore, "Connection of IPv6 Domains via
         IPv4 Clouds",
   RFC3056, Aprilruary RFC 3056, February 2001.

[RFC2473]
   Conta A., Deering S.,

   [4]   Conta, A. and S. Deering, "Generic Packet tunneling Tunneling in IPv6
         Specification", RFC 2473, December 1998.

[RFC2893]
   Gilligan R., Nordmark E.,

   [5]   Gilligan, R. and E. Nordmark, "Transition Mechanisms for IPv6
         Hosts and Routers", RFC 2893, August 2000.

[RFC2529]
   Carpenter B., Jung

   [6]   Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4
         Domains without Explicit Tunnels", RFC 2529, March 1999

[RFC3904]
   Huitema 1999.

   [7]   Huitema, C., Austein Austein, R., Satapati Satapati, S., and R. van der Pol R., Pol,
         "Evaluation of IPv6 Transition Mechanisms for Unmanaged
         Networks", RFC 3904, September 2004.

   [8]   IAB and IESG, "IAB/IESG Recommendations on IPv6 Address
         Allocations to Sites", RFC 3177, September 2000

[RFC3513] 2001.

   [9]   Hinden, R. Hinden and S. Deering, "IP "Internet Protocol Version 6 (IPv6)
         Addressing Architecture",
   RFC3513, RFC 3513, April 2003.

[RFC3736]

   [10]  Droms, R., "Stateless Dynamic Host Configuration Protocol
         (DHCP) Service for IPv6", RFC3736, RFC 3736, April 2004.

[RFC3315]

   [11]  Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M.
         Carney, "Dynamic Host Configuration Protocol for IPv6
         (DHCPv6)",
   RFC3315, RFC 3315, July 2003.

[RFC2462]

   [12]  Thomson, S. and T. Narten, T., "IPv6 Stateless Address
         Autoconfiguration", RFC2462, RFC 2462, December 1998.

[RFC3633]

   [13]  Troan, O. and R. Droms, R., "IPv6 Prefix Options for Dynamic Host
         Configuration Protocol (DHCP) version 6", RFC3633, RFC 3633,
         December 2003.

[RFC3041]

   [14]  Narten, T. Narten and R. Draves, "Privacy Extensions for Stateless
         Address Autoconfiguration in IPv6," RFC3041, April IPv6", RFC 3041, January 2001.

[RFC2516]

   [15]  Mamakos, L., Lidl, K., Evarts, J., Carrel, D., Simone, D., and
         R. Wheeler, "A Method for Transmitting PPP Over Ethernet
         (PPPoE)",
   RFC2516, Aprilruary RFC 2516, February 1999.

[RFC2364]

   [16]  Gross, G., Kaycee, M., Lin, A., Malis, A., and J. Stephens,
         "PPP Over AAL5 (PPPoA)", RFC2516, AAL5", RFC 2364, July 1998.

[RFC2472]

   [17]  Haskin, D. and E. Allen, E., "IP Version 6 over PPP", RFC2472, RFC 2472,
         December 1998.

[RFC2461]

   [18]  Narten, T., Nordmark, E. E., and W. Simpson, W., "Neighbor Discovery
         for IP Version 6 (IPv6)", RFC2461, RFC 2461, December 1998.

[RFC2770]
   Meyer. D.,

   [19]  Meyer, D. and P. Lothberg, "GLOP Addressing in 233/8", RFC2770, April 2000

[RFC3646]
         RFC 2770, February 2000.

   [20]  St. Johns, M., "DOCSIS Cable Device MIB Cable Device Management
         Information Base for DOCSIS compliant Cable Modems and Cable
         Modem Termination Systems", RFC 2669, August 1999.

   [21]  Droms, R., "DNS Configuration options for Dynamic Host
         Configuration Protocol for IPv6 (DHCPv6)", RFC3646, RFC 3646,
         December 2003.

[RFC3618]
   Fenner B., Meyer D.,

   [22]  Fenner, B. and D. Meyer, "Multicast Source Discovery Protocol
         (MSDP)",
   RFC3618, RFC 3618, October 2003 2003.

   [23]  Baker, F. and P. Savola, "Ingress Filtering for Multihomed
         Networks", BCP 84, RFC 3704, March 2004.

   [24]  Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in
         IPv6", RFC 3775, June 2004.

   [25]  Lind, M., Ksinant, V., Park, S., Baudot, A., and P. Savola,
         "Scenarios and Analysis for Introducing IPv6 into ISP
         Networks", RFC 4029, March 2005.

14.2  Informative References

[Dual Stack Access]

   [26]  Shirasaki, et al., Y., Miyakawa, S., and A. Takenouchi, "A Model of
         IPv6/IPv4 Dual Stack Internet Access
   Service", draft-shirasaki-dualstack-service-04.txt (work in
   progress) ,April
         Service(draft-shirasaki-dualstack-service-04.txt)", April 2004.

[6PE]

   [27]  De Clercq Clercq, J., et al., Ooms, D., Prevost, S., and F. Le Faucheur,
         "Connecting IPv6 Islands across IPv4 Clouds with BGP:, draft-ooms-v6ops-bgp-tunnel-04.txt,
         BGP(draft-ooms-v6ops-bgp-tunnel-04.txt)", October 2004

[ISP Networks IPv6 Scenarios]
   Lind et, al., "Scenarios and Analysis for Introducing IPv6 into ISP
   Networks", RFC 4029, March 2005.

[ISATAP]
   Templin 2004.

   [28]  Templin, F., et al., "Intra-Site Gleeson, T., Talwar, M., and D. Thaler, "Intra-
         Site Automatic Tunnel Addressing Protocol
   (ISATAP)", draft-ietf-ngtrans-isatap-12.txt,
         (ISATAP)(draft-ietf-ngtrans-isatap-12.txt)", January 2003.

[Dynamic Tunnel]
   Palet

   [29]  Palet, J., et al., Diaz, M., and P. Savola, "Analysis of IPv6 Tunnel
         End-point Discovery
   Mechanisms", draft-palet-v6ops-tun-auto-disc-01.txt,
         Mechanisms(draft-palet-v6ops-tun-auto-disc-01.txt)", June 2004.

[OPS]
   Nordmark E., Gilligan

   [30]  Nordmark, E. and R. E., Gilligan, "Basic Transition Mechanisms for
         IPv6 Hosts and Routers", draft-ietf-v6ops-mech-v2-06.txt, Routers(draft-ietf-v6ops-mech-v2-06.txt)",
         September 2004.

[DOCSIS 3.0 Proposal]
   Cisco Systems,

   [31]  Cisco, Systems., "DOCSIS 3.0 Proposal", April 2005.

[IPv6 Multicast]

   [32]  Savola, P. P., "IPv6 Multicast Deployment Issues",
   draft-mboned-ipv6-multicast-issues,
         Issues(draft-mboned-ipv6-multicast-issues.txt)", April 2004

[RF Interface]
   Cable Labs, 2004.

   [33]  Cable, Labs., "Radio Frequency Interface Specification
   SP-RFIv2.0-I02-020617", Jun SP-
         RFIv2.0-I02-020617", June 2002.

[BSR]
   Nidhi Bhaskar et all.,

   [34]  Bhaskar, N., Gall, A., and S. Venaas, "Bootstrap Router (BSR)
         Mechanism for PIM",
   draft-ietf-pim-sm-bsr-04.txt, PIM(draft-ietf-pim-sm-bsr-04.txt)", January 2005

[Assisted Tunneling]
   A.Durand, F. Parent,"Requirements for assisted tunneling",
   draft-ietf-v6ops-assisted-tunneling-requirements-00.txt, June 2004

[v6tc]
   J. Pallet, et al., 2005.

   [35]  Palet, J., Nielsent, K., Parent, F., Durand, A.,
         Suryanarayanan, R., and P. Savola, "Goals for Tunneling Configuration",
   draft-palet-v6tc-goals-tunneling-00.txt, August, 2005

[Security considerations for IPv6]
    Sean
         Configuration(draft-palet-v6tc-goals-tunneling-00.txt)",
         August 2005.

   [36]  Convery, Darrin S. and D. Miller, "IPv6 and IPv4 Threat Comparison and
         Best-Practice Evaluation"

Authors Evaluation", March 2004.

Authors' Addresses

   Salman Asadullah
   Cisco Systems, Inc. Systems
   170 West Tasman Drive, Drive
   San Jose, CA 95134,  95134
   USA

   Phone: 408 526 8982
   Email: sasad@cisco.com

   Adeel Ahmed
   Cisco Systems, Inc. Systems
   2200 East President George Bush Turnpike, Turnpike
   Richardson, TX 75082,  75082
   USA

   Phone: 469 255 4122
   Email: adahmed@cisco.com

   Ciprian Popoviciu
   Cisco Systems, Inc. Systems
   7025-6 Kit Creek Road, Road
   Research Triangle Park, NC 27709,  27709
   USA

   Phone: 919 392 3723
   Email: cpopovic@cisco.com

   Jordi Palet Martinez
   Consulintel
   San Jose Artesano, 1
   Alcobendas -
   Alcobendas, Madrid  E-28108 -
   Spain

   Phone: +34 91 151 81 99
   Fax:   +34 91 151 81 98
   Email: jordi.palet@consulintel.es

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