draft-ietf-v6ops-addcon-07.txt   draft-ietf-v6ops-addcon-08.txt 
IPv6 Operations G. Van de Velde IPv6 Operations G. Van de Velde
Internet-Draft C. Popoviciu Internet-Draft C. Popoviciu
Intended status: Informational Cisco Systems Intended status: Informational Cisco Systems
Expires: May 8, 2008 T. Chown Expires: December 7, 2008 T. Chown
University of Southampton University of Southampton
O. Bonness O. Bonness
C. Hahn C. Hahn
T-Systems Enterprise Services GmbH T-Systems Enterprise Services GmbH
November 5, 2007 June 5, 2008
IPv6 Unicast Address Assignment Considerations IPv6 Unicast Address Assignment Considerations
<draft-ietf-v6ops-addcon-07.txt> <draft-ietf-v6ops-addcon-08.txt>
Status of this Memo Status of this Memo
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This Internet-Draft will expire on May 8, 2008. This Internet-Draft will expire on December 7, 2008.
Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract Abstract
One fundamental aspect of any IP communications infrastructure is its One fundamental aspect of any IP communications infrastructure is its
addressing plan. With its new address architecture and allocation addressing plan. With its new address architecture and allocation
policies, the introduction of IPv6 into a network means that network policies, the introduction of IPv6 into a network means that network
designers and operators need to reconsider their existing approaches designers and operators need to reconsider their existing approaches
to network addressing. Lack of guidelines on handling this aspect of to network addressing. Lack of guidelines on handling this aspect of
network design could slow down the deployment and integration of network design could slow down the deployment and integration of
IPv6. This document aims to provide the information and IPv6. This document aims to provide the information and
recommendations relevant to planning the addressing aspects of IPv6 recommendations relevant to planning the addressing aspects of IPv6
deployments. The document also provides IPv6 addressing case studies deployments. The document also provides IPv6 addressing case studies
for both an enterprise and an ISP network. for both an enterprise and an ISP network.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Network Level Addressing Design Considerations . . . . . . . . 5 2. Network Level Addressing Design Considerations . . . . . . . . 5
2.1. Global Unique Addresses . . . . . . . . . . . . . . . . . 5 2.1. Globally Unique Addresses . . . . . . . . . . . . . . . . 5
2.2. Unique Local IPv6 Addresses . . . . . . . . . . . . . . . 6 2.2. Unique Local IPv6 Addresses . . . . . . . . . . . . . . . 5
2.3. 6Bone Address Space . . . . . . . . . . . . . . . . . . . 7 2.3. 6Bone Address Space . . . . . . . . . . . . . . . . . . . 7
2.4. Network Level Design Considerations . . . . . . . . . . . 7 2.4. Network Level Design Considerations . . . . . . . . . . . 7
2.4.1. Sizing the Network Allocation . . . . . . . . . . . . 8 2.4.1. Sizing the Network Allocation . . . . . . . . . . . . 8
2.4.2. Address Space Conservation . . . . . . . . . . . . . . 9 2.4.2. Address Space Conservation . . . . . . . . . . . . . . 9
3. Subnet Prefix Considerations . . . . . . . . . . . . . . . . . 9 3. Subnet Prefix Considerations . . . . . . . . . . . . . . . . . 9
3.1. Considerations for subnet prefixes shorter then /64 . . . 9 3.1. Considerations for Subnet Prefixes Shorter then /64 . . . 9
3.2. Considerations for /64 prefixes . . . . . . . . . . . . . 10 3.2. Considerations for /64 Prefixes . . . . . . . . . . . . . 10
3.3. Considerations for subnet prefixes longer then /64 . . . . 10 3.3. Considerations for Subnet Prefixes Longer then /64 . . . . 10
3.3.1. Anycast addresses . . . . . . . . . . . . . . . . . . 10 3.3.1. Anycast Addresses . . . . . . . . . . . . . . . . . . 11
3.3.2. Addresses used by Embedded-RP (RFC3956) . . . . . . . 12 3.3.2. Addresses Used by Embedded-RP (RFC3956) . . . . . . . 12
3.3.3. ISATAP addresses . . . . . . . . . . . . . . . . . . . 12 3.3.3. ISATAP Addresses . . . . . . . . . . . . . . . . . . . 13
3.3.4. /126 addresses . . . . . . . . . . . . . . . . . . . . 13 3.3.4. /126 Addresses . . . . . . . . . . . . . . . . . . . . 13
3.3.5. /127 addresses . . . . . . . . . . . . . . . . . . . . 13 3.3.5. /127 Addresses . . . . . . . . . . . . . . . . . . . . 14
3.3.6. /128 addresses . . . . . . . . . . . . . . . . . . . . 13 3.3.6. /128 Addresses . . . . . . . . . . . . . . . . . . . . 14
4. Allocation of the IID of an IPv6 Address . . . . . . . . . . . 13 4. Allocation of the IID of an IPv6 Address . . . . . . . . . . . 14
4.1. Automatic EUI-64 Format Option . . . . . . . . . . . . . . 14 4.1. Automatic EUI-64 Format Option . . . . . . . . . . . . . . 14
4.2. Using Privacy Extensions . . . . . . . . . . . . . . . . . 14 4.2. Using Privacy Extensions . . . . . . . . . . . . . . . . . 14
4.3. Manual/Dynamic Assignment Option . . . . . . . . . . . . . 14 4.3. Manual/Dynamic Assignment Option . . . . . . . . . . . . . 15
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
6. Security Considerations . . . . . . . . . . . . . . . . . . . 15 6. Security Considerations . . . . . . . . . . . . . . . . . . . 15
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
8.1. Normative References . . . . . . . . . . . . . . . . . . . 15 8.1. Normative References . . . . . . . . . . . . . . . . . . . 16
8.2. Informative References . . . . . . . . . . . . . . . . . . 15 8.2. Informative References . . . . . . . . . . . . . . . . . . 16
Appendix A. Case Studies . . . . . . . . . . . . . . . . . . . . 17 Appendix A. Case Studies . . . . . . . . . . . . . . . . . . . . 18
A.1. Enterprise Considerations . . . . . . . . . . . . . . . . 17 A.1. Enterprise Considerations . . . . . . . . . . . . . . . . 19
A.1.1. Obtaining general IPv6 network prefixes . . . . . . . 18 A.1.1. Obtaining General IPv6 Network Prefixes . . . . . . . 19
A.1.2. Forming an address (subnet) allocation plan . . . . . 19 A.1.2. Forming an Address (subnet) Allocation Plan . . . . . 20
A.1.3. Other considerations . . . . . . . . . . . . . . . . . 19 A.1.3. Other Considerations . . . . . . . . . . . . . . . . . 21
A.1.4. Node configuration considerations . . . . . . . . . . 20 A.1.4. Node Configuration Considerations . . . . . . . . . . 21
A.2. Service Provider Considerations . . . . . . . . . . . . . 21 A.2. Service Provider Considerations . . . . . . . . . . . . . 22
A.2.1. Investigation of objective Requirements for an A.2.1. Investigation of objective Requirements for an
IPv6 addressing schema of a Service Provider . . . . 21 IPv6 addressing schema of a Service Provider . . . . 22
A.2.2. Exemplary IPv6 address allocation plan for a A.2.2. Exemplary IPv6 Address Allocation Plan for a
Service Provider . . . . . . . . . . . . . . . . . . . 24 Service Provider . . . . . . . . . . . . . . . . . . . 25
A.2.3. Additional Remarks . . . . . . . . . . . . . . . . . . 28 A.2.3. Additional Remarks . . . . . . . . . . . . . . . . . . 30
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 31 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 32
Intellectual Property and Copyright Statements . . . . . . . . . . 33 Intellectual Property and Copyright Statements . . . . . . . . . . 34
1. Introduction 1. Introduction
The Internet Protocol Version 6 (IPv6) Addressing Architecture [26] The Internet Protocol Version 6 (IPv6) Addressing Architecture
defines three main types of addresses: unicast, anycast and [RFC4291] defines three main types of addresses: unicast, anycast and
multicast. This document focuses on unicast addresses, for which multicast. This document focuses on unicast addresses, for which
there are currently two principal allocated types: Global Unique there are currently two principal allocated types: Globally Unique
Addresses [14] ('globals') and Unique Local IPv6 Addresses [22] Addresses [RFC3587] ('globals') and Unique Local IPv6 Addresses
(ULAs). In addition until recently there has been 'experimental' [RFC4193] (ULAs). In addition until recently there has been
6bone address space [3], though its use has been deprecated since 'experimental' 6bone address space [RFC3701], though its use has been
June 2006 [17]. deprecated since June 2006 [RFC3701].
The document covers aspects that should be considered during IPv6 The document covers aspects that should be considered during IPv6
deployment for the design and planning of an addressing scheme for an deployment for the design and planning of an addressing scheme for an
IPv6 network. The network's IPv6 addressing plan may be for an IPv6- IPv6 network. The network's IPv6 addressing plan may be for an IPv6-
only network, or for a dual-stack infrastructure where some or all only network, or for a dual-stack infrastructure where some or all
devices have addresses in both protocols. These considerations will devices have addresses in both protocols. These considerations will
help an IPv6 network designer to efficiently and prudently assign the help an IPv6 network designer to efficiently and prudently assign the
IPv6 address space that has been allocated to their organization. IPv6 address space that has been allocated to their organization.
The address assignment considerations are analyzed separately for the The address assignment considerations are analyzed separately for the
two major components of the IPv6 unicast addresses, namely 'Network two major components of the IPv6 unicast addresses, namely 'Network
Level Addressing' (the allocation of subnets) and the 'interface-id'. Level Addressing' (the allocation of subnets) and the 'interface-id'
Thus the document includes a discussion of aspects of address (the identification of the interface within a subnet). Thus the
assignment to nodes and interfaces in an IPv6 network. Finally the document includes a discussion of aspects of address assignment to
document provides two examples of deployed address plans in a service nodes and interfaces in an IPv6 network. Finally the document
provider (ISP) and an enterprise network. provides two examples of deployed address plans in a service provider
(ISP) and an enterprise network.
Parts of this document highlight the differences that an experienced Parts of this document highlight the differences that an experienced
IPv4 network designer should consider when planning an IPv6 IPv4 network designer should consider when planning an IPv6
deployment, for example: deployment, for example:
o IPv6 devices will more likely be multi-addressed in comparison o IPv6 devices will more likely be multi-addressed in comparison
with their IPv4 counterparts with their IPv4 counterparts
o The practically unlimited size of an IPv6 subnet (2^64 bits) o The practically unlimited size of an IPv6 subnet (2^64 bits)
reduces the requirement to size subnets to device counts for the reduces the requirement to size subnets to device counts for the
purposes of (IPv4) address conservation purposes of (IPv4) address conservation
o Even though there is no broadcast for the IPv6 protocol, there is
still need to consider the number of devices in a given subnet due
to traffic storm and level of traffic generated by hosts
o The implications of the vastly increased subnet size on the threat o The implications of the vastly increased subnet size on the threat
of address-based host scanning and other scanning techniques, as of address-based host scanning and other scanning techniques, as
discussed in [30]. discussed in [RFC5157].
We do not discuss here how a site or ISP should proceed with We do not discuss here how a site or ISP should proceed with
acquiring its globally routable IPv6 address prefix. In each case acquiring its globally routable IPv6 address prefix. In each case
the prefix received is provider assigned (PA) or provider independent the prefix received is either provider assigned (PA) or provider
(PI). independent (PI).
We do not discuss PI policy here. The observations and We do not discuss PI policy here. The observations and
recommendations of this text are largely independent of the PA or PI recommendations of this text are largely independent of the PA or PI
nature of the address block being used. At this time we assume that nature of the address block being used. At this time we assume that
most commonly an IPv6 network which changes provider will need to most commonly an IPv6 network which changes provider will need to
undergo a renumbering process, as described in [21]. A separate undergo a renumbering process, as described in [RFC4192]. A separate
document [32] makes recommendations to ease the IPv6 renumbering document [THINKABOUT] makes recommendations to ease the IPv6
process. renumbering process.
This document does not discuss implementation aspects related to the This document does not discuss implementation aspects related to the
transition between the ULA addresses and the now obsoleted site-local transition between the ULA addresses and the now obsoleted site-local
addresses. Most implementations know about Site-local addresses even addresses. Some implementations know about Site-local addresses even
though they are deprecated, and do not know about ULAs - even though though they are deprecated, and do not know about ULAs - even though
they represent current specification. As result transitioning they represent current specification. As result transitioning
between these types of addresses may cause difficulties. between these types of addresses may cause difficulties.
2. Network Level Addressing Design Considerations 2. Network Level Addressing Design Considerations
This section discusses the kind of IPv6 addresses used at the network This section discusses the kind of IPv6 addresses used at the network
level for the IPv6 infrastructure. The kind of addresses that can be level for the IPv6 infrastructure. The kind of addresses that can be
considered are Global Unique Addresses and ULAs. We also comment considered are Globally Unique Addresses and ULAs. We also comment
here on the deprecated 6bone address space. here on the deprecated 6bone address space.
2.1. Global Unique Addresses 2.1. Globally Unique Addresses
The most commonly used unicast addresses will be Global Unique The most commonly used unicast addresses will be Globally Unique
Addresses ('globals'). No significant considerations are necessary Addresses ('globals'). No significant considerations are necessary
if the organization has an address space assignment and a single if the organization has an address space assignment and a single
prefix is deployed through a single upstream provider. prefix is deployed through a single upstream provider.
However, a multihomed site may deploy addresses from two or more However, a multihomed site may deploy addresses from two or more
Service Provider assigned IPv6 address ranges. Here, the network Service Provider assigned IPv6 address ranges. Here, the network
Administrator must have awareness on where and how these ranges are Administrator must have awareness on where and how these ranges are
used on the multihomed infrastructure environment. The nature of the used on the multihomed infrastructure environment. The nature of the
usage of multiple prefixes may depend on the reason for multihoming usage of multiple prefixes may depend on the reason for multihoming
(e.g. resilience failover, load balancing, policy-based routing, or (e.g. resilience failover, load balancing, policy-based routing, or
multihoming during an IPv6 renumbering event). IPv6 introduces multihoming during an IPv6 renumbering event). IPv6 introduces
improved support for multi-addressed hosts through the IPv6 default improved support for multi-addressed hosts through the IPv6 default
address selection methods described in RFC3484 [12]. A multihomed address selection methods described in RFC3484 [RFC3484]. A
host may thus have two addresses, one per prefix (provider), and multihomed host may thus have two or more addresses, one per prefix
select source and destination addresses to use as described in that (provider), and select source and destination addresses to use as
RFC. However multihoming also has some operative and administrative described in that RFC. However multihoming also has some operational
burdens besides chosing multiple addresses per interface [33] and administrative burdens besides chosing multiple addresses per
[25][24]. interface [RFC4219][RFC4218].
2.2. Unique Local IPv6 Addresses 2.2. Unique Local IPv6 Addresses
ULAs have replaced the originally conceived Site Local addresses in ULAs have replaced the originally conceived Site Local addresses in
the IPv6 addressing architecture, for reasons described in [19]. the IPv6 addressing architecture, for reasons described in [RFC3879].
ULAs improve on site locals by offering a high probability of the ULAs improve on site locals by offering a high probability of the
global uniqueness of the prefix used, which can be beneficial in the global uniqueness of the prefix used, which can be beneficial in the
case of (deliberate or accidental) leakage, or where networks are case of (deliberate or accidental) leakage, or where networks are
merged. ULAs are akin to the private address space [1] assigned for merged. ULAs are akin to the private address space [RFC1918]
IPv4 networks, except that in IPv6 networks we may expect to see ULAs assigned for IPv4 networks, except that in IPv6 networks we may
used alongside global addresses, with ULAs used internally and expect to see ULAs used alongside global addresses, with ULAs used
globals used externally. Thus use of ULAs does not imply use of NAT internally and globals used externally. Thus use of ULAs does not
for IPv6. imply use of NAT for IPv6.
The ULA address range allows network administrators to deploy IPv6 The ULA address range allows network administrators to deploy IPv6
addresses on their network without asking for a globally unique addresses on their network without asking for a globally unique
registered IPv6 address range. A ULA prefix is 48 bits, i.e. a /48, registered IPv6 address range. A ULA prefix is 48 bits, i.e. a /48,
the same as the currently recommended allocation for a site from the the same as the currently recommended allocation for a site from the
globally routable IPv6 address space [9]. globally routable IPv6 address space [RFC3177].
A site willing to use ULA address space can have either (a) multiple A site willing to use ULA address space can have either (a) multiple
/48 prefixes (e.g. a /44) and wishes to use ULAs, or (b) has one /48 /48 prefixes (e.g. a /44) and wishes to use ULAs, or (b) has one /48
and wishes to use ULAs or (c) a site has a less-than-/48 prefix (e.g. and wishes to use ULAs or (c) a site has a less-than-/48 prefix (e.g.
a /56 or /64) and wishes to use ULAs. In all above cases the ULA a /56 or /64) and wishes to use ULAs. In all above cases the ULA
addresses can be randomly chosen according the principles specified addresses can be randomly chosen according the principles specified
in [19]. Using a random chosen ULA address will be conform in case in [RFC4193]. Using random chosen ULA addresses will provide in case
(a) provide suboptimal aggregation capability, while in case (c) (a) suboptimal aggregation capabilities, while in case (c) a /48 ULA
there will be overconsumption of address space. address is larger then the less-than-/48 prefix and will hence result
in address space overconsumption.
ULAs provide the means to deploy a fixed addressing scheme that is ULAs provide the means to deploy a fixed addressing scheme that is
not affected by a change in service provider and the corresponding PA not affected by a change in service provider and the corresponding PA
global addresses. Internal operation of the network is thus global addresses. Internal operation of the network is thus
unaffected during renumbering events. Nevertheless, this type of unaffected during renumbering events. Nevertheless, this type of
address must be used with caution. address must be used with caution.
A site using ULAs may or may not also deploy global addresses. In an A site using ULAs may or may not also deploy global addresses. In an
isolated network ULAs may be deployed on their own. In a connected isolated network ULAs may be deployed on their own. In a connected
network, that also deploys global addresses, both may be deployed, network, that also deploys global addresses, both may be deployed,
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will be selected where both the source and destination hosts have ULA will be selected where both the source and destination hosts have ULA
addresses. Because a ULA and a global site prefix are both /48 addresses. Because a ULA and a global site prefix are both /48
length, an administrator can choose to use the same subnetting (and length, an administrator can choose to use the same subnetting (and
host addressing) plan for both prefixes. host addressing) plan for both prefixes.
As an example of the problems ULAs may cause, when using IPv6 As an example of the problems ULAs may cause, when using IPv6
multicast within the network, the IPv6 default address selection multicast within the network, the IPv6 default address selection
algorithm prefers the ULA address as the source address for the IPv6 algorithm prefers the ULA address as the source address for the IPv6
multicast streams. This is NOT a valid option when sending an IPv6 multicast streams. This is NOT a valid option when sending an IPv6
multicast stream to the IPv6 Internet for two reasons. For one, multicast stream to the IPv6 Internet for two reasons. For one,
these addresses are not globally routable so RPF checks for such these addresses are not globally routable so Reverse Path Forwarding
traffic will fail outside the internal network. The other reason is checks for such traffic will fail outside the internal network. The
that the traffic will likely not cross the network boundary due to other reason is that the traffic will likely not cross the network
multicast domain control and perimeter security policies. boundary due to multicast domain control and perimeter security
policies.
In principle ULAs allow easier network mergers than RFC1918 addresses In principle ULAs allow easier network mergers than RFC1918 addresses
do for IPv4 because ULA prefixes have a high probability of do for IPv4 because ULA prefixes have a high probability of
uniqueness, if the prefix is chosen as described in the RFC. uniqueness, if the prefix is chosen as described in the RFC.
The usage of ULAs should be carefully considered even when not
attached to the IPv6 Internet as some IPv6 specifications were
created before the existence of ULA addresses.
2.3. 6Bone Address Space 2.3. 6Bone Address Space
The 6Bone address space was used before the RIRs started to The 6Bone address space was used before the Regional Internet
distribute 'production' IPv6 prefixes. The 6Bone prefixes have a Registries (RIRs) started to distribute 'production' IPv6 prefixes.
common first 16 bits in the IPv6 Prefix of 3FFE::/16. This address The 6Bone prefixes have a common first 16 bits in the IPv6 Prefix of
range is deprecated as of 6th June 2006 [17] and must not be used on [RFC3701] and must not be used on any new IPv6 network deployments.
any new IPv6 network deployments. Sites using 6bone address space Sites using 6bone address space should renumber to production address
should renumber to production address space using procedures as space using procedures as defined in [RFC4192].
defined in [21].
2.4. Network Level Design Considerations 2.4. Network Level Design Considerations
IPv6 provides network administrators with a significantly larger IPv6 provides network administrators with a significantly larger
address space, enabling them to be very creative in how they can address space, enabling them to be very creative in how they can
define logical and practical address plans. The subnetting of define logical and practical address plans. The subnetting of
assigned prefixes can be done based on various logical schemes that assigned prefixes can be done based on various logical schemes that
involve factors such as: involve factors such as:
o Using existing systems o Using existing systems
* translate the existing subnet number into IPv6 subnet id * translate the existing subnet number into IPv6 subnet id
* translate the VLAN id into IPv6 subnet id * translate the VLAN id into IPv6 subnet id
o Rethink o Redesign
* allocate according to your need * allocate according to your need
o Aggregation o Aggregation
* Geographical Boundaries - by assigning a common prefix to all * Geographical Boundaries - by assigning a common prefix to all
subnets within a geographical area subnets within a geographical area
* Organizational Boundaries - by assigning a common prefix to an * Organizational Boundaries - by assigning a common prefix to an
entire organization or group within a corporate infrastructure entire organization or group within a corporate infrastructure
* Service Type - by reserving certain prefixes for predefined * Service Type - by reserving certain prefixes for predefined
services such as: VoIP, Content Distribution, wireless services such as: VoIP, Content Distribution, wireless
services, Internet Access, Security areas etc. This type of services, Internet Access, Security areas etc. This type of
addressing may create dependencies on IP addresses that can addressing may create dependencies on IP addresses that can
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The network designer must however keep in mind several factors when The network designer must however keep in mind several factors when
developing these new addressing schemes for networks with and without developing these new addressing schemes for networks with and without
global connectivity: global connectivity:
o Prefix Aggregation - The larger IPv6 addresses can lead to larger o Prefix Aggregation - The larger IPv6 addresses can lead to larger
routing tables unless network designers are actively pursuing routing tables unless network designers are actively pursuing
aggregation. While prefix aggregation will be enforced by the aggregation. While prefix aggregation will be enforced by the
service provider, it is beneficial for the individual service provider, it is beneficial for the individual
organizations to observe the same principles in their network organizations to observe the same principles in their network
design process design process
o Network growth - The allocation mechanism for flexible growth of a o Network growth - The allocation mechanism for flexible growth of a
network prefix, documented in RFC3531 [13] can be used to allow network prefix, documented in RFC3531 [RFC3531] can be used to
the network infrastructure to grow and be numbered in a way that allow the network infrastructure to grow and be numbered in a way
is likely to preserve aggregation (the plan leaves 'holes' for that is likely to preserve aggregation (the plan leaves 'holes'
growth) for growth)
o ULA usage in large networks - Networks which have a large number o ULA usage in large networks - Networks which have a large number
of 'sites' that each deploy a ULA prefix which will by default be of 'sites' that each deploy a ULA prefix which will by default be
a 'random' /48 under fc00::/7 will have no aggregation of those a 'random' /48 under fc00::/7 will have no aggregation of those
prefixes. Thus the end result may be cumbersome because the prefixes. Thus the end result may be cumbersome because the
network will have large amounts of non-aggregated ULA prefixes. network will have large amounts of non-aggregated ULA prefixes.
However, there is no rule to disallow large networks to use a However, there is no rule to disallow large networks to use a
single ULA for all 'sites', as a ULA still provides 16 bits for single ULA prefix for all 'sites', as a ULA still provides 16 bits
subnetting to be used internally for subnetting to be used internally
o It is possible that as registry policies evolve, a small site may o It is possible that as registry policies evolve, a small site may
experience an increase in prefix length when renumbering, e.g. experience an increase in prefix length when renumbering, e.g.
from /48 to /56. For this reason, the best practice is number from /48 to /56. For this reason, the best practice is number
subnets compactly rather than sparsely, and to use low-order bits subnets compactly rather than sparsely, and to use low-order bits
as much as possible when numbering subnets. In other words, even as much as possible when numbering subnets. In other words, even
if a /48 is allocated, act as though only a /56 is available. if a /48 is allocated, act as though only a /56 is available.
Clearly, this advice does not apply to large sites and enterprises Clearly, this advice does not apply to large sites and enterprises
that have an intrinsic need for a /48 prefix. that have an intrinsic need for a /48 prefix.
o A small site may want to enable routing amongst interfaces
connected to a gateway device. For example, a residential gateway
which receives a /48, is situated in a home with multiple LANs of
different media types (sensor network, wired, wifi, etc.), or has
a need for traffic segmentation (home, work, kids, etc.) and could
benefit greatly from multiple subnets and routing in IPv6.
Ideally, residential networks would be given an address range of a
/48 or /56 [reference2] such that multiple /64 subnets could be
used within the residence.
2.4.1. Sizing the Network Allocation 2.4.1. Sizing the Network Allocation
We do not discuss here how a network designer sizes their application We do not discuss here how a network designer sizes their application
for address space. By default a site will receive a /48 prefix [9] , for address space. By default a site will receive a /48 prefix
however different RIR service regions policies may suggest [RFC3177] , however different RIR service regions policies may
alternative default assignments or let the ISPs to decide on what suggest alternative default assignments or let the ISPs to decide on
they believe is more appropriate for their specific case [29]. The what they believe is more appropriate for their specific case [ARIN].
default provider allocation via the RIRs is currently a /32 [31]. The default provider allocation via the RIRs is currently a /32
These allocations are indicators for a first allocation for a [reference2]. These allocations are indicators for a first
network. Different sizes may be obtained based on the anticipated allocation for a network. Different sizes may be obtained based on
address usage [31]. There are examples of allocations as large as the anticipated address usage [reference2]. There are examples of
/19 having been made from RIRs to providers at the time of writing. allocations as large as /19 having been made from RIRs to providers
at the time of writing.
2.4.2. Address Space Conservation 2.4.2. Address Space Conservation
Despite the large IPv6 address space which enables easier subnetting, Despite the large IPv6 address space which enables easier subnetting,
it still is important to ensure an efficient use of this resource. it still is important to ensure an efficient use of this resource.
Some addressing schemes, while facilitating aggregation and Some addressing schemes, while facilitating aggregation and
management, could lead to significant numbers of addresses being management, could lead to significant numbers of addresses being
unused. Address conservation requirements are less stringent in IPv6 unused. Address conservation requirements are less stringent in IPv6
but they should still be observed. but they should still be observed.
The proposed HD [10] value for IPv6 is 0.94 compared to the current The proposed Host-Density (HD) [RFC3194] value for IPv6 is 0.94
value of 0.96 for IPv4. Note that for IPv6 HD is calculated for compared to the current value of 0.96 for IPv4. Note that for IPv6
sites (e.g. on a basis of /48), instead of based on addresses like HD is calculated for sites (e.g. on a basis of /48), instead of based
with IPv4. on addresses like with IPv4.
3. Subnet Prefix Considerations 3. Subnet Prefix Considerations
This section analyzes the considerations applied to define the subnet This section analyzes the considerations applied to define the subnet
prefix of the IPv6 addresses. The boundaries of the subnet prefix prefix of the IPv6 addresses. The boundaries of the subnet prefix
allocation are specified in RFC4291 [26]. In this document we allocation are specified in RFC4291 [RFC4291]. In this document we
analyze their practical implications. Based on RFC4291 [26] it is analyze their practical implications. Based on RFC4291 [RFC4291] it
legal for any IPv6 unicast address starting with binary address '000' is legal for any IPv6 unicast address starting with binary address
to have a subnet prefix larger than, smaller than or of equal to 64 '000' to have a subnet prefix larger than, smaller than or equal to
bits. Each of these three options is discussed in this document. 64 bits. Each of these three options is discussed in this document.
This document mainly considers global addresses (assigned from RIR/
LIR) and ULAs and while neither of these address types starts with
binary "000" only /64 prefixes are allowed on these types of
addresses.
3.1. Considerations for subnet prefixes shorter then /64 3.1. Considerations for Subnet Prefixes Shorter then /64
An allocation of a prefix shorter then 64 bits to a node or interface An allocation of a prefix shorter then 64 bits to a node or interface
is considered bad practice. One exception to this statement is when is considered bad practice. One exception to this statement is when
using 6to4 technology where a /16 prefix is utilised for the pseudo- using 6to4 technology where a /16 prefix is utilized for the pseudo-
interface [8]. The shortest subnet prefix that could theoretically interface [RFC3056]. The shortest subnet prefix that could
be assigned to an interface or node is limited by the size of the theoretically be assigned to an interface or node is limited by the
network prefix allocated to the organization. size of the network prefix allocated to the organization.
A possible reason for choosing the subnet prefix for an interface A possible reason for choosing the subnet prefix for an interface
shorter then /64 is that it would allow more nodes to be attached to shorter then /64 is that it would allow more nodes to be attached to
that interface compared to a prescribed length of 64 bits. This that interface compared to a prescribed length of 64 bits. This
however is unnecessary for most networks considering that 2^64 however is unnecessary for most networks considering that 2^64
provides plenty of node addresses. provides plenty of node addresses.
The subnet prefix assignments can be made either by manual The subnet prefix assignments can be made either by manual
configuration, by a stateful Host Configuration Protocol [11], by a configuration, by a stateful Host Configuration Protocol [RFC3315],
stateful prefix delegation mechanism [16] or implied by stateless by a stateful prefix delegation mechanism [RFC3633] or implied by
autoconfiguration from prefix RAs. stateless autoconfiguration from prefix RAs.
3.2. Considerations for /64 prefixes 3.2. Considerations for /64 Prefixes
Based on RFC3177 [9], 64 bits is the prescribed subnet prefix length Based on RFC3177 [RFC3177], 64 bits is the prescribed subnet prefix
to allocate to interfaces and nodes. length to allocate to interfaces and nodes.
When using a /64 subnet length, the address assignment for these When using a /64 subnet length, the address assignment for these
addresses can be made either by manual configuration, by a stateful addresses can be made either by manual configuration, by a stateful
Host Configuration Protocol [11] [18] or by stateless Host Configuration Protocol [RFC3315] [RFC3736] or by stateless
autoconfiguration [2]. autoconfiguration [RFC4862].
Note that RFC3177 strongly prescribes 64 bit subnets for general Note that RFC3177 strongly prescribes 64 bit subnets for general
usage, and that stateless autoconfiguration option is only defined usage, and that stateless autoconfiguration option is only defined
for 64 bit subnets. However, implementations could use proprietary for 64 bit subnets. However, implementations could use proprietary
mechanism for stateless autoconfiguration for different then 64 bit mechanism for stateless autoconfiguration with other than 64 bit
prefix length. prefix length.
3.3. Considerations for subnet prefixes longer then /64 3.3. Considerations for Subnet Prefixes Longer then /64
Address space conservation is the main motivation for using a subnet Address space conservation is the main motivation for using a subnet
prefix length longer than 64 bits, however this kind of address prefix length longer than 64 bits, however this kind of address
conservation is of futile benefit compared with the additional conservation is of little benefit compared with the additional
considerations one must make when creating and maintain an IPv6 considerations one must make when creating and maintain an IPv6
address plan. address plan.
Using a subnet prefix length of longer then a /64 will break amongst
other technologies for example Neighborship Discovery (ND), Secure
Neighborship Discovery (SeND) and privacy extensions (RFC4193)
The address assignment can be made either by manual configuration or The address assignment can be made either by manual configuration or
by a stateful Host Configuration Protocol [11]. by a stateful Host Configuration Protocol [RFC3315].
When assigning a subnet prefix of more then 70 bits, according to When assigning a subnet prefix of more then 70 bits, according to
RFC4291 [26] "u" and "g" bits (respectively the 71st and 72nd bit) RFC4291 [RFC4291] 'u' and 'g' bits (respectively the 71st and 72nd
need to be taken into consideration and should be set correctly. In bit) need to be taken into consideration and should be set correct.
currently implemented IPv6 protocol stacks, the relevance of the "u"
(universal/local) bit and "g" (the individual/group) bit are marginal The 'u' (universal/local) bit is the 71st bit of IPv6 address and is
and typically will not show an issue when configured wrongly, however used to determine whether the address is universally or locally
future implementations may turn out differently. administered. If 0, the IEEE, through the designation of a unique
company ID, has administered the address. If 1, the address is
locally administered. The network administrator has overridden the
manufactured address and specified a different address.
The 'g' (the individual/group) bit is the 72st bit and is used to
determine whether the address is an individual address (unicast) or a
group address (multicast). If '0', the address is a unicast address.
If '1', the address is a multicast address.
In current IPv6 protocol stacks, the relevance of the 'u' and 'g' bit
is marginal and typically will not show an issue when configured
wrongly, however future implementations may turn out differently if
they would be processing the 'u' and 'g' bit in IEEE like behavior.
When using subnet lengths longer then 64 bits, it is important to When using subnet lengths longer then 64 bits, it is important to
avoid selecting addresses that may have a predefined use and could avoid selecting addresses that may have a predefined use and could
confuse IPv6 protocol stacks. The alternate usage may not be a confuse IPv6 protocol stacks. The alternate usage may not be a
simple unicast address in all cases. The following points should be simple unicast address in all cases. The following points should be
considered when selecting a subnet length longer then 64 bits. considered when selecting a subnet length longer then 64 bits.
3.3.1. Anycast addresses 3.3.1. Anycast Addresses
3.3.1.1. Subnet Router Anycast Address 3.3.1.1. Subnet Router Anycast Address
RFC4291 [26] provides a definition for the required Subnet Router RFC4291 [RFC4291] provides a definition for the required Subnet
Anycast Address as follows: Router Anycast Address as follows:
| n bits | 128-n bits | | n bits | 128-n bits |
+--------------------------------------------+----------------+ +--------------------------------------------+----------------+
| subnet prefix | 00000000000000 | | subnet prefix | 00000000000000 |
+--------------------------------------------+----------------+ +--------------------------------------------+----------------+
It is recommended to avoid allocating this IPv6 address to an device It is recommended to avoid allocating this IPv6 address to a device
which expects to have a normal unicast address. No additional which expects to have a normal unicast address. There is no
dependencies for the subnet prefix while the EUI-64 and IID additional dependency for the subnet prefix with the exception of the
dependencies will be discussed later in this document. 64-bit extended unique identifier (EUI-64) and an Interface
Identifier (IID) dependency. These will be discussed later in this
document.
3.3.1.2. Reserved IPv6 Subnet Anycast Addresses 3.3.1.2. Reserved IPv6 Subnet Anycast Addresses
RFC2526 [4] stated that within each subnet, the highest 128 interface RFC2526 [RFC2526] stated that within each subnet, the highest 128
identifier values are reserved for assignment as subnet anycast interface identifier values are reserved for assignment as subnet
addresses. anycast addresses.
The construction of a reserved subnet anycast address depends on the The construction of a reserved subnet anycast address depends on the
type of IPv6 addresses used within the subnet, as indicated by the type of IPv6 addresses used within the subnet, as indicated by the
format prefix in the addresses. format prefix in the addresses.
The first type of Subnet Anycast addresses have been defined as The first type of Subnet Anycast addresses have been defined as
follows for EUI-64 format: follows for EUI-64 format:
| 64 bits | 57 bits | 7 bits | | 64 bits | 57 bits | 7 bits |
+------------------------------+------------------+------------+ +------------------------------+------------------+------------+
| subnet prefix | 1111110111...111 | anycast ID | | subnet prefix | 1111110111...111 | anycast ID |
+------------------------------+------------------+------------+ +------------------------------+------------------+------------+
The anycast address structure implies that it is important to avoid The anycast address structure implies that it is important to avoid
creating a subnet prefix where the bits 65 to 121 are defined as creating a subnet prefix where the bits 65 to 121 are defined as
"1111110111...111" (57 bits in total) so that confusion can be "1111110111...111" (57 bits in total) so that confusion can be
avoided. avoided.
For other IPv6 address types (that is, with format prefixes other For other IPv6 address types (that is, with format prefixes other
than those listed above), the interface identifier is not in EUI-64 than those listed above), the interface identifier is not in 64-bit
format and may be other than 64 bits in length; these reserved subnet extended unique identifier (EUI-64) format and may be other than 64
anycast addresses for such address types are constructed as follows: bits in length; these reserved subnet anycast addresses for such
address types are constructed as follows:
| n bits | 121-n bits | 7 bits | | n bits | 121-n bits | 7 bits |
+------------------------------+------------------+------------+ +------------------------------+------------------+------------+
| subnet prefix | 1111111...111111 | anycast ID | | subnet prefix | 1111111...111111 | anycast ID |
+------------------------------+------------------+------------+ +------------------------------+------------------+------------+
| interface identifier field | | interface identifier field |
In the case discussed above there is no additional dependency for the It is recommended to avoid allocating this IPv6 address to a device
subnet prefix with the exception of the EUI-64 and an IID dependency. which expects to have a normal unicast address. There is no
These will be discussed later in this document. additional dependency for the subnet prefix with the exception of the
EUI-64 and an Interface Identifier (IID) dependency. These will be
discussed later in this document.
3.3.2. Addresses used by Embedded-RP (RFC3956) 3.3.2. Addresses Used by Embedded-RP (RFC3956)
Embedded-RP [20] reflects the concept of integrating the Rendezvous Embedded-RP [RFC3956] reflects the concept of integrating the
Point (RP) IPv6 address into the IPv6 multicast group address. Due Rendezvous Point (RP) IPv6 address into the IPv6 multicast group
to this embedding and the fact that the length of the IPv6 address address. Due to this embedding and the fact that the length of the
AND the IPv6 multicast address are 128 bits, it is not possible to IPv6 address AND the IPv6 multicast address are 128 bits, it is not
have the complete IPv6 address of the multicast RP embedded as such. possible to have the complete IPv6 address of the multicast RP
embedded as such.
This resulted in a restriction of 15 possible RP-addresses per prefix This resulted in a restriction of 15 possible RP-addresses per prefix
that can be used with embedded-RP. The space assigned for the that can be used with embedded-RP. The space assigned for the
embedded-RP is based on the 4 low order bits, while the remainder of embedded-RP is based on the 4 low order bits, while the remainder of
the Interface ID [RIID] is set to all '0'. the Interface ID (RIID) is set to all '0'.
[IPv6-prefix (64 bits)][60 bits all '0'][RIID] (IPv6-prefix (64 bits))(60 bits all '0')(RIID)
Where: [RIID] = 4 bit. Where: (RIID) = 4 bit.
This format implies that when selecting subnet prefixes longer then This format implies that when selecting subnet prefixes longer then
64, and the bits beyond the 64th one are non-zero, the subnet can not 64, and the bits beyond the 64th one are non-zero, the subnet can not
use embedded-RP. use embedded-RP.
In addition it is discouraged to assign a matching embedded-RP IPv6 In addition it is discouraged to assign a matching embedded-RP IPv6
address to a device that is not a real Multicast Rendezvous Point, address to a device that is not a real Multicast Rendezvous Point,
eventhough it would not generate major problems. eventhough it would not generate major problems.
3.3.3. ISATAP addresses 3.3.3. ISATAP Addresses
ISATAP [23] is an experimental automatic tunneling protocol used to ISATAP [RFC5214] is an experimental automatic tunneling protocol used
provide IPv6 connectivity over an IPv4 campus or enterprise to provide IPv6 connectivity over an IPv4 campus or enterprise
environment. In order to leverage the underlying IPv4 environment. In order to leverage the underlying IPv4
infrastructure, the IPv6 addresses are constructed in a special infrastructure, the IPv6 addresses are constructed in a special
format. format.
An IPv6 ISATAP address has the IPv4 address embedded, based on a An IPv6 ISATAP address has the IPv4 address embedded, based on a
predefined structure policy that identifies them as an ISATAP predefined structure policy that identifies them as an ISATAP
address. address.
[IPv6 Prefix (64 bits)][0000:5EFE][IPv4 address] [IPv6 Prefix (64 bits)][0000:5EFE][IPv4 address]
When using subnet prefix length longer then 64 bits it is good When using subnet prefix length longer then 64 bits it is good
engineering practice that the portion of the IPv6 prefix from bit 65 engineering practice that the portion of the IPv6 prefix from bit 65
to the end of the host-id does not match with the well-known ISATAP to the end of the host-id does not match with the well-known ISATAP
[0000:5EFE] address when assigning an IPv6 address to a non-ISATAP [0000:5EFE] address when assigning an IPv6 address to a non-ISATAP
interface. interface.
In its actual definition there is no multicast support on ISATAP. Note that the definition of ISATAP does not support multicast.
3.3.4. /126 addresses 3.3.4. /126 Addresses
The 126 bit subnet prefixes are typically used for point-to-point 126 bit subnet prefixes are typically used for point-to-point links
links similar to a the IPv4 address conservative /30 allocation for similar to a the IPv4 address conservative /30 allocation for point-
point-to-point links. The usage of this subnet address length does to-point links. The usage of this subnet address length does not
not lead to any additional considerations other than the ones lead to any additional considerations other than the ones discussed
discussed earlier in this section, particularly those related to the earlier in this section, particularly those related to the "u" and
"u" and "g" bits. "g" bits.
3.3.5. /127 addresses 3.3.5. /127 Addresses
The usage of the /127 addresses, the equivalent of IPv4's RFC3021 [5] The usage of the /127 addresses, the equivalent of IPv4's RFC3021
is not valid and should be strongly discouraged as documented in [RFC3021] is not valid and should be strongly discouraged as
RFC3627 [15]. documented in RFC3627 [RFC3627].
3.3.6. /128 addresses 3.3.6. /128 Addresses
The 128 bit address prefix may be used in those situations where we The 128 bit address prefix may be used in those situations where we
know that one, and only one address is sufficient. Example usage know that one, and only one address is sufficient. Example usage
would be the off-link loopback address of a network device. would be the off-link loopback address of a network device.
When choosing a 128 bit prefix, it is recommended to take the "u" and When choosing a 128 bit prefix, it is recommended to take the "u" and
"g" bits into consideration and to make sure that there is no overlap "g" bits into consideration and to make sure that there is no overlap
with either the following well-known addresses: with either the following well-known addresses:
o Subnet Router Anycast Address o Subnet Router Anycast Address
o Reserved Subnet Anycast Address o Reserved Subnet Anycast Address
skipping to change at page 14, line 4 skipping to change at page 14, line 35
4. Allocation of the IID of an IPv6 Address 4. Allocation of the IID of an IPv6 Address
In order to have a complete IPv6 address, an interface must be In order to have a complete IPv6 address, an interface must be
associated a prefix and an Interface Identifier (IID). Section 3 of associated a prefix and an Interface Identifier (IID). Section 3 of
this document analyzed the prefix selection considerations. This this document analyzed the prefix selection considerations. This
section discusses the elements that should be considered when section discusses the elements that should be considered when
assigning the IID portion of the IPv6 address. assigning the IID portion of the IPv6 address.
There are various ways to allocate an IPv6 address to a device or There are various ways to allocate an IPv6 address to a device or
interface. The option with the least amount of caveats for the interface. The option with the least amount of caveats for the
network administrator is that of EUI-64 [2] based addresses. For the network administrator is that of EUI-64 [RFC4862] based addresses.
manual or dynamic options, the overlap with well known IPv6 addresses For the manual or dynamic options, the overlap with well known IPv6
should be avoided. addresses should be avoided.
4.1. Automatic EUI-64 Format Option 4.1. Automatic EUI-64 Format Option
When using this method the network administrator has to allocate a When using this method the network administrator has to allocate a
valid 64 bit subnet prefix. The EUI-64 [2] allocation procedure can valid 64 bit subnet prefix. The EUI-64 [RFC4862] allocation
from that moment onward assign the remaining 64 IID bits in a procedure can from that moment onward assign the remaining 64 IID
stateless manner. All the considerations for selecting a valid IID bits in a stateless manner. All the considerations for selecting a
have been incorporated in the EUI-64 methodology. valid IID have been incorporated in the EUI-64 methodology.
4.2. Using Privacy Extensions 4.2. Using Privacy Extensions
The main purpose of IIDs generated based on RFC3041 [6] is to provide The main purpose of IIDs generated based on RFC4941 [RFC4941] is to
privacy to the entity using this address. While there are no provide privacy to the entity using this address. While there are no
particular constraints in the usage of these addresses as defined in particular constraints in the usage of these addresses as defined in
[6] there are some implications to be aware of when using privacy [RFC4941] there are some implications to be aware of when using
addresses as documented in section 4 of RFC3041 [6] privacy addresses as documented in section 4 of RFC4941 [RFC4941]
4.3. Manual/Dynamic Assignment Option 4.3. Manual/Dynamic Assignment Option
This section discusses those IID allocations that are not implemented This section discusses those IID allocations that are not implemented
through stateless address configuration (Section 4.1). They are through stateless address configuration (Section 4.1). They are
applicable regardless of the prefix length used on the link. It is applicable regardless of the prefix length used on the link. It is
out of scope for this section to discuss the various assignment out of scope for this section to discuss the various assignment
methods (e.g. manual configuration, DHCPv6, etc). methods (e.g. manual configuration, DHCPv6, etc).
In this situation the actual allocation is done by human intervention In this situation the actual allocation is done by human intervention
skipping to change at page 15, line 7 skipping to change at page 15, line 37
current infrastructure. Following these two recommendations will current infrastructure. Following these two recommendations will
make it more difficult for malicious third parties to guess targets make it more difficult for malicious third parties to guess targets
for attack, and thus reduce security threats to a certain extent. for attack, and thus reduce security threats to a certain extent.
5. IANA Considerations 5. IANA Considerations
There are no extra IANA consideration for this document. There are no extra IANA consideration for this document.
6. Security Considerations 6. Security Considerations
This IPv6 addressing document does not have any direct impact on This document doesn't add any new security considerations that aren't
Internet infrastructure security. already outlined in the security considerations of the references.
7. Acknowledgements 7. Acknowledgements
Constructive feedback and contributions have been received from Marla Constructive feedback and contributions have been received during
Azinger, Stig Venaas, Pekka Savola, John Spence, Patrick Grossetete, IESG review cycle and from Marla Azinger, Stig Venaas, Pekka Savola,
Carlos Garcia Braschi, Brian Carpenter, Mark Smith, Janos Mohacsi, John Spence, Patrick Grossetete, Carlos Garcia Braschi, Brian
Jim Bound, Fred Templin, Ginny Listman and Krishnan Thirukonda. Carpenter, Mark Smith, Janos Mohacsi, Jim Bound, Fred Templin, Ginny
Listman, Salman Assadullah and Krishnan Thirukonda.
8. References 8. References
8.1. Normative References 8.1. Normative References
8.2. Informative References 8.2. Informative References
[1] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and E. [RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
Lear, "Address Allocation for Private Internets", BCP 5, E. Lear, "Address Allocation for Private Internets",
RFC 1918, February 1996. BCP 5, RFC 1918, February 1996.
[2] Thomson, S. and T. Narten, "IPv6 Stateless Address
Autoconfiguration", RFC 2462, December 1998.
[3] Hinden, R., Fink, R., and J. Postel, "IPv6 Testing Address
Allocation", RFC 2471, December 1998.
[4] Johnson, D. and S. Deering, "Reserved IPv6 Subnet Anycast [RFC2526] Johnson, D. and S. Deering, "Reserved IPv6 Subnet Anycast
Addresses", RFC 2526, March 1999. Addresses", RFC 2526, March 1999.
[5] Retana, A., White, R., Fuller, V., and D. McPherson, "Using 31- [RFC3021] Retana, A., White, R., Fuller, V., and D. McPherson,
Bit Prefixes on IPv4 Point-to-Point Links", RFC 3021, "Using 31-Bit Prefixes on IPv4 Point-to-Point Links",
December 2000. RFC 3021, December 2000.
[6] Narten, T. and R. Draves, "Privacy Extensions for Stateless
Address Autoconfiguration in IPv6", RFC 3041, January 2001.
[7] Durand, A., Fasano, P., Guardini, I., and D. Lento, "IPv6 [RFC3053] Durand, A., Fasano, P., Guardini, I., and D. Lento, "IPv6
Tunnel Broker", RFC 3053, January 2001. Tunnel Broker", RFC 3053, January 2001.
[8] Carpenter, B. and K. Moore, "Connection of IPv6 Domains via [RFC3056] Carpenter, B. and K. Moore, "Connection of IPv6 Domains
IPv4 Clouds", RFC 3056, February 2001. via IPv4 Clouds", RFC 3056, February 2001.
[9] IAB and IESG, "IAB/IESG Recommendations on IPv6 Address [RFC3177] IAB and IESG, "IAB/IESG Recommendations on IPv6 Address
Allocations to Sites", RFC 3177, September 2001. Allocations to Sites", RFC 3177, September 2001.
[10] Durand, A. and C. Huitema, "The H-Density Ratio for Address [RFC3180] Meyer, D. and P. Lothberg, "GLOP Addressing in 233/8",
Assignment Efficiency An Update on the H ratio", RFC 3194, BCP 53, RFC 3180, September 2001.
November 2001.
[11] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. [RFC3194] Durand, A. and C. Huitema, "The H-Density Ratio for
Carney, "Dynamic Host Configuration Protocol for IPv6 Address Assignment Efficiency An Update on the H ratio",
(DHCPv6)", RFC 3315, July 2003. RFC 3194, November 2001.
[12] Draves, R., "Default Address Selection for Internet Protocol [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
version 6 (IPv6)", RFC 3484, February 2003. and M. Carney, "Dynamic Host Configuration Protocol for
IPv6 (DHCPv6)", RFC 3315, July 2003.
[13] Blanchet, M., "A Flexible Method for Managing the Assignment of [RFC3484] Draves, R., "Default Address Selection for Internet
Bits of an IPv6 Address Block", RFC 3531, April 2003. Protocol version 6 (IPv6)", RFC 3484, February 2003.
[14] Hinden, R., Deering, S., and E. Nordmark, "IPv6 Global Unicast [RFC3531] Blanchet, M., "A Flexible Method for Managing the
Address Format", RFC 3587, August 2003. Assignment of Bits of an IPv6 Address Block", RFC 3531,
April 2003.
[15] Savola, P., "Use of /127 Prefix Length Between Routers [RFC3587] Hinden, R., Deering, S., and E. Nordmark, "IPv6 Global
Unicast Address Format", RFC 3587, August 2003.
[RFC3627] Savola, P., "Use of /127 Prefix Length Between Routers
Considered Harmful", RFC 3627, September 2003. Considered Harmful", RFC 3627, September 2003.
[16] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic Host [RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
Configuration Protocol (DHCP) version 6", RFC 3633, Host Configuration Protocol (DHCP) version 6", RFC 3633,
December 2003. December 2003.
[17] Fink, R. and R. Hinden, "6bone (IPv6 Testing Address [RFC3701] Fink, R. and R. Hinden, "6bone (IPv6 Testing Address
Allocation) Phaseout", RFC 3701, March 2004. Allocation) Phaseout", RFC 3701, March 2004.
[18] Droms, R., "Stateless Dynamic Host Configuration Protocol [RFC3736] Droms, R., "Stateless Dynamic Host Configuration Protocol
(DHCP) Service for IPv6", RFC 3736, April 2004. (DHCP) Service for IPv6", RFC 3736, April 2004.
[19] Huitema, C. and B. Carpenter, "Deprecating Site Local [RFC3879] Huitema, C. and B. Carpenter, "Deprecating Site Local
Addresses", RFC 3879, September 2004. Addresses", RFC 3879, September 2004.
[20] Savola, P. and B. Haberman, "Embedding the Rendezvous Point [RFC3956] Savola, P. and B. Haberman, "Embedding the Rendezvous
(RP) Address in an IPv6 Multicast Address", RFC 3956, Point (RP) Address in an IPv6 Multicast Address",
November 2004. RFC 3956, November 2004.
[21] Baker, F., Lear, E., and R. Droms, "Procedures for Renumbering [RFC4192] Baker, F., Lear, E., and R. Droms, "Procedures for
an IPv6 Network without a Flag Day", RFC 4192, September 2005. Renumbering an IPv6 Network without a Flag Day", RFC 4192,
September 2005.
[22] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
Addresses", RFC 4193, October 2005. Addresses", RFC 4193, October 2005.
[23] Templin, F., Gleeson, T., Talwar, M., and D. Thaler, "Intra- [RFC4218] Nordmark, E. and T. Li, "Threats Relating to IPv6
Site Automatic Tunnel Addressing Protocol (ISATAP)", RFC 4214, Multihoming Solutions", RFC 4218, October 2005.
October 2005.
[24] Nordmark, E. and T. Li, "Threats Relating to IPv6 Multihoming
Solutions", RFC 4218, October 2005.
[25] Lear, E., "Things Multihoming in IPv6 (MULTI6) Developers [RFC4219] Lear, E., "Things Multihoming in IPv6 (MULTI6) Developers
Should Think About", RFC 4219, October 2005. Should Think About", RFC 4219, October 2005.
[26] Hinden, R. and S. Deering, "IP Version 6 Addressing [RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
Protocol 4 (BGP-4)", RFC 4271, January 2006.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006. Architecture", RFC 4291, February 2006.
[27] Chown, T., Venaas, S., and C. Strauf, "Dynamic Host [RFC4477] Chown, T., Venaas, S., and C. Strauf, "Dynamic Host
Configuration Protocol (DHCP): IPv4 and IPv6 Dual-Stack Configuration Protocol (DHCP): IPv4 and IPv6 Dual-Stack
Issues", RFC 4477, May 2006. Issues", RFC 4477, May 2006.
[28] De Clercq, J., Ooms, D., Prevost, S., and F. Le Faucheur, [RFC4798] De Clercq, J., Ooms, D., Prevost, S., and F. Le Faucheur,
"Connecting IPv6 Islands over IPv4 MPLS Using IPv6 Provider "Connecting IPv6 Islands over IPv4 MPLS Using IPv6
Edge Routers (6PE)", RFC 4798, February 2007. Provider Edge Routers (6PE)", RFC 4798, February 2007.
[29] ARIN, "http://www.arin.net/policy/nrpm.html#six54". [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862, September 2007.
[30] Chown, T., "IPv6 Implications for TCP/UDP Port Scanning [RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy
(draft-ietf-v6ops-scanning-implications-03.txt)", March 2007. Extensions for Stateless Address Autoconfiguration in
IPv6", RFC 4941, September 2007.
[31] APNIC, ARIN, RIPE NCC, "IPv6 Address Allocation and Assignment [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site
Policy (www.ripe.net/ripe/docs/ipv6policy.html)", January 2003. Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214,
March 2008.
[32] Chown, T., Thompson, M., Ford, A., and S. Venaas, "Things to [RFC5157] Chown, T., "IPv6 Implications for Network Scanning",
think about when Renumbering an IPv6 network RFC 5157, March 2008.
(draft-chown-v6ops-renumber-thinkabout-05.txt)", March 2007.
[33] "List of Internet-Drafts relevant to the Multi6-WG [ARIN] ARIN, "http://www.arin.net/policy/nrpm.html#six54".
(http://ops.ietf.org/multi6/draft-list.html )".
[reference2]
APNIC, ARIN, RIPE NCC, "www.ripe.net/ripe/docs/
ipv6policy.html", July 2007.
[reference3]
APNIC, ARIN, RIPE NCC,
"http://www.ripe.net/ripe/docs/ripe-412.html", July 2007.
[reference4]
ARIN, "http://www.arin.net/policy/nrpm.html#ipv6",
March 2008.
[reference5]
APNIC,
"http://www.apnic.net/policy/ipv6-address-policy.html",
March 2007.
[reference6]
LACNIC, "http://lacnic.net/en/politicas/ipv6.html".
[reference7]
AFRINIC, "http://www.afrinic.net/docs/policies/
afpol-v6200407-000.htm", March 2004.
[THINKABOUT]
Chown, T., Thompson, M., Ford, A., and S. Venaas, "Things
to think about when Renumbering an IPv6 network
(draft-chown-v6ops-renumber-thinkabout-05.txt)",
March 2007.
Appendix A. Case Studies Appendix A. Case Studies
This appendix contains two case studies for IPv6 addressing schemas This appendix contains two case studies for IPv6 addressing schemas
that have been based on the statements and considerations of this that have been based on the statements and considerations of this
draft. These case studies illustrate how this draft has been used in draft. These case studies illustrate how this draft has been used in
two specific network scenarios. The case studies may serve as basic two specific network scenarios. The case studies may serve as basic
considerations for an administrator who designs the IPv6 addressing considerations for an administrator who designs the IPv6 addressing
schema for an enterprise or ISP network, but are not intended to schema for an enterprise or ISP network, but are not intended to
serve as general design proposal for every kind of IPv6 network. All serve as general design proposal for every kind of IPv6 network. All
subnet sizes used in this appendix are for practical visualization subnet sizes used in this appendix are for practical visualization
and do not dictate RIR policy. and do not dictate RIR policy.
A.1. Enterprise Considerations A.1. Enterprise Considerations
In this section we consider a case study of a campus network that is In this section one considers a case study of a campus network that
deploying IPv6 in parallel with existing IPv4 protocols in a dual- is deploying IPv6 in parallel with existing IPv4 protocols in a dual-
stack environment. The specific example is the University of stack environment. The specific example is the University of
Southampton (UK), focusing on a large department within that network. Southampton (UK), focusing on a large department within that network.
The deployment currently spans around 1,000 hosts and over 1,500 The deployment currently spans around 1,000 hosts and over 1,500
users. users.
A.1.1. Obtaining general IPv6 network prefixes A.1.1. Obtaining General IPv6 Network Prefixes
In the case of a campus network, the site will typically take its In the case of a campus network, the site will typically take its
connectivity from its National Research and Education Network (NREN). connectivity from its National Research and Education Network (NREN).
Southampton connects to JANET, the UK academic network, via its local Southampton connects to JANET, the UK academic network, via its local
regional network LeNSE. JANET currently has a /32 allocation from regional network LeNSE. JANET currently has a /32 allocation from
RIPE NCC. The current recommended practice is for sites to receive a RIPE NCC. The current recommended practice is for sites to receive a
/48 allocation, and on this basis Southampton has received such a /48 allocation, and on this basis Southampton has received such a
prefix for its own use. The regional network also uses its own prefix for its own use. The regional network also uses its own
allocation from the NREN provider. allocation from the NREN provider.
No ULA addressing is used on site. The campus is not multihomed No ULA addressing is used on site. The campus is not multihomed
(JANET is the sole provider), nor does it expect to change service (JANET is the sole provider), nor does it expect to change service
provider, and thus does not plan to use ULAs for the (perceived) provider, and thus does not plan to use ULAs for the (perceived)
benefit of easing network renumbering. Indeed, the campus has benefit of easing network renumbering. Indeed, the campus has
renumbered following the aforementioned renumbering procedure [21] on renumbered following the aforementioned renumbering procedure
two occasions, and this has proven adequate (with provisos documented [RFC4192] on two occasions, and this has proven adequate (with
in [32]. We also do not see any need to deploy ULAs for in or out of provisos documented in [THINKABOUT]. The campus do not see any need
band network management; there are enough IPv6 prefixes available in to deploy ULAs for in or out of band network management; there are
the site allocation for the infrastructure. In some cases, use of enough IPv6 prefixes available in the site allocation for the
private IP address space in IPv4 creates problems, so we believe that infrastructure. In some cases, use of private IP address space in
the availability of ample global IPv6 address space for IPv4 creates problems, so University of Southampton believe that the
infrastructure may be a benefit for many sites. availability of ample global IPv6 address space for infrastructure
may be a benefit for many sites.
No 6bone addressing is used on site any more. We note that since the No 6bone addressing is used on site any more. Since the 6bone
6bone phaseout of June 2006 [17] most transit ISPs have begun phaseout of June 2006 [RFC3701] most transit ISPs have begun
filtering attempted use of such prefixes. filtering attempted use of such prefixes.
Southampton does participate in global and organization scope IPv6 Southampton does participate in global and organization scope IPv6
multicast networks. Multicast address allocations are not discussed multicast networks. Multicast address allocations are not discussed
here as they are not in scope for the document. We note that IPv6 here as they are not in scope for the document. It is noted that
has advantages for multicast group address allocation. In IPv4 a IPv6 has advantages for multicast group address allocation. In IPv4
site needs to use techniques like GLOP to pick a globally unique a site needs to use techniques like GLOP [RFC3180] to pick a globally
multicast group to use. This is problematic if the site does not use unique multicast group to use. This is problematic if the site does
BGP and have an ASN. In IPv6 unicast-prefix-based IPv6 multicast not use Border Gateway Protocol (BGP) [RFC4271] and have an
addresses empower a site to pick a globally unique group address Autonomous System Number (ASN). In IPv6 unicast-prefix-based IPv6
based on its unicast own site or link prefix. Embedded RP is also in multicast addresses empower a site to pick a globally unique group
use, is seen as a potential advantage for IPv6 and multicast, and has address based on its unicast own site or link prefix. Embedded RP is
been tested successfully across providers between sites (including also in use, is seen as a potential advantage for IPv6 and multicast,
paths to/from the US and UK). and has been tested successfully across providers between sites
(including paths to/from the US and UK).
A.1.2. Forming an address (subnet) allocation plan A.1.2. Forming an Address (subnet) Allocation Plan
The campus has a /16 prefix for IPv4 use; in principle 256 subnets of The campus has a /16 prefix for IPv4 use; in principle 256 subnets of
256 addresses. In reality the subnetting is muddier, because of 256 addresses. In reality the subnetting is muddier, because of
concerns of IPv4 address conservation; subnets are sized to the hosts concerns of IPv4 address conservation; subnets are sized to the hosts
within them, e.g. a /26 IPv4 prefix is used if a subnet has 35 hosts within them, e.g. a /26 IPv4 prefix is used if a subnet has 35 hosts
in it. While this is efficient, it increases management burden when in it. While this is efficient, it increases management burden when
physical deployments change, and IPv4 subnets require resizing (up or physical deployments change, and IPv4 subnets require resizing (up or
down), even with DHCP in use. down), even with DHCP in use.
The /48 IPv6 prefix is considerably larger than the IPv4 allocation The /48 IPv6 prefix is considerably larger than the IPv4 allocation
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effectively unlimited subnet address size (2^64) compared to 256 in effectively unlimited subnet address size (2^64) compared to 256 in
the IPv4 equivalent. The increased subnet size means that /64 IPv6 the IPv4 equivalent. The increased subnet size means that /64 IPv6
prefixes can be used on all subnets, without any requirement to prefixes can be used on all subnets, without any requirement to
resize them at a later date. The increased subnet volume allows resize them at a later date. The increased subnet volume allows
subnets to be allocated more generously to schools and departments in subnets to be allocated more generously to schools and departments in
the campus. While address conservation is still important, it is no the campus. While address conservation is still important, it is no
longer an impediment on network management. Rather, address (subnet) longer an impediment on network management. Rather, address (subnet)
allocation is more about embracing the available address space and allocation is more about embracing the available address space and
planning for future expansion. planning for future expansion.
In a dual-stack network, we choose to deploy our IP subnets In a dual-stack network, it was chosen to deploy our IP subnets
congruently for IPv4 and IPv6. This is because the systems are still congruently for IPv4 and IPv6. This is because the systems are still
in the same administrative domains and the same geography. We do not in the same administrative domains and the same geography. It is not
expect to have IPv6-only subnets in production use for a while yet, expected to have IPv6-only subnets in production use for a while yet,
outside our test beds and our early Mobile IPv6 trials. With outside the test beds and some early Mobile IPv6 trials. With
congruent addressing, our firewall policies are also aligned for IPv4 congruent addressing, our firewall policies are also aligned for IPv4
and IPv6 traffic at our site border. and IPv6 traffic at the site border.
The subnet allocation plan required a division of the address space The subnet allocation plan required a division of the address space
per school or department. Here a /56 was allocated to the school per school or department. Here a /56 was allocated to the school
level of the university; there are around 30 schools currently. A level of the university; there are around 30 schools currently. A
/56 of IPv6 address space equates to 256 /64 size subnet allocations. /56 of IPv6 address space equates to 256 /64 size subnet allocations.
Further /56 allocations were made for central IT infrastructure, for Further /56 allocations were made for central IT infrastructure, for
the network infrastructure and the server side systems. the network infrastructure and the server side systems.
A.1.3. Other considerations A.1.3. Other Considerations
The network uses a Demilitarized Zone (DMZ) topology for some level The network uses a Demilitarized Zone (DMZ) topology for some level
of protection of 'public' systems. Again, this topology is congruent of protection of 'public' systems. Again, this topology is congruent
with the IPv4 network. with the IPv4 network.
There are no specific transition methods deployed internally to the There are no specific transition methods deployed internally to the
campus; everything is using the conventional dual-stack approach. campus; everything is using the conventional dual-stack approach.
There is no use of ISATAP [23] for example. There is no use of ISATAP [RFC5214] for example.
For the Mobile IPv6 early trials, we have allocated one prefix for For the Mobile IPv6 early trials there is one allocated prefix for
Home Agent (HA) use. We have not yet considered in detail how Mobile Home Agent (HA) use. However there has been no detailed
IPv6 usage may grow, and whether more or even every subnet will consideration yet how Mobile IPv6 usage may grow, and whether more or
require HA support. even every subnet will require HA support.
The university operates a tunnel broker [7] service on behalf of The university operates a tunnel broker [RFC3053] service on behalf
UKERNA for JANET sites. This uses separate address space from JANET, of UKERNA for JANET sites. This uses separate address space from
not our university site allocation. JANET, not our university site allocation.
A.1.4. Node configuration considerations A.1.4. Node Configuration Considerations
We currently use stateless autoconfiguration on most subnets for IPv6 Currently stateless autoconfiguration is used on most subnets for
hosts. There is no DHCPv6 service deployed yet, beyond tests of IPv6 hosts. There is no DHCPv6 service deployed yet, beyond tests of
early code releases. We plan to deploy DHCPv6 for address assignment early code releases. It is planned to deploy DHCPv6 for address
when robust client and server code is available (at the time of assignment when robust client and server code is available (at the
writing the potential for this looks good, e.g. via the ISC time of writing the potential for this looks good, e.g. via the ISC
implementation). We also are seeking a common integrated DHCP/DNS implementation). University of Southampton is also investigating a
management platform, even if the servers themselves are not co- common integrated DHCP/DNS management platform, even if the servers
located, including integrated DHCPv4 and DHCPv6 server configuration, themselves are not co-located, including integrated DHCPv4 and DHCPv6
as discussed in [27]. Currently we add client statelessly server configuration, as discussed in [RFC4477]. Currently clients
autoconfigured addresses to the DNS manually, though dynamic DNS is with statelessly autoconfigured addresses are added to the DNS
an option. Our administrators would prefer the use of DHCP because manually, though dynamic DNS is an option. The network
they believe it gives them more management control. administrators would prefer the use of DHCP because they believe it
gives them more management control.
Regarding the implications of the larger IPv6 subnet address space on Regarding the implications of the larger IPv6 subnet address space on
scanning attacks [30], we note that all our hosts are dual-stack, and scanning attacks [RFC5157], it is noted that all the hosts are dual-
thus are potentially exposed over both protocols anyway. We publish stack, and thus are potentially exposed over both protocols anyway.
all addresses in DNS, and do not operate a two faced DNS. All addresses or published in DNS, and hence do not operate a two
faced DNS.
We have internal usage of RFC3041 privacy addresses [6] currently There is internal usage of RFC4941 privacy addresses [RFC4941]
(certain platforms currently ship with it on by default), but may currently (certain platforms currently ship with it on by default),
wish to administratively disable this (perhaps via DHCP) to ease but may desire to administratively disable this (perhaps via DHCP) to
management complexity. However, we need to determine the feasibility ease management complexity. However, it is desired to determine the
of this on all systems, e.g. for guests on wireless LAN or other feasibility of this on all systems, e.g. for guests on wireless LAN
user-maintained systems. Network management and monitoring should be or other user-maintained systems. Network management and monitoring
simpler without RFC3041 in operation, in terms of identifying which should be simpler without RFC4941 in operation, in terms of
physical hosts are using which addresses. We note that RFC3041 is identifying which physical hosts are using which addresses. Note
only an issue for outbound connections, and that there is potential that RFC4941 is only an issue for outbound connections, and that
to assign privacy addresses via DHCPv6. there is potential to assign privacy addresses via DHCPv6.
We manually configure server addresses to avoid address changes on a Manually configured server addresses are used to avoid address
change of network adaptor. With IPv6 you can choose to pick ::53 for changes based upon change of network adaptor. With IPv6 you can
a DNS server, or can pick 'random' addresses for obfuscation, though choose to pick ::53 for a DNS server, or can pick 'random' addresses
that's not an issue for publicly advertised addresses (dns, mx, web, for obfuscation, though that's not an issue for publicly advertised
etc). addresses (dns, mx, web, etc).
A.2. Service Provider Considerations A.2. Service Provider Considerations
In this section an IPv6 addressing schema is sketched that could In this section an IPv6 addressing schema is sketched that could
serve as an example for an Internet Service Provider. serve as an example for an Internet Service Provider.
Sub-section A.2.1 starts with some thoughts regarding objective Sub-section A.2.1 starts with some thoughts regarding objective
requirements of such an addressing schema and derives a few general requirements of such an addressing schema and derives a few general
thumb rules that have to be kept in mind when designing an ISP IPv6 rules of thumb that have to be kept in mind when designing an ISP
addressing plan. IPv6 addressing plan.
Sub-section A.2.2 illustrates these findings of A.2.1 with an Sub-section A.2.2 illustrates these findings of A.2.1 with an
exemplary IPv6 addressing schema for an MPLS-based ISP offering exemplary IPv6 addressing schema for an MPLS-based ISP offering
Internet Services as well as Network Access services to several Internet Services as well as Network Access services to several
millions of customers. millions of customers.
A.2.1. Investigation of objective Requirements for an IPv6 addressing A.2.1. Investigation of objective Requirements for an IPv6 addressing
schema of a Service Provider schema of a Service Provider
The first step of the IPv6 addressing plan design for a Service The first step of the IPv6 addressing plan design for a Service
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deployed by different ISPs. Nevertheless the addressing schema of deployed by different ISPs. Nevertheless the addressing schema of
sub-section A.2.2 is one possible example. sub-section A.2.2 is one possible example.
For this document it is assumed that our exemplary ISP has to fulfill For this document it is assumed that our exemplary ISP has to fulfill
several roles for its customers as there are: several roles for its customers as there are:
o Local Internet Registry o Local Internet Registry
o Network Access Provider o Network Access Provider
o Internet Service Provider o Internet Service Provider
A.2.1.1. Requirements for an IPv6 addressing schema from the LIR A.2.1.1. Recommendations for an IPv6 Addressing Schema from the LIR
perspective of the Service Provider Perspective of the Service Provider
In their role as LIR the Service Providers have to care about the In their role as Local Internet Registry (LIR) the Service Providers
policy constraints of the RIRs and the standards of the IETF have to care about the policy constraints of the RIRs and the
regarding IPv6 addressing. In this context, the following basic standards of the IETF regarding IPv6 addressing. In this context,
requirements and recommendations have to be considered and should be the following basic recommendations have to be considered and should
satisfied by the IPv6 address allocation plan of a Service Provider: be satisfied by the IPv6 address allocation plan of a Service
o As recommended in RFC 3177 [9] and in several RIR policies Provider:
o As recommended in RFC 3177 [RFC3177] and in several RIR policies
"Common" customers sites (normally private customers) should "Common" customers sites (normally private customers) should
receive a /48 prefix from the aggregate of the Service Provider. receive a /48 prefix from the aggregate of the Service Provider.
(Note: The addressing plan must be flexible enough and take into (Note: The addressing plan must be flexible enough and take into
account the possible change of the minimum allocation size for end account the possible change of the minimum allocation size for end
users currently under definition by the RIRs.) users currently under definition by the RIRs.)
o "Big customers" (like big enterprises, governmental agencies etc.) o "Big customers" (like big enterprises, governmental agencies etc.)
may receive shorter prefixes according to their needs when this may receive shorter prefixes according to their needs when this
need could be documented and justified to the RIR. need could be documented and justified to the RIR.
o The IPv6 address allocation schema has to be able to meet the HD- o The IPv6 address allocation schema has to be able to meet the HD-
ratio that is proposed for IPv6. This requirement corresponds to ratio that is proposed for IPv6. This requirement corresponds to
the demand for an efficient usage of the IPv6 address aggregate by the demand for an efficient usage of the IPv6 address aggregate by
the Service Provider. (Note: The currently valid IPv6 HD-ratio of the Service Provider. (Note: The currently valid IPv6 HD-ratio of
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o The IPv6 address allocation schema has to be able to meet the HD- o The IPv6 address allocation schema has to be able to meet the HD-
ratio that is proposed for IPv6. This requirement corresponds to ratio that is proposed for IPv6. This requirement corresponds to
the demand for an efficient usage of the IPv6 address aggregate by the demand for an efficient usage of the IPv6 address aggregate by
the Service Provider. (Note: The currently valid IPv6 HD-ratio of the Service Provider. (Note: The currently valid IPv6 HD-ratio of
0.94 means an effective usage of about 31% of a /20 prefix of the 0.94 means an effective usage of about 31% of a /20 prefix of the
Service Provider on the basis of /48 assignments.) Service Provider on the basis of /48 assignments.)
o All assignments to customers have to be documented and stored into o All assignments to customers have to be documented and stored into
a database that can also be queried by the RIR. a database that can also be queried by the RIR.
o The LIR has to make available means for supporting the reverse DNS o The LIR has to make available means for supporting the reverse DNS
mapping of the customer prefixes. mapping of the customer prefixes.
o IPv6 Address Allocation and Assignment Policies can be found at
RIRs and are similar in many aspects:
[reference2][reference3][reference4] [reference5][reference6]
A.2.1.2. IPv6 addressing schema requirements from the ISP perspective A.2.1.2. IPv6 Addressing Schema Recommendations from the ISP
of the Service Provider Perspective of the Service Provider
From ISP perspective the following basic requirements could be From ISP perspective the following basic requirements could be
identified: identified:
o The IPv6 address allocation schema must be able to realize a o The IPv6 address allocation schema must be able to realize a
maximal aggregation of all IPv6 address delegations to customers maximal aggregation of all IPv6 address delegations to customers
into the address aggregate of the Service Provider. Only this into the address aggregate of the Service Provider. Only this
provider aggregate will be routed and injected into the global provider aggregate will be routed and injected into the global
routing table (DFZ). This strong aggregation keeps the routing routing table (DFZ). This strong aggregation keeps the routing
tables of the DFZ small and eases filtering and access control tables of the DFZ small and eases filtering and access control
very much. very much.
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From ISP perspective the following basic requirements could be From ISP perspective the following basic requirements could be
identified: identified:
o The IPv6 address allocation schema must be able to realize a o The IPv6 address allocation schema must be able to realize a
maximal aggregation of all IPv6 address delegations to customers maximal aggregation of all IPv6 address delegations to customers
into the address aggregate of the Service Provider. Only this into the address aggregate of the Service Provider. Only this
provider aggregate will be routed and injected into the global provider aggregate will be routed and injected into the global
routing table (DFZ). This strong aggregation keeps the routing routing table (DFZ). This strong aggregation keeps the routing
tables of the DFZ small and eases filtering and access control tables of the DFZ small and eases filtering and access control
very much. very much.
o The IPv6 addressing schema of the SP should contain optimal o The IPv6 addressing schema of the SP should contain optimal
flexibility since the infrastructure of the SP will change over flexibility since the infrastructure of the SP will change over
the time with new customers, transport technologies and business the time with new customers, transport technologies and business
cases. The requirement of optimal flexibility is contrary to the cases. The requirement of optimal flexibility is contrary to the
requirements of strong IPv6 address aggregation and efficient recommendation of strong IPv6 address aggregation and efficient
address usage, but at this point each SP has to decide which of address usage, but at this point each SP has to decide which of
these requirements to prioritize. these requirements to prioritize.
o Keeping the multilevel network hierarchy of an ISP in mind, due to o Keeping the multilevel network hierarchy of an ISP in mind, due to
addressing efficiency reasons not all hierarchy levels can and addressing efficiency reasons not all hierarchy levels can and
should be mapped into the IPv6 addressing schema of an ISP. should be mapped into the IPv6 addressing schema of an ISP.
Sometimes it is much better to implement a more "flat" addressing Sometimes it is much better to implement a more "flat" addressing
for the ISP network than to loose big chunks of the IPv6 address for the ISP network than to loose big chunks of the IPv6 address
aggregate in addressing each level of network hierarchy. (Note: aggregate in addressing each level of network hierarchy. (Note:
In special cases it is even recommendable for really "small" ISPs In special cases it is even recommendable for really "small" ISPs
to design and implement a totally flat IPv6 addressing schema to design and implement a totally flat IPv6 addressing schema
without any level of hierarchy.) without any level of hierarchy.)
o Besides that a decoupling of provider network addressing and o Besides that a decoupling of provider network addressing and
customer addressing is recommended. (Note: A strong aggregation customer addressing is recommended. (Note: A strong aggregation
e.g. on POP, aggregation router or Label Edge Router (LER) level e.g. on POP, aggregation router or Label Edge Router (LER) level
limits the numbers of customer routes that are visible within the limits the numbers of customer routes that are visible within the
ISP network but brings also down the efficiency of the IPv6 ISP network but brings also down the efficiency of the IPv6
addressing schema. That's why each ISP has to decide how many addressing schema. That's why each ISP has to decide how many
internal aggregation levels it wants to deploy.) internal aggregation levels it wants to deploy.)
A.2.1.3. IPv6 addressing schema requirements from the Network Access A.2.1.3. IPv6 Addressing Schema Recommendations from the Network Access
provider perspective of the Service Provider provider Perspective of the Service Provider
As already done for the LIR and the ISP roles of the SP it is also As already done for the LIR and the ISP roles of the SP it is also
necessary to identify requirements that come from its Network Access necessary to identify requirements that come from its Network Access
Provider role. Some of the basic requirements are: Provider role. Some of the basic requirements are:
o The IPv6 addressing schema of the SP must be chosen in a way that o The IPv6 addressing schema of the SP must be chosen in a way that
it can handle new requirements that are triggered from customer it can handle new requirements that are triggered from customer
side. This can be for instance the growing needs of the customers side. This can be for instance the growing needs of the customers
regarding IPv6 addresses as well as customer driven modifications regarding IPv6 addresses as well as customer driven modifications
within the access network topology (e.g. when the customer moves within the access network topology (e.g. when the customer moves
from one point of network attachment (POP) to another). (See from one point of network attachment (POP) to another). (See
skipping to change at page 23, line 35 skipping to change at page 25, line 6
prefixes. prefixes.
o The IPv6 addressing schema of the SP must deal with multiple- o The IPv6 addressing schema of the SP must deal with multiple-
attachments of a single customer to the SP network infrastructure attachments of a single customer to the SP network infrastructure
(i.e. multi-homed network access with the same SP). (i.e. multi-homed network access with the same SP).
These few requirements are only part of all the requirements a These few requirements are only part of all the requirements a
Service Provider has to investigate and keep in mind during the Service Provider has to investigate and keep in mind during the
definition phase of its addressing architecture. Each SP will most definition phase of its addressing architecture. Each SP will most
likely add more constraints to this list. likely add more constraints to this list.
A.2.1.4. A few thumb rules for designing an IPv6 ISP addressing A.2.1.4. A Few Rules of Thumb for Designing an IPv6 ISP Addressing
architecture Architecture
As outcome of the above enumeration of requirements regarding an ISP As outcome of the above enumeration of requirements regarding an ISP
IPv6 addressing plan the following design "thumb rules" have been IPv6 addressing plan the following design "rules of thumb" have been
derived: derived:
o No "One size fits all". Each ISP must develop its own IPv6 o No "One size fits all". Each ISP must develop its own IPv6
address allocation schema depending on its concrete business address allocation schema depending on its concrete business
needs. It is not practicable to design one addressing plan that needs. It is not practicable to design one addressing plan that
fits for all kinds of ISPs (Small / big, Routed / MPLS-based, fits for all kinds of ISPs (Small / big, Routed / MPLS-based,
access / transit, LIR / No-LIR, etc.). access / transit, LIR / No-LIR, etc.).
o The levels of IPv6 address aggregation within the ISP addressing o The levels of IPv6 address aggregation within the ISP addressing
schema should strongly correspond to the implemented network schema should strongly correspond to the implemented network
structure and their number should be minimized because of structure and their number should be minimized because of
efficiency reasons. It is assumed that the SPs own infrastructure efficiency reasons. It is assumed that the SPs own infrastructure
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o The ISP IPv6 addressing schema should provide maximal flexibility. o The ISP IPv6 addressing schema should provide maximal flexibility.
This has to be realized for supporting different sizes of customer This has to be realized for supporting different sizes of customer
IPv6 address aggregates ("big" customers vs. "small" customers) as IPv6 address aggregates ("big" customers vs. "small" customers) as
well as to allow future growing rates (e.g. of customer well as to allow future growing rates (e.g. of customer
aggregates) and possible topological or infrastructural changes. aggregates) and possible topological or infrastructural changes.
o A limited number of aggregation levels and sizes of customer o A limited number of aggregation levels and sizes of customer
aggregates will ease the management of the addressing schema. aggregates will ease the management of the addressing schema.
This has to be weighed against the previous "thumb rule" - This has to be weighed against the previous "thumb rule" -
flexibility. flexibility.
A.2.2. Exemplary IPv6 address allocation plan for a Service Provider A.2.2. Exemplary IPv6 Address Allocation Plan for a Service Provider
In this example, the Service Provider is assumed to operate an MPLS In this example, the Service Provider is assumed to operate an MPLS
based backbone and implements 6PE [28] to provide IPv6 backbone based backbone and implements 6PE [RFC4798] to provide IPv6 backbone
transport between the different locations (POPs) of a fully dual- transport between the different locations (POPs) of a fully dual-
stacked network access and aggregation area. stacked network access and aggregation area.
Besides that it is assumed that the Service Provider: Besides that it is assumed that the Service Provider:
o has received a /20 from its RIR o has received a /20 from its RIR
o operates its own LIR o operates its own LIR
o has to address its own IPv6 infrastructure o has to address its own IPv6 infrastructure
o delegates prefixes from this aggregate to its customers o delegates prefixes from this aggregate to its customers
This addressing schema should illustrate how the /20 IPv6 prefix of This addressing schema should illustrate how the /20 IPv6 prefix of
the SP can be used to address the SP-own infrastructure and to the SP can be used to address the SP-own infrastructure and to
delegate IPv6 prefixes to its customers following the above mentioned delegate IPv6 prefixes to its customers following the above mentioned
requirements and thumb rules as far as possible. requirements and rules of thumb as far as possible.
The below figure summarizes the device types in a SP network and the The below figure summarizes the device types in a SP network and the
typical network design of a MPLS-based service provider. The network typical network design of a MPLS-based service provider. The network
hierarchy of the SP has to be taken into account for the design of an hierarchy of the SP has to be taken into account for the design of an
IPv6 addressing schema and defines its basic shape and the various IPv6 addressing schema and defines its basic shape and the various
levels of aggregation. levels of aggregation.
+------------------------------------------------------------------+ +------------------------------------------------------------------+
| LSRs of the MPLS Backbone of the SP | | LSRs of the MPLS Backbone of the SP |
+------------------------------------------------------------------+ +------------------------------------------------------------------+
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kind of aggregation network (e.g. DSL customers behind a BB- kind of aggregation network (e.g. DSL customers behind a BB-
RAR or Dial-In customers behind a RAR). RAR or Dial-In customers behind a RAR).
* The IPv6 address delegation within each Pool (end customer * The IPv6 address delegation within each Pool (end customer
delegation or also the aggregates that are dedicated to the delegation or also the aggregates that are dedicated to the
LERs itself) should be chosen with an additional buffer zone of LERs itself) should be chosen with an additional buffer zone of
100% - 300% for future growth. I.e. 1 or 2 additional prefix 100% - 300% for future growth. I.e. 1 or 2 additional prefix
bits should be reserved according to the expected future growth bits should be reserved according to the expected future growth
rate of the corresponding customer / the corresponding network rate of the corresponding customer / the corresponding network
device aggregate. device aggregate.
A.2.2.1. Defining an IPv6 address allocation plan for customers of the A.2.2.1. Defining an IPv6 Address Allocation Plan for Customers of the
Service Provider Service Provider
A.2.2.1.1. 'Big' customers A.2.2.1.1. 'Big' Customers
SP's "big" customers receive their prefix from the /24 IPv6 address SP's "big" customers receive their prefix from the /24 IPv6 address
aggregate that has been reserved for their "big" customers. A aggregate that has been reserved for their "big" customers. A
customer is considered as "big" customer if it has a very complex customer is considered as "big" customer if it has a very complex
network infrastructure and/or huge IPv6 address needs (e.g. because network infrastructure and/or huge IPv6 address needs (e.g. because
of very large customer numbers) and/or several uplinks to different of very large customer numbers) and/or several uplinks to different
POPs of the SP network. POPs of the SP network.
The assigned IPv6 address prefixes can have a prefix length in the The assigned IPv6 address prefixes can have a prefix length in the
range 32-48 and for each assignment a 100 or 300% future growing zone range 32-48 and for each assignment a 100 or 300% future growing zone
is marked as "reserved" for this customer. This means for instance is marked as "reserved" for this customer. This means for instance
that with a delegation of a /34 to a customer the corresponding /32 that with a delegation of a /34 to a customer the corresponding /32
prefix (which contains this /34) is reserved for the customers future prefix (which contains this /34) is reserved for the customers future
usage. usage.
The prefixes for the "big" customers can be chosen from the The prefixes for the "big" customers can be chosen from the
corresponding "big customer" pool by either using an equidistant corresponding "big customer" pool by either using an equidistant
algorithm or using mechanisms similar to the Sparse Allocation algorithm or using mechanisms similar to the Sparse Allocation
Algorithm (SAA) [31]. Algorithm (SAA) [reference2].
A.2.2.1.2. 'Common' customers A.2.2.1.2. 'Common' Customers
All customers that are not "big" customers are considered as "common" All customers that are not "big" customers are considered as "common"
customers. They represent the majority of customers hence they customers. They represent the majority of customers hence they
receive a /48 out of the IPv6 customer address pool of the LER where receive a /48 out of the IPv6 customer address pool of the LER where
they are directly connected or aggregated. they are directly connected or aggregated.
Again a 100 - 300% future growing IPv6 address range is reserved for Again a 100 - 300% future growing IPv6 address range is reserved for
each customer, so that a "common" customer receives a /48 allocation each customer, so that a "common" customer receives a /48 allocation
but has a /47 or /46 reserved. but has a /47 or /46 reserved.
(Note: If it is obvious that the likelyhood of needing a /47 or /46 (Note: If it is obvious that the likelyhood of needing a /47 or /46
in the future is very small for a "common" customer, than no growing in the future is very small for a "common" customer, than no growing
buffer should be reserved for it and only a /48 will be assigned buffer should be reserved for it and only a /48 will be assigned
without any growing buffer.) without any growing buffer.)
In the network access scenarios where the customer is directly In the network access scenarios where the customer is directly
connected to the LER the customer prefix is directly taken out of the connected to the LER the customer prefix is directly taken out of the
customer IPv6 address aggregate (e.g. /38) of the corresponding LER. customer IPv6 address aggregate (e.g. /38) of the corresponding LER.
In all other cases (e.g. the customer is attached to a RAR that is In all other cases (e.g. the customer is attached to a RAR that is
themselves aggregated to an AG or to a LER) at least 2 different themselves aggregated to an AG or to a LER-BB) at least 2 different
approaches are possible. approaches are possible.
1) Mapping of Aggregation Network Hierarchy into Customer IPv6 1) Mapping of Aggregation Network Hierarchy into Customer IPv6
Addressing Schema. The aggregation network hierarchy could be mapped Addressing Schema. The aggregation network hierarchy could be mapped
into the design of the customer prefix pools of each network level in into the design of the customer prefix pools of each network level in
order to achieve a maximal aggregation at the LER level as well as at order to achieve a maximal aggregation at the LER level as well as at
the intermediate levels. (Example: Customer - /48, RAR - /38, AG - the intermediate levels. (Example: Customer - /48, RAR - /38, AG -
/32, LER-BB - /30). At each network level an adequate growing zone /32, LER-BB - /30). At each network level an adequate growing zone
should be reserved. (Note: This approach requires of course some should be reserved. (Note: This approach requires of course some
"fine tuning" of the addressing schema based on a very good knowledge "fine tuning" of the addressing schema based on a very good knowledge
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at LER level is realized as required above. at LER level is realized as required above.
(Note: The handling of (e.g. technically triggered) changes within (Note: The handling of (e.g. technically triggered) changes within
the ISP access network is shortly discussed in section A.2.3.5.) the ISP access network is shortly discussed in section A.2.3.5.)
If the actual observed growing rates show that the reserved growing If the actual observed growing rates show that the reserved growing
zones are not needed than these growing areas can be freed and used zones are not needed than these growing areas can be freed and used
for assignments for prefix pools to other devices at the same level for assignments for prefix pools to other devices at the same level
of the network hierarchy. of the network hierarchy.
A.2.2.2. Defining an IPv6 address allocation plan for the Service A.2.2.2. Defining an IPv6 Address Allocation Plan for the Service
Provider Network Infrastructure Provider Network Infrastructure
For the IPv6 addressing of SPs own network infrastructure a /32 (or For the IPv6 addressing of SPs own network infrastructure a /32 (or
/40) from the "big" customers address pool can be chosen. /40) from the "big" customers address pool can be chosen.
This SP infrastructure prefix is used to code the network This SP infrastructure prefix is used to code the network
infrastructure of the SP by assigning a /48 to every POP/location and infrastructure of the SP by assigning a /48 to every POP/location and
using for instance a /56 for coding the corresponding router within using for instance a /56 for coding the corresponding router within
this POP. Each SP internal link behind a router interface could be this POP. Each SP internal link behind a router interface could be
coded using a /64 prefix. (Note: While it is suggested to choose a coded using a /64 prefix. (Note: While it is suggested to choose a
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through plain manual configuration e.g. for coding additional network through plain manual configuration e.g. for coding additional network
or operational information into the IID. or operational information into the IID.
It is assumed that again 100 - 300% growing zones for each level of It is assumed that again 100 - 300% growing zones for each level of
network hierarchy and additional prefix bits may be assigned to POPs network hierarchy and additional prefix bits may be assigned to POPs
and/or routers if needed. and/or routers if needed.
Loopback interfaces of routers may be chosen from the first /64 of Loopback interfaces of routers may be chosen from the first /64 of
the /56 router prefix (in the example above). the /56 router prefix (in the example above).
(Note: The /32 prefix that has been chosen for addressing SPs own (Note: The /32 (or /40) prefix that has been chosen for addressing
IPv6 network infrastructure gives enough place to code additional SPs own IPv6 network infrastructure gives enough place to code
functionalities like security levels or private and test additional functionalities like security levels or private and test
infrastructure although such approaches haven't been considered in infrastructure although such approaches haven't been considered in
more detail for the above described SP until now.) more detail for the above described SP until now.)
Point-to-point links to customers (e.g. PPP links, dedicated line Point-to-point links to customers (e.g. PPP links, dedicated line
etc.) may be addressed using /126 prefixes out of the first /64 of etc.) may be addressed using /126 prefixes out of the first /64 of
the access routers that could be reserved for this reason. the access routers that could be reserved for this reason.
A.2.3. Additional Remarks A.2.3. Additional Remarks
A.2.3.1. ULA A.2.3.1. ULA
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customer. Because this results in additional administrative effort customer. Because this results in additional administrative effort
and will stress the router resources (label space, memory) of the ISP and will stress the router resources (label space, memory) of the ISP
this solution will only be offered to the most valuable customers of this solution will only be offered to the most valuable customers of
an ISP (like e.g. "big customers" or "enterprise customers"). an ISP (like e.g. "big customers" or "enterprise customers").
Nevertheless the ISP has again to find a fair trade-off between Nevertheless the ISP has again to find a fair trade-off between
customer renumbering and sub-optimal address aggregation (i.e. the customer renumbering and sub-optimal address aggregation (i.e. the
generation of additional more-specific routing entries within the IGP generation of additional more-specific routing entries within the IGP
and the waste of MPLS Label space). and the waste of MPLS Label space).
A.2.3.5. Restructuring of SP (access) network and Renumbering A.2.3.5. Restructuring of SP (access) Network and Renumbering
A technically triggered restructuring of the SP (access) network (for A technically triggered restructuring of the SP (access) network (for
instance because of split of equipment or installation of new instance because of split of equipment or installation of new
equipment) should not lead to a customer network renumbering. This equipment) should not lead to a customer network renumbering. This
challenge should be handled in advance by an intelligent network challenge should be handled in advance by an intelligent network
design and IPv6 address planing. design and IPv6 address planing.
In the worst case the customer network renumbering could be avoided In the worst case the customer network renumbering could be avoided
through the implementation of more specific customer routes. (Note: through the implementation of more specific customer routes. (Note:
Since this kind of network restructuring will mostly happen within Since this kind of network restructuring will mostly happen within
the access network (at the level) below the LER, the LER aggregation the access network (at the level) below the LER, the LER aggregation
level will not be harmed and the more-specific routes will not level will not be harmed and the more-specific routes will not
consume additional MPLS label space.) consume additional MPLS label space.)
A.2.3.6. Extensions needed for the later IPv6 migration phases A.2.3.6. Extensions Needed for the Later IPv6 Migration Phases
The proposed IPv6 addressing schema for a SP needs some slight The proposed IPv6 addressing schema for a SP needs some slight
enhancements / modifications for the later phases of IPv6 enhancements / modifications for the later phases of IPv6
integration, for instance in the case when the whole MPLS backbone integration, for instance in the case when the whole MPLS backbone
infrastructure (LDP, IGP etc.) is realized over IPv6 transport and an infrastructure (LDP, IGP etc.) is realized over IPv6 transport and an
IPv6 addressing of the LSRs is needed. Other changes may be IPv6 addressing of the LSRs is needed. Other changes may be
necessary as well but should not be explained at this point. necessary as well but should not be explained at this point.
Authors' Addresses Authors' Addresses
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T-Systems Enterprise Services GmbH T-Systems Enterprise Services GmbH
Goslarer Ufer 35 Goslarer Ufer 35
Berlin, 10589 Berlin, 10589
Germany Germany
Phone: +49 30 3497 3164 Phone: +49 30 3497 3164
Email: HahnC@t-systems.com Email: HahnC@t-systems.com
Full Copyright Statement Full Copyright Statement
Copyright (C) The IETF Trust (2007). Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors contained in BCP 78, and except as set forth therein, the authors
retain all their rights. retain all their rights.
This document and the information contained herein are provided on an This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
skipping to change at page 33, line 44 skipping to change at line 1513
attempt made to obtain a general license or permission for the use of attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr. http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at this standard. Please address the information to the IETF at
ietf-ipr@ietf.org. ietf-ipr@ietf.org.
Acknowledgment
Funding for the RFC Editor function is provided by the IETF
Administrative Support Activity (IASA).
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