draft-ietf-v6ops-design-choices-08.txt   draft-ietf-v6ops-design-choices-09.txt 
V6OPS Working Group P. Matthews V6OPS Working Group P. Matthews
Internet-Draft Alcatel-Lucent Internet-Draft Alcatel-Lucent
Intended status: Informational V. Kuarsingh Intended status: Informational V. Kuarsingh
Expires: January 7, 2016 Dyn Expires: April 21, 2016 Cisco
July 6, 2015 October 19, 2015
Some Design Choices for IPv6 Networks Some Design Choices for IPv6 Networks
draft-ietf-v6ops-design-choices-08 draft-ietf-v6ops-design-choices-09
Abstract Abstract
This document presents advice on certain routing-related design This document presents advice on certain routing-related design
choices that arise when designing IPv6 networks (both dual-stack and choices that arise when designing IPv6 networks (both dual-stack and
IPv6-only). The intended audience is someone designing an IPv6 IPv6-only). The intended audience is someone designing an IPv6
network who is knowledgeable about best current practices around IPv4 network who is knowledgeable about best current practices around IPv4
network design, and wishes to learn the corresponding practices for network design, and wishes to learn the corresponding practices for
IPv6. IPv6.
skipping to change at page 1, line 36 skipping to change at page 1, line 36
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 7, 2016. This Internet-Draft will expire on April 21, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Design Choices . . . . . . . . . . . . . . . . . . . . . . . 3 2. Design Choices . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Addresses . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Addresses . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1.1. Choice of Addresses in the Core . . . . . . . . . . . 3 2.1.1. Choice of Addresses in the Core . . . . . . . . . . . 3
2.2. Interfaces . . . . . . . . . . . . . . . . . . . . . . . 5 2.2. Interfaces . . . . . . . . . . . . . . . . . . . . . . . 7
2.2.1. Mix IPv4 and IPv6 on the Same Layer-3 Interface? . . 5 2.2.1. Mix IPv4 and IPv6 on the Same Layer-3 Interface? . . 7
2.2.2. Interfaces with Only Link-Local Addresses? . . . . . 6 2.2.2. Interfaces with Only Link-Local Addresses? . . . . . 8
2.3. Static Routes . . . . . . . . . . . . . . . . . . . . . . 8 2.3. Static Routes . . . . . . . . . . . . . . . . . . . . . . 9
2.3.1. Link-Local Next-Hop in a Static Route? . . . . . . . 8 2.3.1. Link-Local Next-Hop in a Static Route? . . . . . . . 9
2.4. IGPs . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.4. IGPs . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.4.1. IGP Choice . . . . . . . . . . . . . . . . . . . . . 9 2.4.1. IGP Choice . . . . . . . . . . . . . . . . . . . . . 10
2.4.2. IS-IS Topology Mode . . . . . . . . . . . . . . . . . 11 2.4.2. IS-IS Topology Mode . . . . . . . . . . . . . . . . . 12
2.4.3. RIP . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.4.3. RIP . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.5. BGP . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2.5. BGP . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.5.1. Which Transport for Which Routes? . . . . . . . . . . 12 2.5.1. Which Transport for Which Routes? . . . . . . . . . . 13
2.5.1.1. BGP Sessions for Unlabeled Routes . . . . . . . . 13 2.5.1.1. BGP Sessions for Unlabeled Routes . . . . . . . . 15
2.5.1.2. BGP sessions for Labeled or VPN Routes . . . . . 14 2.5.1.2. BGP sessions for Labeled or VPN Routes . . . . . 16
2.5.2. eBGP Endpoints: Global or Link-Local Addresses? . . . 14 2.5.2. eBGP Endpoints: Global or Link-Local Addresses? . . . 16
3. General Observations . . . . . . . . . . . . . . . . . . . . 16 3. General Observations . . . . . . . . . . . . . . . . . . . . 17
3.1. Use of Link-Local Addresses . . . . . . . . . . . . . . . 16 3.1. Use of Link-Local Addresses . . . . . . . . . . . . . . . 17
3.2. Separation of IPv4 and IPv6 . . . . . . . . . . . . . . . 16 3.2. Separation of IPv4 and IPv6 . . . . . . . . . . . . . . . 18
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
5. Security Considerations . . . . . . . . . . . . . . . . . . . 17 5. Security Considerations . . . . . . . . . . . . . . . . . . . 19
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 19
7. Informative References . . . . . . . . . . . . . . . . . . . 18 7. Informative References . . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24
1. Introduction 1. Introduction
This document discusses certain choices that arise when designing a This document discusses foundational choices that arise when
IPv6-only or dual-stack network. The focus is on routing-related designing a IPv6-only or dual-stack network. The focus is on routing
design choices that do not usually come up when designing an related design choices that are not normally addressed when designing
IPv4-only network. The document presents each choice and the an IPv4-only network. The document presents each topic area along
alternatives, and then discusses the pros and cons of the with the most common design choices along with the pros and cons of
alternatives in detail. Where consensus currently exists around the each choice (or alternative) in detail. Where consensus currently
best practice, this is documented; otherwise the document simply exists around the best practice, this is documented; otherwise the
summarizes the current state of the discussion. Thus this document document simply summarizes the current state of the discussion. Thus
serves to both document the reasoning behind best current practices this document serves to both document the reasoning behind the best
for IPv6, and to allow a designer to make an informed choice where no current practices for IPv6, and to allow a designer to make an
such consensus exists. informed choice where no such consensus exists.
The design choices presented apply to both Service Provider and
Enterprise network environments. The design areas with the relative
choices are not specific to Service Provider or Enterprise networks,
but the designer should be aware of their network requirements to
best utilize the guidance or choice selection which may differ in
each of these general network environments. Where specific choices
have selection criteria or analysis requirements which may differ
between a Service Provider or Enterprise environment, that will be
noted in the text. The designer is encouraged to ensure that they
familiarize themselves with any of the discussed technologies to
ensure the best selection is made for their environment.
This document does not present advice on strategies for adding IPv6 This document does not present advice on strategies for adding IPv6
to a network, nor does it discuss transition mechanisms. For advice to a network, nor does it discuss transition in these areas, see
in these areas, see [RFC6180] for general advice, [RFC6782] for [RFC6180] for general advice,[RFC6782] for wireline service
wireline service providers, [RFC6342] for mobile network providers, providers, [RFC6342]for mobile network providers, [RFC5963] for
[RFC5963] for exchange point operators, [RFC6883] for content exchange point operators, [RFC6883] for content providers, and both
providers, and both [RFC4852] and [RFC7381] for enterprises. Nor [RFC4852] and [RFC7381] for enterprises. Nor does this document
does this document discuss the particulars of creating an IPv6 discuss the particulars of creating an IPv6 addressing plan; for
addressing plan; for advice in this area, see [RFC5375] or advice in this area, see [RFC5375] or [v6-addressing-plan]. The
[v6-addressing-plan]. The details of ULA usage is also not details of ULA usage is also not discussed; for this the reader is
discussed; for this the reader is referred to referred to [I-D.ietf-v6ops-ula-usage-recommendations].
[I-D.ietf-v6ops-ula-usage-recommendations].
Finally, this document focuses on unicast routing design only and Finally, this document focuses on unicast routing design only and
does not cover multicast or the issues involved in running MPLS over does not cover multicast or the issues involved in running MPLS over
IPv6 transport. IPv6 transport.
2. Design Choices 2. Design Choices
Each subsection below presents a design choice and discusses the pros Each subsection below presents a design choice and discusses the pros
and cons of the various options. If there is consensus in the and cons of the various options. If there is consensus in the
industry for a particular option, then the consensus position is industry for a particular option, then the consensus position is
noted. noted.
2.1. Addresses 2.1. Addresses
2.1.1. Choice of Addresses in the Core 2.1.1. Choice of Addresses in the Core
One of the first choices a network designer needs to make is the type One of the first choices a network designer needs to make is the type
of addresses to be used in the network core. Should the network use of IPv6 addresses to be used in the network core. IPv6, unlike IPv4,
provider-independent global addresses, "private" addresses (either introduces new addressing techniques and concepts, as introduced in
RFC 1918 addresses or unique-local addresses) or something else? [RFC4291] which requires specific attention. The introduction of
concepts such as using multiple-addresses per interface or the
introduction of linked scoped address-types like Link-Local, mean the
designer needs to think beyond the constraints of IPv4. There are
also operational considerations as with the concept of a provider
assign PA (Provider Aggregatable assigned via upstream provider)
versus a Regional Internet Registry assigned PI (Provider Independent
assigned from Registry) address type.
At the time of writing, there are still some known operational issues
with IPv6 deployments which expose near term deployments to
functional or operational gaps that may one day be eliminated. Once
such gap is host address selection challenges as noted in [RFC5220]
and renumbering challenges as described in [RFC6879] and [RFC7010].
Within this document, Unique Local Addresses (ULA) [RFC4193] are
likened to [RFC1918] addresses from an operational perspective.
Although ULAs are not architecturally similar to [RFC1918] private
addresses, the reasons for selecting them, and the challenge that may
arise if they are the only address type available to achieve external
network connectivity are similar. "Private" in this document refers
to the nature that ULAs would be typically used for internal
communications only, or externally with assistance from technologies
like NAT, given the addresses are not routed directly with external
networks.
A related choice is whether to use only link-local addresses on A related choice is whether to use only link-local addresses on
certain links. That choice is discussed later in the document; this certain links. That choice is discussed later in the document; this
section is about those addresses that must be visible throughout the section is about those addresses that must be visible throughout the
network. network.
The following table lists the main options available. The following table lists the main options available.
+---------+------------+-------------------+------------------------+ +---------+------------+---------------------+----------------------+
| GRT | End-User | ISP | Enterprise | | GRT | End-User | ISP | Enterprise |
| Address | Traffic | | | | Address | Traffic | | |
| Type | | | | | Type | | | |
+---------+------------+-------------------+------------------------+ +---------+------------+---------------------+----------------------+
| | | | | | | | | |
+---------+------------+-------------------+------------------------+ +---------+------------+---------------------+----------------------+
| PI | Hop-by-hop | Works | Works | | PI | Hop-by-hop | Works | Works |
+---------+------------+-------------------+------------------------+ +---------+------------+---------------------+----------------------+
| PI | Tunneled | Works. Using | Works. Using private | | PI | Tunneled | Works. Using | Works. Using private |
| | | private space | space likely a better | | | | private space | space likely a |
| | | likely a better | option. | | | | likely a better | better option. |
| | | option. | | | | | option. | |
+---------+------------+-------------------+------------------------+ +---------+------------+---------------------+----------------------+
| PA | Hop-by-hop | Works | Works | | PA | Hop-by-hop | Works | Works |
+---------+------------+-------------------+------------------------+ +---------+------------+---------------------+----------------------+
| PA | Tunneled | Works. Using | Works. Using private | | PA | Tunneled | Works. Using | Works. Using private |
| | | private addresses | addresses likely | | | | private addresses | addresses likely |
| | | likely better | better option. | | | | likely better | better option. |
| | | option. | | | | | option. | |
+---------+------------+-------------------+------------------------+ +---------+------------+---------------------+----------------------+
| Private | Hop-by-hop | Will likely cause | Works. Will probably | | Private | Hop-by-hop | Will likely cause | Works. Careful |
| | | problems. See | require some sort of | | | | problems. See | consideration due to |
| | | discussion below. | NAT on links to the | | | | discussion below. | NAT implications. |
| | | | Internet. | +---------+------------+---------------------+----------------------+
+---------+------------+-------------------+------------------------+ | Private | Tunneled | Works | Works |
| Private | Tunneled | Works | Works | +---------+------------+---------------------+----------------------+
+---------+------------+-------------------+------------------------+
As the table indicates, there are three options for the type of As the table indicates, there are three options for the type of
addresses a network designer can use in the network core: addresses a network designer can use in the network core:
o PI - Globally-unique IPv4 or IPv6 addresses obtained directly from o PI - Globally-unique IPv4 or IPv6 addresses obtained directly from
an address registry. An organization which has such addresses is an address registry. An organization which has such addresses is
considered to have "its own" address space. considered to have "its own" address space.
o PA - Globally-unique IPv4 or IPv6 addresses obtained from an o PA - Globally-unique IPv4 or IPv6 addresses obtained from an
upstream provider. Such addresses must be returned if the upstream provider. Such addresses must be returned if the
relationship with the upstream provider ceases. relationship with the upstream provider ceases.
o Private - Either RFC 1918 IPv4 addresses or unique-local IPv6 o Private - Either IPv4 addresses as per [RFC1918] or unique-local
addresses [RFC4193]. IPv6 addresses [RFC4193].
In all cases, we are talking about the type of addresses used in the In all cases, we are talking about the type of addresses used in the
GRT context (Global Routing Table aka base router). If end-user GRT context (Global Routing Table aka base router). If end-user
traffic is routed hop-by-hop through the network based on the traffic is routed hop-by-hop through the network based on the
destination address in the IP header, then this context is visible to destination address in the IP header, then this context is visible to
the end-user. However, if all end-user traffic is tunneled through the end-user. However, if all end-user traffic is tunneled through
the core (for example, using MPLS) then this context is not visible the core (for example, using MPLS) then this context is not visible
to the end-user. to the end-user.
First, consider the case where at least some end-user traffic is First, consider the case where at least some end-user traffic is
routed hop-by-hop. In this case, the use of PI space is the best routed hop-by-hop. In this case, the use of PI space is the best
option, as it gives the most flexibility in the future. However, option, as it gives the most flexibility in the future. However,
some organizations may be unable or unwilling to obtain PI space - in some organizations may be unable or unwilling to obtain PI space - in
this case PA space is the next-best choice. For an ISP, the use of this case PA space is the next-best choice. For an ISP, the use of
private address space is problematic - see [RFC6752] for a private address space is problematic - see [RFC6752] for a
discussion. For an enterprise, the use of private address space is discussion. For an enterprise, the use of private address space is
reasonable, but the enterprise will need to use NAT44 and/or an option and may be seen as favourable operationally, but should
NPT[RFC6296] on links to the Internet. If the network has no only be used after careful consideration of the technological
connection to the Internet, then obviously this is not a problem. drawbacks. If ULAs are the only non-Link-Local address available the
hosts, the enterprise will need to use translation technologies such
as NPT[RFC6296] or NAT66 to reach the Internet. If the network has
no connection to the Internet, or the hosts only assigned a ULA do
not need external connectivity, then this limitation is not a
problem.
Now consider the case where all end-user traffic is tunneled through Now consider the case where all end-user traffic is tunneled through
the core and thus the core is not visible to other networks. In this the core and thus the core is not visible to other networks. In this
case, the use of private addresses is the most reasonable and re- case, the use of private addresses in the core is the most reasonable
enforces the desire that these addresses have limited visibility. and re-enforces the desire that these addresses have limited
The use of PI space is the next-best option - two reasons for visibility. The use of PI space is the next-best option - two
selecting this option is to provide flexibility in case some traffic reasons for selecting this option is to provide flexibility in case
needs to be carried hop-by-hop in the future and to be absolutely some traffic needs to be carried hop-by-hop in the future and to be
ensure that there are no address conflicts. Getting IPv4 PI space at absolutely sure that there are no address conflicts. Getting IPv4 PI
this time will be difficult, but IPv6 PI space is fairly easy. The space at this time will be difficult, but IPv6 PI space is fairly
use of PA space is likely a poor option, since there is no short-term easy.
advantage and a high likelihood of having to give back the address
space sometime in the future. The use of PA space is likely a poor option for many organizations
since these networks are connected to more then one upstream provider
and/or may need flexibility on how Internet reachability needs to be
managed. Using PA space subjects the end network to possible
reclamation of address space in the future, which requires a
renumbering activity.
Not shown in the table above are combinations of the basic options. Not shown in the table above are combinations of the basic options.
An example of a combination is using both PA and ULA address space in An example of a combination is using both PA and ULA address space in
the hop-by-hop enterprise case. Combinations can reduce the the hop-by-hop enterprise case or multiple PA and/or PI addresses.
magnitude of the deficiency with a basic option, but does not Combinations can reduce the magnitude of the deficiency with a basic
eliminate it completely. For example, using PA + ULA for the hop-by- option, but does not eliminate it completely. For example, using PA
hop enterprise case reduces the amount of renumbering required when + ULA for the hop-by-hop enterprise case reduces the amount of
changing providers compared with the pure PA case, but does not renumbering required when changing providers compared with the pure
eliminate it completely. PA case, but does not eliminate it completely. Additional work
analyzing the opportunities for using multiple addresses and
overcoming limitations can be found in
[I-D.ietf-v6ops-host-addr-availability].
2.2. Interfaces 2.2. Interfaces
2.2.1. Mix IPv4 and IPv6 on the Same Layer-3 Interface? 2.2.1. Mix IPv4 and IPv6 on the Same Layer-3 Interface?
If a network is going to carry both IPv4 and IPv6 traffic, as many If a network is going to carry both IPv4 and IPv6 traffic, as many
networks do today, then a fundamental question arises: Should an networks do today, then a fundamental question arises: Should an
operator mix IPv4 and IPv6 traffic or keep them separated? More operator mix IPv4 and IPv6 traffic or keep them separated? More
specifically, should the design: specifically, should the design:
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address, as described in the previous section. address, as described in the previous section.
Today most operators use GUAs as next-hop addresses. Today most operators use GUAs as next-hop addresses.
2.4. IGPs 2.4. IGPs
2.4.1. IGP Choice 2.4.1. IGP Choice
One of the main decisions for a network operator looking to deploy One of the main decisions for a network operator looking to deploy
IPv6 is the choice of IGP (Interior Gateway Protocol) within the IPv6 is the choice of IGP (Interior Gateway Protocol) within the
network. The main options are OSPF, IS-IS and EIGRP. RIP is another network. The main options are OSPF, IS-IS and EIGRP. RIPng is
option, but very few networks run RIP in the core these days, so it another option, but very few networks run RIP in the core these days,
is covered in a separate section below. so it is covered in a separate section below.
OSPF [RFC2328] [RFC5340] and IS-IS [RFC5120][RFC5120] are both OSPF [RFC2328] [RFC5340] and IS-IS [RFC5120][RFC5120] are both
standardized and link-state protocols. Standardized means they are standardized and link-state protocols. Standardized means they are
widely supported by vendors, while link-state means amongst other widely supported by vendors, while link-state means amongst other
things that they can support RSVP-TE, which is widely used for MPLS things that they can support RSVP-TE, which is widely used for MPLS
signaling. Both of these protocols are widely deployed. By signaling. Both of these protocols are widely deployed. By
contrast, EIGRP [ref] is a proprietary distance-vector protocol. contrast, EIGRP [ref] is a proprietary distance-vector protocol.
EIGRP is rarely deployed in service-provider networks, but is quite EIGRP is rarely deployed in service-provider networks, but is quite
common in enterprise networks. common in enterprise networks.
The table below sets out possible combinations of protocols to route
both IPv4 and IPv6, and makes some observations on each combination.
+---------+---------+---------------+-------------+-----------------+ +---------+---------+---------------+-------------+-----------------+
| IGP for | IGP for | Multiple | Protocol | Similar | | IGP for | IGP for | Multiple | Protocol | Similar |
| IPv4 | IPv6 | Known | separation | configuration | | IPv4 | IPv6 | Known | separation | configuration |
| | | Deployments | | possible | | | | Deployments | | possible |
+---------+---------+---------------+-------------+-----------------+ +---------+---------+---------------+-------------+-----------------+
| | | | | | | | | | | |
+---------+---------+---------------+-------------+-----------------+ +---------+---------+---------------+-------------+-----------------+
| OSPFv2 | OSPFv3 | YES | YES | YES | | OSPFv2 | OSPFv3 | YES (8) | YES | YES |
+---------+---------+---------------+-------------+-----------------+ +---------+---------+---------------+-------------+-----------------+
| OSPFv2 | IS-IS | YES | YES | - | | OSPFv2 | IS-IS | YES (3) | YES | - |
+---------+---------+---------------+-------------+-----------------+ +---------+---------+---------------+-------------+-----------------+
| OSPFv2 | EIGRP | - | YES | - | | OSPFv2 | EIGRP | - | YES | - |
+---------+---------+---------------+-------------+-----------------+ +---------+---------+---------------+-------------+-----------------+
| OSPFv3 | IS-IS | - | YES | - | | OSPFv3 | IS-IS | - | YES | - |
+---------+---------+---------------+-------------+-----------------+ +---------+---------+---------------+-------------+-----------------+
| OSPFv3 | EIGRP | - | YES | - | | OSPFv3 | EIGRP | - | YES | - |
+---------+---------+---------------+-------------+-----------------+ +---------+---------+---------------+-------------+-----------------+
| IS-IS | OSPFv3 | YES | YES | - | | IS-IS | OSPFv3 | YES (2) | YES | - |
+---------+---------+---------------+-------------+-----------------+ +---------+---------+---------------+-------------+-----------------+
| IS-IS | IS-IS | YES | - | YES | | IS-IS | IS-IS | YES (12) | - | YES |
+---------+---------+---------------+-------------+-----------------+ +---------+---------+---------------+-------------+-----------------+
| IS-IS | EIGRP | - | YES | - | | IS-IS | EIGRP | - | YES | - |
+---------+---------+---------------+-------------+-----------------+ +---------+---------+---------------+-------------+-----------------+
| EIGRP | OSPFv3 | ? | YES | - | | EIGRP | OSPFv3 | ? (1) | YES | - |
+---------+---------+---------------+-------------+-----------------+ +---------+---------+---------------+-------------+-----------------+
| EIGRP | IS-IS | - | YES | - | | EIGRP | IS-IS | - | YES | - |
+---------+---------+---------------+-------------+-----------------+ +---------+---------+---------------+-------------+-----------------+
| EIGRP | EIGRP | ? | - | YES | | EIGRP | EIGRP | ? (2) | - | YES |
+---------+---------+---------------+-------------+-----------------+ +---------+---------+---------------+-------------+-----------------+
Three of the options above are marked as "Mutiple Known In the column "Multiple Known Deployments", a YES indicates that a
Deploymentsl". These options have seen significant deployments and significant number of production networks run this combination, with
are generally considered to be good choices. The other options the number of such networks indicated in parentheses following, while
represent valid choices, but have not seen widespread use at time of a "?" indicates that the authors are only aware of one or two small
writing. In particular, two if the options use OSPFv3 to route IPv4 networks that run this combination. Data for this column was
[RFC5838], which is still rather new and untested. gathered from an informal poll of operators on a number of mailing
lists. This poll was not intended to be a thorough scientific study
of IGP choices, but to provide a snapshot of known operator choices
at the time of writing (Mid-2015) for successful production dual
stack network deployments. There were twenty six (26) network
implementations represented by 17 respondents. Some respondents
provided information on more then one network or network deployment.
Due to privacy considerations, the networks' represented and
respondents are not listed in this document.
A number of options are marked "Protocol separation". These options A number of combinations are marked as offering "Protocol
use a different IGP protocol for IPv4 vs IPv6. With these options, a separation". These options use a different IGP protocol for IPv4 vs
problem with routing IPv6 is unlikely to affect IPv4 or visa-versa. IPv6. With these options, a problem with routing IPv6 is unlikely to
Some operator may consider this as a benefit when first introducing affect IPv4 or visa-versa. Some operator may consider this as a
dual stack capabilities or for ongoing technical reasons. benefit when first introducing dual stack capabilities or for ongoing
technical reasons.
Three options are marked "Similar configuration possible". This Three combinations are marked "Similar configuration possible". This
means it is possible (but not required) to use very similar IGP means it is possible (but not required) to use very similar IGP
configuration for IPv4 and IPv6: for example, the same area configuration for IPv4 and IPv6: for example, the same area
boundaries, area numbering, link costing, etc. If you are happy with boundaries, area numbering, link costing, etc. If you are happy with
your IPv4 IGP design, then this will likely be a consideration. By your IPv4 IGP design, then this will likely be a consideration. By
contrast, the options that use, for example, IS-IS for one IP version contrast, the options that use, for example, IS-IS for one IP version
and OSPF for the other version will require considerably different and OSPF for the other version will require considerably different
configuration, and will also require the operations staff to become configuration, and will also require the operations staff to become
familiar with the difference between the two protocols. familiar with the difference between the two protocols.
With option (a), there is an additional choice of whether to run IS-
IS in single-topology mode (where IPv4 and IPv6 share a single
topology and a single set of link costs[RFC5308]) or multi-topology
mode (where IPv4 and IPv6 have separate topologies and potentially
different link costs[RFC5120]). A big problem with single-topology
mode is that it cannot easily accommodate devices that support
IPv4-only or IPv6-only. Thus, today there is general agreement that
multi-topology is the right choice as this gives the greatest
flexibility in network design.
It should be noted that a number of ISPs have run OSPF as their IPv4 It should be noted that a number of ISPs have run OSPF as their IPv4
IGP for quite a few years, but have selected IS-IS as their IPv6 IGP. IGP for quite a few years, but have selected IS-IS as their IPv6 IGP.
However, there are very few (none?) that have made the reverse However, there are very few (none?) that have made the reverse
choice. This is, in part, because routers generally support more choice. This is, in part, because routers generally support more
nodes in an IS-IS area than in the corresponding OSPF area, and nodes in an IS-IS area than in the corresponding OSPF area, and
because IS-IS is seen as more secure because it runs at layer 2. because IS-IS is seen as more secure because it runs at layer 2.
2.4.2. IS-IS Topology Mode 2.4.2. IS-IS Topology Mode
When IS-IS is used to route both IPv4 and IPv6, then there is an When IS-IS is used to route both IPv4 and IPv6, then there is an
additional choice of whether to run IS-IS in single-topology or additional choice of whether to run IS-IS in single-topology or
multi-topology mode. Single-topology mode allows IPv4 and IPv6 to multi-topology mode. Single-topology mode allows IPv4 and IPv6 to
share a single topology and a single set of link costs[RFC5308]. share a single topology and a single set of link costs[RFC5308].
Multi-topology mode allows separate IPv4 and IPv6 topologies with Multi-topology mode allows separate IPv4 and IPv6 topologies with
potentially different link costs. potentially different link costs.
In the informal poll of operators, out of 12 production networks that
ran IS-IS for both IPv4 and IPv6, 6 used Single Topology mode, 4 used
Multi-Topology mode, and 2 did not specify. One motivation often
cited by then operators for using Single Topology mode was because
some device did not support multi-topology mode.
Traditional thinking has been that multi-topology mode offers the Traditional thinking has been that multi-topology mode offers the
most flexibility. Never-the-less, a number of operators have used most flexibility. Never-the-less, as shown by the poll results, a
single-topology mode successfully, usually because some device does number of operators have used single-topology mode successfully.
not support multi-topology mode.
2.4.3. RIP 2.4.3. RIP
A protocol option described in the table in this section is RIP A protocol option not described in the table above is RIPng
[RFC2080]. RIP is a distance vector protocol with limitations in [RFC2080]. RIPng is a distance vector protocol with limitations in
larger networks. However there is prevalent use case in large larger networks. However there is prevalent use case in large
operator networks where RIP is used for edge facing core interfaces operator networks where RIP is used for edge facing core interfaces
to manage high count aggregation of dynamic routing endpoints. to manage high count aggregation of dynamic routing endpoints.
Although not a mainline option for the network core as a whole, it is Although not a mainline option for the network core as a whole, it is
commonly used in IPv4, and potentially in IPv6 for a common set of commonly used in IPv4, and potentially in IPv6 for a common set of
links/functions. links/functions.
2.5. BGP 2.5. BGP
2.5.1. Which Transport for Which Routes? 2.5.1. Which Transport for Which Routes?
skipping to change at page 18, line 28 skipping to change at page 20, line 17
[I-D.ietf-idr-bgp-multisession] [I-D.ietf-idr-bgp-multisession]
Scudder, J., Appanna, C., and I. Varlashkin, "Multisession Scudder, J., Appanna, C., and I. Varlashkin, "Multisession
BGP", draft-ietf-idr-bgp-multisession-07 (work in BGP", draft-ietf-idr-bgp-multisession-07 (work in
progress), September 2012. progress), September 2012.
[I-D.ietf-idr-dynamic-cap] [I-D.ietf-idr-dynamic-cap]
Ramachandra, S. and E. Chen, "Dynamic Capability for BGP- Ramachandra, S. and E. Chen, "Dynamic Capability for BGP-
4", draft-ietf-idr-dynamic-cap-14 (work in progress), 4", draft-ietf-idr-dynamic-cap-14 (work in progress),
December 2011. December 2011.
[I-D.ietf-v6ops-host-addr-availability]
Colitti, L., Cerf, V., Cheshire, S., and D. Schinazi,
"Host address availability recommendations", draft-ietf-
v6ops-host-addr-availability-01 (work in progress),
September 2015.
[I-D.ietf-v6ops-ula-usage-recommendations] [I-D.ietf-v6ops-ula-usage-recommendations]
Liu, B. and S. Jiang, "Considerations For Using Unique Liu, B. and S. Jiang, "Considerations For Using Unique
Local Addresses", draft-ietf-v6ops-ula-usage- Local Addresses", draft-ietf-v6ops-ula-usage-
recommendations-05 (work in progress), May 2015. recommendations-05 (work in progress), May 2015.
[ISO10589] [ISO10589]
International Standards Organization, "Intermediate system International Standards Organization, "Intermediate system
to Intermediate system intra-domain routeing information to Intermediate system intra-domain routeing information
exchange protocol for use in conjunction with the protocol exchange protocol for use in conjunction with the protocol
for providing the connectionless-mode Network Service (ISO for providing the connectionless-mode Network Service (ISO
8473)", International Standard 10589:2002, Nov 2002. 8473)", International Standard 10589:2002, Nov 2002.
[RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.,
and E. Lear, "Address Allocation for Private Internets",
BCP 5, RFC 1918, DOI 10.17487/RFC1918, February 1996,
<http://www.rfc-editor.org/info/rfc1918>.
[RFC2080] Malkin, G. and R. Minnear, "RIPng for IPv6", RFC 2080, [RFC2080] Malkin, G. and R. Minnear, "RIPng for IPv6", RFC 2080,
January 1997. DOI 10.17487/RFC2080, January 1997,
<http://www.rfc-editor.org/info/rfc2080>.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998. [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,
DOI 10.17487/RFC2328, April 1998,
<http://www.rfc-editor.org/info/rfc2328>.
[RFC2545] Marques, P. and F. Dupont, "Use of BGP-4 Multiprotocol [RFC2545] Marques, P. and F. Dupont, "Use of BGP-4 Multiprotocol
Extensions for IPv6 Inter-Domain Routing", RFC 2545, March Extensions for IPv6 Inter-Domain Routing", RFC 2545,
1999. DOI 10.17487/RFC2545, March 1999,
<http://www.rfc-editor.org/info/rfc2545>.
[RFC3107] Rekhter, Y. and E. Rosen, "Carrying Label Information in [RFC3107] Rekhter, Y. and E. Rosen, "Carrying Label Information in
BGP-4", RFC 3107, May 2001. BGP-4", RFC 3107, DOI 10.17487/RFC3107, May 2001,
<http://www.rfc-editor.org/info/rfc3107>.
[RFC4193] 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, DOI 10.17487/RFC4193, October 2005,
<http://www.rfc-editor.org/info/rfc4193>.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <http://www.rfc-editor.org/info/rfc4291>.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, February 2006. Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
2006, <http://www.rfc-editor.org/info/rfc4364>.
[RFC4472] Durand, A., Ihren, J., and P. Savola, "Operational [RFC4472] Durand, A., Ihren, J., and P. Savola, "Operational
Considerations and Issues with IPv6 DNS", RFC 4472, April Considerations and Issues with IPv6 DNS", RFC 4472,
2006. DOI 10.17487/RFC4472, April 2006,
<http://www.rfc-editor.org/info/rfc4472>.
[RFC4552] Gupta, M. and N. Melam, "Authentication/Confidentiality [RFC4552] Gupta, M. and N. Melam, "Authentication/Confidentiality
for OSPFv3", RFC 4552, June 2006. for OSPFv3", RFC 4552, DOI 10.17487/RFC4552, June 2006,
<http://www.rfc-editor.org/info/rfc4552>.
[RFC4852] Bound, J., Pouffary, Y., Klynsma, S., Chown, T., and D. [RFC4852] Bound, J., Pouffary, Y., Klynsma, S., Chown, T., and D.
Green, "IPv6 Enterprise Network Analysis - IP Layer 3 Green, "IPv6 Enterprise Network Analysis - IP Layer 3
Focus", RFC 4852, April 2007. Focus", RFC 4852, DOI 10.17487/RFC4852, April 2007,
<http://www.rfc-editor.org/info/rfc4852>.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
September 2007. DOI 10.17487/RFC4861, September 2007,
<http://www.rfc-editor.org/info/rfc4861>.
[RFC4942] Davies, E., Krishnan, S., and P. Savola, "IPv6 Transition/ [RFC4942] Davies, E., Krishnan, S., and P. Savola, "IPv6 Transition/
Co-existence Security Considerations", RFC 4942, September Co-existence Security Considerations", RFC 4942,
2007. DOI 10.17487/RFC4942, September 2007,
<http://www.rfc-editor.org/info/rfc4942>.
[RFC5082] Gill, V., Heasley, J., Meyer, D., Savola, P., and C. [RFC5082] Gill, V., Heasley, J., Meyer, D., Savola, P., Ed., and C.
Pignataro, "The Generalized TTL Security Mechanism Pignataro, "The Generalized TTL Security Mechanism
(GTSM)", RFC 5082, October 2007. (GTSM)", RFC 5082, DOI 10.17487/RFC5082, October 2007,
<http://www.rfc-editor.org/info/rfc5082>.
[RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
Topology (MT) Routing in Intermediate System to Topology (MT) Routing in Intermediate System to
Intermediate Systems (IS-ISs)", RFC 5120, February 2008. Intermediate Systems (IS-ISs)", RFC 5120,
DOI 10.17487/RFC5120, February 2008,
<http://www.rfc-editor.org/info/rfc5120>.
[RFC5220] Matsumoto, A., Fujisaki, T., Hiromi, R., and K. Kanayama,
"Problem Statement for Default Address Selection in Multi-
Prefix Environments: Operational Issues of RFC 3484
Default Rules", RFC 5220, DOI 10.17487/RFC5220, July 2008,
<http://www.rfc-editor.org/info/rfc5220>.
[RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic [RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic
Authentication", RFC 5304, October 2008. Authentication", RFC 5304, DOI 10.17487/RFC5304, October
2008, <http://www.rfc-editor.org/info/rfc5304>.
[RFC5308] Hopps, C., "Routing IPv6 with IS-IS", RFC 5308, October [RFC5308] Hopps, C., "Routing IPv6 with IS-IS", RFC 5308,
2008. DOI 10.17487/RFC5308, October 2008,
<http://www.rfc-editor.org/info/rfc5308>.
[RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, July 2008. for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,
<http://www.rfc-editor.org/info/rfc5340>.
[RFC5375] Van de Velde, G., Popoviciu, C., Chown, T., Bonness, O., [RFC5375] Van de Velde, G., Popoviciu, C., Chown, T., Bonness, O.,
and C. Hahn, "IPv6 Unicast Address Assignment and C. Hahn, "IPv6 Unicast Address Assignment
Considerations", RFC 5375, December 2008. Considerations", RFC 5375, DOI 10.17487/RFC5375, December
2008, <http://www.rfc-editor.org/info/rfc5375>.
[RFC5838] Lindem, A., Mirtorabi, S., Roy, A., Barnes, M., and R. [RFC5838] Lindem, A., Ed., Mirtorabi, S., Roy, A., Barnes, M., and
Aggarwal, "Support of Address Families in OSPFv3", RFC R. Aggarwal, "Support of Address Families in OSPFv3",
5838, April 2010. RFC 5838, DOI 10.17487/RFC5838, April 2010,
<http://www.rfc-editor.org/info/rfc5838>.
[RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP [RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP
Authentication Option", RFC 5925, June 2010. Authentication Option", RFC 5925, DOI 10.17487/RFC5925,
June 2010, <http://www.rfc-editor.org/info/rfc5925>.
[RFC5963] Gagliano, R., "IPv6 Deployment in Internet Exchange Points [RFC5963] Gagliano, R., "IPv6 Deployment in Internet Exchange Points
(IXPs)", RFC 5963, August 2010. (IXPs)", RFC 5963, DOI 10.17487/RFC5963, August 2010,
<http://www.rfc-editor.org/info/rfc5963>.
[RFC6180] Arkko, J. and F. Baker, "Guidelines for Using IPv6 [RFC6180] Arkko, J. and F. Baker, "Guidelines for Using IPv6
Transition Mechanisms during IPv6 Deployment", RFC 6180, Transition Mechanisms during IPv6 Deployment", RFC 6180,
May 2011. DOI 10.17487/RFC6180, May 2011,
<http://www.rfc-editor.org/info/rfc6180>.
[RFC6296] Wasserman, M. and F. Baker, "IPv6-to-IPv6 Network Prefix [RFC6296] Wasserman, M. and F. Baker, "IPv6-to-IPv6 Network Prefix
Translation", RFC 6296, June 2011. Translation", RFC 6296, DOI 10.17487/RFC6296, June 2011,
<http://www.rfc-editor.org/info/rfc6296>.
[RFC6342] Koodli, R., "Mobile Networks Considerations for IPv6 [RFC6342] Koodli, R., "Mobile Networks Considerations for IPv6
Deployment", RFC 6342, August 2011. Deployment", RFC 6342, DOI 10.17487/RFC6342, August 2011,
<http://www.rfc-editor.org/info/rfc6342>.
[RFC6752] Kirkham, A., "Issues with Private IP Addressing in the [RFC6752] Kirkham, A., "Issues with Private IP Addressing in the
Internet", RFC 6752, September 2012. Internet", RFC 6752, DOI 10.17487/RFC6752, September 2012,
<http://www.rfc-editor.org/info/rfc6752>.
[RFC6782] Kuarsingh, V. and L. Howard, "Wireline Incremental IPv6", [RFC6782] Kuarsingh, V., Ed. and L. Howard, "Wireline Incremental
RFC 6782, November 2012. IPv6", RFC 6782, DOI 10.17487/RFC6782, November 2012,
<http://www.rfc-editor.org/info/rfc6782>.
[RFC6879] Jiang, S., Liu, B., and B. Carpenter, "IPv6 Enterprise
Network Renumbering Scenarios, Considerations, and
Methods", RFC 6879, DOI 10.17487/RFC6879, February 2013,
<http://www.rfc-editor.org/info/rfc6879>.
[RFC6883] Carpenter, B. and S. Jiang, "IPv6 Guidance for Internet [RFC6883] Carpenter, B. and S. Jiang, "IPv6 Guidance for Internet
Content Providers and Application Service Providers", RFC Content Providers and Application Service Providers",
6883, March 2013. RFC 6883, DOI 10.17487/RFC6883, March 2013,
<http://www.rfc-editor.org/info/rfc6883>.
[RFC7010] Liu, B., Jiang, S., Carpenter, B., Venaas, S., and W.
George, "IPv6 Site Renumbering Gap Analysis", RFC 7010,
DOI 10.17487/RFC7010, September 2013,
<http://www.rfc-editor.org/info/rfc7010>.
[RFC7217] Gont, F., "A Method for Generating Semantically Opaque [RFC7217] Gont, F., "A Method for Generating Semantically Opaque
Interface Identifiers with IPv6 Stateless Address Interface Identifiers with IPv6 Stateless Address
Autoconfiguration (SLAAC)", RFC 7217, April 2014. Autoconfiguration (SLAAC)", RFC 7217,
DOI 10.17487/RFC7217, April 2014,
<http://www.rfc-editor.org/info/rfc7217>.
[RFC7381] Chittimaneni, K., Chown, T., Howard, L., Kuarsingh, V., [RFC7381] Chittimaneni, K., Chown, T., Howard, L., Kuarsingh, V.,
Pouffary, Y., and E. Vyncke, "Enterprise IPv6 Deployment Pouffary, Y., and E. Vyncke, "Enterprise IPv6 Deployment
Guidelines", RFC 7381, October 2014. Guidelines", RFC 7381, DOI 10.17487/RFC7381, October 2014,
<http://www.rfc-editor.org/info/rfc7381>.
[RFC7404] Behringer, M. and E. Vyncke, "Using Only Link-Local [RFC7404] Behringer, M. and E. Vyncke, "Using Only Link-Local
Addressing inside an IPv6 Network", RFC 7404, November Addressing inside an IPv6 Network", RFC 7404,
2014. DOI 10.17487/RFC7404, November 2014,
<http://www.rfc-editor.org/info/rfc7404>.
[v6-addressing-plan] [v6-addressing-plan]
SurfNet, "Preparing an IPv6 Address Plan", 2013, SurfNet, "Preparing an IPv6 Address Plan", 2013,
<http://www.ripe.net/lir-services/training/material/ <http://www.ripe.net/lir-services/training/material/
IPv6-for-LIRs-Training-Course/ IPv6-for-LIRs-Training-Course/
Preparing-an-IPv6-Addressing-Plan.pdf>. Preparing-an-IPv6-Addressing-Plan.pdf>.
Authors' Addresses Authors' Addresses
Philip Matthews Philip Matthews
Alcatel-Lucent Alcatel-Lucent
600 March Road 600 March Road
Ottawa, Ontario K2K 2E6 Ottawa, Ontario K2K 2E6
Canada Canada
Phone: +1 613-784-3139 Phone: +1 613-784-3139
Email: philip_matthews@magma.ca Email: philip_matthews@magma.ca
Victor Kuarsingh Victor Kuarsingh
Dyn Cisco
150 Dow Street 88 Queens Quay
Manchester, NH 03101 Toronto, ON M5J0B8
USA Canada
Email: victor@jvknet.com Email: victor@jvknet.com
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