draft-ooms-v6ops-bgp-tunnel-07.txt   rfc4798.txt 
Internet Engineering Task Force J. De Clercq Network Working Group J. De Clercq
Internet-Draft Alcatel-Lucent Request for Comments: 4798 Alcatel-Lucent
Intended status: Standards Track D. Ooms Category: Standards Track D. Ooms
Expires: June 15, 2007 OneSparrow OneSparrow
S. Prevost S. Prevost
BTexact Technologies BT
F. Le Faucheur F. Le Faucheur
Cisco Cisco
December 12, 2006 February 2007
Connecting IPv6 Islands over IPv4 MPLS using IPv6 Provider Edge Routers
(6PE)
draft-ooms-v6ops-bgp-tunnel-07.txt
Status of this Memo
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http://www.ietf.org/ietf/1id-abstracts.txt. IPv6 Provider Edge Routers (6PE)
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This Internet-Draft will expire on June 15, 2007. This document specifies an Internet standards track protocol for the
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and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice Copyright Notice
Copyright (C) The IETF Trust (2006). Copyright (C) The IETF Trust (2007).
Abstract Abstract
This document explains how to interconnect IPv6 islands over a Multi- This document explains how to interconnect IPv6 islands over a
Protocol Label Switching (MPLS)-enabled IPv4 cloud. This approach Multiprotocol Label Switching (MPLS)-enabled IPv4 cloud. This
relies on IPv6 Provider Edge routers (6PE) which are Dual Stack in approach relies on IPv6 Provider Edge routers (6PE), which are Dual
order to connect to IPv6 islands and to the MPLS core which is only Stack in order to connect to IPv6 islands and to the MPLS core, which
required to run IPv4 MPLS. The 6PE routers exchange the IPv6 is only required to run IPv4 MPLS. The 6PE routers exchange the IPv6
reachability information transparently over the core using the Multi- reachability information transparently over the core using the
Protocol Border Gateway Protocol (MP-BGP) over IPv4. In doing so, Multiprotocol Border Gateway Protocol (MP-BGP) over IPv4. In doing
the BGP Next Hop field is used to convey the IPv4 address of the 6PE so, the BGP Next Hop field is used to convey the IPv4 address of the
router so that dynamically established IPv4-signaled MPLS Label 6PE router so that dynamically established IPv4-signaled MPLS Label
Switched Paths (LSPs) can be used without explicit tunnel Switched Paths (LSPs) can be used without explicit tunnel
configuration. configuration.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction ....................................................2
2. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 5 1.1. Requirements Language ......................................4
3. Transport over IPv4-signaled LSPs and IPv6 label binding . . . 6 2. Protocol Overview ...............................................4
4. Crossing Multiple IPv4 Autonomous Systems . . . . . . . . . . 8 3. Transport over IPv4-signaled LSPs and IPv6 Label Binding ........5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 10 4. Crossing Multiple IPv4 Autonomous Systems .......................7
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 5. Security Considerations ........................................10
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11 6. Acknowledgements ...............................................10
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11 7. References .....................................................11
8.1. Normative References . . . . . . . . . . . . . . . . . . . 11 7.1. Normative References ......................................11
8.2. Informative References . . . . . . . . . . . . . . . . . . 12 7.2. Informative References ....................................11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
Intellectual Property and Copyright Statements . . . . . . . . . . 14
1. Introduction 1. Introduction
There are several approaches for providing IPv6 connectivity over an There are several approaches for providing IPv6 connectivity over an
MPLS core network [RFC4029] including (i) requiring that MPLS MPLS core network [RFC4029] including (i) requiring that MPLS
networks support setting up IPv6-signaled Label Switched Paths (LSPs) networks support setting up IPv6-signaled Label Switched Paths (LSPs)
and establish IPv6 connectivity by using those LSPs, (ii) use and establish IPv6 connectivity by using those LSPs, (ii) use
configured tunneling over IPv4-signaled LSPs, or (iii) use the IPv6 configured tunneling over IPv4-signaled LSPs, or (iii) use the IPv6
Provider Edge (6PE) approach defined in this document. Provider Edge (6PE) approach defined in this document.
The 6PE approach is required as an alternative to the use of standard The 6PE approach is required as an alternative to the use of standard
tunnels, because it provides a solution for an MPLS environment where tunnels. It provides a solution for an MPLS environment where all
all tunnels are established dynamically, thereby addressing tunnels are established dynamically, thereby addressing environments
environments where the effort to configure and maintain explicitly where the effort to configure and maintain explicitly configured
configured tunnels is not acceptable. tunnels is not acceptable.
This document specifies operations of the 6PE approach for This document specifies operations of the 6PE approach for
interconnection of IPv6 islands over an IPv4 MPLS cloud. The interconnection of IPv6 islands over an IPv4 MPLS cloud. The
approach requires the edge routers that are connected to IPv6 islands approach requires that the edge routers connected to IPv6 islands be
to be Dual Stack Multi-Protocol-BGP-speaking routers [RFC2858bis] Dual Stack Multiprotocol-BGP-speaking routers [RFC4760], while the
while the core routers are only required to run IPv4 MPLS. The core routers are only required to run IPv4 MPLS. The approach uses
approach uses MP-BGP over IPv4, relies on identification of the 6PE MP-BGP over IPv4, relies on identification of the 6PE routers by
routers by their IPv4 address and uses IPv4-signaled MPLS LSPs that their IPv4 address, and uses IPv4-signaled MPLS LSPs that do not
don't require any explicit tunnel configuration. require any explicit tunnel configuration.
Throughout this document, the terminology of [RFC2460] and [RFC4364] Throughout this document, the terminology of [RFC2460] and [RFC4364]
is used. is used.
In this document an 'IPv6 island' is a network running native IPv6 as In this document an 'IPv6 island' is a network running native IPv6 as
per [RFC2460]. A typical example of an IPv6 island would be a per [RFC2460]. A typical example of an IPv6 island would be a
customer's IPv6 site connected via its IPv6 Customer Edge (CE) router customer's IPv6 site connected via its IPv6 Customer Edge (CE) router
to one (or more) Dual Stack Provider Edge router(s) of a Service to one (or more) Dual Stack Provider Edge router(s) of a Service
Provider. These IPv6 Provider Edge routers (6PE) are connected to an Provider. These IPv6 Provider Edge routers (6PE) are connected to an
IPv4 MPLS core network. IPv4 MPLS core network.
skipping to change at page 4, line 4 skipping to change at page 3, line 17
+--------+ | | | +--------+ +--------+ | | | +--------+
6PE-+ IPv4 MPLS core +-6PE--CE site C | 6PE-+ IPv4 MPLS core +-6PE--CE site C |
+--------+ | | | +--------+ +--------+ | | | +--------+
|site B CE---+ +-----------------+ |site B CE---+ +-----------------+
+--------+ +--------+
IPv6 islands IPv4 cloud IPv6 island IPv6 islands IPv4 cloud IPv6 island
<-------------><---------------------><--------------> <-------------><---------------------><-------------->
Figure 1 Figure 1
The interconnection method described in this document typically The interconnection method described in this document typically
applies to an Internet Service Provider (ISP) that has an IPv4 MPLS applies to an Internet Service Provider (ISP) that has an IPv4 MPLS
network and is familiar with BGP (possibly already offering BGP/MPLS network, that is familiar with BGP (possibly already offering
VPN services) and that wants to offer IPv6 services to some of its BGP/MPLS VPN services), and that wants to offer IPv6 services to some
customers. However, the ISP may not (yet) want to upgrade its of its customers. However, the ISP may not (yet) want to upgrade its
network core to IPv6 nor use only IPv6-over-IPv4 tunneling. With the network core to IPv6, nor use only IPv6-over-IPv4 tunneling. With
6PE approach described here, the provider only has to upgrade some the 6PE approach described here, the provider only has to upgrade
Provider Edge (PE) routers to Dual Stack operations so they behave as some Provider Edge (PE) routers to Dual Stack operations so that they
6PE routers (and route reflectors if those are used for exchange of behave as 6PE routers (and route reflectors if those are used for the
IPv6 reachability among 6PE routers) while leaving the IPv4 MPLS core exchange of IPv6 reachability among 6PE routers) while leaving the
routers untouched. These 6PE routers provide connectivity to IPv6 IPv4 MPLS core routers untouched. These 6PE routers provide
islands. They may also provide other services simultaneously (IPv4 connectivity to IPv6 islands. They may also provide other services
connectivity, IPv4 L3VPN services, L2VPN services, etc.). Also with simultaneously (IPv4 connectivity, IPv4 L3VPN services, L2VPN
the 6PE approach, no tunnels need to be explicitly configured, and no services, etc.). Also with the 6PE approach, no tunnels need to be
IPv4 headers need to be inserted in front of the IPv6 packets between explicitly configured, and no IPv4 headers need to be inserted in
the customer and provider edge. front of the IPv6 packets between the customer and provider edge.
The ISP obtains IPv6 connectivity to its peers and upstreams using The ISP obtains IPv6 connectivity to its peers and upstreams using
means outside of the scope of this memo, and its 6PE routers means outside of the scope of this document, and its 6PE routers
readvertise it over the IPv4 MPLS core with MP-BGP. readvertise it over the IPv4 MPLS core with MP-BGP.
The interface between the edge router of the IPv6 island (Customer The interface between the edge router of the IPv6 island (Customer
Edge (CE) router) and the 6PE router is a native IPv6 interface which Edge (CE) router) and the 6PE router is a native IPv6 interface which
can be physical or logical. A routing protocol (IGP or EGP) may run can be physical or logical. A routing protocol (IGP or EGP) may run
between the CE router and the 6PE router for the distribution of IPv6 between the CE router and the 6PE router for the distribution of IPv6
reachability information. Alternatively, static routes and/or a reachability information. Alternatively, static routes and/or a
default route may be used on the 6PE router and the CE router to default route may be used on the 6PE router and the CE router to
control reachability. An IPv6 island may connect to the provider control reachability. An IPv6 island may connect to the provider
network over more than one interface. network over more than one interface.
skipping to change at page 4, line 46 skipping to change at page 4, line 12
additionally require an IPv6 service, as well as for customers that additionally require an IPv6 service, as well as for customers that
require only IPv6 connectivity. require only IPv6 connectivity.
The scenario is also described in [RFC4029]. The scenario is also described in [RFC4029].
Note that the 6PE approach specified in this document provides global Note that the 6PE approach specified in this document provides global
IPv6 reachability. Support of IPv6 VPNs is not within the scope of IPv6 reachability. Support of IPv6 VPNs is not within the scope of
this document and is addressed in [RFC4659]. this document and is addressed in [RFC4659].
Deployment of the 6PE approach over an existing IPv4 MPLS cloud does Deployment of the 6PE approach over an existing IPv4 MPLS cloud does
not require introduction of new mechanisms in the core (other than not require an introduction of new mechanisms in the core (other than
potentially those described at the end of section 3 for dealing with potentially those described at the end of Section 3 for dealing with
dynamic MTU discovery). Configuration and operations of the 6PE dynamic MTU discovery). Configuration and operations of the 6PE
approach has a lot of similarities with the configuration and approach have a lot of similarities with the configuration and
operations of an IPv4 VPN service ([RFC4364]) or IPv6 VPN service operations of an IPv4 VPN service ([RFC4364]) or IPv6 VPN service
([RFC4659]) over an IPv4 MPLS core since they all use MP-BGP to ([RFC4659]) over an IPv4 MPLS core because they all use MP-BGP to
distribute non-IPv4 reachability information for transport over an distribute non-IPv4 reachability information for transport over an
IPv4 MPLS Core. However, the configuration and operations of the 6PE IPv4 MPLS Core. However, the configuration and operations of the 6PE
approach is somewhat simpler, since it does not involve all the VPN approach is somewhat simpler, since it does not involve all the VPN
concepts such as VRFs. concepts such as Virtual Routing and Forwarding (VRFs) tables.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
2. Protocol Overview 2. Protocol Overview
Each IPv6 site is connected to at least one Provider Edge router that Each IPv6 site is connected to at least one Provider Edge router that
is located on the border of the IPv4 MPLS cloud. We call such a is located on the border of the IPv4 MPLS cloud. We call such a
router a 6PE router. The 6PE router MUST be dual stack IPv4 and router a 6PE router. The 6PE router MUST be dual stack IPv4 and
IPv6. The 6PE router MUST be configured with at least one IPv4 IPv6. The 6PE router MUST be configured with at least one IPv4
address on the IPv4 side and at least one IPv6 address on the IPv6 address on the IPv4 side and at least one IPv6 address on the IPv6
side. The configured IPv4 address needs to be routable in the IPv4 side. The configured IPv4 address needs to be routable in the IPv4
cloud, and there needs to be a label bound via an IPv4 label cloud, and there needs to be a label bound via an IPv4 label
distribution protocol to this IPv4 route. distribution protocol to this IPv4 route.
As a result of this, every considered 6PE router knows which MPLS As a result of this, every considered 6PE router knows which MPLS
label to use to send packets to any other 6PE router. Note that an label to use to send packets to any other 6PE router. Note that an
MPLS network offering BGP/MPLS IP VPN services already fulfills these MPLS network offering BGP/MPLS IP VPN services already fulfills these
requirements. requirements.
No extra routes need to be injected in the IPv4 cloud. No extra routes need to be injected in the IPv4 cloud.
We call the 6PE router receiving IPv6 packets from an IPv6 site an We call the 6PE router receiving IPv6 packets from an IPv6 site an
Ingress 6PE router (relative to these IPv6 packets). We call a 6PE ingress 6PE router (relative to these IPv6 packets). We call a 6PE
router forwarding IPv6 packets to an IPv6 site an Egress 6PE router router forwarding IPv6 packets to an IPv6 site an egress 6PE router
(relative to these IPv6 packets). (relative to these IPv6 packets).
Interconnecting IPv6 islands over an IPv4 MPLS cloud takes place Interconnecting IPv6 islands over an IPv4 MPLS cloud takes place
through the following steps: through the following steps:
1. Exchange IPv6 reachability information among 6PE routers with MP- 1. Exchange IPv6 reachability information among 6PE routers with MP-
BGP [RFC2545]: BGP [RFC2545]:
The 6PE routers MUST exchange the IPv6 prefixes over MP-BGP The 6PE routers MUST exchange the IPv6 prefixes over MP-BGP
sessions as per [RFC2545] running over IPv4. The MP-BGP Address sessions as per [RFC2545] running over IPv4. The MP-BGP Address
Family Identifier (AFI) used MUST be IPv6 (value 2). In doing Family Identifier (AFI) used MUST be IPv6 (value 2). In doing so,
so, the 6PE routers convey their IPv4 address as the BGP Next Hop the 6PE routers convey their IPv4 address as the BGP Next Hop for
for the advertised IPv6 prefixes. The IPv4 address of the egress the advertised IPv6 prefixes. The IPv4 address of the egress 6PE
6PE router MUST be encoded as an IPv4-mapped IPv6 address in the router MUST be encoded as an IPv4-mapped IPv6 address in the BGP
BGP Next Hop field. This encoding is consistent with the Next Hop field. This encoding is consistent with the definition
definition of an IPv4-mapped IPv6 address in [RFC3513] as an of an IPv4-mapped IPv6 address in [RFC4291] as an "address type
"address type used to represent the address of IPv4 nodes as IPv6 used to represent the address of IPv4 nodes as IPv6 addresses".
addresses". In addition, the 6PE MUST bind a label to the IPv6 In addition, the 6PE MUST bind a label to the IPv6 prefix as per
prefix as per [RFC3107]. The Subsequence Address Family [RFC3107]. The Subsequence Address Family Identifier (SAFI) used
Identifier (SAFI) used in MP-BGP MUST be the "label" SAFI (value in MP-BGP MUST be the "label" SAFI (value 4) as defined in
4) as defined in [RFC3107]. Rationale for this and label [RFC3107]. Rationale for this and label allocation policies are
allocation policies are discussed in section 3. discussed in Section 3.
2. Transport IPv6 packets from Ingress 6PE router to Egress 6PE 2. Transport IPv6 packets from the ingress 6PE router to the egress
router over IPv4-signaled LSPs: 6PE router over IPv4-signaled LSPs:
The Ingress 6PE router MUST forward IPv6 data over the IPv4- The ingress 6PE router MUST forward IPv6 data over the IPv4-
signaled LSP towards the Egress 6PE router identified by the IPv4 signaled LSP towards the egress 6PE router identified by the IPv4
address advertised in the IPv4-mapped IPv6 address of the BGP address advertised in the IPv4-mapped IPv6 address of the BGP Next
Next Hop for the corresponding IPv6 prefix. Hop for the corresponding IPv6 prefix.
As required by the BGP specification [RFC4271], PE routers form a As required by the BGP specification [RFC4271], PE routers form a
full peering mesh unless Route Reflectors are used. full peering mesh unless Route Reflectors are used.
3. Transport over IPv4-signaled LSPs and IPv6 label binding 3. Transport over IPv4-signaled LSPs and IPv6 Label Binding
In this approach, the IPv4-mapped IPv6 addresses allow a 6PE router In this approach, the IPv4-mapped IPv6 addresses allow a 6PE router
that has to forward an IPv6 packet to automatically determine the that has to forward an IPv6 packet to automatically determine the
IPv4-signaled LSP to use for a particular IPv6 destination by looking IPv4-signaled LSP to use for a particular IPv6 destination by looking
at the MP-BGP routing information. at the MP-BGP routing information.
The IPv4-signaled LSPs can be established using any existing The IPv4-signaled LSPs can be established using any existing
technique for label setup [RFC3031] (LDP, RSVP-TE, ...). technique for label setup [RFC3031] (LDP, RSVP-TE, etc.).
To ensure interoperability among systems that implement the 6PE To ensure interoperability among systems that implement the 6PE
approach described in this document, all such systems MUST support approach described in this document, all such systems MUST support
tunneling using IPv4-signaled MPLS LSPs established by LDP [RFC3036]. tunneling using IPv4-signaled MPLS LSPs established by LDP [RFC3036].
When tunneling IPv6 packets over the IPv4 MPLS backbone, rather than When tunneling IPv6 packets over the IPv4 MPLS backbone, rather than
successively prepend an IPv4 header and then perform label imposition successively prepend an IPv4 header and then perform label imposition
based on the IPv4 header, the ingress 6PE Router MUST directly based on the IPv4 header, the ingress 6PE Router MUST directly
perform label imposition of the IPv6 header without prepending any perform label imposition of the IPv6 header without prepending any
IPv4 header. The (outer) label imposed MUST correspond to the IPv4- IPv4 header. The (outer) label imposed MUST correspond to the IPv4-
signaled LSP starting on the ingress 6PE Router and ending on the signaled LSP starting on the ingress 6PE Router and ending on the
egress 6PE Router. egress 6PE Router.
While this approach could theoretically operate in some situations While this approach could theoretically operate in some situations
using a single level of labels, there are significant advantages in using a single level of labels, there are significant advantages in
using a second level of labels which are bound to IPv6 prefixes via using a second level of labels that are bound to IPv6 prefixes via
MP-BGP advertisements in accordance with [RFC3107]. MP-BGP advertisements in accordance with [RFC3107].
For instance, use of a second level label allows Penultimate Hop For instance, the use of a second level label allows Penultimate Hop
Popping (PHP) on the IPv4 Label Switch Router (LSR) upstream of the Popping (PHP) on the IPv4 Label Switch Router (LSR) upstream of the
egress 6PE router without any IPv6 capabilities/upgrade on the egress 6PE router, without any IPv6 capabilities/upgrades on the
penultimate router; this is because it still transmits MPLS packets penultimate router; this is because it still transmits MPLS packets
even after the PHP (instead of having to transmit IPv6 packets and even after the PHP (instead of having to transmit IPv6 packets and
encapsulate them appropriately). encapsulate them appropriately).
Also, an existing IPv4-signaled LSP which is using "IPv4 Explicit Also, an existing IPv4-signaled LSP that is using "IPv4 Explicit NULL
NULL label" over the last hop (say because that LSP is already used label" over the last hop (e.g., because that LSP is already being
to transport IPv4 traffic with the Pipe Diff-Serv Tunneling Model as used to transport IPv4 traffic with the Pipe Diff-Serv Tunneling
defined in [RFC3270]) could not be used to carry IPv6 with a single Model as defined in [RFC3270]) could not be used to carry IPv6 with a
label since the "IPv4 Explicit NULL label" can not be used to carry single label since the "IPv4 Explicit NULL label" cannot be used to
native IPv6 traffic (see [RFC3032]), while it could be used to carry carry native IPv6 traffic (see [RFC3032]), while it could be used to
labeled IPv6 traffic (see [RFC4182]). carry labeled IPv6 traffic (see [RFC4182]).
This is why a second label MUST be used with the 6PE approach. This is why a second label MUST be used with the 6PE approach.
The label bound by MP-BGP to the IPv6 prefix indicates to the Egress The label bound by MP-BGP to the IPv6 prefix indicates to the egress
6PE Router that the packet is an IPv6 packet. This label advertised 6PE Router that the packet is an IPv6 packet. This label advertised
by the Egress 6PE Router with MP-BGP MAY be an arbitrary label value by the egress 6PE Router with MP-BGP MAY be an arbitrary label value,
which identifies an IPv6 routing context or outgoing interface to which identifies an IPv6 routing context or outgoing interface to
send the packet to, or MAY be the IPv6 Explicit Null Label. An send the packet to, or MAY be the IPv6 Explicit Null Label. An
Ingress 6PE Router MUST be able to accept any such advertised label. ingress 6PE Router MUST be able to accept any such advertised label.
[RFC2460] requires that every link in the IPv6 Internet have an MTU [RFC2460] requires that every link in the IPv6 Internet have an MTU
of 1280 octets or larger. Therefore, on MPLS links that are used for of 1280 octets or larger. Therefore, on MPLS links that are used for
transport of IPv6 as per the 6PE approach and that do not support transport of IPv6, as per the 6PE approach, and that do not support
link-specific fragmentation and reassembly, the MTU must be link-specific fragmentation and reassembly, the MTU must be
configured to at least 1280 octets plus the encapsulation overhead. configured to at least 1280 octets plus the encapsulation overhead.
Some IPv6 hosts might be sending packets larger than the MTU Some IPv6 hosts might be sending packets larger than the MTU
available in the IPv4 MPLS core and rely on Path MTU discovery to available in the IPv4 MPLS core and rely on Path MTU discovery to
learn about those links. To simplify MTU discovery operations, one learn about those links. To simplify MTU discovery operations, one
option is for the network administrator to engineer the MTU on the option is for the network administrator to engineer the MTU on the
core facing interfaces of the ingress 6PE, consistent with the core core facing interfaces of the ingress 6PE consistent with the core
MTU, so that ICMP 'Packet Too Big' messages can be sent back by the MTU. ICMP 'Packet Too Big' messages can then be sent back by the
ingress 6PE without the corresponding packets ever entering the MPLS ingress 6PE without the corresponding packets ever entering the MPLS
core. Otherwise, routers in the IPv4 MPLS network have the option to core. Otherwise, routers in the IPv4 MPLS network have the option to
generate an ICMP "Packet Too Big" message using mechanisms as generate an ICMP "Packet Too Big" message using mechanisms as
described in section 2.3.2 "Tunneling Private Addresses through a described in Section 2.3.2, "Tunneling Private Addresses through a
Public Backbone" of [RFC3032]. Public Backbone" of [RFC3032].
In that case, note that, should a core router with an outgoing link Note that in the above case, should a core router with an outgoing
with a MTU smaller than 1280 receive an encapsulated IPv6 packet link with an MTU smaller than 1280 receive an encapsulated IPv6
larger than 1280, then the mechanisms of [RFC3032] may result in the packet larger than 1280, then the mechanisms of [RFC3032] may result
"Packet Too Big" message never reaching the sender. This is because, in the "Packet Too Big" message never reaching the sender. This is
according to [RFC2463], the core router will build an ICMP "Packet because, according to [RFC4443], the core router will build an ICMP
Too Big" message filled with the invoking packet up to 1280 bytes and "Packet Too Big" message filled with the invoking packet up to 1280
when forwarding downstream towards the egress PE as per [RFC3032], bytes, and when forwarding downstream towards the egress PE as per
the MTU of the outgoing link will cause the packet to be dropped. [RFC3032], the MTU of the outgoing link will cause the packet to be
This may cause significant operational problems; the originator of dropped. This may cause significant operational problems; the
the packets will notice that his data is not getting through, without originator of the packets will notice that his data is not getting
knowing why and where they are discarded. This issue would only through, without knowing why and where they are discarded. This
occur if the above recommendation (to configure MTU on MPLS links of issue would only occur if the above recommendation (to configure MTU
at least 1280 octets plus encapsulation overhead) is not adhered to on MPLS links of at least 1280 octets plus encapsulation overhead) is
(perhaps by misconfiguration). not adhered to (perhaps by misconfiguration).
4. Crossing Multiple IPv4 Autonomous Systems 4. Crossing Multiple IPv4 Autonomous Systems
This section discusses the case where two IPv6 islands are connected This section discusses the case where two IPv6 islands are connected
to different Autonomous Systems. to different Autonomous Systems (ASes).
Like in the case of multi-AS backbone operations for IPv4 VPNs Like in the case of multi-AS backbone operations for IPv4 VPNs
described in section 10 of [RFC4364], three main approaches can be described in Section 10 of [RFC4364], three main approaches can be
distinguished: distinguished:
a. EBGP redistribution of IPv6 routes from AS to neighboring AS a. eBGP redistribution of IPv6 routes from AS to neighboring AS
This approach is the equivalent for exchange of IPv6 routes to This approach is the equivalent for exchange of IPv6 routes to
procedure (a) described in section 10 of [RFC4364] for the procedure (a) described in Section 10 of [RFC4364] for the
exchange of VPN-IPv4 routes. exchange of VPN-IPv4 routes.
In this approach, the 6PE routers use IBGP (according to In this approach, the 6PE routers use IBGP (according to [RFC2545]
[RFC2545] and [RFC3107] and as described in this document for the and [RFC3107] and as described in this document for the single-AS
single-AS situation) to redistribute labeled IPv6 routes either situation) to redistribute labeled IPv6 routes either to an
to an Autonomous System Border Router (ASBR) 6PE router, or to a Autonomous System Border Router (ASBR) 6PE router, or to a route
route reflector of which an ASBR 6PE router is a client. The reflector of which an ASBR 6PE router is a client. The ASBR then
ASBR then uses EBGP to redistribute the (non-labeled) IPv6 routes uses eBGP to redistribute the (non-labeled) IPv6 routes to an ASBR
to an ASBR in another AS, which in turn distributes them to the in another AS, which in turn distributes them to the 6PE routers
6PE routers in that AS as described earlier in this in that AS as described earlier in this specification, or perhaps
specification, or perhaps to another ASBR which in turn to another ASBR, which in turn distributes them etc.
distributes them etc.
There may be one, or multiple, ASBR interconnection(s) across any There may be one, or multiple, ASBR interconnection(s) across any
two ASes. IPv6 needs to be activated on the inter-ASBR links and two ASes. IPv6 needs to be activated on the inter-ASBR links and
each ASBR 6PE router has at least one IPv6 address on the each ASBR 6PE router has at least one IPv6 address on the
interface to that link. interface to that link.
No inter-AS LSPs are used. There is effectively a separate mesh No inter-AS LSPs are used. There is effectively a separate mesh
of LSPs across the 6PE routers within each AS. of LSPs across the 6PE routers within each AS.
In this approach, the ASBR exchanging IPv6 routes may peer over In this approach, the ASBR exchanging IPv6 routes may peer over
IPv6 or over IPv4. The exchange of IPv6 routes MUST be carried IPv6 or IPv4. The exchange of IPv6 routes MUST be carried out as
out as per [RFC2545]. per [RFC2545].
Note that the peering ASBR in the neighboring AS to which the Note that the peering ASBR in the neighboring AS to which the IPv6
IPv6 routes were distributed with EBGP, should in its turn routes were distributed with eBGP, should in its turn redistribute
redistribute these routes to the 6PEs in its AS using IBGP and these routes to the 6PEs in its AS using IBGP and encoding its own
encoding its own IPv4 address as the IPv4-mapped IPv6 BGP Next IPv4 address as the IPv4-mapped IPv6 BGP Next Hop.
Hop.
b. EBGP redistribution of labeled IPv6 routes from AS to neighboring b. eBGP redistribution of labeled IPv6 routes from AS to neighboring
AS AS
This approach is the equivalent for exchange of IPv6 routes to This approach is the equivalent for exchange of IPv6 routes to
procedure (b) described in section 10 of [RFC4364] for the procedure (b) described in Section 10 of [RFC4364] for the
exchange of VPN-IPv4 routes. exchange of VPN-IPv4 routes.
In this approach, the 6PE routers use IBGP (as described earlier In this approach, the 6PE routers use IBGP (as described earlier
in this document for the single-AS situation) to redistribute in this document for the single-AS situation) to redistribute
labeled IPv6 routes either to an Autonomous System Border Router labeled IPv6 routes either to an Autonomous System Border Router
(ASBR) 6PE router, or to a route reflector of which an ASBR 6PE (ASBR) 6PE router, or to a route reflector of which an ASBR 6PE
router is a client. The ASBR then uses EBGP to redistribute the router is a client. The ASBR then uses eBGP to redistribute the
labeled IPv6 routes to an ASBR in another AS, which in turn labeled IPv6 routes to an ASBR in another AS, which in turn
distributes them to the 6PE routers in that AS as described distributes them to the 6PE routers in that AS as described
earlier in this specification, or perhaps to another ASBR which earlier in this specification, or perhaps to another ASBR, which
in turn distributes them etc. in turn distributes them, etc.
There may be one, or multiple, ASBR interconnection(s) across any There may be one, or multiple, ASBR interconnection(s) across any
two ASes. IPv6 may or may not be activated on the inter-ASBR two ASes. IPv6 may or may not be activated on the inter-ASBR
links. links.
This approach requires that there be label switched paths This approach requires that there be label switched paths
established across ASes. Hence the corresponding considerations established across ASes. Hence the corresponding considerations
described for procedure (b) in section 10 of [RFC4364] apply described for procedure (b) in Section 10 of [RFC4364] apply
equally to this approach for IPv6. equally to this approach for IPv6.
In this approach, the ASBR exchanging IPv6 routes may peer over In this approach, the ASBR exchanging IPv6 routes may peer over
IPv4 or IPv6 (in which case, IPv6 obviously needs to be activated IPv4 or IPv6 (in which case IPv6 obviously needs to be activated
on the inter-ASBR link). When peering over IPv6, the exchange of on the inter-ASBR link). When peering over IPv6, the exchange of
labeled IPv6 routes MUST be carried out as per [RFC2545] and labeled IPv6 routes MUST be carried out as per [RFC2545] and
[RFC3107]. When peering over IPv4, the exchange of labeled IPv6 [RFC3107]. When peering over IPv4, the exchange of labeled IPv6
routes MUST be carried out as per [RFC2545] and [RFC3107] with routes MUST be carried out as per [RFC2545] and [RFC3107] with
encoding of the IPv4 address of the ASBR as an IPv4-mapped IPv6 encoding of the IPv4 address of the ASBR as an IPv4-mapped IPv6
address in the BGP Next Hop field. address in the BGP Next Hop field.
c. Multihop EBGP redistribution of labeled IPv6 routes between c. Multi-hop eBGP redistribution of labeled IPv6 routes between
source and destination ASes, with EBGP redistribution of labeled source and destination ASes, with eBGP redistribution of labeled
IPv4 routes from AS to neighboring AS. IPv4 routes from AS to neighboring AS.
This approach is the equivalent for exchange of IPv6 routes to This approach is the equivalent for exchange of IPv6 routes to
procedure (c) described in section 10 of [RFC4364] for exchange procedure (c) described in Section 10 of [RFC4364] for exchange of
of VPN- IPv4 routes. VPN-IPv4 routes.
In this approach, IPv6 routes are neither maintained nor In this approach, IPv6 routes are neither maintained nor
distributed by the ASBR routers. The ASBR routers need not be distributed by the ASBR routers. The ASBR routers need not be
dual stack and may be IPv4/MPLS-only routers. An ASBR needs to dual stack, but may be IPv4/MPLS-only routers. An ASBR needs to
maintain labeled IPv4 /32 routes to the 6PE routers within its maintain labeled IPv4 /32 routes to the 6PE routers within its AS.
AS. It uses EBGP to distribute these routes to other ASes. It uses eBGP to distribute these routes to other ASes. ASBRs in
ASBRs in any transit ASes will also have to use EBGP to pass any transit ASes will also have to use eBGP to pass along the
along the labeled IPv4 /32 routes. This results in the creation labeled IPv4 /32 routes. This results in the creation of an IPv4
of an IPv4 label switched path from the ingress 6PE router to the label switched path from the ingress 6PE router to the egress 6PE
egress 6PE router. Now 6PE routers in different ASes can router. Now 6PE routers in different ASes can establish multi-hop
establish multi-hop EBGP connections to each other over IPv4, and eBGP connections to each other over IPv4, and can exchange labeled
can exchange labeled IPv6 routes (with an IPv4-mapped IPv6 BGP IPv6 routes (with an IPv4-mapped IPv6 BGP Next Hop) over those
Next Hop) over those connections. connections.
IPv6 need not be activated on the inter-ASBR links. IPv6 need not be activated on the inter-ASBR links.
The considerations described for procedure (c) in section 10 of The considerations described for procedure (c) in Section 10 of
[RFC4364] with respect to possible use of multi-hop EBGP [RFC4364] with respect to possible use of multi-hop eBGP
connections via route-reflectors in different ASes, as well as connections via route-reflectors in different ASes, as well as
with respect to the use of a third label in case the IPv4 /32 with respect to the use of a third label in case the IPv4 /32
routes for the PE routers are NOT made known to the P routers, routes for the PE routers are NOT made known to the P routers,
apply equally to this approach for IPv6. apply equally to this approach for IPv6.
This approach requires that there be IPv4 label switched paths This approach requires that there be IPv4 label switched paths
established across the ASes leading form a packet's ingress 6PE established across the ASes leading from a packet's ingress 6PE
router to its egress 6PE router. Hence, the considerations router to its egress 6PE router. Hence the considerations
described for procedure (c) in section 10 of [RFC4364] with described for procedure (c) in Section 10 of [RFC4364], with
respect to LSPs spanning multiple ASes apply equally to this respect to LSPs spanning multiple ASes, apply equally to this
approach for IPv6. approach for IPv6.
Note also that the exchange of IPv6 routes can only start after Note also that the exchange of IPv6 routes can only start after
BGP has created IPv4 connectivity between the ASes. BGP has created IPv4 connectivity between the ASes.
5. Security Considerations 5. Security Considerations
The extensions defined in this document allow BGP to propagate The extensions defined in this document allow BGP to propagate
reachability information about IPv6 routes over an MPLS IPv4 core reachability information about IPv6 routes over an MPLS IPv4 core
network. As such, no new security issues are raised beyond those network. As such, no new security issues are raised beyond those
that already exist in BGP-4 and use of MP-BGP for IPv6. that already exist in BGP-4 and use of MP-BGP for IPv6.
The security features of BGP and corresponding security policy The security features of BGP and corresponding security policy
defined in the ISP domain are applicable. defined in the ISP domain are applicable.
For the inter-AS distribution of IPv6 routes according to case (a) of For the inter-AS distribution of IPv6 routes according to case (a) of
section 4 of this document, no new security issues are raised beyond Section 4 of this document, no new security issues are raised beyond
those that already exist in the use of EBGP for IPv6 [RFC2545]. those that already exist in the use of eBGP for IPv6 [RFC2545].
For the inter-AS distribution of IPv6 routes according to case (b) For the inter-AS distribution of IPv6 routes according to case (b)
and (c) of section 4 of this document, the procedures require that and (c) of Section 4 of this document, the procedures require that
there be label switched paths established across the AS boundaries. there be label switched paths established across the AS boundaries.
Hence the appropriate trust relationships must exist between and Hence the appropriate trust relationships must exist between and
among the set of ASes along the path. Care must be taken to avoid among the set of ASes along the path. Care must be taken to avoid
"label spoofing". To this end an ASBR 6PE SHOULD only accept labeled "label spoofing". To this end an ASBR 6PE SHOULD only accept labeled
packets from its peer ASBR 6PE if the topmost label is a label that packets from its peer ASBR 6PE if the topmost label is a label that
it has explicitly signaled to that peer ASBR 6PE. it has explicitly signaled to that peer ASBR 6PE.
Note that for the inter-AS distribution of IPv6 routes according to Note that for the inter-AS distribution of IPv6 routes, according to
case (c) of section 4 of this document, label spoofing may be more case (c) of Section 4 of this document, label spoofing may be more
difficult to prevent. Indeed, the MPLS label distributed with the difficult to prevent. Indeed, the MPLS label distributed with the
IPv6 routes via multi-hop EBGP is directly sent from the egress 6PE IPv6 routes via multi-hop eBGP is directly sent from the egress 6PE
to ingress 6PEs in an other AS (or through route reflectors). This to ingress 6PEs in an other AS (or through route reflectors). This
label is advertised transparently through the AS boundaries. When label is advertised transparently through the AS boundaries. When
the egress 6PE that sent the labeled IPv6 routes receives a data the egress 6PE that sent the labeled IPv6 routes receives a data
packet that has this particular label on top of its stack, it may not packet that has this particular label on top of its stack, it may not
be able to verify whether the label was pushed on the stack by an be able to verify whether the label was pushed on the stack by an
ingress 6PE that is allowed to do so. As such one AS may be ingress 6PE that is allowed to do so. As such, one AS may be
vulnerable to label spoofing in a different AS. The same issue vulnerable to label spoofing in a different AS. The same issue
equally applies to the option (c) of section 10 of [RFC4364]. Just equally applies to the option (c) of Section 10 of [RFC4364]. Just
like it is the case for [RFC4364], addressing this particular as it is the case for [RFC4364], addressing this particular security
security issue is for further study. issue is for further study.
6. IANA Considerations
This document has no actions for IANA.
7. Acknowledgements 6. Acknowledgements
We wish to thank Gerard Gastaud and Eric Levy-Abegnoli who We wish to thank Gerard Gastaud and Eric Levy-Abegnoli who
contributed to this document, and we wish to thank Tri T. Nguyen who contributed to this document. We also wish to thank Tri T. Nguyen,
initiated this document, but who unfortunately passed away much too who initiated this document, but unfortunately passed away much too
soon. We also thank Pekka Savola for his valuable comments and soon. We also thank Pekka Savola for his valuable comments and
suggestions. suggestions.
8. References 7. References
8.1. Normative References 7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998. (IPv6) Specification", RFC 2460, December 1998.
[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, Extensions for IPv6 Inter-Domain Routing", RFC 2545, March
March 1999. 1999.
[RFC2858bis]
Bates, T., Rekhter, Y., Chandra, R., and D. Katz,
"Multiprotocol Extensions for BGP-4",
draft-ietf-idr-rfc2858bis-10.txt, work in progress.
[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y., [RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
Encoding", RFC 3032, January 2001. Encoding", RFC 3032, January 2001.
[RFC3036] Andersson, L., Doolan, P., Feldman, N., Fredette, A., and [RFC3036] Andersson, L., Doolan, P., Feldman, N., Fredette, A., and
B. Thomas, "LDP Specification", RFC 3036, January 2001. B. Thomas, "LDP Specification", RFC 3036, January 2001.
[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, May 2001.
[RFC3513] Hinden, R. and S. Deering, "Internet Protocol Version 6 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
(IPv6) Addressing Architecture", RFC 3513, April 2003. Architecture", RFC 4291, February 2006.
8.2. Informative References [RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
"Multiprotocol Extensions for BGP-4", RFC 4760, January
2007.
[RFC2463] Conta, A. and S. Deering, "Internet Control Message 7.2. Informative References
Protocol (ICMPv6) for the Internet Protocol Version 6
(IPv6) Specification", RFC 2463, December 1998.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031, January 2001. Label Switching Architecture", RFC 3031, January 2001.
[RFC3270] Le Faucheur, F., Wu, L., Davie, B., Davari, S., Vaananen, [RFC3270] Le Faucheur, F., Wu, L., Davie, B., Davari, S., Vaananen,
P., Krishnan, R., Cheval, P., and J. Heinanen, "Multi- P., Krishnan, R., Cheval, P., and J. Heinanen, "Multi-
Protocol Label Switching (MPLS) Support of Differentiated Protocol Label Switching (MPLS) Support of Differentiated
Services", RFC 3270, May 2002. Services", RFC 3270, May 2002.
[RFC4029] Lind, M., Ksinant, V., Park, S., Baudot, A., and P. [RFC4029] Lind, M., Ksinant, V., Park, S., Baudot, A., and P.
skipping to change at page 12, line 50 skipping to change at page 12, line 11
[RFC4182] Rosen, E., "Removing a Restriction on the use of MPLS [RFC4182] Rosen, E., "Removing a Restriction on the use of MPLS
Explicit NULL", RFC 4182, September 2005. Explicit NULL", RFC 4182, September 2005.
[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway [RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
Protocol 4 (BGP-4)", RFC 4271, January 2006. Protocol 4 (BGP-4)", RFC 4271, January 2006.
[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, February 2006.
[RFC4443] Conta, A., Deering, S., and M. Gupta, "Internet Control
Message Protocol (ICMPv6) for the Internet Protocol
Version 6 (IPv6) Specification", RFC 4443, March 2006.
[RFC4659] De Clercq, J., Ooms, D., Carugi, M., and F. Le Faucheur, [RFC4659] De Clercq, J., Ooms, D., Carugi, M., and F. Le Faucheur,
"BGP-MPLS IP Virtual Private Network (VPN) Extension for "BGP-MPLS IP Virtual Private Network (VPN) Extension for
IPv6 VPN", RFC 4659, September 2006. IPv6 VPN", RFC 4659, September 2006.
Authors' Addresses Authors' Addresses
Jeremy De Clercq Jeremy De Clercq
Alcatel-Lucent Alcatel-Lucent
Copernicuslaan 50 Copernicuslaan 50
Antwerpen 2018 Antwerpen 2018
Belgium Belgium
Email: jeremy.de_clercq@alcatel-lucent.be EMail: jeremy.de_clercq@alcatel-lucent.be
Dirk Ooms Dirk Ooms
OneSparrow OneSparrow
Belegstraat 13 Belegstraat 13
Antwerpen 2018 Antwerpen 2018
Belgium Belgium
Email: dirk@onesparrow.com EMail: dirk@onesparrow.com
Stuart Prevost Stuart Prevost
BTexact Technologies BT
Room 136 Polaris House, Adastral Park, Martlesham Heath Room 136 Polaris House, Adastral Park, Martlesham Heath
Ipswich Suffolk IP5 3RE Ipswich Suffolk IP5 3RE
England England
EMail: stuart.prevost@bt.com
Email: stuart.prevost@bt.com
Francois Le Faucheur Francois Le Faucheur
Cisco Cisco
Domaine Green Side 400, Avenue de Roumanille, Batiment T3 Domaine Green Side, 400 Avenue de Roumanille
Biot, Sophia Antipolis 06410 Biot, Sophia Antipolis 06410
France France
Email: flefauch@cisco.com EMail: flefauch@cisco.com
Full Copyright Statement Full Copyright Statement
Copyright (C) The IETF Trust (2006). Copyright (C) The IETF Trust (2007).
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 14, line 45 skipping to change at page 14, line 45
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 Acknowledgement
Funding for the RFC Editor function is provided by the IETF Funding for the RFC Editor function is currently provided by the
Administrative Support Activity (IASA). Internet Society.
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