One document matched: draft-rosen-l3vpn-mvpn-infra-addrs-00.txt
Network Working Group Rahul Aggarwal
Internet Draft Juniper Networks, Inc.
Intended Status: Proposed Standard
Expires: December 10, 2010 Eric C. Rosen
Cisco Systems, Inc.
June 10, 2010
IPv4 and IPv6 Infrastructure Addresses in MCAST-VPN Routes
draft-rosen-l3vpn-mvpn-infra-addrs-00.txt
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Internet Draft draft-rosen-l3vpn-mvpn-infra-addrs-00.txt June 2010
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Abstract
To provide Multicast VPN service, a provider edge router originates
"MCAST-VPN" BGP routes. These routes encode addresses from the
customer's address space as well as addresses from the provider's
address space. The customer's address space may be either IPv4 or
IPv6. Independently, the provider's address space may be either IPv4
or IPv6. The MCAST-VPN BGP routes always contain an "address family"
field that specifies whether the customer addresses are IPv4
addresses or whether they are IPv6 addresses. However, there is no
field that explicitly specifies whether the provider addresses are
IPv4 addresses or whether they are IPv6 addresses. The existing
specifications do not explicitly say how to determine whether a given
provider address is IPv4 or IPv6, and there are differing precedents
about the method used to encode IPv4 addresses in messages that also
contain IPv6 addresses. This document removes any ambiguity by
specifying that MCAST-VPN routes always encode provider IPv4
addresses as four-octet addresses, and that the distinction between
an IPv4 address and an IPv6 address is signaled solely by the length
of the address field.
Table of Contents
1 Specification of requirements ......................... 3
2 Introduction .......................................... 3
3 PE Addresses in MCAST-VPN Routes ...................... 4
4 PMSI Tunnel Attributes in I-PMSI A-D Routes ........... 5
4.1 Relationship to AFI Value ............................. 5
4.2 Relationship to Next Hop Address Family ............... 5
5 IANA Considerations ................................... 6
6 Security Considerations ............................... 6
7 Acknowledgments ....................................... 6
8 Authors' Addresses .................................... 6
9 Normative References .................................. 7
10 Informational References .............................. 7
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1. Specification of requirements
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 [RFC2119].
2. Introduction
[MVPN-BGP] defines a new set of BGP route types that are used by
Service Providers (SPs) to provide Multicast Virtual Private Network
service to their customers. These routes have a newly defined BGP
NLRI, the "MCAST-VPN" NLRI. MCAST-VPN NLRI is carried in the NLRI
field of the MP_REACH_NLRI/MP_UNREACH_NLRI attributes defined in
[BGP-MP]. The SAFI field of the MP_REACH_NLRI/MP_UNREACH_NLRI
attribute is used to identify the NLRI as being an MCAST-VPN NLRI.
When the SAFI field of an MP_REACH_NLRI/MP_UNREACH_NLRI attribute has
the "MCAST-VPN" value, the AFI field has two defined values: 1 and 2.
AFI 1 indicates that any customer multicast addresses occurring in
the MP_REACH_NLRI/MP_UNREACH_NLRI attribute are IPv4 addresses; AFI 2
indicates that any such addresses are IPv6 addresses.
However, some of the MCAST-VPN routes also contain addresses of
Provider Edge (PE) routers in the SP network. An SP with an IPv4
network may provide MVPN service for customers that use IPv6, and an
SP with an IPv6 network may provide MVPN service for customers that
use IPv4. Therefore the address family of the PE addresses MUST NOT
be inferred from the AFI field of the associated
MP_REACH_NLRI/MP_UNREACH_NLRI attribute.
The purpose of this document is to make it clear that whenever a PE
address occurs in an MCAST-VPN route (whether in the NLRI or in an
attribute), the IP address family of that address is determined by
the length of the address (a length of 4 octets for IPv4 addresses, a
length of 16 octets for IPv6 addresses), NOT by the AFI field of the
route.
In particular, if a SP with an IPv4 core network is providing
MVPN/IPv6 service to a customer, the PE addresses in the MCAST-VPN
routes will be four-octet IPv4 routes, even though the AFI of those
routes will have the value 2.
Some previous specifications (e.g., [RFC4659] and [RFC4798]) have
taken a different approach, requiring that in any routes containing
IPv6 or VPN-IPv6 customer addresses, the IPv4 PE addresses be
represented as IPv6-mapped IPv4 addresses. This document does not
use that approach. Rather, this specification uses the approach
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adopted in [RFC4684] and [RFC5549]. The MCAST-VPN routes contain
enough information to enable the IP address family of the PE
addresses to be inferred from the address lengths.
3. PE Addresses in MCAST-VPN Routes
PE addresses occur in MCAST-VPN routes in the following places:
1. "Network Address of Next Hop" field in the MP_REACH_NLRI
attribute, as defined in section 3 of [BGP-MP]. This field is
preceded by a "length of next hop address" field. Hence it is
always clear whether the address is an IPv4 address (length is
4) or an IPv6 address (length is 16). If the length of next
hop address is neither 4 nor 16, the MP_REACH_NLRI attribute
MUST be considered to be "incorrect", and MUST be handled as
specified in section 7 of [BGP-MP].
2. "Intra-AS I-PMSI A-D route". All MCAST-VPN routes begin with a
one-octet route type field, followed by a one-octet "NLRI
length" field. In the Intra-AS I-PMSI A-D route, the length is
followed by an 8-octet RD, which is then followed by the
"Originating Router's IP Address" field. The length of this
field (4 octets for IPv4 or 16 octets for IPv6 can thus be
inferred from the NLRI length field (which will be either 12 or
24, respectively). If the inferred length of the "Originating
Router's IP Address" field is neither 4 nor 16, the
MP_REACH_NLRI attribute MUST be considered to be "incorrect",
and MUST be handled as specified in section 7 of [BGP-MP].
3. "S-PMSI A-D Route". In this route, the "NLRI length" field is
followed by an 8-octet RD, a variable length "multicast source"
field, a variable length "multicast group" field, and an
"Originating Router's IP Address" field. The two variable
length fields have their own length fields. From these two
length fields and the NLRI length field, one can compute the
length of the "Originating Router's IP Address" field, which
again is either 4 for IPv4 or 16 for IPv6. If the computed
length of the "Originating Router's IP Address" field is
neither 4 nor 16, the MP_REACH_NLRI attribute MUST be
considered to be "incorrect", and MUST be handled as specified
in section 7 of [BGP-MP].
4. "Leaf A-D Route". In this route, the "NLRI length" field is
following by a variable length "route key", which is followed
by the "Originating Router's IP Address" field. The Route Key
has its own length field. From the NLRI length and the route
key length, one can compute the length of the "Originating
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Router's IP Address" field. If the computed length of the
"Originating Router's IP Address" field is neither 4 nor 16,
the MP_REACH_NLRI attribute MUST be considered to be
"incorrect", and MUST be handled as specified in section 7 of
[BGP-MP].
5. "VRF Route Import Extended Community". The "VRF Route Import
Extended Community", as specified in [MVPN-BGP], can only carry
an IPv4 address. To carry an IPv6 address, the "IPv6 Address
Specific Route Target" as specified in [RFC5701] MUST be used.
4. PMSI Tunnel Attributes in I-PMSI A-D Routes
When a PMSI Tunnel Attribute occurs in an I-PMSI A-D route originated
by a particular PE or ASBR, it identifies a tunnel that the PE/ASBR
uses by default for carrying the multicast traffic of a particular
customer MVPN. The proper encoding and interpretation of the PMSI
Tunnel attribute is affected by both the AFI and "Network Address of
Next Hop" fields.
4.1. Relationship to AFI Value
When the PMSI Tunnel Attribute occurs in a BGP Update message with a
MP_REACH_NLRI attribute whose AFI is 1, the meaning is that the
identified tunnel is used by default to carry IPv4 MVPN traffic for a
particular customer MVPN. When the PMSI Tunnel Attribute occurs in a
BGP Update message with a MP_REACH_NLRI attribute whose AFI is 2, the
meaning is that the identified tunnel is used by default to carry
IPv6 MVPN traffic for a particular customer MVPN. To assign both
IPv4 and IPv6 MVPN traffic to an I-PMSI tunnel, two I-PMSI A-D routes
MUST be used, one whose MP_REACH_NLRI has an AFI of 1, and one whose
MP_REACH_NLRI has an AFI of 2. To use the same tunnel for both IPv4
and IPv6 traffic, the same value of the PMSI Tunnel attribute can be
used in each route.
4.2. Relationship to Next Hop Address Family
If the "Network Address of Next Hop" field in the MP_REACH_NLRI
attribute contains an IPv4 address, then any IP addresses appearing
in the "Tunnel Identifier" field of the PMSI Tunnel Attribute MUST be
IPv4 addresses.
If the "Network Address of Next Hop" field in the MP_REACH_NLRI
attribute contains an IPv6 address, then any IP addresses appearing
in the "Tunnel Identifier" field of the PMSI Tunnel Attribute MUST be
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IPv6 addresses.
If these conditions are not met, the PMSI Tunnel Attribute MUST be
handled as a "malformed" PMSI Tunnel Attribute, as specified in
section 5 [MVPN-BGP].
5. IANA Considerations
This document has no actions for IANA.
6. Security Considerations
This document does not raise any security considerations beyond those
raised by [MVPN-BGP].
7. Acknowledgments
The authors wish to thank Dongling Duan, Yakov Rekhter, and Karthik
Subramanian.
8. Authors' Addresses
Rahul Aggarwal
Juniper Networks
1194 North Mathilda Ave.
Sunnyvale, CA 94089
Email: rahul@juniper.net
Eric C. Rosen
Cisco Systems, Inc.
1414 Massachusetts Avenue
Boxborough, MA, 01719
E-mail: erosen@cisco.com
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9. Normative References
[BGP-MP] "Multiprotocol Extensions for BGP-4", T. Bates, R. Chandra,
D. Katz, Y. Rekhter, RFC 4760, January 2007
[MVPN-BGP], "BGP Encodings and Procedures for Multicast in MPLS/BGP
IP VPNs", Rahul Aggarwal, Eric Rosen, Thomas Morin, Yakov Rekhter,
30-Sep-09, draft-ietf-l3vpn-2547bis-mcast-bgp-08.txt
[RFC2119] "Key words for use in RFCs to Indicate Requirement
Levels.", Bradner, March 1997
10. Informational References
[RFC4659] "BGP-MPLS IP Virtual Private Network (VPN) Extension for
IPv6 VPN", J. De Clercq, D. Ooms, M. Carugi, F. Le Faucheur. RFC
4659, September 2006
[RFC4798] "Connecting IPv6 Islands over IPv4 MPLS Using IPv6 Provider
Edge Routers (6PE)", J. De Clercq, D. Ooms, S. Prevost, F. Le
Faucheur. RFC 4798, February 2007
[RFC4684] "Constrained Route Distribution for Border Gateway
Protocol/MultiProtocol Label Switching (BGP/MPLS) Internet Protocol
(IP) Virtual Private Networks (VPNs)", P. Marques, R. Bonica, L.
Fang, L. Martini, R. Raszuk, K. Patel, J. Guichard. RFC 4684 November
2006
[RFC5549] "Advertising IPv4 Network Layer Reachability Information
with an IPv6 Next Hop" F. Le Faucheur, E. Rosen. RFC 5549, May 2009
[RFC5701] "IPv6 Address Specific BGP Extended Community Attribute" Y.
Rekhter. RFC 5701, November 2009
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