Internet Engineering Task Force (IETF) Y. Cai Request for Comments: 6516 E. Rosen, Ed. Category: Standards Track IJ. Wijnands ISSN: 2070-1721 Cisco Systems February 2012
IPv6 Multicast VPN (MVPN) Support Using PIM Control Plane and Selective Provider Multicast Service Interface (S-PMSI) Join Messages
The specification for Multicast Virtual Private Networks (MVPNs) contains an option that allows the use of PIM as the control protocol between provider edge routers. It also contains an option that allows UDP-based messages, known as Selective Provider Multicast Service Interface (S-PMSI) Join messages, to be used to bind particular customer multicast flows to particular tunnels through a service provider's network. This document extends the MVPN specification (RFC 6513) so that these options can be used when the customer multicast flows are IPv6 flows.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 5741.
Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved.
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to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.
Table of Contents
1. Introduction ....................................................2 2. Specification of Requirements ...................................3 3. S-PMSI Joins Binding IPv6 Flows to GRE/IPv4 P-Tunnels ...........3 3.1. Encoding ...................................................3 3.2. Encapsulation of S-PMSI Joins in UDP Datagrams .............4 4. PE-PE PIM/IPv6 over an IPv4 P-Tunnel ............................4 5. IANA Considerations .............................................5 6. Security Considerations .........................................5 7. Acknowledgments .................................................5 8. Normative References ............................................5
The Multicast Virtual Private Network (MVPN) specification [RFC6513] defines the notion of a "PMSI" (Provider Multicast Service Interface) and specifies how a PMSI can be instantiated by various kinds of tunnels through a service provider's network ("P-tunnels"). It also specifies the procedures for using PIM (Protocol Independent Multicast [RFC4601]) as the control protocol between Provider Edge (PE) routers. When PIM is used as the control protocol, PIM messages are sent through a P-tunnel from one PE in an MVPN to others in the same MVPN. These PIM messages carry customer multicast routing information. However, [RFC6513] does not cover the case where the customer is using IPv6, but the service provider is using P-tunnels created by PIM over an IPv4 infrastructure.
The MVPN specification [RFC6513] also specifies "S-PMSI (Selective PMSI) Join" messages, which are optionally used to bind particular customer multicast flows to particular P-tunnels. However, the specification does not cover the case where the customer flows are IPv6 flows.
This document extends [RFC6513] by adding the specification for handling customer IPv6 multicast flows when a service provider is using PE-PE PIM and/or S-PMSI Join messages over an IPv4 infrastructure. This document also specifies how to send multiple S-PMSI Join messages in a single UDP datagram.
This document uses terminology defined in [RFC6513]: C-source, C-group, C-flow, P-group, and (C-S,C-G).
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].
3. S-PMSI Joins Binding IPv6 Flows to GRE/IPv4 P-Tunnels
The S-PMSI Join message is defined in Section 188.8.131.52 of [RFC6513]. These messages contain a type field, and [RFC6513] defines only Type 1 S-PMSI Joins. A Type 1 S-PMSI Join may be used to assign a customer IPv4 (C-S,C-G) flow to a P-tunnel that is created by PIM/IPv4. To transmit data or control packets over such a P-tunnel, the packets are encapsulated in GRE (Generic Routing Encapsulation) within IPv4, as specified in Section 12 of [RFC6513].
In this document, we define the Type 4 S-PMSI Join. A Type 4 S-PMSI Join may be used to assign a customer IPv6 (C-S,C-G) flow to a P-tunnel that is created by PIM/IPv4. GRE/IPv4 encapsulation is used to send data or control packets on the P-tunnel.
Length (16 bits): 40, the length in octets of the entire S-PMSI Join message, including the Type, Length, Reserved, C-source, C-group, and P-group fields.
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RFC 6516 IPv6 MVPN Support February 2012
Reserved (8 bits): this field SHOULD be zero when transmitted and MUST be ignored when received.
C-source (128 bits): the IPv6 address of the traffic source in the VPN.
C-group (128 bits): the IPv6 group address of the multicast traffic.
P-group (32 bits): the IPv4 group address identifying the P-tunnel. Data packets sent on this tunnel are encapsulated in IPv4 GRE packets with this group address in the IP destination address field of the outer header.
3.2. Encapsulation of S-PMSI Joins in UDP Datagrams
All S-PMSI Joins are encapsulated in UDP datagrams [RFC768]. A Type 4 S-PMSI Join MUST be encapsulated in an IPv6 UDP datagram. The IPv6 source address field of these datagrams SHOULD be the IPv4-mapped IPv6 address [RFC4291] corresponding to the IPv4 address that the originating PE router uses as its source address in the instance of PIM that is used to create the specified P-tunnel.
A single UDP datagram MAY carry multiple S-PMSI Join messages, as many as can fit entirely within it. If there are multiple S-PMSI Joins in a UDP datagram, they MUST be of the same S-PMSI Join type. The end of the last S-PMSI Join (as determined by the S-PMSI Join length field) MUST coincide with the end of the UDP datagram, as determined by the UDP length field. When processing a received UDP datagram that contains one or more S-PMSI Joins, a router MUST process all the S-PMSI Joins that fit into the datagram.
If a VPN customer is using PIM over IPv6, but the SP (service provider) is using an IPv4 infrastructure (i.e., is using an IPv4-based control protocol to construct its P-tunnels), then the PE routers will need to originate IPv6 PIM control messages. The IPv6 Source Address field of any such IPv6 PIM control message SHOULD be the IPv4-mapped IPv6 address [RFC4291] corresponding to the IPv4 address that the originating PE router uses as its source address in the instance of PIM that is used to create the specified P-tunnel. If the IPv6 Destination Address field is the multicast address ALL- PIM-ROUTERS, the IPv6 form of the address (ff02::d) is used. These IPv6 PIM control messages are, of course, not transmitted natively over the service provider's network but rather are encapsulated in GRE/IPv4.