IPv6 MVPN with PIM: IPv6 Multicast VPN (MVPN) Support Using PIM Control Plane and Selective Provider Multicast Service Interface (S-PMSI) Join Messages
Lets IPv6 customer multicast ride across a provider network that builds its tunnels with IPv4 PIM.
Cai, Y., Rosen, E., Ed., and I. Wijnands, "IPv6 Multicast VPN (MVPN) Support Using PIM Control Plane and Selective Provider Multicast Service Interface (S-PMSI) Join Messages", RFC 6516, DOI 10.17487/RFC6516, February 2012, <https://www.rfc-editor.org/info/rfc6516>.
@misc{rfc6516,
series = {Request for Comments},
number = 6516,
howpublished = {RFC 6516},
publisher = {RFC Editor},
doi = {10.17487/RFC6516},
url = {https://www.rfc-editor.org/info/rfc6516},
author = {Y. Cai and E. Rosen and I. Wijnands},
title = {{IPv6 Multicast VPN (MVPN) Support Using PIM Control Plane and Selective Provider Multicast Service Interface (S-PMSI) Join Messages}},
pagetotal = 6,
year = 2012,
month = feb,
} RFC text
Contents
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
Abstract
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.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6516.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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
1. Introduction
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).
2. 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].
3. S-PMSI Joins Binding IPv6 Flows to GRE/IPv4 P-Tunnels
The S-PMSI Join message is defined in Section 7.4.2.2 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.
3.1. Encoding
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| C-source |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| C-group |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| P-group |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type (8 bits): 4
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.
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.
4. PE-PE PIM/IPv6 over an IPv4 P-Tunnel
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.
5. IANA Considerations
[RFC6513] created an IANA registry for the "S-PMSI Join Message Type
Field". This document registers a new value in that registry:
Value: 4
Description: GRE S-PMSI for IPv6 traffic (unaggregated)
6. Security Considerations
There are no additional security considerations beyond those of
[RFC6513].
7. Acknowledgments
The authors wish to thank DP Ayyadevara, Arjen Boers, Rayen Mohanty,
Rajesh Sharma, and Karthik Subramanian.
8. Normative References
[RFC768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
August 1980.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.
[RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
"Protocol Independent Multicast - Sparse Mode (PIM-SM):
Protocol Specification (Revised)", RFC 4601, August 2006.
[RFC6513] Rosen, E., Ed., and R. Aggarwal, Ed., "Multicast in
MPLS/BGP IP VPNs", RFC 6513, February 2012.
Authors' Addresses
Yiqun Cai
Cisco Systems, Inc.
170 Tasman Drive
San Jose, CA 95134
EMail: ycai@cisco.com
Eric C. Rosen (editor)
Cisco Systems, Inc.
1414 Massachusetts Avenue
Boxborough, MA 01719
EMail: erosen@cisco.com
IJsbrand Wijnands
Cisco Systems, Inc.
De kleetlaan 6a Diegem 1831
Belgium
EMail: ice@cisco.com
AI ELI5
On this page
§1The Gap in the MVPN Specification
The Multicast VPN (MVPN) specification, RFC 6513, defines a PMSI (Provider Multicast Service Interface) and says how it can be built from tunnels across a service provider network, called P-tunnels. It also describes using PIM (Protocol Independent Multicast, RFC 4601) as the control protocol between Provider Edge (PE) routers. In that mode, PIM messages carrying customer multicast routing information travel through a P-tunnel from one PE to the others in the same MVPN.
RFC 6513 does not cover a customer that uses IPv6 while the provider builds its P-tunnels with PIM over an IPv4 infrastructure. It also defines optional S-PMSI Join messages, which bind particular customer multicast flows to particular P-tunnels, but only for IPv4 customer flows. This RFC fills both gaps and adds a rule for packing several S-PMSI Joins into one UDP datagram.
The old rulebook only explained how to deliver mail with old-style addresses. This new note adds the missing rules for the new-style addresses.
§2Terms Borrowed from RFC 6513
The RFC reuses the vocabulary of RFC 6513: C-source, C-group, C-flow, P-group and (C-S,C-G). The C-prefixed terms describe the customer's multicast traffic: the source, the group address and the flow made of the two. The P-group is the address that identifies the provider's tunnel.
An existing Type 1 S-PMSI Join can assign a customer IPv4 (C-S,C-G) flow to a P-tunnel created by PIM over IPv4. Packets on such a tunnel are encapsulated in GRE (Generic Routing Encapsulation) within IPv4, as RFC 6513 specifies in its Section 12. The new message in this RFC keeps that same GRE/IPv4 tunnel and changes only the customer side.
The customer has a name for the thing being sent and the provider has a name for the truck carrying it. This RFC just reuses those names.
§3The Type 4 S-PMSI Join
S-PMSI Join messages begin with a type field, and RFC 6513 defines only Type 1. This RFC defines Type 4, which assigns a customer IPv6 (C-S,C-G) flow to a P-tunnel created by PIM over IPv4. Data and control packets on the tunnel use GRE/IPv4 encapsulation.
Type(8 bits): 4.Length(16 bits): 40, the length in octets of the whole message.Reserved(8 bits): SHOULD be zero when sent 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 on that tunnel carry this address as the destination of the outer IPv4 GRE header.
The message is a short note that says: this stream from this sender to this group should travel on that truck. The sender and group use long addresses, and the truck uses a short one.
| Field | Name | Size | Value | Description |
|---|---|---|---|---|
TYPE | Type | 1 byte | 4 | Set to 4. |
LENGTH | Length | 2 bytes | 40 | Length in octets of the whole message. |
RESERVED | Reserved | 1 byte | SHOULD be zero when sent; MUST be ignored when received. | |
C-SOURCE | C-source | 16 bytes | IPv6 address of the traffic source in the VPN. | |
C-GROUP | C-group | 16 bytes | IPv6 group address of the multicast traffic. | |
P-GROUP | P-group | 4 bytes | IPv4 group address identifying the P-tunnel. |
§4UDP Encapsulation and IPv6 PIM Over IPv4
All S-PMSI Joins travel in UDP datagrams. A Type 4 S-PMSI Join MUST be sent in an IPv6 UDP datagram. The IPv6 source address of that datagram SHOULD be the IPv4-mapped IPv6 address (RFC 4291) that matches the IPv4 address the originating PE uses as its source in the PIM instance that creates the P-tunnel.
A single UDP datagram MAY carry several S-PMSI Joins, as many as fit entirely inside it. They MUST all be of the same type. The end of the last Join, found using the Join length field, MUST coincide with the end of the datagram given by the UDP length field. A router that receives such a datagram MUST process every Join in it.
When a customer runs PIM over IPv6 and the provider uses an IPv4-based control protocol for its P-tunnels, the PE routers must originate IPv6 PIM control messages. Their IPv6 source address SHOULD be the same kind of IPv4-mapped address. If the destination is the ALL-PIM-ROUTERS group, the IPv6 form ff02::d is used. These messages are not sent natively across the provider network but are encapsulated in GRE/IPv4.
The notes go inside envelopes, and one envelope can hold several notes of the same kind. The sender's return address is made from its old-style address so replies know where to go.
§5IANA and Security Considerations
RFC 6513 created an IANA registry called the S-PMSI Join Message Type Field. This document registers a new value there: 4, described as GRE S-PMSI for IPv6 traffic (unaggregated).
The security section is one sentence: there are no additional security considerations beyond those of RFC 6513.
The new note type gets its own number in the official list. Nothing new needs guarding beyond what the old rules already cover.