One document matched: draft-ietf-pim-ipv6-03.txt
Differences from draft-ietf-pim-ipv6-02.txt
PIM Working Group B. Haberman
Internet Draft H. Sandick
draft-ietf-pim-ipv6-03.txt Nortel Networks
March 2000 G. Kump
Expires October 2000 IBM
Protocol Independent Multicast Routing
in the Internet Protocol Version 6 (IPv6)
Status of this Memo
This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Task
Force (IETF), its areas, and its working groups. Note that other groups
may also distribute working documents as Internet-Drafts. Internet-
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inappropriate to use Internet- Drafts as reference material or to cite
them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
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Abstract
This document outlines recommendations in the use of the Protocol
Independent Multicast routing protocol to support Internet Protocol
version 6. It describes the changes needed in order to handle the
differences between IPv6 and IPv4 and conform to the logic introduced
by other routing protocols enabled for IPv6.
1. Terminology
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].
2. Introduction
This document describes protocol clarifications within the Protocol
Independent Multicast routing protocol [PIM-SM, PIM-DM] for efficiently
routing to multicast groups communicating with the Internet Protocol
version 6 (IPv6) [RFC 2460]. This document will only describe
recommendations for making PIM conform to practices implemented by
other IPv6 routing protocols. The existing PIM drafts should be
referenced for actual protocol operation.
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3. Definitions and Assumptions
- Link Local Address: A local-use, non-routable unicast IPv6 address
[RFC 2373]
- All-PIM-Routers multicast address: A permanently assigned link-
scoped IPv6 multicast address for the PIM protocol [RFC 2375]
It is assumed that a router running PIM for IPv6 will have a network
unique, domain-wide reachable IPv6 address that will be used for
multiple hop messages.
4. Protocol Impact
The following will outline changes to the values used in the PIM
protocol messages in order to utilize standard IPv6 protocol features.
All messages will be affected by the change to the checksum field in
the PIM header. For most messages, other changes involve the addresses
used in the IPv6 and PIM headers.
4.1 PIM Header Checksum
The checksum field in the PIM [PIM-SM, PIM-DM] header covers the entire
PIM message (excluding the data portion in the Register message). When
running PIM over IPv6, it must use the standard checksum calculation
for IPv6 applications: the 16-bit one's complement of the one's
complement sum of the entire contents of the packet, starting with the
PIM packet header, and prepending a "pseudo-header" of IPv6 header
fields, as specified in [RFC 2460, section 8.1]. The "Upper-Layer
Packet Length" in the pseudo-header is set to the length of the PIM
message. The Next Header value used in the pseudo-header is 103. If
the packet's length is not an integral number of 16-bit words, the
packet is padded with a byte of zero before performing the checksum
calculation. Before computing the checksum, the checksum field in the
PIM packet header is set to 0.
4.2 Hello Message
When sending a Hello Message, a PIM router must use a different set of
IPv6 addresses in the IPv6 header. The IPv6 destination address must
be the All-PIM-Routers multicast address. The IPv6 source address must
be the IPv6 link local address of the interface on which the message is
being forwarded. The link local address in the source address field
will be used to determine neighbor adjacency and for Designated Router
(DR) election.
4.3 Register Message
The Register Message is addressed to the domain-wide reachable IPv6
address of the Rendezvous Point (RP). The source address of the
message is the domain-wide reachable IPv6 address of the DR. The DR
sending the Register Message obtains the domain-wide reachable IPv6
address of the RP from the local RP-set information.
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4.4 Register-Stop Message
The Register-Stop Message is addressed in the same manner as the
Register Message. The RP addresses the message to the domain-wide
reachable IPv6 address of the DR. The source address is the domain-
wide reachable address of the RP. The RP obtains the domain-wide
reachable address of the DR from the source address field of the
Register Message received from the DR.
4.5 Join/Prune, Graft, and Graft-Ack Messages
In the transmission of a Join/Prune, Graft, or Graft-Ack Message, a
router sets the IPv6 destination address to the All-PIM-Routers
multicast address. The IPv6 source address is set to the link local
address of the interface on which the message is forwarded. The
Upstream Neighbor Address field is set to the link local address of the
next hop router, which is obtained from the RPF lookup. If a link
local address cannot be obtained for the upstream neighbor, the
Upstream Neighbor Address field is set to a known IPv6 address for that
neighbor.
4.6 Bootstrap Message
When sending a Bootstrap Message, a PIM router sets the IPv6
destination address field to the All-PIM-Routers multicast address.
The source address is set to the link local address of the interface on
which the message is forwarded. The Bootstrap Router (BSR) Address is
set to the domain-wide reachable IPv6 address of the BSR.
4.7 Assert Message
The Assert Message has an IPv6 destination address of the All-PIM-
Routers multicast address and an IPv6 source address of the link local
address of the interface forwarding the message. The link local
address in the IPv6 source address field is used to resolve ties in the
assert process. Downstream routers save the winning assert router's
link local address to resolve any future RPF requirements.
4.8 Candidate-RP-Advertisement Message
The Candidate-RP-Advertisement Message uses the domain-wide reachable
IPv6 address of the BSR as the IPv6 destination address. The source
address is a domain-wide reachable IPv6 address unique to the candidate
RP. The RP Address field is set to a domain-wide reachable IPv6
address of the candidate RP. Each candidate RP router creates this
message and unicasts it to the BSR.
5. IPv6 Address Scoping
With the introduction of scoped addresses in IPv6, new issues arise in
the distribution of scoped routes and the forwarding of packets
containing scoped addresses. With regards to the PIM protocol, the
main scoping issue involves the bootstrap mechanism. The bootstrap
mechanism is a centralized function, e.g. there is one bootstrap server
per PIM domain. If the PIM-SM domain is not a subset of the scoped
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Internet Draft PIM for IPv6 March 2000
address domain then the bootstrap mechanism, in its current form,
cannot support scoped RP addresses and scoped group addresses.
Therefore, in order for the bootstrap mechanism to function properly,
the PIM domain must be a subset of the scoped address domain or all
multiple hop messages must use globally reachable IPv6 addresses.
6. Security Considerations
This document does not introduce any protocol changes that require
additional security considerations above and beyond those described in
the PIM protocol specifications.
7. References
[RFC 2119] S. Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, BCP14, March 1999.
[PIM-SM] L. Wei, et. al, "Protocol Independent Multicast-Sparse
Mode (PIM-SM): Protocol Specification",
draft-ietf-pim-v2-sm-00.txt, October 1999.
[PIM-DM] L. Wei, et. al, "Protocol Independent Multicast Version 2
Dense Mode Specification", draft-ietf-pim-v2-dm-03.txt,
June 1999.
[RFC 2460] R. Hinden and S. Deering, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.
[RFC 2373] R. Hinden and S. Deering, "IP Version 6 Addressing
Architecture", RFC 2373, July 1998.
[RFC 2375] R. Hinden and S. Deering, "IPv6 Multicast Address
Assignments", RFC 2375, July 1998.
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Authors' Addresses
Brian Haberman
Hal Sandick
Nortel Networks
4309 Emperor Blvd.
Suite 200
Durham, NC 27703
1-919-992-4439
1-919-992-9046
Email : haberman@nortelnetworks.com
Email : hsandick@nortelnetworks.com
Garry Kump
IBM Corporation
800 Park Office Drive
Research Triangle Park, NC 27709
1-919-254-2395
Email: kump@us.ibm.com
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