draft-ietf-pim-mtid-09.txt   draft-ietf-pim-mtid-10.txt 
PIM WG Yiqun Cai PIM WG Yiqun Cai
Internet Draft Heidi Ou Internet Draft Heidi Ou
Intended Status: Proposed Standard Intended Status: Proposed Standard
Expires: February 17, 2012 Cisco Systems, Inc. Expires: March 27, 2012 Cisco Systems, Inc.
August 17, 2011 September 27, 2011
PIM Multi-Topology ID (MT-ID) Join Attribute PIM Multi-Topology ID (MT-ID) Join Attribute
draft-ietf-pim-mtid-09.txt draft-ietf-pim-mtid-10.txt
Status of this Memo Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
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and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on February 17, 2012. This Internet-Draft will expire on March 27, 2012.
Copyright Notice Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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Some unicast protocols, such as OSPF and IS-IS, allow a single Some unicast protocols, such as OSPF and IS-IS, allow a single
network to be viewed as multiple topologies [RFC4915], [RFC5120]. network to be viewed as multiple topologies [RFC4915], [RFC5120].
Deploying multi-topology (MT) routing allows different paths through Deploying multi-topology (MT) routing allows different paths through
the network to be selected to support different traffic, or to offer the network to be selected to support different traffic, or to offer
protection paths in the event of failures. protection paths in the event of failures.
PIM [RFC4601] employs a technique known as Reverse Path Forwarding PIM [RFC4601] employs a technique known as Reverse Path Forwarding
(RPF) to construct forwarding trees between multicast sources and (RPF) to construct forwarding trees between multicast sources and
receivers. The procedure of RPF uses topology information provided receivers. The procedure of RPF uses topology information provided
by routing protocols, such as OSPF and IS-IS. If PIM was able to by routing protocols, such as OSPF and IS-IS. Using the PIM MT-ID
access the multiple topologies created by the routing protocols, it Join Attribute specified in this document enables PIM to access the
would be possible to construct multicast forwarding trees using multiple topologies created by the routing protocols and construct
separate network paths even when the roots of the trees are the same. multicast forwarding trees using separate network paths even when the
roots of the trees are the same.
This capability would facilitate an improvement to the resilience of This capability would allow for an improvement to the resilience of
multicast applications. For instance, a multicast stream can be multicast applications. For instance, a multicast stream can be
duplicated and transported using two source trees, (S1, G1) and (S1, duplicated and transported using two source trees, (S1, G1) and (S1,
G2), simultaneously. By using MT capable unicast routing protocols G2), simultaneously. By using MT capable unicast routing protocols
and procedures described in this document, it is possible to and procedures described in this document, it is possible to
construct two source trees for (S1, G1) and (S1, G2) in such a way construct two source trees for (S1, G1) and (S1, G2) in such a way
that they do not share any transit network segment. As a result, a that they do not share any transit network segment. As a result, a
single network failure will not cause any loss to the stream. single network failure will not cause any loss to the stream.
This document introduces a new type of PIM Join Attribute [RFC5384], This document introduces a new type of PIM Join Attribute [RFC5384],
named MT-ID Join Attribute. It is used to encode the numerical named MT-ID Join Attribute. It is used to encode the numerical
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When a PIM router originates a PIM Join/Assert packet, it may choose When a PIM router originates a PIM Join/Assert packet, it may choose
to encode PIM MT-ID of the topology in which RPF lookup is to take to encode PIM MT-ID of the topology in which RPF lookup is to take
place for the corresponding (*,G) or (S,G) entry. The PIM MT-ID place for the corresponding (*,G) or (S,G) entry. The PIM MT-ID
identifies the topology chosen by local policy/configuration or is identifies the topology chosen by local policy/configuration or is
the value received from downstream routers after MT-ID conflict the value received from downstream routers after MT-ID conflict
resolution procedures have been applied (See Section 4.2.4 for resolution procedures have been applied (See Section 4.2.4 for
further detail). further detail).
The following are the exceptions, The following are the exceptions,
- A router MUST NOT include the attribute if PIM MT-ID is 0. The - A router SHOULD NOT include the attribute if PIM MT-ID is 0. The
value of 0 is ignored on reception. value of 0 is ignored on reception.
- A router SHOULD NOT include PIM MT-ID in its Join/Assert packets - A router SHOULD NOT include PIM MT-ID in its Join/Assert packets
if the upstream router, or any of the routers on the LAN does not if the upstream router, or any of the routers on the LAN does not
include "PIM Join Attribute" or "PIM MT-ID" Option in its Hello include "PIM Join Attribute" or "PIM MT-ID" Option in its Hello
packets. packets.
- A router SHOULD NOT attach PIM MT-ID for pruned sources. PIM - A router SHOULD NOT attach PIM MT-ID for pruned sources. PIM
MT-ID MUST be ignored for a pruned source by a router processing MT-ID MUST be ignored for a pruned source by a router processing
the Prune message. the Prune message.
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4.2.3. Validating PIM MT-ID Join Attribute 4.2.3. Validating PIM MT-ID Join Attribute
An upstream router MUST be known to support this document in order An upstream router MUST be known to support this document in order
for a downstream router to include the PIM MT-ID attribute in its for a downstream router to include the PIM MT-ID attribute in its
Join packets. But an upstream router doesn't need to know if a Join packets. But an upstream router doesn't need to know if a
downstream router supports this document or not when deciding whether downstream router supports this document or not when deciding whether
to accept the attribute. Hence, if the Join packet sender doesn't to accept the attribute. Hence, if the Join packet sender doesn't
include "PIM Join Attribute" or "PIM MT-ID" options in its Hello include "PIM Join Attribute" or "PIM MT-ID" options in its Hello
packets, the PIM MT-ID attribute in the Join may still be considered packets, the PIM MT-ID attribute in the Join may still be considered
valid. This is also in accordance with the "Robustness Principle" valid. This is also in accordance with the "Robustness Principle"
outlined in [RFC761]. outlined in [RFC793].
The following text specifies the detail of the validity check. The following text specifies the detail of the validity check.
- There is at most 1 PIM MT-ID attribute encoded. If there are - There is at most 1 PIM MT-ID attribute encoded. If there are
multiple PIM MT-ID Join Attributes included (possibly due to an multiple PIM MT-ID Join Attributes included (possibly due to an
error in the implementation), only the last one is accepted for error in the implementation), only the last one is accepted for
this particular source. Processing of the rest of the Join this particular source. Processing of the rest of the Join
message continues. message continues.
- The length field must be 2. If the length field is not 2, the - The length field must be 2. If the length field is not 2, the
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[RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas, [RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
"Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol "Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol
Specification (Revised)", RFC 4601, August 2006. Specification (Revised)", RFC 4601, August 2006.
[RFC5384] A. Boers, I. Wijnands, E. Rosen, "The Protocol Independent [RFC5384] A. Boers, I. Wijnands, E. Rosen, "The Protocol Independent
Multicast (PIM) Join Attribute Format", RFC 5384, November 2008 Multicast (PIM) Join Attribute Format", RFC 5384, November 2008
11. Informative References 11. Informative References
[RFC761] ISI, "Transmission Control Protocol", RFC 761, January 1980. [RFC793] ISI, "Transmission Control Protocol", RFC 793, September
1981.
[RFC4915] P. Psenak, S. Mirtorabi, A. Roy, L. Nguyen, P. Pillay- [RFC4915] P. Psenak, S. Mirtorabi, A. Roy, L. Nguyen, P. Pillay-
Esnault, "Multi-Topology (MT) Routing in OSPF", RFC 4915, June 2007. Esnault, "Multi-Topology (MT) Routing in OSPF", RFC 4915, June 2007.
[RFC5120] T. Przygienda, N. Shen, N. Sheth, "M-ISIS: Multi Topology [RFC5120] T. Przygienda, N. Shen, N. Sheth, "M-ISIS: Multi Topology
(MT) Routing in Intermediate System to Intermediate Systems (IS- (MT) Routing in Intermediate System to Intermediate Systems (IS-
ISs)", RFC 5120, February 2008. ISs)", RFC 5120, February 2008.
[RFC5496] I. Wijnands, A. Boers, E. Rosen, "The Reverse Path [RFC5496] I. Wijnands, A. Boers, E. Rosen, "The Reverse Path
Forwarding (RPF) Vector TLV", RFC 5496, March 2009. Forwarding (RPF) Vector TLV", RFC 5496, March 2009.
 End of changes. 9 change blocks. 
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