Internet DRAFT - draft-zzhang-pim-pds
draft-zzhang-pim-pds
PIM Z. Zhang
Internet-Draft Juniper Networks
Intended status: Informational K. Patel
Expires: April 21, 2016 Cisco Systems
October 19, 2015
Protocol Dependent Multicast Signaling
draft-zzhang-pim-pds-00
Abstract
This document describes a general idea of multicast signaling based
on extensions to unicast protocols.
Requirements Language
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.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 21, 2016.
Copyright Notice
Copyright (c) 2015 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
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publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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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. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. BGP Based PIM-PDS . . . . . . . . . . . . . . . . . . . . . . 3
3. IGP Based PIM-PDS . . . . . . . . . . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . 4
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
6.1. Normative References . . . . . . . . . . . . . . . . . . 4
6.2. Informative References . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Motivation
Protocol Independent Multicast (PIM) has been the prevailing
multicast protocol for many years. Despite its success, it has two
drawbacks:
o Complexity originated from RPT/SPT switchover and data driven
nature for PIM-ASM.
o Periodical protocol state refreshes due to the soft state nature.
While PIM-SSM removes the complexity of PIM-ASM, there have not been
a good way of discovering sources, limiting its deployment. PIM-Port
(PIM over Reliable Transport) solves the soft state issue, though its
deployment has also been limited.
Partly because of the complexity concern, some Data Center operators
have been avoiding deploying multicast in their networks.
Data Center operators are also inclined to reduce the number of
routing protocols as much as possible, to reduce operational
complexity and expenses. For example, with [draft-ietf-rtgwg-bgp-
routing-large-dc], BGP is used as the only routing protocol, w/o any
IGPs. Some other data centers may still choose to run traditional
IGPs, but in either case, it may be desired to not run another
protocol for multicast purposes.
PIM builds multicast distribution trees from the receiver ends
towards the sources or Rendezvous Points. Traffic flows from the
sources/RPs towards receivers in the reverse direction of unicast
traffic from receivers towards the sources/RPs, hence the term
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Reverse Path Forwarding. With PIM, the term "protocol indpendent"
comes from the fact that, the routes used for RPF purpose can be
learned from any protocol, unlike in DVMRP case where the RPF routes
are distributed via DVMRP itself, or in MOSPF case where OSPF routes
are used to build the trees.
Without changing the principle of multicast tree building based on
the reverse path routes learned from any protocol, the tree building
and maintenance do not have to rely on PIM protocol messages.
Rather, it could be done by extensions to whatever unicast protocols
used, so that only one protocol needs to be operated in a network.
For that, we introduce a new flavor of PIM - Protocol Dependent
Signaling (PIM-PDS).
The following sections discussed two options at very high level.
Detailed specifications are out scope of this introductory document.
2. BGP Based PIM-PDS
BGP-MVPN [RFC 6514] uses BGP to signal VPN customer multicast state
over provider networks. It removes the above mentioned problems, and
the deployment experiences have been encouraging. [draft-ietf-bess-
mvpn-pe-ce] adapts the concept of BGP-MVPN to PE-CE links, and
[draft-zzhang-bess-bgp-multicast] extends it further to general
topologies, so that it can deployed in any network where BGP is
running, or can be run, throughout or on most routers.
In a nut shell, [draft-zzhang-bess-bgp-multicast] is PIM with BGP
based join/prune signaling, and BGP based source discovery in case of
ASM. The same RPF procedures as in PIM are used for each router to
determine the RPF neighbor for a particular source or RPA (in case of
Bidirectional Tree). Except in the Bidirectional Tree case, no (*,G)
join is used - LHR routers discover the sources for ASM and then
joins towards the sources directly.
3. IGP Based PIM-PDS
Both MOSPF [RFC 1584] and recent IGP Mutlicast Architecture [draft-
yong-rtgwg-igp-multicast-arch] are based on flooding multicast
membership information everywhere, even though the information is
only needed on the relevant multicast distribution trees. As a
result, the scaling is severely limited. With PIM-PDS, IGP link-
scoped flooding can be used tree construction and maintenance - the
receiver interest is only signaled towards the sources/RPs, and
merging/aggregation will happen along the way.
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4. Security Considerations
This document only describes high level concepts and does not attempt
to address possible security issues. Separate documents, if written,
would address those.
5. Acknowledgements
6. References
6.1. Normative References
[RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
"Protocol Independent Multicast - Sparse Mode (PIM-SM):
Protocol Specification (Revised)", RFC 4601,
DOI 10.17487/RFC4601, August 2006,
<http://www.rfc-editor.org/info/rfc4601>.
6.2. Informative References
[I-D.ietf-bess-mvpn-pe-ce]
Patel, K., Rosen, E., and Y. Rekhter, "BGP as an MVPN PE-
CE Protocol", draft-ietf-bess-mvpn-pe-ce-00 (work in
progress), April 2015.
[I-D.ietf-rtgwg-bgp-routing-large-dc]
Lapukhov, P., Premji, A., and J. Mitchell, "Use of BGP for
routing in large-scale data centers", draft-ietf-rtgwg-
bgp-routing-large-dc-02 (work in progress), April 2015.
[I-D.yong-rtgwg-igp-multicast-arch]
Yong, L., Weiguo, H., Eastlake, D., Qu, A., Hudson, J.,
and U. Chunduri, "IGP Multicast Architecture", draft-yong-
rtgwg-igp-multicast-arch-01 (work in progress), November
2014.
[I-D.zzhang-bess-bgp-multicast]
Zhang, J. and K. Patel, "BGP Based Multicast", draft-
zzhang-bess-bgp-multicast-00 (work in progress), October
2015.
[RFC1075] Waitzman, D., Partridge, C., and S. Deering, "Distance
Vector Multicast Routing Protocol", RFC 1075,
DOI 10.17487/RFC1075, November 1988,
<http://www.rfc-editor.org/info/rfc1075>.
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[RFC1584] Moy, J., "Multicast Extensions to OSPF", RFC 1584,
DOI 10.17487/RFC1584, March 1994,
<http://www.rfc-editor.org/info/rfc1584>.
[RFC6514] Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP
Encodings and Procedures for Multicast in MPLS/BGP IP
VPNs", RFC 6514, DOI 10.17487/RFC6514, February 2012,
<http://www.rfc-editor.org/info/rfc6514>.
Authors' Addresses
Zhaohui Zhang
Juniper Networks
EMail: zzhang@juniper.net
Keyur Patel
Cisco Systems
EMail: keyupate@cisco.com
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