PIM WG A. Boers
Internet-Draft IJ. Wijnands
Expires: August 5, 2005 E. Rosen
Cisco Systems, Inc.
february 2005
Format for using PIM proxies
draft-ietf-pim-proxy-00
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Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This document describes a generic TLV encoding format to be added to
PIM.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Use of the Proxy Field in Join Messages . . . . . . . . . . . 3
2.1 Proxy join . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2 Transitive proxies . . . . . . . . . . . . . . . . . . . . 3
2.3 Proxy Hello Option . . . . . . . . . . . . . . . . . . . . 3
2.4 Conflicting Proxies . . . . . . . . . . . . . . . . . . . 3
2.5 Proxy Convergence . . . . . . . . . . . . . . . . . . . . 4
2.6 Multiple Proxies . . . . . . . . . . . . . . . . . . . . . 4
3. PIM Proxy packet format . . . . . . . . . . . . . . . . . . . 5
3.1 PIM Join packet format . . . . . . . . . . . . . . . . . . 5
3.2 PIM Proxy Hello option . . . . . . . . . . . . . . . . . . 5
4. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.1 Normative References . . . . . . . . . . . . . . . . . . . 6
5.2 Informative References . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 6
Intellectual Property and Copyright Statements . . . . . . . . 7
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1. Introduction
It is sometimes convenient to add additional information to PIM join
messages. The generic PIM encoding format is not allways optimal
todo this. This document defines a new field in the PIM Join
message, called the "Proxy" field. The contents and purpose of this
proxy field is not outside the scope of this document, only the
generic encoding format is described here.
2. Use of the Proxy Field in Join Messages
2.1 Proxy join
Proxy fields are defined similar to the PIM source encoding type as
defined in [I-D.ietf-pim-sm-v2-new]. A source address without any
additional TLV's should be processed identically to a source address
in the default source encoding.
Multiple TLV's from the same or different type are permitted in a
single source address in any order.
2.2 Transitive proxies
It may be desired to have routers that understand the generic proxy
format, forward the proxies regardless if they understand the TLV's
encoded in the proxy not. For this the first bit in the Type field
is reserved. If this bit is set then the TLV is forwarded upstream
in case the router does not understand that type.
2.3 Proxy Hello Option
A new PIM source type has been defined to include the Proxy field.
This source type is included in a normal PIM Join. Each router on a
connected network needs to be able to understand and parse the Join
message. Therefore we include a new PIM hello option to advertise
our capability to parse and process the new source type. We can only
send a PIM Join which includes a Proxy if ALL routers on the network
support the new option. (Even a router which is not the upstream
neighbor must be able parse the packet in order to do Join
suppression or overriding.) Option value TBD.
2.4 Conflicting Proxies
It's possible that a router receives conflicting proxy information
from different downstream routers. See Figure 2.
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( Edge A1 ) ( Edge B1 )---- [R1]
/ \ /
/ \ /
[S] ( Core )
\ / \
\ / \
( Edge A2 ) ( Edge B2 )---- [R2]
Figure 2
There are 2 receivers for the same group connected to Edge B1 and B2.
Suppose that edge router B1 prefers A1 as the exit point and B2
prefers A2 as exit point to reach the source S. If both Edge B1 and
B2 send a Join including a Proxy to prefer their exit router in the
network and they cross the same core router, the core router will get
conflicting proxy information for the source. If this happens we use
the Proxy from the PIM adjacency with the numerically smallest IP
address. The Proxies from other sending routers may be kept around
in case the best Proxy gets pruned or expires, we are able to
immediately use the second best Proxy and converge quickly without
waiting for the next periodic update. If a TLV has its own
definition for conflict resolution is is preferred over the conflict
resolution above.
2.5 Proxy Convergence
A Proxy is included in a PIM Join message together with the source
information. If the Proxy for this source is changed, we trigger a
new PIM Join message to the upstream router. This causes the new
Proxy to be propagated. This new Proxy implicitly removes the old
Proxy upstream. If processing the new Proxy results in a change in
the distribution tree, a PIM Prune message may be sent. This PIM
Prune does not need to carry any Proxy, the sender of the prune and
the source and group information is enough to identify the entry.
The proxy information is removed immediately and possibly a new proxy
is chosen from the database if available.
2.6 Multiple Proxies
A PIM Join can contain multiple Proxies. The Proxies are encoded as
TLVs associated with a new PIM source type in the PIM message. When
a PIM Join with multiple Proxies is received, the first Proxy is
processed, and the action taken depends upon the Proxy type. This
may or may not result in the processing of the next Proxy. Proxies
not processed are passed upstream unchanged.
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3. PIM Proxy packet format
3.1 PIM Join packet format
There is no space in the default PIM source encoding to include a
Proxy field. Therefore we introduce a new source encoding type. The
proxies are formatted as TLV's. The new Encoded source address looks
like this:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Addr Family | Encoding Type | TLV # |S|W|R| Mask Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|F| Type | Length | Value
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+.....
|F| Type | Length | Value
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+.....
. . .
. . .
TLV # gives the number of TLV's that are included with this source.
With the 5 bits we can include a maximum of 31 TLV's
F bit, Forward Unknown TLV bit. If this bit is set the TLV is
forwarded regardless if the router understands the Type.
Type field of the TLV is 7 bits.
Length field of the TLV is 1 byte.
The other fields are the same as described in the PIM spec.
[I-D.ietf-pim-sm-v2-new].
The source TLV encoding type: TBD.
3.2 PIM Proxy Hello option
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OptionType = XX | OptionLength = 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option type: TBD.
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4. Acknowledgments
The authors would like to thank James Lingard for his comments on
this topic.
5. References
5.1 Normative References
[I-D.ietf-pim-sm-v2-new]
Fenner, B., Handley, M., Holbrook, H. and I. Kouvelas,
"Protocol Independent Multicast - Sparse Mode PIM-SM):
Protocol Specification (Revised)",
Internet-Draft draft-ietf-pim-sm-v2-new-11, October 2004.
5.2 Informative References
Authors' Addresses
Arjen Boers
Cisco Systems, Inc.
Avda. Diagonal, 682
Barcelona 08034
Spain
Email: aboers@cisco.com
IJsbrand Wijnands
Cisco Systems, Inc.
De kleetlaan 6a
Diegem 1831
Belgium
Email: ice@cisco.com
Eric Rosen
Cisco Systems, Inc.
1414 Massachusetts Avenue
Boxborough, Ma 01719
Email: erosen@cisco.com
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