One document matched: draft-tsenevir-pim-sm-snoop-00.txt
IDMR Working Group Tissa Senevirathne
Internet Draft Sridhar Vallepali
Document: draft-tsenevir-pim-sm-snoop-00.txt
Category: Informational Force10 Networks
April, 2002
Protocol Independent Multicast-Sparse Mode (PIM-SM) Snooping
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026 [1].
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Abstract
This document provides PIM-SM snooping solution. In the document we
present the framework and reference model and required PIM-SM
messages for PIM-SM snooping solutions. Also we attempt to discuss
related issues to PIM-SM snooping.
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Conventions used in this document
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].
1. Introduction
IGMP snooping is popularly used to limit the scope of IP multicast
traffic in enterprise Local Area Networks (LAN). With the recent
popularity of Layer 2 Networks in core of the networks, PIM-SM
snooping is gaining popularity as a way of constraining IP multicast
traffic to the section of network that is interested in receiving
such traffic.
| |
| |
------ --------
| | | |
| PIM-R | | PIM-R |
------- \ / --------
\ Multicast Routed /
---------\-------------------- / -----------
----- ------/
| S | | S | Layer 2 Switched/Bridged
| |-------| |
/ ----- ------ \
-------- / --------------------- \---------------
------- / Multicast Routed \ --------
| | | |
| PIM-R | | PIM-R |
------- --------
| |
| |
PIM-R - PIM-SM Routers
S - PIM-SM Snooping Device
Fig: Reference Model of PIM-SM snooping
2. PIM-SM Snooping Framework
Devices that implement PIM-SM snooping are required have ability to
1. Intercept Join/Prune messages [3]
2. Ability to create IP Multicast scope per VLAN (Virtual LAN)
basis.
3. MUST not have impact on other Multicast traffic
4. MUST not modify packet content (such as TTL..) or in other words
MUST be forwarded using Layer 2 forwarding rules.
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3. Theory of Operation
Let assume that
VLAN V has interfaces I == {i1, i2, ..ij...in}
Let assume we identified, by snooping PIM-SM join messages, that
interface set G need to join (*,G) or (S,G). These interfaces Let
call outgoing interfaces.
G == {o1, o2, ..oj..om}; G subset of I.
Now create a sub-scope S within the VLAN such that
input interfaces == I and
out put interfaces == G
3.1 Maintaining outgoing interfaces
outgoing interface (o) is added to the list when a join message is
received from that interface.
When an interface is added to the G a Hold timer is created for each
interface. Periodic Join messages update the life.
When there are more than on Join is received from a given interface
the largest hold time MUST be used.
When hold time expires the interface SHOULD be removed from that
group for that VLAN.
When a Prune message is received the interface SHOULD be removed
from that group for that VLAN.
If more than one Join message was received from an interface and a
Prune message is received the Hold timer MUST be update according to
the other active Joins.
3.2 (*,G) vs (S,G)
Devices that perform PIM-SM snooping is practically operating as a
Layer 2 device. When PIM-SM is not implemented entire VLAN is the IP
Multicast scope. The scope of PIM-SM snooping is to constrain the IP
Multicast data flooding. As such, PIM-SM snooping does not attempt
to disnguish between (*,G) and (S,G). In effect PIM-SM snooping
implement (V,G). Where V is all interface of the VLAN V. Such
generalization, simplify the implementation; servers the purpose and
avoid blackholes when IP routing changes the RPF inetrfaces.
4. Security Considerations
PIM-SM snooping does not affect the security aspects of PIM-SM.
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5. References
1 Bradner, S., "The Internet Standards Process -- Revision 3", BCP
9, RFC 2026, October 1996.
2 Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997
3 Estrin, D., et.al, Protocol Independent Multicast-Sparse Mode
(PIM-SM): Protocol Specification, RFC 2362, June 1998.
10. Acknowledgments
11. Author's Addresses
Tissa Senevirathne
1440 McCarthy Blvd
Milpitas, CA
Phone: 408-965-5103
Email: tsenevir@force10networks.com
Sridhar Vallepali
1440 McCarthy Blvd
Milpitas, CA
Phone: 408-571-3500
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the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into
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