Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1999-06-28
2003-02-25
Kizou, Hassan (Department: 2662)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S395500, C370S466000, C370S401000, C709S249000
Reexamination Certificate
active
06526054
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to communication networks, and, more particularly, to transitioning from DVMRP to BGMP for interdomain multicast routing over the internet multicast backbone.
BACKGROUND OF THE INVENTION
In today's information age, multicasting is gaining popularity as a technique for distributing information to groups of information consumers. Specifically, multicasting allows an information provider (referred to hereinafter as a “multicast source”) to transmit a single unit of multicast information (referred to hereinafter as a “multicast packet”) simultaneously to all information consumers (referred to hereinafter individually as a “multicast client” and collectively as “multicast clients”) in the multicast group, specifically by addressing the multicast packet to the multicast group using a multicast group address. The multicast clients monitor the communication network for multicast packets addressed to the multicast group.
One factor that is spurring the growth of multicast applications is the Internet Multicast Backbone (commonly referred to as the “Mbone”). The MBone is a virtual network that is layered on top of sections of the physical Internet. The Mbone is composed of a number of multicast regions or domains (i.e., sections of the Internet that have been upgraded to support multicasting) that are interconnected over virtual point-to-point links (commonly referred to as “tunnels”). Each tunnel interconnects a multicast border router in one multicast region to a multicast border router in another multicast region. The tunnels allow multicast traffic to pass from one multicast region to another multicast region over sections of the Internet that do not support multicasting.
In order to route multicast packets within a multicast region of the Mbone (i.e., intradomain multicast routing), the multicast routers within the multicast region exchange multicast routing information using a multicast routing protocol, such as Multicast Open Shortest-Path First (MOSPF), Distance Vector Multicast Routing Protocol (DVMRP), or Protocol-Independent Multicast (PIM). The multicast routers within a particular multicast region are required to run the same multicast routing protocol, although each multicast region may run a different multicast routing protocol.
In order to route multicast packets across multicast regions of the Mbone (i.e., interdomain multicast routing), the multicast border routers exchange multicast routing information using a separate multicast routing protocol. The predominant interdomain multicast routing protocol used by multicast border routers in the Mbone is DVMRP, which is a well-known protocol that is described in an Internet Draft of the Internet Engineering Task Force (IETF) entitled
Distance Vector Multicast Routing Protocol
, document draft-ietf-idmr-dvmrp-v3-08.txt (February 1999), hereby incorporated by reference in its entirety. However, the Mbone is migrating from DVMRP to the Border Gateway Multicast Protocol BGMP), which is a well-known protocol that is described in an Internet Draft of the Internet Engineering Task Force (IETF) entitled
Border Gateway Multicast Protocol
(
BGMP
):
Protocol Specification
, document draft-ietf-idmr-gum-04.txt (Nov. 17, 1998), hereby incorporated by reference in its entirety.
In order for BGMP to set up a multicast distribution tree across the Mbone, all multicast border routers in the Mbone would have to support BGMP. Therefore, in order to transition the Mbone from DVMRP to BGMP, it would be necessary to upgrade all multicast border routers to BGMP. Such upgrading of multicast border routers is unlikely within a relatively short period of time.
Instead, it would be preferable to upgrade individual multicast border routers to BGMP. Unfortunately, DVMRP and BGMP create different distribution trees, and therefore a multicast border router running BGMP will not interoperate with a multicast border router running DVMRP.
Thus, a need remains for a way upgrade a multicast border router from DVMRP to BGMP without requiring all multicast border routers to be upgraded to support BGMP.
SUMMARY OF THE INVENTION
In accordance with one aspect of the invention, a number of routers run an extended BGMP protocol in order to transition a piece of the Mbone DVMRP distribution tree to BGMP. The extended BGMP protocol allows the routers to create a regional BGMP tree that is rooted at router that is a member of the Mbone DVMRP distribution tree. The extended BGMP protocol ensures that no fowarding loops are created between the Mbone DVMRP distribution tree and the regional BGMP tree.
REFERENCES:
patent: 5331637 (1994-07-01), Francis et al.
patent: 6215766 (2001-04-01), Ammar et al.
patent: 6216167 (2001-04-01), Momirov
patent: 6330238 (2001-12-01), Ooe
patent: 6331983 (2001-12-01), Haggerty et al.
patent: 6385647 (2002-05-01), Willis et al.
Li Yunzhou
Ng Billy C.
Shieh Shuching
Bromberg & Sunstein LLP
Kizou Hassan
Levitan D L
Nortel Networks Limited
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