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From: Amar Mudrankit Michael, thanks for your reply. But, this gives rise to couple of questions.. 1] If such multicast routing protocol for IB routers is not yet specifid by IBTA or IETF, then current implementation have IP subnet restricted within a IB subnet. According to RFC 4391, section 9.1.1, the link layer address is formed through combination of GID + QPN. If we are not spanning across IB subnets what is the use of GID as we need to get LID from GID? Probably, in that case ARP reply with LID,Q_Key and other path information would be helpful which resolves path in 1 loop than 2 loops in case of GID(first to resolve GID and then to get LID). [Todd Rimmer] Basing IPoIB on the GID keeps open the opportunity for IPoIB to span IB subnets in the future. Also this permits the SM to manage the paths and PathRecord parameters appropriately even in non-routed IB networks. For example, if multi-pathing is used (LMC!=0, hence giving multiple LIDs per port), the SM may respond to PathRecord requests for a given Destination GID with a different LID depending on Source GID. Such a mechanism can be used to manage routes in the fabric, etc. That is just a simple example, since the PathRecord includes lots of other information as well (QOS, routing info, MTU, etc). The SM can provide different PathRecord values for each Source GID talking to a given Destination GID. The IETF needed a "MAC Address" for IPoIB. GID+QPN gave them a unique endpoint with the potential to work through routers and still support the full intentions of IB's QOS and routing options. LID+QPN would severely limit those capabilities. In general it's a bad idea for end nodes to simply exchange LIDs as it bypasses many of the intentions of the IB spec. Such applications will break in fabrics which use the more advanced IB QOS, routing, etc options. Todd Rimmer Chief Architect QLogic System Interconnect Group Voice: 610-233-4852 Fax: 610-233-4777 [EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]> www.QLogic.com
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