Re: GID clarifications
Kanoj Sarcar <[email protected]>
| Newsgroups | gmane.ietf.ipoib |
|---|---|
| Message-ID | <[email protected]> |
Vivek Kashyap wrote: > > Kanoj, > > The port's GUID is it's EUI-64 identifier. A GID, in turn can be formed using this GUID, the CA's GUID or some other value. Any GID is unique in the IB fabric however only by using the port's GUID/EUI-64 identifier can one uniquely identify the port. The other GID's, as noted, can be applied to other ports too - though not concurrently. The GID formed using the EUI-64 identifier is the 'GID at index 0'. I've made note of your comment and can clarify further as needed. > > wrt, using only GID at index 0 as in the MAC address, there have been proponents of using the other GIDs (non EUI-64 GID). > > Vivek Vivek, Per IBA 1.1 section 4.1 EUI-64 subsection and 4.1.1 item 2, manufacturer assigned and SM assigned values are required to be EUI-64 compliant (they differ only in u/l bits). Thus, all GIDs contain an EUI-64 in the lower 64 bits; thus saying "GUID is its EUI-64 identifier" might be confusing. Saying "GUID using manufacturer assigned EUI-64 identifier" or better "GID index 0" removes all confusion. I think we agree on the intent, I just want to make sure if you use the term GUID, you do specifically define what you mean by it. Regarding MUST vs RECOMMENDED, is it worthwhile reconsidering given that 1. SM assigned GIDs are not that popular (anymore?) 2. it allows determination of sender's ipoib address, thus allowing (receiver side) implementations to be dlpiv2 conformant? Thanks. Kanoj > -- > Vivek Kashyap > Linux Technology Center, IBM > [email protected] > [email protected] > Ph: 503 578 3422 T/L: 775 3422 > > Kanoj Sarcar <[email protected]> > Sent by: [email protected] > > 12/02/2003 03:54 PM > Please respond to Kanoj.Sarcar > > Hi, > > It seems that certain parts of the > draft-ietf-ipoib-ip-over-infiniband-05.txt draft might > require clarification. For this discussion, please refer to > > 1. section 9.1 Link Information says: > "The GID, if formed using the GUID, can be used to unambiguously > identify an endpoint." > > 2. section 9.1.1 Link Layer Address/Hardware Address, part c) says: > "It is RECOMMENDED that the GID formed by the combination of the > IB subnet prefix and the port's GUID be included in the > link-layer/hardware address." > > Can comment #2 be safely taken to mean that GID index 0 is > being RECOMMENDED? Port GUID seems somewhat ambiguous, since I > am not sure (after reading IBA 1.1 section 4.1) whether the > term GUID refers only to the manufacturer assigned value that appears > in lower 64 bits of GID index 0, or whether it also includes > lower 64 bits of SM assigned GIDs at higher indices. If GID index 0 > was really intended, the comment should explicitly state so to prevent > confusion. > > Also, to make things simple, is it reasonable to REQUIRE implementations > to always use GID index 0 (maybe this depends on whether existing > implementations all use GID0 only)? The reason this might be > interesting is that when a node receives a packet without a GRH > (whereby it already knows the sender's LID and QPN), it can possibly > reverse lookup the sender's LID to identify the sender's GID index > 0 and concatenate the sender's QPN to figure out the sender's link > address. Thus, a receiver can always figure out the sender's address, > even when a GRH is not present. This would be similar to ethernet, > where a receiver can always determine a sender's address, and thus > is more DLPIv2 (unitdata_indication) friendly. > > Regarding comment #1, what does "unambiguously identify an endpoint" > mean? GIDs are unique in the subnet; and if an IP link contains > members in multiple IBA subnets, the subnet prefixes will disambiguate > which endport is being referred. > > Thanks. > > Kanoj > > _______________________________________________ > IPoverIB mailing list > [email protected] > https://www1.ietf.org/mailman/listinfo/ipoverib