On Fri, May 12, 2006 at 08:11:17AM -0400, Hal Rosenstock wrote: > > To allow what Roland is talking about you need an unambiguous > > mechanism where the SA can signal to the client that the path > > needs a GRH. > > Ah, you are referring to the SA path record response not the request.
Yes.. Though I think we are still talking about different things in a few places ;> How about this, how do you see this scenario: 1) Client gets a DGID from 'someplace' 2) Client sends a SA query to resolve the DGID to a Path Record 3) Client configures a QP based on the Path Record Now, the question I'm interested in is this: During step #3 what test should the client apply to determine if a GRH should be used with the QP. Other issues around the GRH like management MAD responses use and multicast I feel are well specified and don't need more consideration. > > Think of it the other way, HopLimit < 2 means it _can't_ be forwarded > > off subnet, so that result from the SA should _always_ cause the > > requesting client to not use a GRH for that path. > > Not always true in terms of local subnet (multicast and management MAD > response exceptions). Yes, but these are well specified. Multicast must always have a GRH. MAD requests are covered under my scenario above and MAD responses to MAD requests with GRH's are specified to use the GRH and set the HopLimit = 0xFF. Also, I would assume when building a router that multicast packets with a hop limit of 0 are non-forwardable based on the rules in IBA. > Are you saying HopLimit is supplied to the SA in the request ? It could > be but it's optional in general. In the router case, an off subnet DGID > should be sufficient. I would think the HopLimit (as well as the other > GRH fields) would need to be returned by the SA to the client. Talking about a request for a Path to the SA from a client now: I would suggest that if the client wishes to restrict itself to paths that are only on-link then it could send a SA request with the path record HopLimit=0. A SA request with HopLimit=* (masked out of component mask) should let the SA return routed paths. I also think that the SA response should have a HopLimit of 0 for local paths and a HopLimit >= 2 for routed paths. However, I can't find any wording in IBA that would require this behavior. > Not sure exactly what you mean by full control over the routing header > (GRH). The SA supplies the info for the headers to the client and the > client is responsible for putting the correct info in the headers. Do > you mean supplies sufficient info for the client to do this correctly ? > If so, I agree. As far as I can see IBA includes all header information for the GRH and LRH in the PathRecord response. It does not define a how to determine if the path described by a PathRecord response requires a GRH or not. Thanks, Jason _______________________________________________ openib-general mailing list [email protected] http://openib.org/mailman/listinfo/openib-general To unsubscribe, please visit http://openib.org/mailman/listinfo/openib-general
