Quoting r. Hal Rosenstock <[EMAIL PROTECTED]>: > Subject: Re: Re: Re: [PATCH] change Mellanox SDP workaround toa > moduleparameter > > On Tue, 2006-02-21 at 16:09, Michael S. Tsirkin wrote: > > Quoting Hal Rosenstock <[EMAIL PROTECTED]>: > > > > Assuming the spec says as it is, then: > > > > 1. CMA needs to be modified to retry the connection if its rejected > > > > because > > > > of lower MTU. > > > > 2. SDP/SRP protocols specs need a clarification: e.g. current SDP spec > > > > says the connection should be closed when we get a REJ. > > > > > > Can you be specific about the spec citations for SDP and SRP for REJ > > > handling ? Isn't it more the retry strategy once the connection is > > > REJected ? Is that in those specs ? > > > > This is not explicitly explained in spec. I think Dror discussed the use of > > REJ/retry to get the MTU in his mail in sufficient detail. > > Sorry for being dense but this is what Dror wrote: > "The SWG defined a generic mechanism which uses REJ to indicate that > the passive side does not accept a certain REQ fields, and allows the > passive side to indicate an alternative value. Indirection is also > supported through the same protocol. It also allows the active side, > following the REJ, to use an alternate value, other than the one > suggested by the passive side, i.e. passive side only has a veto > capability."
I think problems that need resolution are: 1. Some of places in spec require the connection to be terminated after REJ. It does not seem to describe what Dror says anywhere. For example, see SDP spec: A4.5.1.2 ABORTING CONNECTION SETUP CA4-43: When a CM REJ MAD is received by either the connecting or accepting peer the connection setup shall be aborted. If a CM REJ MAD is sent for an SDP-specific error, the reject reason code value shall be 28 (Consumer Reject -- 12.6.7.2 Rejection Reason on page 665. An SDP implementation is expected to cleanup any resources associated with an aborted connection. 2. The implementation is still missing: does it belong as part of CM, or should it be a higher level thing like CMA? 3. Is there some solution for backward compatibility? There does not seem to exist a way to figure out whether sending REJ makes sense since the remote side will retry the connection with a better MTU value, or not. > So the only issue here is the inefficiency in terms of the back and > forth of CM messages to get to the 1K MTU connection. How important is > connection rate for SDP and SRP ? If not, can't we live with how things > are ? SDP implements sockets, and thats a very wide field, so everything is important. AFAIK, connection rate is very important for some socket applications, and does not matter at all for others. -- Michael S. Tsirkin Staff Engineer, Mellanox Technologies _______________________________________________ openib-general mailing list [email protected] http://openib.org/mailman/listinfo/openib-general To unsubscribe, please visit http://openib.org/mailman/listinfo/openib-general
