[openib-general] Problem is routing CM REQ

[Michael Krause]

At 03:48 PM 2/12/2007, Sean Hefty wrote:
>>An endnode look up should be to find the address vector to the 
>>remote.   A look up may return multiple vectors.   The SLID would 
>>correspond to each local subnet router port that acts as a first-hop 
>>destination to the remote subnet.    I don't see why the router protocol 
>>would not simply enable all paths on the local subnet to a given remote 
>>subnet be acquired.  All of the work is kept local to the SA / SM in the 
>>source subnet when determining a remote path to take.
>>Why is there any need to define more than just this?
>
>For an RC QP, we need at least two sets of LIDs.  In the simplest case, we 
>need the SLID/router DLID for the local subnet, and the router SLID/DLID 
>for the remote subnet.  The problem is in obtaining the SLID/DLID for the 
>remote subnet.

Not quite.   The router protocol should determine the "next hop" LID to be 
used to either reach the destination endnode if in its local subnet or for 
the next router on the path to the remote.   CM only needs to be concerned 
with what is in a local subnet for finding the router or the endnode.  It 
does not need to comprehend the remote subnet(s) LID.   That is the router 
protocol to determine.  CM also must understand the GIDs involved which the 
router will process to figure out its LID mapping to the next hop.

Mike