RE: Connected mode draft and retransmit implosion

At 06:25 PM 8/13/2004, Fab Tillier wrote:
> > From: bill [mailto:[email protected]]
> > Sent: Friday, August 13, 2004 5:59 PM
> >
> > Yes, that is exactly the problem... Both layers retransmitting at the
> > same time
>
>While both layers issue retransmits at the same time, the packets on the
>wire maintain their order.  The first packet sent will be delivered first,
>with the second queued up behind.  The data will not get interleaved.  There
>is no way for the retransmitted packet to get delivered first.
>
> >
> > And possibly not recovering for quite a while
>
>IB recovery is pretty much binary - if an RC QP exceeds its retry limit, it
>will transition to the error state.  At that point, all processing of the
>send queue stops and the consumer gets an error completion and an async
>error notification for that QP.
>
>I still don't see the harm in TCP retransmitting while IB is also
>retransmitting aside from inefficiencies.

Given this is a RC QP, the WR are processed in order and must complete in 
order to make forward progress.  As such, the consumer which is posting WR 
can post new or duplicate packets and the underlying QP will not see these 
until it completes the current WR.  As such, IB retransmission and consumer 
retransmission algorithms are orthogonal to one another in all respects 
sans perhaps doing a poor job configuring the associated IB retransmission 
timers as well as the arbitration policies within the fabric such that the 
consumer falls into its retransmission algorithm too often.

Mike

_______________________________________________
IPoverIB mailing list
[email protected]
https://www1.ietf.org/mailman/listinfo/ipoverib