On Sun, 2005-10-09 at 10:19, Sean Hefty wrote:
> >I think iWARP can be on top of TCP or SCTP. But why wouldn't it care ?
>
> I'm referring to the case that iWarp is running over TCP. I know that it can
> run over SCTP, but I'm not familiar with the details of that protocol. With
> TCP, this is an end-to-end connection, so layering iWarp over it, only the
> endpoints need to deal with it. I believe the same is true for SCTP.
Yes, SCTP is similar in those regards.
SCTP creates a connection and then multiplexes a set of sessions over it. You can conceptually think of it as akin to IB RD but where all QP are bound to the same EEC.
> >Doesn't a routing decision still need to be made at the IP layer ?
>
> Routing of the IP packets is done at the IP layer, but I don't see how this
> affects iWarp.
It does under the "covers", those covers being IP routing.
iWARP uses IP routing so there is zero difference between iWARP and any other IP-based protocol suite that operates above the IP layer.
> >Doesn't the IP next hop need to be determined (e.g. gateway when the
> >destination is off the local IP subnet) ? Is there something that
> >precludes iWARP from working across IP subnets ?
>
> I can't think of anything that would preclude iWarp from working
> across subnets.
Doesn't the IP next hop need determining in that case ? Why is that not
relevant ? I don't think the iWARP connection is end to end in all
cases.
TCP / SCTP are end-to-end thus iWARP is end-to-end. The fact that there is an intermediate router / gateway between does not matter. That is just a bit of IP routing to forward the packets. The ARP / ND protocols determine the next hop for the IP layer thus iWARP just like TCP/SCTP is not affected or cognizant of the underlying fabric topology.
Mike
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