[openib-general] [ANNOUNCE] Contribute RDS (ReliableDatagramSockets) to OpenIB

[Ranjit Pandit]

On 11/4/05, Bob Woodruff <robert.j.woodruff at intel.com> wrote:
> Woody wrote,
> >Perhaps if tunneling udp packets over RC connections rather than
> >UD connections provides better performance, as was seen in the RDS
> >experiment, then why not just convert
> >IPoIB to use a connected model (rather than datagrams)
> >and then all existing IP upper level
> >protocols would could benefit, TCP, UDP, SCTP, ....
>
> Saying this another way.
> Make the hardware run the existing protocols better, don't
> design a new protocol to work around the problems with a
> specific hardware transport.
>

What about SDP? Isn't SDP bypassing the existing TCP protocol stack to
take advantage of a specific harware transport - IB?

RDS is somewhat like SDP in that it offloads/accelerates SOCK_DGRAM
instead of SOCK_STREAM.

> woody
>
>
>
>
> -----Original Message-----
> From: Caitlin Bestler [mailto:caitlinb at broadcom.com]
> Sent: Friday, November 04, 2005 2:31 PM
> To: Woodruff, Robert J; Rick Frank; Ranjit Pandit; Grant Grundler
> Cc: openib-general at openib.org
> Subject: RE: [openib-general] [ANNOUNCE] Contribute RDS (
> ReliableDatagramSockets) to OpenIB
>
>
>
> > -----Original Message-----
> > From: openib-general-bounces at openib.org
> > [mailto:openib-general-bounces at openib.org] On Behalf Of Bob Woodruff
> > Sent: Friday, November 04, 2005 2:15 PM
> > To: 'Rick Frank'; Ranjit Pandit; Grant Grundler
> > Cc: openib-general at openib.org
> > Subject: RE: [openib-general] [ANNOUNCE] Contribute RDS (
> > ReliableDatagramSockets) to OpenIB
> >
> > Rick wrote,
> > >I've atttached a draft proposal for RDS from Oracle which discusses
> > >some of
> >
> > >the motivation for RDS.
> >
> > Couple of questions/comments on the spec.
> >
> >
> > AF_INET_OFFLOAD should be renamed to something like AF_INET_RDS.
> >
> > Would something like SCTP provide the same type of
> > capabilities (relaible datagrams) that you are suggesting to
> > add with RDP ?
> >
>
> Each stream within an SCTP association provides a reliable,
> ordered service.
>
> There would be two primary constraints in using SCTP for
> this usage profile:
>
> 1) The Stream ID is 16 bits, and the natural mapping would
>    be to have each stream represent a source/destination
>    pairing. That would imply fewer than 256 endpoints per
>    host. If the source were encoded by hand then the limitation
>    would be 64K, but that's an awkard mix of application and
>    transport layer encoding.
> 2) The network has to be composed of SCTP friendly equipment.
>    When IP network equipment operated exclusively at L2/L3,
>    and L4 was left to the endpoints, SCTP would have had no
>    problem being deployed. But because of security and IPV4
>    address shortages there are a lot of middleboxes that are
>    L4 aware, and generally that L4 awareness is limited to
>    TCP and UDP.
>
> SCTP support would also have to be part of the offload device.
> RDS enables reliable datagrams using existing offloaded RC
> services (IB RC, iWARP, TOE). No NIC enhancements are required.
>
>
>
>
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