Subject: [Tsvwg] RE: ICSC Sockets API Extensions Charter Approved

From: "Teisberg, Robert" <[email-masked]>
Date: Fri, 8 Feb 2002 09:26:19 -0600

Comments interspersed.

> 
> There is work establishing a DDP (Direct Data Placement) and 
> perhaps an RDMA
> layer or shim for SCTP.  This provides methods for allowing 
> direct placement
> with/without tags and would also allow emulation of TCP 
> partial writes.
> Please note this allows "TCP/IP stack bypass" while providing 
> congestion
> avoidance without introducing new IP protocols.  SCTP is used without
> modification for this purpose.

There is also work that has been ongoing toward a transport-independent
RDMA protocol that precedes the SCTP work by about a year.  The latter
was the subject of a BOF at the 52nd IETF in Salt Lake City last
December.

A couple of points to avoid misunderstanding: 1) No IETF working group
has yet been chartered to develop RDMA specifications; 2) None of the
proposals within the IETF for RDMA protocols that I've seen requires
changes to transport or lower layer protocols.

> 
> There are already documents addressing Socket Descriptions 
> for SCTP at:
> http://www.ietf.org/internet-drafts/draft-ietf-tsvwg-sctpsocket-03.txt
> 
> How do you envision a collaboration with this ongoing effort?

And lest there be any misunderstanding about how official the IETF work
is at this point, I refer you to
http://www.ietf.org/ietf/1id-guidelines.txt, about midway through the
document:

     Internet-Drafts are draft documents valid for a maximum of six
     months and may be updated, replaced, or obsoleted by other
     documents at any time.  It is inappropriate to use Internet-
     Drafts as reference material or to cite them other than as
     "work in progress."

In other words, it's good to learn from Internet Drafts, and sometimes
standards develop from them, but they aren't standards and in many cases
never will be standards.

> 
> A DDP/(RDMA)/SCTP draft will be available soon.  Presently 
> this document is
> being reviewed by Stephen Bailey [mailto:[email-masked]] and
Allyn
> Romanow [mailto:[email-masked]] of the RDMA effort and will be posted
to
> the IETF and announced on tsvwg:

As will a set of drafts describing a transport-independent DDP/RDMA
framework.

> An RDMA reflector is at: RDMA [mailto:[email-masked]]
> http://groups.yahoo.com/group/RDMA/

This reflector has had extensive traffic for over a year and is followed
by 260 subscribers.

> An SCTP-DDP reflector is at: SCTP-DDP
[mailto:[email-masked]]
> http://groups.yahoo.com/group/SCTP-DDP/

This one was founded in January, and as far as I know contains no
substantive traffic except cross-posts to the rdma reflector.

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---

From: "Douglas Otis" <[email-masked]>
Date: Fri, 8 Feb 2002 10:34:49 -0800

Robert,

> > perhaps an RDMA layer or shim for SCTP.  This provides methods
> > for allowing direct placement with/without tags and would also
> > allow emulation of TCP partial writes.  Please note this allows
> > "TCP/IP stack bypass" while providing congestion avoidance
> > without introducing new IP protocols.  SCTP is used without

There is ongoing work in creating a DDP layer for SCTP as indicated in the
pending announcement of a draft within the tsvwg.  The only IP protocol
suitable for RDMA would be SCTP unless there is interest in something like
UDP or RDP which would incur acceptance issues.

> > How do you envision a collaboration with this ongoing effort?
<snip>
> standards develop from them, but they aren't standards and in many cases

A draft such as this can become an informational RFC.  None the less, it
indicates ongoing efforts.  Unless you wish to exclude SCTP, there should be
interest in this effort.

> > this document is being reviewed by Stephen Bailey
> > [mailto:[email-masked]] and Allyn Romanow
> > [mailto:[email-masked]] of the RDMA effort and will be posted
> > to the IETF and announced on tsvwg:
>

That is correct.  RDMA has been the sole focus prior to the BOF.  It is not
clear however if there is interest within this group to focus on SCTP as
anything more than a compatibility point for RDMA.  It would appear there is
a conflict within this group regarding transport.  The consideration of DDP
as related to SCTP would be an example rather than being classified as just
a subset of RDMA (RDMA write) devoid of SCTP features.

> substantive traffic except cross-posts to the rdma reflector.

This is also correct.  SCTP with DDP is the sole focus for this reflector
but it only contains related cross posts at this time.  Adopting an SCTP-DDP
layer into other protocols such as RPC or entire stacks would be interesting
topics separate from RDMA.  It would also allow a departure from RDMA work
that must conform to InfiniBand or some other unspecified transport to allow
utilization of features unique to SCTP.

If it becomes clear the RDMA group is interested in expanding their charter
to include such topics, then this reflector will likely become moribund.

Doug