Subject: RE: TCP/IP Framing Assists

From: [email-masked]
Date: Sat, 10 Mar 2001 16:21:21 -0500

Copying the list on a response to a question of general interest ...

Charles Monia writes:
> At the last IPS WG, you said you felt there was a possibility that the
IETF
> community might be persuaded to accept some sort of framing assists for
> TCP/IP (At the time, I characterized this as 'SCTP lite').
> 
> Has there been any progress on this front? This could impact the outcome
of
> the common encapsulation effort.

It is still a definite possibility.  There has been progress, but it's not
exactly
visible, yet.  As indicated in the IPS Agenda for Minneapolis, work on this
will be conducted through the tsvwg Working Group - I have not seen a
Minneapolis Agenda for tsvwg, so I don't know if/when this issue will be
taken up.  I'll try to get an update (no discussion) on this topic included
in the initial 10 minutes of Agenda Bashing and Administrivia.

For the FCIP/iFCP common encapsulation, I would recommend separating
framing from data representation, and adopting an approach along the lines
of
that in Section 1.2.8 of the iSCSI draft in which framing logically occurs
between the block storage protocol and TCP.  In particular, this means
that the 0xfcfcfcfc reserved value/word-stuffing approach in Section 2 of
the weber draft should be specified separately as a "shim" protocol 
at this level if it is to be carried forward - this is the right way to
think
about it in any case because any protocol headers at higher layers in
the stack have to be word-stuffed if the reserved value sequence (4
occurrences of the reserved value in the weber draft) occurs there.

The result could be three TCP framing approaches
	- SCTP-lite
	- Markers (iSCSI appendix)
	- Reserved value/word stuffing (weber draft)
Each could be independently chosen/used by any of the IPS block storage
protocols, provided that suitable negotiation mechanisms are specified to
make sure that both sides of a connection understand exactly what is being
used in which direction.

--David

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David L. Black, Senior Technologist
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