Path: utzoo!mnetor!uunet!husc6!uwvax!dogie!uwmcsd1!ig!agate!ucbvax!PESCADERO.STANFORD.EDU!cheriton
From: cheriton@PESCADERO.STANFORD.EDU ("David Cheriton")
Newsgroups: comp.protocols.tcp-ip
Subject: Re:  offloading the protocols
Message-ID: <8803160106.AA05728@Pescadero>
Date: 16 Mar 88 01:06:02 GMT
Sender: usenet@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 23

VMTP (RFC 1045) is specifically designed to work well with hardware support
on a network adaptor board with its own processing power.  In fact, we have
designed and are implementing such a board to support VMTP, and this process,
concurrent with the protocol design and refinement, has significantly
influenced the design of the protocol.  I would agree there are severe limits
on what such intelligent interfaces can provide with current protocols
independent of how well the boards are designed.  I would also agree that
most intelligent interfaces to date are slower than the dumb fast ones
when you look at transport-level performance.  However, my experience
with VMTP and the NAB (Network adaptor Board) we are building convinces
me that this approach is essential for transport-level performance in the
same general range as the network when we go to 100 Mb networks and higher.
Moreover, offboarding the processing load of protocols seems to have
additional advatnages on multiprocessors machines because the interrupts
and cache demands of protocols leans on the critical resources, namely the
system bus.

Interested parties can send to my secretary (nevena@pescadero.stanford.edu)
for a copy of our draft paper on the NAB.  The VMTP spec is of course
available as an RFC - only the first 30 pages are really needed to get
a feeling for the protocol.

David Cheriton