Subject: Re: Last Call: Transmission of IPv6 Packets over IEEE 1394 Networ ks to Proposed Standard

From: Bill Nowicki <[email-masked]>
Date: Wed, 28 Feb 2001 11:23:41 -0800

Hello Eric!

My opinion is that both sides are right to an extent. Omneon did work on IP
over 1394, and also noticed poor performance. From what we can tell, these
are mostly issues with the OHCI and NDIS layers: the interface between the
controller chip and the host, and the interface between the hardware and the
operating systems' (at least one leading brand) TCP/IP stack. So yes there
are indeed practical problems with FIFOs for IP.

The important point is that IETF deals with **PROTOCOLS**, not host
interfaces. Yes, the protocols should be implementable with good
performance. But host interface problems should be fixed by fixing the host
interfaces. For example, doing some of the OS or interface chip
optimizations that Ethernet has been doing for many years. Making the
protocols more complicated to work around host interface limitations seems a
bad choice. On balance I have to agree with Eric on this.

(personal opinion, not company's!)

Bill Nowicki, Omneon Video

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From: Peter Johansson <[email-masked]>
Date: Wed, 28 Feb 2001 17:31:21 -0800

Hello, Bill! Thanks for sharing some actual implementation experience.

At 11:23 AM 2/28/01, Bill Nowicki wrote:

>But host interface problems should be fixed by fixing the host interfaces.
>For example, doing some of the OS or interface chip
>protocols more complicated to work around host interface limitations seems
>a bad choice.

Depending upon one's frame of mind, it's a blessing or a curse that IEEE
1394 is neither 100% bus nor 100% network. Pragmatically, it is what it is.
Which is why I question your observation that efficiency problems are
principally within the host interface.

If IEEE 1394 were used for nothing but network traffic, one would expect
the host interface to be optimized for that traffic---just as Ethernet NICs
have been. End of story.

But the memory-mapped model in Serial Bus works very well for a lot of
applications, many of them not inherently network applications. The
"practical throughput" I alluded to in an earlier message is the informally
reported result observed by a major operating systems vendor for SBP-2 mass
storage devices. If we can get impressive throughput for these devices, why
not for Internet Protocol transported over IEEE 1394?

I think an assertion that a protocol suited to IEEE 1394 would of necessity
be "more complicated" may not be true. At the least, it's backed up no
better than my assertions that a protocol more closely tied to a Serial Bus
DMA architecture would necessarily be "more efficient".

I agree with a lot of what Myron has to say, namely that the exact causes
of inefficiency have not been adequately measured. I remain of the opinion
that there is enough uncertainty to warrant a reexamination of this
matter---but I can see that I am in a minority position (at least with
respect to delaying the advance of Draft-IETF-IPNGWG-1394-01 to Proposed
Standard).

Regards,

Peter Johansson

Congruent Software, Inc.
98 Colorado Avenue
Berkeley, CA  94707

(510) 527-3926
(510) 527-3856 FAX

[email-masked]