Subject: Practical throughput

From: "Hattig, Myron" <[email-masked]>
Date: Wed, 28 Feb 2001 09:51:24 -0800

Peter,

Where and how is this "practical throughput" test documented.  In working
with many other link layer technologies people generally don't do a good job
of testing throughput. For example, many use FTP transfers to test
throughput. FTP uses TCP. TCP throughput is gated by ACKs. If ACKs are slow
in the TCP/IP stack then throughput suffers.

In addition to describing the test, a description of where the problem
reside in the protocol stacks is required. The 1394 WDM bus architecture is
not well suited for connecting to NDIS interfaces in Windows. This could
easily be one source of the problems you are seeing.

Here is very clear example to try, determine the "practical throughput" of a
memory mapped model that only passes 1500 bytes. It is possible that it may
not be any better than the current scheme because of the way the 1394 stacks
parse packets. Has this been tried?

The claims below are very broad and could have many reasons. Without more
information it is very hard for me to accept the need to re-open the spec or
delay ipv6/1394.

-myron

> When I say "practical"
> throughput, I do not
> mean a theoretical maximum but an empirical value observable
> when other
> protocols well-suited to mass data transfer (e.g., SBP-2) are
> scrutinized.
> For example, the BEST end-to-end throughput on a 400 Mbps bus
> observed to
> date is a wretched 100 Mbps. Instead of the 25% efficiency
> achieved, a more
> efficient IP1394 protocol should be able to effect 85%!