Subject: (IPng 6477) Re: Host Fragmentation

From: [email-masked]
Date: Wed, 16 Sep 1998 08:06:49 EDT

In a message dated 9/15/98 3:07:45 PM Eastern Daylight Time,
[email-masked] writes:

> [email-masked] writes:
>  > Not true.  The following paragraph has been left out.

>  >   The tests were conducted using a single-processor Intel 400-MHz
>  >   Xeon-based server and four 333-MHz Pentium II clients. An Alteon
>  >   Gigabit Ethernet server switch connected the servers and clients.
 
>  > The Alteon Gigabit Ethernet server switch is a fragmenting
>  > gigabit/10/100Mbps switch or extruder, but it could
>  > just as well have been a fragmenting gigabit 10/100Mbps
>  > router.  The point is that server performance goes
>  > up if the server does not do the fragmentation but
>  > instead the fragmentation is off-loaded to an intermediate
>  > packet switch.

>  Read the damned datasheet, please.  The Alteon Gb Ethernet switch
>  supports jumbograms on BOTH the Gb Ethernet ports AND the 100Mb ports.
>  Without question, that's what this test was using.  That's why they
>  mentioned the types of cards in the clients.
>  	http://www.alteon.com/pdf/ace110.pdf?124,174

So?  The device apparently uses the same ASIC on every port, and I
suppose if the Alteon Gigabit adapter is used in 100Mbps fallback mode
on a 10/100 Mbps port, it makes sense to transceive jumbograms on the
100Mbps medium.  But such is not the situation here.

The article only mentions the use of a single Gbps jumbogram capable
adapter card only in the server.

  Microsoft officials said they achieved 920Mbps throughput on a server
  using the AceNIC 180, a Gigabit Ethernet network interface card from
  Alteon, which also supplied the proprietary jumbo-frame technology.

I just checked the 82558/82557 and 21140 manuals.  The common
10/100Mbps adapters do not support jumbogram.  While I do not have a
21143 manual here, it is unlikely that this part supports jumbograms.
I have to assume that the tests were run as we run similar tests and
as described in Alteon white papers: the clients were using some
common 100 Mbps adapter cards, which do not support
jumbograms. Otherwise one would think that that the article would have
stated something like the following.

  Microsoft officials said they achieved 920Mbps throughput on a server
  using the AceNIC 180, a Gigabit Ethernet network interface card from
  Alteon, which also supplied the proprietary jumbo-frame technology
  when that server communicated with four clients all of which used
  the same AceNIC 180 adapter in jumbo-frame mode.

In point of fact all throughout the Alteon white papers and
documentation the standard described configuration is 

*) a server on one of the gigabit ports,

*) perhaps another server on the other gigabit port and

*)10/100 Mbps clients (using standard 10/100 Mbps non-jumbogram
supporting adapters -- Alteon does not sell a jumbogram capable 10/100
Mbps adapter card for clients) attached to the 10/100 Mbps ports.

The performance test that Alteon sees using WindowsNT servers is about
the performance that we see with Alteon cards in Compaq Alpha Servers
that run Unix.  Clients with 32bit busses and 100 Mbps ethernet
adapter cards support a throughput of approximately 240Mbps.  We find
that 64 bit buss clients with 64 bit adapter cards can support
approximately 450 Mbps.  When a 64 bit server is used with jumbogram
technology where the Alteon switch performs the dreaded network
fragmentation, the server can support a throughput over 900 Mbps,
essentially doubling the number of clients that can be supported.

Thus the use of jumbograms at the server with network fragmentation
doubles the number of clients that the server can support.  The
designers of IPv6 have for no obvious reason chosen to ban
configurations that can provide tremendous performance wins.  The much
touted PMTU procedures would completely thwart the benefits that the
Alteon technology provides.
  
>  That I'm even replying shows how much the tie I'm wearing today has
>  severely constricted the blood flow above the neck.

And has apparently affected Carlson's ability to read as well.

I have to admit that Alteon is perhaps being a little bit obscure with
regard to their exact procedures with all this discussion in the white
papers of VLANs, intranets and P802.1q.  But in the face of the
irrationality of the anti-network fragmentation point of view that we
see in this forum, I am hardly surprised.

>  *Plonk*  Must remember to add this thread to the kill file.

Understandable given the apparent reading disability.

BTW, I obtained a copy of Mogul's fragmentation paper.  Briefly
skimming, practically every point refers to technological problems
that existed 10 years ago and that are essentially irrelevant today.
If this sort of analysis provides the foundation of IPv6, IPv6 should
be described as "The Protocol of Tomorrow, Designed to Address the
Problems of Yesteryear."  I will try to provide a critique of the
paper later today or tomorrow.

Joachim Martillo
<A HREF="http://members.aol.com/Telford001/">Telford Tools, Inc.</A>

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