Chelsio CEO rips jumbo frames

NETWORK WORLD NEWSLETTER: JEFF CARUSO ON HIGH SPEED LANS
08/11/05
Today's focus: Chelsio CEO rips jumbo frames

Dear networking.world@gmail.com,

In this issue:

* Chelsio CEO Kianoosh Naghshineh speaks out
* Links related to High Speed LANs
* Featured reader resource
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Today's focus: Chelsio CEO rips jumbo frames

By Jeff Caruso

Last month I wrote a couple of newsletters on jumbo frames and
another on Chelsio Communications' TCP Offload technology. I
mentioned in passing that the CPU utilization improvements
researchers had found with the technology obviated the need for
jumbo frames.

Chelsio CEO Kianoosh Naghshineh saw those articles and responded
in e-mail with some thoughts of his own. I'd like to share some
of those thoughts here. First, he discussed the shortcomings of
jumbo frames - despite the fact that plenty of vendors say they
support the non-standard feature:

"It has now become fully obvious that IEEE 802.3 will not move
to standardize large frames, and this perpetuates the major
interoperability problems (even among equipment from the same
vendor!) experienced by end users who attempt to enable jumbo
frames. The team which used Chelsio's TOE [TCP Offload Engine]
to break the Internet2 Land Speed record reported facing
insurmountable difficulties getting jumbo frames to work well
over the path. Keep in mind that the link used the latest and
greatest equipment available - all supposedly jumbo
frame-capable... The conclusion of these experiments was that
equipment which may pass jumbo frames may not be capable of
doing so at high speeds or without increased drop rates -
perhaps due to buffering problems."

Naghshineh went on to limit the role that jumbo frames might
also have in high-performance computing (HPC) environments:

"When it comes to the performance impact of jumbo frames on HPC
applications, it is important to remember that jumbo frames are
one solution for one problem: bulk data transfer. The
applications of interest in HPC environments are mostly
transaction-based, as we have come to learn. Therefore, they are
mostly latency-sensitive, and that's why 10 Gigabit Ethernet,
having finally approached the golden 10 microsecond limit, is
doing so much better than Gigabit Ethernet when compared to
specialized interconnects.

"It is clear that increasing the frame size on the wire does not
help in this case, but what may be less intuitive is that [jumbo
frames] actually result in decreased performance. In some cases
we have seen 30% to 50% decrease in transaction rates compared
to standard Ethernet frames. Having looked into it further, the
reason appears to be the weak pipelining of large frames, which
when sent repeatedly over PCI buses and Ethernet links, causes
store-and-forward delays to accumulate and increase the latency
of a transfer. In contrast, the offload engine, which is capable
of operating at line rate with frames as small as 256 bytes,
does not face this problem and was able to match or exceed the
performance of InfiniBand and Myrinet."

Bear in mind that this is a vendor's perspective, but it's
interesting nonetheless.

The top 5: Today's most-read stories

1. Microsoft open source exec: Not the loneliest guy in Redmond
<http://www.networkworld.com/nllan4939>

2. EMC announces surveillance management application
<http://www.networkworld.com/news/2005/080905-emc.html?t5>

3. DKIM fights phishing and e-mail forgery
<http://www.networkworld.com/nllan4940>

4. Microsoft fixes Print Spooler, Plug and Play flaw
<http://www.networkworld.com/nllan4941>

5. Sprint, Nextel expect to finish merger Friday
<http://www.networkworld.com/nllan4942>
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To contact: Jeff Caruso

Jeff Caruso is managing editor of online news for Network World.
He oversees daily online news posting and newsletter editing,
and writes the NetFlash daily news summary, the High-Speed LANs
newsletter and the Voices of Networking newsletter. Contact him
at <mailto:jcaruso@nww.com>
_______________________________________________________________
This newsletter is sponsored by Tacit Networks
Network World Executive Guide: Staying Focused on the Moving
Target that is Storage

Keeping pace with evolving storage strategies, architectures,
and trends is not unlike keeping pace with your organizations
underlying capacity needs. From ILM strategies to SAN management
to the threat of those USB memory sticks, this Network World
Executive Guide will help you stay focused on the moving target
that is Storage. Register now and get a free copy of Network
World's Storage Executive Guide.
http://www.fattail.com/redir/redirect.asp?CID=109980
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