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Re: [HSSG] Topics for Consideration: Jumbo Frames



Marcus,

 

Looking at the article on Jumbo frames that you referenced at http://sd.wareonearth.com/~phil/jumbo.html, it includes the statement:

“while the number of packets larger than 1500 bytes appears small, more than 50% of the bytes were carried by such packets because of their larger size.”

 

However, when you look at the source of this information (reference 1), what it actually says is:

“over half of the bytes are carried in packets of size 1500 bytes or larger”

 

This is, of course, totally different.  As the red curve of figure 3b of http://www.caida.org/publications/papers/1998/Inet98/Inet98.html shows, it is the 1500 byte packets that contain ~ 55% of the bytes in the analysis and in fact the total number of bytes in all packets above 1500 is a negligible percentage of the total.

 

Regards,

Pete Anslow

 

Nortel Networks UK Limited, London Rd, Harlow, Essex CM17 9NA, UK

External +44 1279 402540 Fax +44 1279 405670  ESN 742 2540

 

Email: pja@xxxxxxxxxx

 


From: Marcus Duelk [mailto:duelk@xxxxxxxxxx]
Sent: 10 August 2006 16:21
To: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [HSSG] Topics for Consideration: Jumbo Frames

 


Hi Arthur,

there is a nice little "tutorial" about the Pros and Cons
of jumbo frames at http://sd.wareonearth.com/~phil/jumbo.html,
it also includes actual frame size distribution measurement on the
MCI backbone from 1998 in which you can see that there are a lot
of frames >1500B from FDDI and other sources, they mention that
more than 50% of all traffic (measured in Bytes and not in packets)
come from packets >1500B. But, larger packets also have a clear
benefit to TCP/IP performance. The difference in store-and-forward
latency between 1.5kB and 9kB is negligible at higher speeds, time
of flight is much, much higher ...

Marcus


Arthur Marris wrote:

Joel, Mike,

   Don't jumbo frames increase latency in links where there is store and forward?

 

Arthur.  


Both my position and that of the customers I deal with is that higher speeds, 10gbps included, is more efficient with the larger packets.

no argument from me on this one, although the actual efficiency gained comparing 1.5 K frames to 9 K frames is only ~ 2%, but when you're on the cutting/bleeding edge of technology, every bit counts.


 



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Marcus Duelk
Bell Labs / Lucent Technologies
Data Optical Networks Research
 
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