Thread Links Date Links
Thread Prev Thread Next Thread Index Date Prev Date Next Date Index

Re: [HSSG] Topics for Consideration: Jumbo Frames



Looking at the article on Jumbo frames that you referenced at, 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 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.



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,
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 ...


Arthur Marris wrote:

Joel, Mike,

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



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.


Marcus Duelk
Bell Labs / Lucent Technologies
Data Optical Networks Research
Crawford Hill HOH R-237
791 Holmdel-Keyport Road
Holmdel, NJ 07733, USA
fon +1 (732) 888-7086
fax +1 (732) 888-7074