jumbo frames

John Fraizer nanog at Overkill.EnterZone.Net
Fri Apr 27 20:05:16 UTC 2001


On Fri, 27 Apr 2001, Richard A. Steenbergen wrote:

> 
> On Fri, Apr 27, 2001 at 02:10:48PM -0500, Stephen Sprunk wrote:
> >
> > Or unless you actually have >1500 MTU to the hosts, which is quite
> > possible.  A traffic study from MCI's backbone (obviously years ago)
> > showed nearly 40% (byte-wise) of their traffic was in packets >1500
> > bytes.  With the death of FDDI, this has probably come down, but
> > GE-attached servers in colos should push it back up.
> 
> Probably not since GigE defaults to 1500 bytes and there is no agreed upon
> standard for jumbo frames. Right now it doesn't make much sense to attempt
> jumbo frames for packets headed outside of your administrative control,
> because of PMTU-D problems.

Not trying to start flame-wars again but: If we didn't have weirdos using
RFC1918 space on WAN links, the PMTU problem wouldn't be such a problem.

If you're using anything beyond ethernet on your LAN/WAN, the likelihood
is that you already have links with MTUs of 4470, etc.  I don't understand
why people are treating GigE any different than any other layer2 media
capable of MTU larger than 1500.  The fact that there is no standard
"jumbo" size is moot.  You should verify like MTU on the ends of any link.  
Am I mistaken?  Are there folks out there who are setting their ATM
OC-3/12/48 links to 1500 MTUs?

---
John Fraizer
EnterZone, Inc






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