[95519] in North American Network Operators' Group
RE: Jumbo frames
daemon@ATHENA.MIT.EDU (michael.dillon@bt.com)
Thu Mar 29 06:53:11 2007
Date: Thu, 29 Mar 2007 11:54:35 +0100
In-Reply-To: <E1A89C78-7837-4485-AEA9-0A3E9995C740@nosignal.org>
From: <michael.dillon@bt.com>
To: <nanog@merit.edu>
Errors-To: owner-nanog@merit.edu
=20
> The original poster was talking about a streaming application - =20
> increasing the frame size can cause it take longer for frames=20
> to fill =20
> a packet and then hit the wire increasing actual latency in your =20
> application.
>=20
> Probably doesn't matter when the stream is text, but as voice and =20
> video get pushed around via IP more and more, this will matter.
Increasing the MTU is not the same as increasing the frame size. MTU
stands for Maximum Transmission Unit and is a ceiling on the frame size.
Frames larger than the MTU must be fragmented. Clearly it is dumb for a
voice application or a realtime video application to use large frames,
but setting the MTU on a WAN interface to something higher than 1500
does not require the application to fill up its frames. Also, if a video
application is not realtime, then use of large frames is more likely to
do good than to do harm.=20
--Michael Dillon
