[Gllug] pppd MRU/MTU optimisations?

[home at alexhudson.com]

On Thu, Aug 23, 2001 at 01:40:34PM +0100, Rev Simon Rumble wrote:
> I would imagine the defaults are designed for slower ppp links such as
> modems, so I may want to make them larger.  Will this improve
> performance?  What's a good way to test an improvement in performance?

A 1500 default is actually for quick links - ethernet uses it, for example.
But it's a bandwidth vs. latency issue. Smaller frames are better for low
latency apps (like Quake), bigger frames get you more bandwidth (better ftp
transfers). Bigger frames are also more susceptible to errors - bigger
target to hit. If your link is pretty much error-free, no problem, but if it
suffers regular errors bringing the MTU down means the retries will be
quicker. 

I would leave it at 1500 to be honest. Although slower links (like modems)
often benefit from sizes of around a third of that.

Cheers,

Alex.

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