Re: MTU Settings

Greg Stark ( )
25 Aug 1998 10:12:27 -0400

"John David M. Miller" <> writes:

> With all the stuff I am reading about MTU settings
> would it improve performance to my dial up customers
> to set the MTU to 576 on our Max 4048's? If the MTU
> setting was changed do I need to change the MTU on
> our NT servers (Mail, News, WWW) also?
> How about the client side? Would they also need to
> make the change or would the fact that they are set
> to a higher number already preclude the need to change?

It would improve interactive performance, possibly at the expense of
total bandwidth. I'm not sure what it would do to the all-popular

Note that there are some services which require a minimum size
unfragmented packet (for reasons that aren't clear to me), NFS
directory listings typically stop working if you set the mru below
about 1k.

So setting it on the server may not be a great idea, since there's no
easy way for the client to bypass that setting and raise the limit.

Also if you just set the mtu on the servers, that would only affect
packets going in one direction. You also want to find a setting for
the MRU, which is a parameter sent when establishing PPP to request a
maximum MTU from the peer.