North American Network Operators Group

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Re: MTU of the Internet?

  • From: Perry E. Metzger
  • Date: Thu Feb 05 20:25:27 1998

Its really amazing how people who know very little seem to think they
have so much to say.

Do any of you rocket scientists have even the smallest inkling of the
fact that there are people out there who actually DO know what they
are talking about, and have produced standards explaining how to do
the stuff?


Phil Howard writes:
> Steve Carter writes...
> > Theory tells me that for both types of traffic it is probably better,
> > for response times sake, to have an asymetrical MTU (send = smaller,
> > receive = bigger from the clients perspective).  Servers set big MTU's,
> > clients set their's smaller.
> > 
> > Irrespective of your MTU size, the file or web page, etc. size is always
> > going to be the same, therefore, if you set a smaller MTU at the server
> > or within the network, fragmentation occurs, meaning greater overhead
> > for a file of a given size and due to this the end station will have to
> > reconstitute the data stream out of smaller packets, meaning more CPU
> > overhead.
> I still think there has to be some kind of better approach to what it is
> we are doing when we have such extreme ranges of bandwidth capacity and
> the resultant extremes of optimal MTU.  One idea I'm thinking of, and I
> may well even give it a try between a couple of Linux boxes over a phone
> line, is what I call "cell multiplexed PPP".  Basically this would be a
> channelized stream that can parallel multiple packets.  Small ones can
> come right through while the big ones are still working.  That may only
> help minimally for parallelizing image loading unless there is added
> logic that detects the TCP ports and ensures that only one port at a
> time is taking up a channel.