Re: Another proposal to think about

William Westfield <BILLW@MATHOM.CISCO.COM> Fri, 01 December 1989 13:54 UTC

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Date: Fri 1 Dec 89 05:54:06-PST
From: William Westfield <BILLW@MATHOM.CISCO.COM>
Subject: Re: Another proposal to think about
To: mogul
Cc: mtudwg
In-Reply-To: <8911291833.AA00675@acetes.pa.dec.com>
Message-Id: <12546625828.8.BILLW@MATHOM.CISCO.COM>

    NFS (+ Sun RPC) provide a textbook example of both the possibility of
    doing this right, and the dangers of doing this wrong.  Sun RPC loves
    to send 8kb UDP packets over an Ethernet (with a 1.5kb MTU).  This is
    often a disaster when a gateway (or slow receiver interface) is
    involved.

This common example raises some interesting questions.  A SUN knows very
well that the MTU is at most 1500 bytes, and then decides to use 8k packets
anyway.  Since using a smaller packet size allows "slow hosts and routers"
to work better, it is fairly clear that it is slower this way (unless it
doesn't work at all with big packets).  Is fragmentation that occurs at
the originating host that much less "harmfull" than fragmentation that
occurs at routers?  (I think perhaps so.)  Why doesn't sun use 8k tcp
packets too, anyway?

BillW
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