Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!cornell!uw-beaver!rice!sun-spots-request
From: murthy@thir.cs.cornell.edu (Chet Murthy)
Newsgroups: comp.sys.sun
Subject: Re: How does SUNRPC/UDP work?
Keywords: SunOS
Message-ID: <1903@brazos.Rice.edu>
Date: 2 Oct 89 15:20:53 GMT
Sender: root@rice.edu
Organization: Sun-Spots
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Approved: Sun-Spots@rice.edu
X-Sun-Spots-Digest: Volume 8, Issue 151, message 2 of 15

Well, I got some answers back.  It seems that SUN has a limit of 8kBytes
on the size of a UDP packet.  The SUNRPC implementation encapsulates an
RPC message into a single UDP packet, so if your implementation doesn't
support large enough packets (the PC-NFS implementation apparently only
supports 1KByte UDP packets) then your RPC implementation won't do
reassembly, etc, to allow you to do large size RPC's.

Also, from the paper that someone posted to the net about recently (about
comparing different RPC implementations), I infer that at some point above
8kbytes (I think it was 12Kbytes) using TCP becomes cheaper than UDP (in
terms of time).

So the thing to do, I suppose, is to add a minimal functionality to SUNRPC
to do packet fragmentation/reassembly for meduim-length (8-16Kbytes)
messages, and for longer messages, use TCP.

Does that sound right?

	murthy@cs.cornell.edu