Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!apple!sun-barr!cs.utexas.edu!uunet!auspex!guy
From: guy@auspex.auspex.com (Guy Harris)
Newsgroups: comp.protocols.nfs
Subject: Re: Question on RPC over X25
Keywords: X25 RPC
Message-ID: <2260@auspex.auspex.com>
Date: 19 Jul 89 23:00:20 GMT
References: <43@ttsi.UUCP>
Reply-To: guy@auspex.auspex.com (Guy Harris)
Organization: Auspex Systems, Santa Clara
Lines: 23

>Is RPC available over X.25? The documents I have indicate that it is 
>based on TCP/IP and relies on this as the transport mechanism.

The Sun RPC implementation is set up to allow RPC to run over different
transports (even on "TCP/IP", it runs over two transports - TCP and
UDP).  You might want to look at the "clnt_{tcp,udp}.c" and
"svc_{tcp,udp}.c" files to get a feel for how transport implementations
are done (the documentation may cover this as well), and see what would
be involved in doing an implementation across whatever X.25 interface
you have.

Some particular RPC features (e.g., broadcast RPC) may, of course,
depend on features of specific transports (e.g., broadcasts). 

The biggest problem appears to be to be the portmapper; at present, it
seems to "know" that it's running in a TCP/UDP/IP environment, so you'd
have to figure out how to handle registration of program/version pairs
for X.25.  It also appears that the RPC code would like to have
transport-level addresses be composed of a host address and something
like a TCP/UDP port number - e.g., it would want to find the portmapper
for a given host given only the host's "address", or name, and then
construct the address for some service on that host based on the host's
"address" and the data it gets back from the portmapper.