Path: utzoo!attcan!uunet!munnari!murtoa.cs.mu.oz.au!cs.mu.oz.au!kre
From: kre@cs.mu.oz.au (Robert Elz)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: IP over X.25 (request for info)
Keywords: X.25, Internet Protocol, virtual circuit
Message-ID: <1207@murtoa.cs.mu.oz.au>
Date: 5 Feb 89 16:57:57 GMT
References: <220@cutter.nbi.com>
Sender: news@cs.mu.oz.au
Lines: 26

In article <220@cutter.nbi.com>, chm@nbires.nbi.com (Paul Chmielewski) writes:
> Is there a standard mechanism for telling the called end
> of a virtual circuit what the internet address of the calling host is?

I doubt that looking at the address on the first datagram is the right
way, that may have come from anywhere, and just happens to be being routed
through this X.25 connection (the calling site may have restrictions on
for whom it will forward datagrams over x.25, but then again, it also
might not).

A useful question might be "Do you care?"

I think not, datagrams arrive over the link, they carry source addresses,
the address of the particular site at the other end of the link shouldn't
matter much.

When you come to sending out a datagram, you need (somehow) to translate
the IP address to a DTE address - you have to be able to do this to
cope with the case where your end initiates the connection anyway.

Its likely that this translation will produce the same DTE address as
was in the "calling address" x.25 field in the initial call packet.
In that case, you can send your datagram(s) back out over this same
call (if its still active).

kre