Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!ames!lll-tis!SUN.COM!pv
From: pv@SUN.COM (Peter Vanderbilt)
Newsgroups: comp.protocols.iso.x400.gateway
Subject: Re: Proposed delta to RFC 987
Message-ID: <8807061805.AA24532@polya.sun.com>
Date: 6 Jul 88 18:05:57 GMT
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Approved: post-x400-gateway@tis.llnl.gov

I think the header/envelope distinction is important.  There are two
uses of source routes: (a) for testing and measurement and (b) to
compensate for limited routing knowledge.  Compensating for limited
routing knowledge is such a swamp that it's not at all clear that we
could do the right thing even if we wanted to; I would vote that we put
our efforts into getting the routing knowledge distributed correctly
and modify RFC 987 to say that all source route info is removed from
header addresses before translation.

But for (a), it does make sense to allow for source routing in the
envelope -- an X.400 administrator should be able to add routing info
to the envelope's recipient addresses to control the path that a
message takes (like through the gateway and back or use the Internet
for some of the hops).  To accomplish this, we need only handle source
routes in the envelope.  Your mail transport system may do this already
because some systems forward by adding an "@gateway:" (or
"...%...@gateway") to envelope addresses (so your system would have to
strip the "@gateway").

Actually, forwarding as described above is a third legitimate use of
source routes -- if my 822 system (sendmail) wants to forward through
X.400 to another 822 system, it does so by prepending "@gateway2:" to
the recipient's address (where gateway2 is the 822 address of the
remote gateway) and passing the message to the local gateway.

What we need to define is what source routes we allow for in recipient
addresses (P1.recipient ORNames with rfc-822 DDA's).  Do we allow for
822-style "@host1,@host2,...:user@hostn" or the informal
"user%hostn%...%host2@host1" or both?  Must host1 be the destination
gateway's 822 address or must host1 *not* be the destination gateway's
822 address or doesn't it matter?  My answers are "both" and "doesn't
matter" respectively.

Pete