MRC@PANDA.PANDA.COM (Mark Crispin) (02/17/88)
I've been in the NWG for at least 12 years, and I remember no pronouncement that implementations *must* try all possible IP addresses. I can think of just as many cases where it is undesirable as I can of ones where it is desirable. Let's set the record straight on one thing. The mailer in question has no knowledge whatsoever of how to look up an address in a host table or from a domain server. It hasn't any notion of multi-homed hosts. It simply knows that it has to send a set of bits to a set of mailboxes at a set of hosts. The hosts are stored by name. When the mailer attempts to deliver a message, it does an operating system call which takes the host name as an argument and returns a single IP address. Any change in IP address selection would have to be done at the software at the other end of that system call. One way for be for the mailer to pass "advice" that a particular IP address has been shown to fail. Nobody is going to work on the host table software to do this. The amount of work to do such a task is much more work that it would be for Clive Dawson to upgrade his system to support domains. It would, I think, be relatively simple to put in such a function into the domain software. The only change to the mailer would be to pass "advice"; presumably a 3 or 4 line code change. I don't know what sort of effort it would take to put this in the domain software. The question then becomes, what sort of criterion should the domain software use beyond the current choice of "best" network, modified with mailer "advice"? Nobody has offered any suggestions. I again want to emphasize that the DEC-20 mailer does NOT "use the first address and ignore the rest". It has no way of knowing that any other addresses exist; it is totally dependent upon external software for any host information. Don't assume that because your mailer has internalized host table parsing routines that all mailers are written that way. I am a bit annoyed that the same people who are willing to accept BITNET mailers which toss away RFC821 return path information are quite happy to crucify software that isn't at fault. -------