Xref: utzoo comp.mail.sendmail:318 comp.mail.uucp:2513 Path: utzoo!attcan!uunet!seismo!sundc!pitstop!sun!decwrl!vixie From: vixie@decwrl.dec.com (Paul A Vixie) Newsgroups: comp.mail.sendmail,comp.mail.uucp Subject: Re: Pathalias and routing of mail Message-ID: Date: 10 Dec 88 13:28:03 GMT References: <2189@unmvax.unm.edu> <1665@valhalla.ee.rochester.edu> <4199@mailgw.cc.umich.edu> <2194@unmvax.unm.edu> Sender: vixie@decwrl.dec.com Followup-To: comp.mail.uucp Organization: DEC Western Research Lab Lines: 28 In-reply-to: mike@turing.unm.edu's message of 10 Dec 88 10:56:58 GMT [ Followups to comp.mail.uucp ] [Bushnell] # This allows us to handle two cases of passive routing: where we are given # only an address and no path at all, and where the next hop of the path is # unreacheable. In the second case, we are justified in rerouting since the # original path was invalid. You are certainly justified in finding a route to the first host in the path (or the only host in an address) is not a direct neighbor. There is great controversy over the practice of peeking ahead, beyond the first host in the path, no matter what kicked your mailer into that mode. Canonically, this is usually put: "given a!b!c!user, go ahead and get to 'a' by any means available, but don't assume that your 'c' is the same as the 'c' known to 'b'". Details such as 'c' being a fully qualified domain are not really that interesting, since your route to that fully qualified domain may not be as good as the one that's being chosen, and you have no way of knowing that unless you monitor all the links as they go through their daily dance of the yo-yo. Forgive me, everyone, if this seems like I'm picking nits. The word "reroute" in the above-quoted text can be taken two ways. I support one way, and oppose the other. The difference seems very important to me. -- Paul Vixie Work: vixie@decwrl.dec.com decwrl!vixie +1 415 853 6600 Play: paul@vixie.sf.ca.us vixie!paul +1 415 864 7013