Path: utzoo!mnetor!uunet!epiwrl!epimass!jbuck
From: jbuck@epimass.EPI.COM (Joe Buck)
Newsgroups: comp.mail.uucp
Subject: Re: Rerouting of explicit paths
Message-ID: <2024@epimass.EPI.COM>
Date: 22 Mar 88 17:33:10 GMT
References: <327@vsi1.UUCP> <9@tness7.UUCP> <3544@bloom-beacon.MIT.EDU> <410@ontenv.UUCP> <128@heart-of-gold> <2117@phoenix.Princeton.EDU>
Reply-To: jbuck@epimass.EPI.COM (Joe Buck)
Organization: Entropic Processing, Inc., Cupertino, CA
Lines: 37
Keywords: don't do it

In article <2117@phoenix.Princeton.EDU> towfigh@phoenix.Princeton.EDU (Mark Towfigh) writes:
>Since it is generally agreed that certain kinds of rerouting are
>bad, why not have a mailer which reroutes mail by starting at the
>right of the ! path, trying to connect to each host, until it gets a
>direct connection, and then pass it on?  At the very least it will
>connect to the leftmost host, as the path should be correct.

This is the kind of routing that many of us think is very bad.  It
would work in a static UUCP network where every site always had the
correct routing information.  But sites go down and connections
change.  Even the UUCP project people's latest maps always contain
errors (sometimes serious ones), simply because people don't always
send in their updates right away.  To get around these areas, we can
use bang paths -- as long as bang paths are not munged with.

A couple of years ago just about every "optimal" long-distance route
went through ihnp4.  Partly because of this enormous load, ihnp4
was sick a lot, and people connected with it would frequently post
pleas not to route through ihnp4.  But many users were unable to
cooperate because "smart" mailers would change the paths to go
through ihnp4 again, because that is the "optimal" route.

Rerouting also makes the network untestable.  It's no longer possible
to verify that a connection is alive by sending a short message
through a loop.  One could ask the system administrator at a site,
but it's amazing how many sites on the net are "on automatic", with
no one left at the site who knows much about UUCP or news.  "Well,
Ralph set this all up but he doesn't work here any more."

Correct bang paths ("correct" means that each site talks to the next
one on the chain) should never be rerouted.

As for news: define INTERNET, fix your mailpaths file, and you'll
no longer have long paths to worry about.
-- 
- Joe Buck  {uunet,ucbvax,sun,<smart-site>}!epimass.epi.com!jbuck
	    Old Internet mailers: jbuck%epimass.epi.com@uunet.uu.net