Path: utzoo!attcan!uunet!jetson!john
From: john@jetson.UPMA.MD.US (John Owens)
Newsgroups: comp.mail.misc
Subject: Re: Another example why not to re-route
Message-ID: <174@jetson.UPMA.MD.US>
Date: 13 Dec 88 14:51:38 GMT
References: <321@aber-cs.UUCP> <370@lakart.UUCP>
Distribution: eunet,world
Organization: SMART HOUSE Limited Partnership
Lines: 41

In article <370@lakart.UUCP>, dg@lakart.UUCP (David Goodenough) writes:
> IF I CANT REACH THE FIRST HOP, I'LL PEEK, AND JUSTIFY IT THUSLY:
> 
> I've got to go to my maps WHETHER I GO FOR THE FIRST SITE OR THE LAST.
> 
> HENCE WHICHEVER SITE I CHOSE TO AIM FOR, IF IT'S PATH FROM HERE IS
> WRONG I'M DEAD.

No, you're still missing the essential point.  In the path

	a!b!c!d

you can't be sure that the "c" known to "b" is the same "c" as is in
your maps.  You are, however, justified in looking for "a" in your
maps, because the path

	you!a!b!c!d

wants the "a" that "you" know, the "b" that "a" knows, the "c" that
"b" knows, etc.

As a practical example, I've received a couple of failed mail messages
intended for a site named "jetson" in West Germany.  The failure
message was sent from (if I remember correctly)

	ifistg!MAILER-DAEMON
to
	unido!somewhere!jetson!user

Someone, perhaps unido, did "peeking" and sent it to the jetson in the
maps (me), causing two transatlantic crossings (one for the original
failure message and one for my failure message back to the
MAILER-DAEMON).

If no one had "peeked", it would have gone to "somewhere", which would
have sent it to its "jetson", and everything would have been fine (and
cheaper).

-- 
John Owens		john@jetson.UPMA.MD.US		uunet!jetson!john
+1 301 249 6000		john%jetson.uucp@uunet.uu.net