Date   : Tue, 21 May 1985 13:38:07 EDT (Tue)
From   : Jeff Edelheit <edelheit@MITRE.ARPA>
Subject: usenet mail paths

Thanks to Chuck , I got an explanation of the usenet mail paths.
As several folks sent me msgs. syaing that they were as confused as me,
I have included Chuck's msg.

The only remaining question is, if more than one path is listed, and you
don't know who sends mail to whom and when, which path should you chose?

I guess us Mil/Arpanet users are really spoiled.

------- Forwarded Message

To: hplabs!ucbvax!edelheit@MITRE.ARPA
Subject: Re: Usenet Mail Addresses
In-reply-to: your article <10790@brl-tgr.ARPA>

Jeff, the "{"'s usually symbolize an OR construction, especially if the 
sites are separated by vertical bars (|). So yes {hplabs|dual|qantel}
would mean any one of those sites. As for which path is best, I prefer
to use the least number of hops algorithim unless I know a site is
slow or overloaded in which case I can sacrifice a few hops to go around
it. And as some systems get mail in the morning and send it out at night
one "hop" can represent one day of travel time. So things are slow. On
the arpa side if you see somone with a path that includes ucbvax then
you can use that to mail to them. For instance my path descriptor is

{ihnp4,fortune}!dual\                     
        {qantel,idi}-> !intelca!cem      
 {ucbvax,hao}!hplabs/                   

which has ucbvax in the bottom line. To construct a path out of this
you notice that either ucbvax OR hao can go through hplabs to intelca
so the path becomes "hplabs!intelca!cem" which is everything except 
the ucbvax part, and the arpa address is then 
"hplabs!intelca!cem"@Berkeley because Berkeley is the same as ucbvax on
the usenet side. I have heard that brl-bmd will also gateway messages
in this way to the usenet side. Is this clear now?

- --Chuck


------- End of Forwarded Message

Jeff Edelheit
(edelheit@mitre)