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From: DCP@QUABBIN.SCRC.Symbolics.COM (David C. Plummer)
Newsgroups: comp.protocols.tcp-ip
Subject: Connecting DECnet routers over IP
Message-ID: <870916091634.3.DCP@KOYAANISQATSI.S4CC.Symbolics.COM>
Date: Wed, 16-Sep-87 09:16:00 EDT
Article-I.D.: KOYAANIS.870916091634.3.DCP
Posted: Wed Sep 16 09:16:00 1987
Date-Received: Fri, 18-Sep-87 07:09:24 EDT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The ARPA Internet
Lines: 12

I don't think you want to use TCP or UDP to transport DECnet packets. 
Rather, you probably want to use IP for that purpose.  This would make
DECnet a sibling of TCP, UDP, ICMP, etc.  You probably find it useful to
 - to get an assigned number to stick in the IP protocol field, 
 - circulate a draft RFC to make sure several people find the
   functionality sufficient (such as "How do you translate DECnet
   addresses to IP addresses?"), and
 - perhaps get some prototype implementations working to find the bugs
and then publish your results as an RFC.

I don't know the specifics of DECnet, but I am somewhat interested in
what you come up with, as many of the same issues come up with CHAOSnet.