Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!uunet!seismo!rutgers!mit-eddie!bloom-beacon!mit-hermes!iuvax!pur-ee!uiucdcs!uxc.cso.uiuc.edu!sandrock
From: sandrock@uxc.cso.uiuc.edu
Newsgroups: comp.protocols.tcp-ip
Subject: Re: IBM TCP.
Message-ID: <171500006@uxc.cso.uiuc.edu>
Date: Fri, 31-Jul-87 12:30:00 EDT
Article-I.D.: uxc.171500006
Posted: Fri Jul 31 12:30:00 1987
Date-Received: Sun, 2-Aug-87 19:48:06 EDT
References: <11@<12320729020>
Lines: 24
Nf-ID: #R:<12320729020:11:uxc.cso.uiuc.edu:171500006:000:1260
Nf-From: uxc.cso.uiuc.edu!sandrock    Jul 31 11:30:00 1987


>/* Written  1:30 pm  Jul 29, 1987 by DCP@QUABBIN.SCRC.SYMBOLICS.COM in uxc.cso.uiuc.edu:comp.protocols.tcp-ip */
>
>    Date: Fri, 24 Jul 87 23:32:20 EDT
>    From: "James B. VanBokkelen" <JBVB@AI.AI.MIT.EDU>
>
>    I've heard nothing about aberrant behavior on Ether, so apparently they're
>    only punishing their own pioneering customers at the moment....
>
> Maybe they're just trying to go one up on DEC?  Remember that DEC
> violates the spirit of the Ethernet hardware address by forcing the
> Ethernet address to be algorithmically determined by the DECnet address,
> resulting in Ethernet addresses which do not indicate the vendor of
> hardware interface, as well as not ensuring globally unique addresses.
>
   DECnet uses the node address to set the least significant 16 bits of the
   48-bit Ethernet hardware address while setting the most significant 32
   bits to a "known" constant value.  Specifically, the Ethernet address
   will be AA-00-04-00-xx-xx, where the xx-xx fields are the DECnet node
   address (area-number * 1024) + node-number.
     There may be both certain advantages and also disadvantages to this
   approach, but is it true that these addresses are not globally unique?

     Mark Sandrock, (sandrock@uxc.cso.uiuc.edu)