Path: utzoo!attcan!uunet!samsung!zaphod.mps.ohio-state.edu!rpi!uupsi!ccavax!tinkelman
From: tinkelman@ccavax.camb.com
Newsgroups: comp.dcom.sys.cisco
Subject: Re: poor inter-area routed DECnet performance (long)
Message-ID: <25997.2670ba07@ccavax.camb.com>
Date: 9 Jun 90 12:57:43 GMT
References: <21919@megaron.cs.arizona.edu> <25934.266f66c4@ccavax.camb.com> <21978@megaron.cs.arizona.edu>
Organization: Cambridge Computer Associates, Inc.
Lines: 28

In my prior article <25934.266f66c4@ccavax.camb.com>, I should have made an
additional observation.  I guess I forgot, because it didn't bear on your
_immediate_ performance related question.  But it does bear on the future.

 ***  The pictured configuration will `soon' be illegal.  DECnet/OSI  ***
 ***  (Phase V) will not allow multiple areas on the same Ethernet.   ***

With Phase V you probably will have all the nodes in your picture in the
same area, and therefore avoid the `extra' hops of area routers.  Packets
will flow NodeOnEnet1-Cisco1-Cisco2-NodeOnEnet2 with no `extra' hops at
DECnet area routers.  

I said `probably' in the above.  You could keep the nodes on each physical
Ethernet in separate DECnet areas if the Cisco boxes will be able to act
as DECnet Phase V Level 2 routers.  (Will they be able to do that?)  You
could also maintain separate DECnet areas on the two LANs *and* bridge
them, if you have the bridges filter all the appropriate DECnet level 2 
routing multicasts.  This latter configuration _should_ work, though I'm
not sure if DEC will say it's supported.

Despite the two alternatives in the preceeding paragraph, I still think 
that unless there is some very strong (and strange?) *technical* reason 
not to do so, you will find it better to go to a single DECnet area.
(DEC's position is certainly that DECnet areas should reflect network
topology, not administrative responsiblities.)
-- 
Bob Tinkelman, Cambridge Computer Associates, Inc., 212-425-5830              
bob@camb.com  or ...!{uupsi,uunet}!camb.com!bob