From: slin@cisco.com (Steven Lin)
Newsgroups: comp.protocols.appletalk
Subject: Re: CLAIM: Seed Routers are not Nodes
Date: 19 Nov 92 11:20:36
Organization: cisco Systems, Inc.
NNTP-Posting-Host: regal.cisco.com
In-reply-to: chris@ph-meter.beckman.uiuc.edu's message of Thu, 19 Nov 1992 02:54:19 GMT

In article <chris.722141659@ph-meter.beckman.uiuc.edu> chris@ph-meter.beckman.uiuc.edu (Chris Gressley) writes:

   The manufacturer of our routers has made a very strange claim
   concerning their implementation of AppleTalk. I think I can cite the
   passages in Inside AppleTalk which show that they are just implementing
   this incorrectly, but I could use a direct quote from a Tech Note or
   Inside AppleTalk, or an answer from an Apple person, which would show
   definitively that they are wrong, or alternatively that I am wrong and
   the router folks are correct.

   The folks who make our routers make the following two claims:

   1. A "router" is not a "node". Nodes and routers are distinct sorts of
   things.

   2. Since a router is not a node, if a router is a seed router, it need
   not dynamically acquire a node ID but can instead have one statically
   assigned, since a seed router has statically assigned port descriptor
   information.

I would certainly like to know what manufacturer made these claims.
You may respond via e-mail to protect the guilty.

   I am trying to configure the backbone network that the routers share
   with the campus backbone so that all of the routers are seed routers.
   Because of this, two of my routers are trying to use identical node
   IDs, which all in all is a very bad thing.

   Am I totally confused, or is it true that:

   (a) A router is in fact a node.

   (b) Because a router is a node, it should follow the rules for node
   number acquisition.

   Any authoritative source on this would be greatly appreciated.

Well, I suppose this all hinges upon what one's definition of a node
is.  Based on its two claims, your router's manufacturer seems to
think or imply that the definition of a node is, "Any device that
dynamically acquires its node ID."  Personally, I think this is
poppycock.  A more reasonable definition would be, "Any data-link
addressable entity on the network."  Based on this definition, a
router is, in fact, a node and it should follow the rules for node
number acquisition.

Whether or not a router is operating in seed mode has no bearing on
how it acquires its node ID.  For almost every router that I know of
(Cisco being no exception), one has the option to _recommend_ a node
ID that should be used when starting up.  If that node ID is not used,
which it determines by sending out AARP Probe packets, then it may
safely use it.  Otherwise, it must select another node ID, again
sending out AARP Probes to determine whether or not the new node ID is
used.  Note: this recommendation can be given in seed or non-seed mode.

Now it looks like your router's manufacturer decided that if a router
is operating in seed mode and it has a node ID assigned by the
operator, then that node ID is static and non-negotiable.  If this is
so, then that certainly would lead to the problem you have been
seeing: node ID conflicts.

One of the beauties of AppleTalk is the ease with which one can attach
a node to a network.  There's no need to explicitly assign a network
address for the node, as one must do in the IP world.  One just plugs
it in and off it goes merrily on its way.  Having the option to
specify a static and non-negotiable node ID only introduces problems
that AppleTalk was designed to avoid.

So, it seems that the person you spoke to at your router's company was
either 1) a very confused non-techie or 2) a very confused techie.  If
the latter, then I would very strongly suggest looking for another
manufacturer to buy your routers from.

Steve