Subject: Re: Being DIS on more than 256 LANs

From: Radia Perlman - Boston Center for Networking <[email-masked]>
Date: Fri, 23 Jul 1999 13:38:28 -0400 (EDT)

From: Rajesh Saluja <[email-masked]>

	Are you proposing that a router can have multiple system ids?
	and the router will make adjacency with neighbors on different
	interfaces using different system ids? Does not it mean that you
	need to originate multiple  non-pseudonode LSPs
	corresponding to each  system id and you need to advertise the
	appropriate LSP to each interface.

No. This is not what I'm proposing. The router has one system ID, say
49 (where "49" is a 6-byte quantity.
The LSP it originates on behalf of itself will have the 7-byte ID
49.0.

The names it gives to the first 255 LANs that it is DIS for will be
49.1, 49.2, ...49.255 (just like today).

If there are more, then it just needs to find another 6-byte quantity
that it knows is not being used in the area, let's say 78. And it
can name the next 255 LANs that it's DIS for 78.1, 78.2, ...78.255.
There shouldn't be anything
wrong with having router with system ID 49 naming
the LAN "78.2". There's nothing wrong with a LAN named 78.2 not having
a neighbor 78.0. ANd there shouldn't be anything wrong with having a
pseudonode named "78.2" but there being no LSP from a node named
78.0.

Basically, it's just 7 byte unique numbers, so that every LAN and every
router in the area can have a unique 7 byte number. As a matter of fact,
an alternative design could have been to use 6 byte IDs for all
nodes in the area (routers as well as LANs), and use the MAC
address of the DIS as the name of the LAN, and just make sure that
each router had an additional EUI-48 to use as its system ID.

Radia