Re: [DNA] linkid

[Erik Nordmark <Erik.Nordmark@sun.com>]

> In fact that's what linkID-02 does now.
> (it was updated before the -XX drafts cutoff)

Ah - good. (For some reason my ID cache only had 01.)

> I was saying: Global may be OK, reusing the 
> ND prefix information option is not.

OK. And I agree with that. Sorry for the confusion.

From looking at draft-pentland-mobileip-linkid-02.txt
I have a few comments and questions.

When two routers boot at the same time, them seem to send a request
and then (at about the same time) they will give up and pick their own
linkid and advertise it.
Thus there is a risk that both of them will have different ids for a while.

An alternate approach is that a router will first generate a random number
(which will be used if no other router on the list has a number)
and offer that in the RtR message. If there is an existing router which
has already picked a linkID it will respond with its number.
But if not, i.e., multiple routers boot at the same time, 
the two routers might both receive a proposed random number from their peer.
Having some comparison (such as smallest number) would allow the routers
to pick the same number from the ones they proposed.
This might require defining both a "proposed linkid" option and
a "linkid" option for the RtR message.

BTW: It might make sense to require the routers to keep the linkid in
stable storage so that with high probability even after all the routers
fail (due to power failure) and come back they will have the same linkid.

The draft talks about administrator change of the linkid, which I don't
think is that useful.
But it doesn't talk about the case of the partioned link where multiple
(sets of) routers might pick different linkids and when the partition heals
there is a need for all of them to converge to a single number.

   Erik