Subject: Re: question on link state routing protocols

From: [email-masked] (Noel Chiappa)
Date: Thu, 2 May 2013 12:21:35 -0400 (EDT)

> From: Jon Crowcroft <[email-masked]>

    > you could imagine some new protocol/algorithm which carried an
    > accumulated counter of the number of interfaces the predecessor hop that
    > is forwarding the flooded LSA had seen this LSA on

Umm, maybe I'm misunderstanding your suggestion, because isn't the value of
that counter which would be sent on to the neighbours always going to be '1'?
(I.e. you only forward an update the _first_ time you see it - additional
copies are [basically] ignored?)

Yes, the copy in the node will count up, but I'm not sure what use it can be
put to. Remember, loop prevention requires that everyone be working off
exactly the same page, there are no 'local optimizations'.

	Noel

---

From: Jon Crowcroft <[email-masked]>
Date: Fri, 03 May 2013 10:04:05 +0100

>>copies are [basically] ignored?)

flooding is either done by building a spanning tree and sending it on
that (viz radia perlman) or by copying a packet from any incoming link on
all the interfaces you have NOT seen it - so you can count that and send
it on with the LSA...

 >>exactly the same page, there are no 'local optimizations'.

sure - i'm thinking about how you do incremental dijstra in the next
epoch when an LSA with my new count comes in

 cheers

   jon