Re: [lisp] Questions about draft-saucez-lisp-itr-graceful-03

[Damien Saucez <[e-mail]>]

Hello Marc,

On 18 Feb 2014, at 23:48, Marc Binderberger <[e-mail]> wrote:

> Hello Damien/Olivier/Luigi/Clarence & LISP experts,
> 
> had a look at draft-saucez-lisp-itr-graceful-03. And wonder if there is 
> more to come?

Thank you for the interest.  We are indeed thinking on ways to extend
the document and provide more details on the ways the solutions could
be implemented.


> Somehow section 4 feels a bit "short".
> 
> What I mean: if you try to solve the problem of the _two_ cache-miss 
> storms - first on the 2nd ITR (ITR2) when your restarting ITR (ITR1) 
> goes down, then on the restarting ITR1 when it picks up traffic again - 
> then section 4 would probably need to talk about a permanent cache 
> synchronization (?). Unless you want to solve a planned restart only. 
> But for a failure of the ITR1 I don't see how the solution you describe 
> would work
> 
>   o  ITR cache synchronization: upon startup, the ITR synchronizes its
>      cache with the other ITRs in its synchronization set.  The ITR is
>      marked as available only after the cache is synchronized.
> 
> as ITR2 would trigger the cache-miss storm for the traffic after ITR1 
> failure.
> 
> Or if you want to solve only the cache-miss storm when ITR1 comes back 
> into the traffic stream then the ITR deflection has the advantage to 
> not require any cache-synchronization protocol, IMHO. The rate of 
> Map-Requests could be throttled to turn the storm into a breeze. The 
> method how to transport traffic to ITR2 could be one of many - a direct 
> LAN, GRE, Lisp.
> 
> 
> So my question in short: are you planning to add some words about a 
> permanent cache synchronization?
> 

For now we don't have acceptable techniques to keep caches
synchronised in a permanent way but I don't think it is a big issue as
the purpose of the document is to deal with planned restart of routers
meaning that we know exactly when the routeur will get down then up
(it is controlled by the operator).

If you have a solution to continuously synchronise ITRs caches, we
would be very happy to look at them and integrate them in the proposed
solution.

Thank you,

Damien Saucez

> 
> Thanks & Regards,
> Marc