Subject: [Idr] Re: [RRG] Geoff Huston's article on BGP stability, update statistics and damping

From: Tony Li <[email-masked]>
Date: Thu, 21 Jun 2007 13:34:29 -0700

Hi Noel,

On Jun 21, 2007, at 7:00 AM, Noel Chiappa wrote:

>> From: Robin Whittle <[email-masked]>
>
>> Geoff Huston has a new article "Damping BGP":
>
>>  "... the busiest 1% of prefixes responsible for 24% of the routing
>>  updates for the month."
>
> While I agree that whatever's causing this ought to be fixed, there  
> are some
> points we need to not lose sight of.
>
> First, fixing this would be a *one-time* improvement in the growth  
> curve for
> the update rate (versus long-term time). I.e. you'd see a flat spot  
> (or a
> drop) in the curve, after which it would resume its previous growth.

Hopefully, we would see a flat spot, and then an actual decrease in  
the growth rate of churn.  If we have a mechanism that truly is  
capable of reducing churn, and assuming that the amount of churn is  
proportional to the number of prefixes, then we should be able to  
reduce the update rate to truly reflect the topological events and  
the growth in number of prefixes.

> Second, 25% is not peanuts, but it's also not an order of  
> magnitude, and
> eliminating these wouldn't get us into a whole new operating  
> region. I don't
> know what the current growth rate for BGP updates is, but if it's  
> anything
> like the growth rate of the table itself (as one might reasonably  
> assume it
> is), 25% is not a long calendar time.

I believe that the point that we're making is that the churn rate is  
well _ABOVE_ the growth rate of the table new to new prefixes.  The  
amplification of path hunting is a major contributor to unnecessary  
updates.

> Again, it ought to be fixed, but let's not kid ourselves that this  
> is the
> solution to our problems.

No one was claiming that it was.  As you may recall, we've identified  
two problems: a) the increase in the size of the table is giving us  
concern and b) the subsequent update rate seems to grow unreasonably  
even with respect to (a).  The goal here is to attack only (b), and  
(a) is an entirely separate issue.

Tony

_______________________________________________
Idr mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/idr