Questions about anycasting setup

Fri Mar 9 09:45:24 UTC 2012

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On Mar 9, 2012, at 1:34 AM, Elmar K. Bins wrote:

> Re Bill,
> 
> woody at pch.net (Bill Woodcock) wrote:
> 
>>> Well, let's say, using Quagga/BIRD might not really be best practice for
>>> everybody... (e.g., *we* are using Cisco equipment for this)
>> How does your Cisco know whether an adjacent nameserver is heavily loaded, and adjust its BGP announcements accordingly?
> 
> It doesn't have to.
> 
> I don't know how you guys do it, but we take great care to
> keep min. 70% overhead capacity during standard operation.

RFC 2870 section 2.3 suggests 33%.  How us guys do it is 2%-3%, since "standard operation" is only the case when nobody's getting DDoSed.  And then we have a backup plan, which is to be able to redirect queries away from nodes that are overloaded.  And we have backup plans for the backup plans.  But then, we've been doing anycast DNS for twenty years now, so we've had some time to develop those plans.

I think what you're hearing from other people, though, is that having a backup plan is, indeed, best practice.

                                -Bill

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