Re: ultradns reachability

[Leo Bicknell <bicknell () ufp org>]

In a message written on Fri, Jul 02, 2004 at 10:22:09AM -0400, Joe Abley wrote:
> This leaves the anycast servers providing all the optimisation that 
> they are good for (local nameserver in toplogically distant networks; 
> distributed DDoS traffic sink; reduced transaction RTT) and provides a 
> fall-back in case of effective reachability problems for the anycast 
> nameservers.
>
> This is so trivial, I continue to be amazed that PIR hasn't done it.

I talked to Rodney about this a long time ago, as well as a few
other people.  What in practice seems simple is complicated by some
of the software that is out there.  See:

http://www.nanog.org/mtg-0310/pdf/wessels.pdf

Note in the later pages what happens to particular servers under
packet loss.  They all start to show an affinity for a subset of
the servers.  It's been said that by putting some non-anycasted
servers in with the anycasted servers what can happen is if the
anycast has issues many things will "latch on" to the non-anycasted
servers and not go back even when the anycast is fixed.

How serious this is for something like .org I have no idea, but it's
clear all the software has issues, and until they are fixed I don't
think this is just a slam dunk.

-- 
       Leo Bicknell - bicknell () ufp org - CCIE 3440
        PGP keys at http://www.ufp.org/~bicknell/
Read TMBG List - tmbg-list-request () tmbg org, www.tmbg.org

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