North American Network Operators Group
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Re: Slashdot: Providers Ignoring DNS TTL?

  • From: Patrick W. Gilmore
  • Date: Wed Apr 20 14:22:03 2005 
On Apr 20, 2005, at 2:13 PM, Dean Anderson wrote:
No, you are thinking of the (wrong) claims originally made by ISC about
how anycast would affect TCP to an anycast authoritative server. ISC
wrongly asserted that since BGP routes don't churn very fast compared with
DNS TCP connection lifetimes, that there should be no problem with anycast
and TCP. This view has been shown to be wrong in the face of Per Packet
Load Balancing (PPLB) which has been demonstrated to work on BGP links by
[email protected] Further, I showed that if you have PPLB on interior
(eg OSPF) links leading to different BGP peers, the problem also happens.
Packets are sent on a per packet basis to different places.
And I can show that if you give a pig wings....

Look, it breaks in certain situations. But anycast implementations of TCP apps have worked "well" for a decade now. Deal with the fact that not only do people use it, but users don't notice it.

Or don't. No one here cares if you do. Reality trumps lab tests.



But caching servers are usually setup to load balance. Usually, the
servers with the same IP address share an ethernet along with multiple
routers. So the packets are switched on essentially a per-packet basis.
Or possibly a per-arp basis that alters the MAC-based-forwarding behavior
of a switch. This is fairly fine grained load balancing.
This is complete news to me. Of course, I do not run most of the caching name servers on the Internet, so what do I know. Do you?

Would anyone who runs an anycast recursive name server care to supply data points to support or refute Mr. Anderson's assertion?

Mr. Anderson, do you have any data points to support your assertion?

--
TTFn,
patrick