[dns-operations] Too Open (Was: OpenDNS makes your Internet work better

[Joe Abley]

On 20-Jul-2006, at 11:47, Florian Weimer wrote:

> * Per Heldal:
>
>> The issue with UltraDNS desribed in this thread relates to the  
>> fact that
>> they used multiple anycast IP's in the same address-block. You get
>> problems if you do that and don't control the infrastructure
>> interconnecting the various anycast locations.
>
> I don't see what you gain from controlling those interconnects.

You get to route requests for 199.212.90.1 to a different node if  
199.212.90.1 is unavailable locally, while 199.212.90.3 still works.

> You
> can't use intra-AS connections anyway because you'd need to run an
> IGP, and your typical IGP is a distributed single point of failure.

Avoiding the shared fate of an IGP between nodes is a win in many  
respects, but I wouldn't characterise it as a fundamental no-no.

As with most things, the cost/benefit implications of individual  
design decisions vary widely according to exactly what you're trying  
to accomplish. Anycast is a wide umbrella, and generalisations are  
often impractical.


Joe