resolving differently depending on location?

[Sten Carlsen]

As I understood, it was only intranet servers?
In that case views could be effective, because the views can be selected
by IPs, which typically will be sorted geographically.

Barry Margolin wrote:

>In article <dj17cv$2hks$1 at sf1.isc.org>,
> Kevin Darcy <kcd at daimlerchrysler.com> wrote:
>
>  
>
>>BIND *does* however, have support for "sortlist". One can have the name 
>>resolve to all of the location-specific IPs, and then sort them 
>>according to the source IP of the DNS client. This only works 
>>*reliably*, however, when the sortlist configuration of all resolvers is 
>>tightly controlled.
>>    
>>
>
>Right, so it's useless for a public web site.
>
>  
>
>>Note that the sortlist approach also assumes that the DNS client address 
>>is also the same as, or close to, the client for whatever service one is 
>>trying to provide (HTTP, SMTP, whatever). Due to proxying and numerous 
>>other factors, this isn't always a good assumption. But Akamai and 
>>others seem to do fairly well making exactly the same assumption, so YMMV...
>>    
>>
>
>If you're just trying to select a server on the same continent or ISP 
>backbone as the client, the assumption will be pretty good.  Also, many 
>ISPs make use of anycast for their resolvers, so the resolver will be 
>relatively close to the client on the backbone; therefore, choosing a 
>server close to the resolver should be OK.
>
>While there may be occasional cases where it doesn't choose the optimal 
>server, on average it seems like it can be expected to be better than 
>random choice.  But having the server do it at the application level 
>should generally be even better.
>
>  
>

-- 
Best regards

Sten Carlsen

Let HIM who has an empty INBOX send the first mail.