redirecting overseas requests to local servers
Barry Margolin
barmar at bbnplanet.com
Wed Sep 8 03:49:22 UTC 1999
In article <19990907234535.C5150 at space.net>,
Markus Stumpf <maex-bind-users at Space.Net> wrote:
>On Mon, Sep 06, 1999 at 05:42:40PM -0700, Patrick Greenwell wrote:
>> > > > > UltraDNS provides a service where you can reach the *topologically*
>> > > > > closest server according to BGP. http://www.ultradns.com.
>> Basically: (beware, bad ascii art follows)
>>
>>
>> +--------+ +-----+ +-----+ +-----+ +------+
>> | client |<---->| IGP |<----->| BGP |<------>| BGP |<---->|server|
>> +--------+ +-----+ +-----+<- +-----+ +------+
>> \
>> \
>> \ +-----+ +------+
>> ->| BGP |<---->|server|
>> +-----+ +------+
>>
>
>Ok, so far so good.
>Routers exchange routes via BGP to get their routing straight, but
>(maybe I am too dumb to understand that ...)
>why for heavens sake, would a DNS SERVER want to know anything about
>routing (if it isn't running on a multihomed machine itself).
So that it can give out different answers depending on proximity in the
network. Consider the following diagram:
+--------+ +-----+ +-----+ +-----+ +------+
| client1|<---->| IGP |<----->| BGP |<------>| BGP |<---->|serv1 |
+--------+ +-----+ +-----+ +-----+ +------+
^ ^
| |
v v
+--------+ +-----+ +-----+ +-----+ +------+
| client2|<---->| IGP |<----->| BGP |<------>| BGP |<---->|serv2 |
+--------+ +-----+ +-----+ +-----+ +------+
When client1 looks up www.company.com it should return the address of
serv1, but when client2 looks up www.company.com it should return the
address of serv2.
>To be honest I never really understood what "topology" could be used
>for in a serious way in bind.
>A few days ago I saw an email where someone claimed they had "dramatically"
>increased their DNS answer speed by heavily using the topology feature.
>On the other side I remember a post by Mark Andrews in this forum not to
>long ago where he explained that bind keeps its own statistics on
>reachability and speed of answers (or does this only hold for root DNS
>servers?) and the choosing algorithm is based on this data.
>So, if I do not restart bind every hour or so, why would I want bind
>to know about routing and topology?
BIND can only build up this information dynamically by actually querying
all the servers. In cases where the server operator knows a priori that
certain networks are much closer than others, he can configure explicit
topology statements.
If you don't feel like using it, you don't have to.
--
Barry Margolin, barmar at bbnplanet.com
GTE Internetworking, Powered by BBN, Burlington, MA
*** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to newsgroups.
Please DON'T copy followups to me -- I'll assume it wasn't posted to the group.
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