On Wed, 30 Mar 2005, Bruce Campbell wrote: > On Wed, 30 Mar 2005, jing shen wrote: > > > Maybe I did not explain my situation clearly in previous message. > > > > In fact, what I'm facing is to set up a public DNS service system > > which consist Cache Server ONLY. We do have authoritative servers, but > > those server only serves a few domain name.
Ah. Well, anycast DNS has been mostly thought about wrt authoritative servers. But a cache may also need to make TCP connections for large packets, someday. So the anycast issues are similar and you shouldn't ignore the issue. The load issues are usually a lot different. You can have hundreds of caching servers if you please. Every linux and windows machine can have its own cache, if it wanted. Authoritative servers have a maximum limit of 13. > Hence, adding additional authoritative servers does not help, nor does > adding extra servers to your customer's resolv.confs or equivilant. Cache only servers are found though resolv.conf (and equivalent) on your clients. Adding additional servers to your clients resolv.conf would help. I don't know why Bruce would say it wouldn't help. That seems to need more explanation. Different resolvers do different things with their resolv.conf configuration. Some use the first until it doesn't respond quickly enough, and then goes to the second. (most unix resolvers) Some make a random selection (Windows?). I usually configure the clients to use the closest server, network-wise first. Then the next closest, etc. If there is a cache on their lan, that's the best one for them to use. If that's down, if there's one on a high-speed link to that lan, thats the second best. And so on. And unix resolvers do that. A simple script can take a client IP address and order the resolv.conf. Where order is used by the resolver, it reduces offsite WAN traffic, and responds at ethernet speeds, rather than, say, T1 speeds on routers that might otherwise be congested. -- Av8 Internet Prepared to pay a premium for better service? www.av8.net faster, more reliable, better service 617 344 9000 . dnsop resources:_____________________________________________________ web user interface: http://darkwing.uoregon.edu/~llynch/dnsop.html mhonarc archive: http://darkwing.uoregon.edu/~llynch/dnsop/index.html
