On Thu, 2012-05-17 at 00:13 +0800, Ed Greshko wrote: > when you do a look up on www.cnn.com it will return 4 IP > addresses. Now, since bind would have that in its cache it wouldn't have to > send out > a query. What I don't know is if an application would make a request would > the list > be returned in the same order every time to the requesting application? In > other > words, if the TTL is not set low, would that defeat the round robin technique.
Unfortunately, there is no guarantee that a client resolver will actually use the IP addresses in the order they are presented by the DNS server. Nothing in the DNS spec requires them to do so. > > Interesting things to investigate.....if I really had the time. My experience says that DNS round robining is actually a poor method of load balancing. I'm surprised to see a large site like CNN resorting to this (if that's really what they are doing this for). Perhaps in combination with a low TTL and a modified DNS server, they can send out a completely different set of IPs every few minutes, and achieve a sort of crude load balancing that way, but I think load balancing works better if you just send out a single IP and use a load balancer that you can control, such as LVS (Linux Virtual Server) that can farm out incoming connections to a single virtual address out to multiple real addresses. --Greg -- users mailing list users@lists.fedoraproject.org To unsubscribe or change subscription options: https://admin.fedoraproject.org/mailman/listinfo/users Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines Have a question? Ask away: http://ask.fedoraproject.org
