Global server load balancing
A global server load balancing (GSLB) switch serves as a proxy to an authoritative DNS communicates with numerous site switches which are coupled to host servers serving specific applications. The GSLB switch receives from site switches operational information regarding host servers within the site switches neighborhood. When a client program requests a resolution of a host name, the GSLB switch, acting as a proxy of an authoritative DNS, returns one or more ordered IP addresses for the host name. The IP addresses are ordered using metrics that include the information collected from the site switches. In one instance, the GSLB switch places the address that is deemed “best” at the top of the list.
1. A method comprising:
receiving, by a network device from a domain name server, a plurality of network addresses generated by the domain name server in response to a domain name query originated by a client machine;
determining, by the network device, based upon a first metric associated with a plurality of sites, that a single network address from the plurality of network addresses is not better than all other network addresses in the plurality of network addresses for responding to the domain name query;
responsive to the determining, processing, by the network device, one or more network addresses from the plurality of network addresses using a second metric associated with the plurality of sites, wherein the second set metric is different from the first metric; and
causing, by the network device, a list of multiple network addresses from the plurality of network addresses to be forwarded to the client machine.
2. The method of claim 1 wherein the first metric is round trip times associated with the plurality of sites, wherein the round trip time associated with a site is indicative of time for exchanging a message between a switch at the site and the client machine.
3. The method of claim 1 further comprising:
determining, by the network device, that the processing using the second metric does not yield a single network address as better than other network addresses in the plurality of network addresses for responding to the domain name query;
processing, by the network device, one or more network addresses from the plurality of network addresses using a third metric associated with the plurality of sites, wherein the third metric is different from the first metric and the second metric.
4. The method of claim 1 wherein:
processing the one or more network addresses from the plurality of network addresses using the second metric comprises generating an ordered list of multiple network addresses from the plurality of network addresses;
the causing comprises causing the ordered list of multiple network addresses from the plurality of network addresses to be forwarded to the client machine.
5. The method of claim 1 wherein the plurality of network addresses comprises a first virtual IP address configured at a host server site switch at a first site from the plurality of sites, the host server site switch associated with one or more host servers at the first site, the one or more host servers being reachable via the host server site switch, the method further comprising:
receiving, by the network device, information related to the first metric information and information related to the second metric for the first network address from the host server site switch; and
wherein the determining comprises processing the plurality of network addresses based upon the first metric comprises using the information related to the first metric;
wherein processing the one or more network addresses using the second metric comprises using the information related to the second metric.
6. A network device comprising:
a memory; and
processor;
wherein the network device is configurable to:
receive, from a domain name server, a plurality of network addresses generated by the domain name server in response to a domain name query originated by a client machine;
determine, based upon a first metric associated with a plurality of sites, that a single network address from the plurality of network addresses is not better than all other network addresses in the plurality of network addresses for responding to the domain name query;
process one or more network addresses from the plurality of network addresses using a second metric associated with the plurality of sites, wherein the second set metric is different from the first metric; and
cause a list of multiple network addresses from the plurality of network addresses to be forwarded to the client machine.
7. The network device of claim 5 wherein the first metric is round trip times associated with the plurality of sites, wherein the round trip time associated with a site is indicative of time for exchanging a message between a switch at the site and the client machine.
8. The network device of claim 5 further configurable to:
determine that the processing using the second metric does not yield a single network address as better than other network addresses in the plurality of network addresses for responding to the domain name query; and
process one or more network addresses from the plurality of network addresses using a third metric associated with the plurality of sites, wherein the third metric is different from the first metric and the second metric.
9. The network device of claim 5 further configurable to:
generate an ordered list of multiple network addresses from the plurality of network addresses as a result of processing performed using the second metric; and
cause the ordered list of multiple network addresses to be forwarded to the client machine.