Nortel Networks WEB OS 212777 - Manual (Page 151)

Web OS 10.0 Application Guide
Chapter 6: Server Load Balancing n 151
212777-A, February 2002
Domain Name Server (DNS) Load Balancing
In previous releases of Web OS, DNS load balancing was based on virtual server IP address
and virtual port (VPORT) only. In Web OS 10.0 however, DNS load balancing allows you to
choose the service based on the two forms of DNS queries: UDP and TCP. This enables the
switch to send TCP DNS queries to one group of real servers and UDP DNS queries to another
group of real servers. The requests are then load balanced among the real servers in that group.
Figure 6-11 shows four real servers load balancing UDP and TCP queries between two groups.
Figure 6-11 Layer 4 DNS Load Balancing
N OTE – You can configure both UDP and TCP DNS queries for the same virtual server
IP address.
Web Switch
Group 1
UDP
health udpdns
Internet
Group 2
TCP
health dns
Real servers
Real servers
20
21
22
26
Client
10.10.10.20
10.10.10.21
10.10.10.22
10.10.10.26
vip 20.20.20.20