HP Multi-Site Traffic Director sa9200 - Manual (Page 14)

C H A P T E R 2 HP Multi-Site Traffic Director Server Appliance SA9200 User Guide
8
4. The client DNS server sends a query to the mstd-ex.com
Authoritative DNS server to resolve www.mstd-ex.com.
5. The Authoritative DNS server responds to the client DNS server
with the IP address of www.mstd-ex.com.
6. The client DNS server responds to the client with the IP address
of www.mstd-ex.com.
In the discussion above, the SA9200 acts as authoritative DNS server
for zone.mstd-ex.com, which is the zone in which the name
www.mstd-ex.com resides.
Multi-Site Traffic Management
Using HP Traffic Directors
Multi-site load balancing solves most of the problems inherent in
Round Robin DNS. Under the server load balancing model, servers
are aggregated in a “server farm” behind a load balancer known by a
Virtual IP address or “service.” (The service is the IP address of
which the external network is aware.) By keeping track of such
metrics as number of connections, which services are running,
response time and the like, the load balancer knows the status of the
servers. The SA9200 retrieves metrics from the load balancer. Thus,
when a client requests the service, the SA9200 routes it to the site
who has a server best able to fulfill it.
If the data center has an HP Traffic Director, the SA9200 works in
concert with the “agents” in the load balancers by continually
communicating with each site’s agent through site verification
protocol. This keeps the SA9200 informed of the following:
• Health of the load balancers.
• Individual service health and availability.
• CPU utilization of load balancers.
• Response time for each service.
• Number of connections to each load balancers.
Site verification protocol information is encrypted for secure
communication between an HP Traffic Directors and the SA9200.