NonStop Networking Overview

subnet. All clients requesting an IP address on that subnet are returned the IP address of the host
that is also on that subnet.
• Clients on subnet 192.168.1.1 requesting the IP address of MyCompany.com receive the IP
address of Webserver 1.
• Clients on subnet 192.168.2.1 requesting the IP address of MyCompany.com receive the IP
address of Webserver 2.
• Clients on subnet 192.168.3.1 requesting the IP address of MyCompany.com receive the IP
address of Webserver 3.
• Clients on subnet 192.168.4.1 requesting the IP address of MyCompany.com receive the IP
address of Webserver 4.
Figure 5 (page 16) shows transparent network scalability on multiple hosts.
The other way of achieving transparent network-level scaling is to use DNS round-robin address
rotation where one DNS name server process returns different IP addresses for a given resource
service. With this technique, you would ensure there is a different network interface associated
with each IP address; one name server process would then answer requests for the name with
those IP addresses on a rotating basis. In Figure 6, the DNS server process rotates Webserver
requests for Mycompany.com among interfaces 1.1.1.1, 1.1.2.1, 1.1.3.1 and 1.1.4.1. (On a
multi-homed NonStop server, the separate systems shown inFigure 6 are contained in one system.)
Figure 6 DNS Round-Robin Address Rotation
See the DNS Configuration and Management Manual for more information about configuring a
DNS name server process on your NonStop system.
Application Scalability
Application scalability refers to distributing application-service load across multiple instances of
the application server process. In the example of the scaling mechanism provided by DNS, the
service application (the web server process) is limited when the server instances need to share
data that is not resident on all the hosts. For example, a set of web server processes distributed
over n hosts must either have the data it is servicing duplicated across those hosts or connect to a
back-end shared database so that all the web server processes are accessing up-to-date information.
What’s Unique About Networking on Integrity NonStop Systems 17