Cabletron Systems 9032578-05 manual Session Persistence

Chapter 17: Web Hosting Configuration Guide

redirects the request to the actual server address and port. Server selection is done according to the specified policy.

To add servers to the server group, enter the following command in Configure mode:

Add load balancing servers to a	load-balance add host-to-group
specific server group.	<ipaddr/range> group-name<group name>
	port <port number> [weight <weight>]
Add range of load balancing	load-balance add host-to-vip-range <range>
servers to a range of server	vip-range-name <range name> port <port
groups.	number> [weight <weight>]

Session Persistence

Load balancing clients connect to a virtual IP address, which in reality is redirected to one of several physical servers in a load balancing group. In many web page display applications, a client may have its requests redirected to and serviced by different servers in the group. In certain situations, however, it may be critical that all traffic for the client be directed to the same physical server for the duration of the session; this is the concept of session persistence.

When the SSR receives a new session request from a client for a specific virtual address, the SSR creates a binding between the client (source) IP address/port socket and the (destination) IP address/port socket of the load balancing server selected for this client. Subsequent packets from clients are compared to the list of bindings: if there is a match, the packet is sent to the same server previously selected for this client; if there is not a match, a new binding is created. How the SSR determines the binding match for session persistence is configured with the persistence-leveloption when the load balancing group is created (see “Creating the Server Group” on page 232).

There are four configurable levels of session persistence:

•TCP persistence: a binding is determined by the matching the source IP/port address as well as the virtual destination IP/port address. For example, requests from the client address of 134.141.176.10:1024 to the virtual destination address 207.135.89.16:80 is considered one session and would be directed to the same load balancing server (for example, the server with IP address 10.1.1.1). A request from a different source socket from the same client address to the same virtual destination address would be considered another session and may be directed to a different load balancing server (for example, the server with IP address 10.1.1.2). This is the default level of session persistence.

•SSL persistence: a binding is determined by matching the source IP address and the virtual destination IP/port address. Note that requests from any source socket with the client IP address are considered part of the same session. For example, requests from the client IP address of 134.141.176.10:1024 or 134.141.176.10:1025 to the virtual destination address 207.135.89.16:80 would be considered one session and would be

SmartSwitch Router User Reference Manual 233