F5 BIG-IP LTM Load Balancer Persistence Profile:--

Persistence Profile

Introduction to Persistence: -
--> The basic concept behind Persistence is the request from same client should go to the same server.

--> This feature most commonly used if the application which we are using is stateful.

--> The persistence feature is used to change the load balancing behavior of a virtual server.

--> New clients will be load balanced based on the load balancing method configured in the pool.

--> All subsequent connection requests from the same client  are direct back to the same pool member if they occur prior to the persistence record time out.

Session Data

àUpon the initial connection, BIG-IP will track and store session data in persistence record. The persistence record includes information like client characteristics and the pool member that secured the client request. This information is used to identify a returning client and direct it back to the same pool member that initially serviced the client request.

àIt is important to define what is meant by a persistence session. A session is a virtual communication link between a client and a pool member that lasts for a period of time, devoted to specific activity.

àA session is a series of separate connection between the same client and same pool member. The session is not continues connection, like the SSH protocol, but consist of connections to the same pool member over a defined time period.

àThe session for creating and storing persistence records is to ensure subsequent connection requests from the same client will be sent to same pool member for the life of the persistence record.

àKeep in mind, the difficulty part of any persistence method is to accurately identifying returning clients.

When the BIG-IP receives a packet for an existing connection through a virtual server with the following configuration, the BIG-IP will not reset the persistence timer:

• The default TCP profile with a 300-second idle timeout
• Simple Persistence with a 180-second idle timeout

For example:

virtual 172.17.1.200:http node 10.10.10.100:http age 300sec

The persistence record age will continue to increment past the persistence idle timeout value, until one of the following conditions is met:

• A new connection matching the persistence record is opened, resetting the persistence record timer to 0.
• The last connection matching the persistence record is removed from the connection table, resetting the persistence record timer to 0.
• The persistence record timer has reached the persistence idle timeout, and no matching entries remain in the connection table. At that time, the persistence record is removed from the persistence table.

Therefore, regardless of the age displayed for a persistence entry, persistence will remain in effect until the entry is removed from the persistence table as described above

Sourcs:F5.com