Extreme Networks Px Series manual Learned Cookie Persistence Mode

•The client transmits its first TCP request (A) to www.mybank.com at its publicly-known VIP address, 64.1.1.7.

•The Px series application switch responds (B) on behalf of 64.1.1.7, and the three-way TCP handshake is established between the client and the Px series application switch.

•Using its configured load balancing policy, the Px series application switch selects one of the web servers. In this example, server 1.

•A three-way TCP handshake is established between the Px series application switch

(C) and server 1 (D).

•The application switch forwards the first data request (E) from the client to server 1.

•Server 1 sends a cookie to the client (via the application switch) (F). The cookie contains unique identifying information for this client session. For example, the cookie could contain the username:

user=samsmith96754

•Each subsequent request sent from the client to the website contains the cookie.

•The client sends another data request to the website (via the application switch).

•The application switch examines the cookie and performs a mathematical hash operation on the cookie, rendering a numeric value.

The selected server may or may not be the same server that provided the client cookie.

•The application switch examines the cookie, performs the same mathematical hash on the cookie, renders the same numeric value each time, and sends each subsequent request from this client to server 3.

Learned Cookie Persistence Mode

Using learned cookie persistence, the Px series application switch creates a database that stores historical information about each session. The database contains the following information:

•Cookie

•Source IP address

•Destination VIP address

•Real server IP address

The application switch uses the stored information to match the incoming cookie with the previous connection made by the same client.

6-10 Px Series Application Switch Installation and Configuration Guide