BROCADE IP PRIMER

Session PersistenceWhen a sticky session is initiated, a timer is created. When communicationstops from the client, the timer starts. If it reaches its configurable expiration(defined by “sticky age”), the client will no longer stick to the same real server.If it hasn't quite reached its configurable expiration, and the client initiatesmore traffic, the timer will restart.By default, sticky sessions are not enabled on virtual server ports, with theexception of Secure Sockets Layer (SSL). Due to the way SSL negotiates a session(involving several TCP sessions), it will not function in any way other thansticky. The ServerIron automatically adds the sticky line to the virtual serverconfig when SSL is defined.Configurable TCP/UDP Application GroupsThis is also referred to as “port tracking.” This function is very similar to concurrentand sticky. Like concurrent, it accounts for applications that requirethe client to make several successive connections for the application to function.For this reason, we need to make sure that all of those connections reachthe same real server.In our concurrent example, we talked about passive FTP. It requires the clientto make a second connection on a random port. For Application Groups, theclient is required to make a second connection on a fixed or known port. Inother words, we can anticipate on what port the second client connection willbe made.All Configurable TCP/UDP Application Groups have one port that is consideredthe “primary.” This is the port that the client initially connects to. You candefine your Application Group with up to four other ports that the client maysuccessively initiate connections to. Because Application Groups are defined,the ServerIron makes sure that the same source IP's successive connectionsare handed off to the same real server.One of the things that makes Application Groups similar to sticky is that theyuse the same timer (the “sticky age” timer). When the client connection starts,the ServerIron watches communication coming from the client. If the clientcommunication stops (even briefly), the timer starts. If it reaches the timedefined by the “sticky age” setting, the ServerIron no longer sends successivecommunication from that client to the same real server. However, if the timer'sexpiration has not been reached, and the client sends additional communication,the timer is reset.CookiesMake mine chocolate chip, please. What? Oh! You're still here! Excuse me.How embarrassing!What were we talking about? Ah, yes! Cookies! In the mid-1990's, the competingweb browsers of the day brought us a new feature: HTTP cookies. Theseare simply chunks of text that are sent from the web server to the client. Oncethe client has received a cookie, it automatically includes the cookie in futurecommunications to that same web site. This is often used to track an individ-Brocade IP Primer 359