Keep Alive characteristics

keepalive is a parameter that was offically added to HTTP 1.1, but you can find certain 1.0 versions that will use it. Actually you can add the parameter yourself to a 1.0 request if you are creating your own packtes. The keepalive command is simplyan option that is added to the header of the HTTP packet when a connection request is made. It asks the WEB server --if it supports keepalives--to keep the connection alive so that all future traffic on the same session will not have to recreate the connection everytime a request is made. It makes things faster. Basically any HTTP packet can make the keepalive request, but it is up to the server to honor it. Most web servers today will honor a keepalive request, but older ones may not. Oncea connection is made with a kepalive then all subsequesnt trafic on the same socket will simply flow, it does not have to recreate a connection to the server with every request. If you need more detail than this please email.

The TCP keepalive capability allows a terminal server to detect when the host with which it is communicating experiences a system failure, even if data stops being transmitted (in either direction). This is most useful on incoming connections. For example, if a host failure occurs while talking to a printer, the terminal server may never notice, since the printer does not generate any traffic in the opposite direction. If keepalives are enabled, they are sent once every minute on otherwise idleconnections. If five minutes pass and no keepalives are detected, the connection is closed. The connection will also be closed if the host replies to a keepalive packet with a reset packet. This will happen if the host crashes and comes back up again.

Keepalives are also used for router so to keep track of routers or links going down. Different types of data is transmitted in these keep alives. Cisco, for instance, use LMI which can be further look into when a router goes down.

Kashif

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