Question about SPI (stateful packet inspection)

[mkygod]

I have a Trendnet Mimo TWE-611BRP router.

I have SPI turned on. In my status area where i check on my active sessions I can see the last few hundred packet sessions. For each session, under the "state" column it lists a state for each session. There are abbreviations such as EST, SS, CL, TW, or NO. Do any of you knows what this means?

The help section in the router only says the following about it "When SPI (Stateful Packet Inspection) is enabled, this is the state for sessions that use the TCP protocol. "

 

[spidey07]

It's the state of TCP for that connection.

You really don't need to pay much attention to it.

est = establishished = an open tcp connection
ss = syn sent = the start of a tcp session
cl = probably closed or closing
tw = time wait, the end of a tcp connection, but not yet finished

google tcp state machine if you really want to get deep into it.