TCP half-open: Difference between revisions

Revision as of 07:38, 31 August 2012

Revision as of 05:14, 28 October 2012

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Nowadays, however, the term ''half-open connection'' is most often used to describe an '''embryonic connection''', i.e. a [[Transmission Control Protocol|TCP]] connection which is in the process of being established.

The TCP protocol has a [[Three-way handshake|three state system]] for opening a connection. First, the originating endpoint (A) sends a [[SYN (TCP)|SYN packet]] to the destination (B). A is now in an embryonic state (specifically, SYN_SENT), and awaiting a response. B now updates its kernel information to indicate the incoming connection from A, and sends out a request to open a channel back (the [[SYN/ACK]] packet).

At this point, B is also in an embryonic state (specifically, SYN_RCVD). Note that B was put into this state by another machine, outside of B's control.