3 way handshake: Difference between revisions
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A three way handshake is part of [[TCP]] to create an established connection between two hosts. It is based on sequence numbers and acknoledgements. | A three way handshake is part of [[TCP]] to create an established connection between two hosts. It is based on sequence numbers and acknoledgements. | ||
1. Host A writes SYN sequence 999 to Host B. | 1. Host A writes SYN sequence 999 to Host B. | ||
2. Host B writes SYN sequence 444 to host A and acks 1000. | 2. Host B writes SYN sequence 444 to host A and acks 1000. | ||
3. Host A writes ACK sequence 1000 ack 445 to host B. | 3. Host A writes ACK sequence 1000 ack 445 to host B. | ||
When this is done the connection is thought of as connected. | When this is done the connection is thought of as connected. | ||
At the same time the states change in this three way handshake | At the same time the [[tcp states|states]] change in this three way handshake | ||
like so. | like so. | ||
1. Host A == SYN_SENT, Host B LISTEN | 1. Host A == SYN_SENT, Host B == LISTEN | ||
2. Host A == SYN_RCPT, Host B == SYN_SENT | 2. Host A == SYN_RCPT, Host B == SYN_SENT | ||
3. Host A -- ESTABLISHED, Host B == SYN_RCPT | 3. Host A -- ESTABLISHED, Host B == SYN_RCPT | ||
Finally all of them are in ESTABLISHED state. | Finally all of them are in ESTABLISHED state. | ||
To tear this connection down properly a [[ | To tear this connection down properly a [[4 way close]] is done. | ||
Latest revision as of 06:15, 27 April 2010
A three way handshake is part of TCP to create an established connection between two hosts. It is based on sequence numbers and acknoledgements.
1. Host A writes SYN sequence 999 to Host B. 2. Host B writes SYN sequence 444 to host A and acks 1000. 3. Host A writes ACK sequence 1000 ack 445 to host B.
When this is done the connection is thought of as connected. At the same time the states change in this three way handshake like so.
1. Host A == SYN_SENT, Host B == LISTEN 2. Host A == SYN_RCPT, Host B == SYN_SENT 3. Host A -- ESTABLISHED, Host B == SYN_RCPT
Finally all of them are in ESTABLISHED state.
To tear this connection down properly a 4 way close is done.
