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Transmission Control Protocol Overview

1-3

Connections and Connection States

TCP establishes a set of access points, referred to as

ports

, for each host. It

associates each port with a network and host address to form a

socket

. A pair of

sockets, together with sequence numbers, window sizes, and status information,

form a

TCP connection

Table 1-1 lists the states through which a TCP connection proceeds during its

lifetime.

Table 1-1. TCP Connection States

State Deﬁnition

LISTEN (2) TCP listens for a connection request from any remote TCP.

SYN SENT (3) TCP sent a connection request (SYN segment) and waits for a

matching connection request and acknowledgment from the

remote TCP.

SYNRECEIVED (4) TCP sent a connection request, received a matching request,

and waits for a conﬁrming connection request acknowledgment

from the remote TCP.

ESTABLISHED (5) Connection open. Data can be received and sent. This is the

normal state for the data transfer phase of the connection.

FINWAIT-1 (6) TCP waits for a connection termination request (FIN segment)

from the remote TCP, or for an acknowledgment of a previously

sent connection termination request.

FINWAIT-2 (7) TCP waits for a connection termination request from the remote

TCP.

CLOSEWAIT (8) TCP waits for a connection termination request from the client.

CLOSING (10) TCP waits for a connection termination request acknowledgment

from the remote TCP.

LASTACK (9) TCP waits for acknowledgment of the connection termination

request previously sent to the remote TCP.

TIMEWAIT (11) TCP waits for enough time to pass to ensure that the remote TCP

received the acknowledgment of its connection termination

request.

CLOSED (1) No connection.

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Avaya Configuring TCP Services Manual de usuario Pagina 19