What is 3 way handshaking? Explain connection establishment using TCP.
1 Answer


TCP transmits data in full-duplex mode When two TOPs in two machines are connected, they are able to send segments to each other simultaneously This implies that each party must initialize com - munication \& get approval from the other party before any data are transferred.

Three-Way Handshaking:

The connection establishment in TCP is called three-way handshaking. ECG.

An application program, called the client, wants to make a connection with another application program, called the server, using TCP as the trans-

The client program issues a request for an active open. A client that. wishes to connect to an open server tells its. TCP to connect to a particular Server. TCP can now start the three-way handshaking process.

The three steps in this phase are as follows:

(1) The client sends the first segment, an sYN segment, in which only the SYN flag is set. This segment is for the synchronization of sequence numbers. The client chooses a random number as the first seq- Science number of sends this number to the server.

This sequence number is called the initial - sequence number (ISN). This segment does $r$ contain an acknowledgment number. It does not define the window size either; a window size - finition makes sense only when a segment is acknowledged.

SYN segment is a cont segment \& carries no data. However, it cons one sequence number. When the data transfer starts, the ISN is incremented by 1. Thus, the SYN segment carries the actual data, but it is one imaginary byte.

(2) The client sends the third segment:

This is j an ACK segment. It acknowledges the receipt of the second segment with the ACK flag \& act - Ledgment number field. The sequence numb in this segment is the same as the one in the SYN segment; the ACK segment does not c - sump any sequence numbers.

Also, define the server window size some insole-mentations allow this third segment in the connection phase to carry the first chunk of data from the client.

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In this case, the third seq-mint must have a new sequence number showing the byte number of the first byte in the data. In general, the third segment usually does not carry data \& consumes. no sequence number.

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