Knowlegde training #1:TCP/IP Handshake

TCP/IP Handshake :

Transmission Control Protocol/Internet Protocol.
A method used to establish TCP socket connection and enable data transfer via a reliable network.
Three way handshake or three message handshake(SYN,SYN+ACK,ACK).

How TCP handhske happens:

1. Local device sends sequence number , maximum segment size,destination IP Address.(SYN)
2. Destination device responds by sending its sequence number and maximum segment size back to local device.(SYN+ACK).
3. Local device acknowledges receipt of the sequence number and segment size information.(ACK)


 SYNchronize and ACKnowledge messages are indicated by a bit inside the header of the TCP segment.
These SYN and ACK messages are used to establish and break connections.

When the communication between two computers ends, another 3-way communication is performed to tear down the TCP socket connection. This setup and teardown of a TCP socket connection is part of what qualifies TCP a reliable protocol. TCP also acknowledges that data is successfully received and guarantees the data is reassenbled in the correct order.

Unlike TCP, UDP(User Datagram Protocol) is connectionless. UDP directly estsablishes connection with any destination host without verifying whether its a reliable host,it does not perform this 3-way handshake and therefore, it is referred to as an unreliable protocol.

Note that FTP, Telnet, HTTP, HTTPS, SMTP, POP3, IMAP, SSH and any other protocol that succeeds TCP also has a three way handshake performed before connection is established. HTTP web requests, SMTP emails, FTP file transfers  manages the messages  transmission using TCP handshake.

TCP 'rides' on top of Internet Protocol (IP) in the protocol stack, that is why the combined pair of Internet protocols is called TCP/IP (TCP over IP). TCP segments are passed inside the payload section of the IP packets. IP handles IP addressing and routing and gets the packets from one place to another, but TCP manages the actual communication sockets between endpoints (computers at either end of the network or internet connection).

Question:

1.What is TCP/IP Handshake?
2.How it works?
3.Difference between reliable and unreliable protocols?eg:?

Kindly post your queries related to this concept and your suggestions to improve.

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