TCP/IP Layers

Transmission Control Protocol (TCP) and Internet Protocol (IP) are two distinct computer network protocols. A protocol is an agreed-upon set of procedures and rules. When two computers follow the same protocols—the same set of rules—they can understand each other and exchange data. TCP and IP are so commonly used together, however, that TCP/IP has become standard terminology for referring to this suite of protocols.

Transmission Control Protocol divides a message or file into packets that are transmitted over the internet and then reassembled when they reach their destination. Internet Protocol is responsible for the address of each packet so it is sent to the correct destination. TCP/IP functionality is divided into four layers, each with its own set of agreed-upon protocols:

Datalink layer: The Datalink layer consists of methods and protocols that operate only on a link, which is the network component that interconnects nodes or hosts in the network. Protocols in the layer include Ethernet and ARP.

Networking layer: The Internet or Networking layer connects independent networks to transport the packets containing the data across network boundaries. Protocols are IP and ICMP.
Transport layer: The Transport layer handles communications between hosts and is responsible for flow control, reliability and multiplexing. Protocols include TCP and UDP.

Application layer: The Application layer standardizes data exchange for applications. Protocols include HTTP, FTP, POP3, SMTP, and SNMP.

TCP/IP technically applies to network communications where the TCP transport is used to deliver data across IP networks. A so-called “connection-oriented” protocol, TCP works by establishing a virtual connection between two devices via a series of request and reply messages sent across the physical network.

Most computers users have heard the term TCP/IP even if they don’t know what it means. The average person on the internet works in a predominately TCP/IP environment. Web browsers, for example, use TCP/IP to communicate with Web servers. Millions of people use TCP/IP every day to send email, chat online and play online games without knowing how it works.

Source: Lifeware- Bradley Mitchell

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