TCP/IP

 

Transmission Control Protocol(TCP) and Internet Protocol(IP) are two distinct computer network protocols. TCP and IP are so commonly used together ,however ,that TCP/IP has become standard terminology for referring to this suite of protocols.

TCP divides a message or a file into packets that are transmitted over the internet and then reassembled when they reach their destination. IP is responsible for the address of each packet so that it gets to the correct destination. TCP/IP was developed in the 1970s and adopted as the protocol standard for ARPANET (the predecessor to the Internet) in 1983.

TCP/IP technically applies to network communications in which the TCP transport is used to deliver data across IP networks. Known as a 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.

The Defense Advanced Research Projects Agency (DARPA), the research branch of the U.S. Department of Defense, created the TCP/IP model in the 1970s for use in ARPANET, a wide area network that preceded the internet. TCP/IP was originally designed for the Unixoperating system, and it has been built into all of the operating systems that came after it.

 

 

 

TCP/IP Functionality 

TCP/IP functionality is divided into four layers, each with its own set of agreed-upon protocols:

 

• 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 (Address Resolution Protocol).


• The internet (or networking) layer connects independent networks to transport the packets containing the data across network boundaries. Protocols  are IP and ICMP (Internet Control Message Protocol).


• The transport layer handles communications between hosts and is responsible for flow control, reliability, and multiplexing. Protocols include TCP and UDP (User Datagram Protocol).


• The application layer standardizes data exchange for applications. Protocols include HTTP,FTP,POP3,SMTP, and SNMP (respectively, HyperText Transfer Protocol, File Transfer Protocol, Post Office Protocol Version 3, Simple Mail Transfer Protocol, and Simple Network Time Protocol).

 

 

 

Three of the most common TCP/IP protocols

 

HTTP - Used between a web client and a web server, for non-secure data transmissions. A web client (i.e., Internet browser on a computer) sends a request to a web server to view a web page. The web server receives that request and sends the web page information back to the web client.

HTTPS - Used between a web client and a web server, for secure data transmissions. Often used for sending credit card transaction data or private data from a web client (i.e., Internet browser on a computer) to a web server.

FTP - Used between two or more computers. One computer sends data to or receives data from another computer directly.

How TCP/IP works

 

 

TCP/IP uses the client/server model of communication in which a user or machine (a client) is provided a service (like sending a webpage) by another computer (a server) in the network.

Collectively, the TCP/IP suite of protocols is classified as stateless, which means each client request is considered new because it is unrelated to previous requests. Being stateless frees up network paths so they can be used continuously.

The Internet Protocol standard dictates the logistics of packets sent out over networks; it tells packets where to go and how to get there. IP has a method that lets any computer on the Internet forward a packet to another computer that is one or more intervals closer to the packet's recipient. You can think of it like workers in a line passing boulders from a quarry to a mining cart.

 

The transport layer itself, however, is stateful. It transmits a single message, and its connection remains in place until all the packets in a message have been received and reassembled at the destination.

The Transmission Control Protocol is responsible for ensuring the reliable transmission of data across Internet-connected networks. TCP checks packets for errors and submits requests for re-transmissions if any are found.

For example, when an email is sent over TCP, a connection is established and a 3-way handshake is made. First, the source send an SYN “initial request” packet to the target server in order to start the dialogue. Then the target server then sends a SYN-ACK packet to agree to the process. Lastly, the source sends an ACK packet to the target to confirm the process, after which the message contents can be sent. The email message is ultimately broken down into packets before each packet is sent out into the internet, where it traverses a series of gateways before arriving at the target device where the group of packets are reassembled by TCP into the original contents of the email.

 

 

The primary version of IP used on the internet today is Internet Protocol Version 4 (IPv4). Due to size constraints with the total number of possible addresses in IPv4, a newer protocol was developed. The newer protocol is called IPv6 and it makes many more addresses available and is increasing in adoption.

 

 

 

Importance of TCP/IP

TCP/IP is nonproprietary and, as a result, is not controlled by any single company. Therefore, the internet protocol suite can be modified easily. It is compatible with all operating systems, so it can communicate with any other system. The internet protocol suite is also compatible with all types of computer hardware and networks.

 

TCP/IP is highly scalable and, as a routable protocol, can determine the most efficient path through the network.