TCP/IP Overview
TCP/IP, Transmission Control Protocol/Internet Protocol, standard Internet communications protocols that allow digital computers to communicate over long distances. The Internet is a packet-switched network, in which information is divided into small packets, dispatched individually over many different routes simultaneously, and then reassembled at the receiving end.
TCP defines how applications can create channels of communication across a network. It also manages how a message is assembled into smaller packets before they are then transmitted over the internet and reassembled in the right order at the destination address. IP is responsible for how to address and route each packet to make sure it reaches the right destination. Each gateway computer on the network checks this IP address to determine where to forward the message. In brief, TCP is the data. IP is the Internet location GPS. TCP/IP consists of four layers.
1.Application Layer
The Application layer, the top most layer in the TCP/IP model, is responsible for handling high-level protocols, issues of representation. This layer allows the user to interact with the application. Some of the protocols present in this layer are: HTTP, HTTPS, FTP, TFTP, Telnet, SSH, SMTP, SNMP, NTP, DNS, DHCP, NFS, X Window, LPD.
2.Transport Layer
The transport layer is in charge of reliability, flow control, and correction of data which is being sent over the network. The two protocols used in the transport layer are UDP(User Datagram Protocol) and TCP.
UDP, provides connectionless service and end-to-end delivery of transmission, is an unreliable protocol as it discovers the errors but not specify the error.
TCP provides a full transport layer services to applications.It creates a virtual circuit between the sender and receiver, and it is active for the duration of the transmission. TCP is a reliable protocol as it detects the error and retransmits the damaged frames. Therefore, it ensures all the segments must be received and acknowledged before the transmission is considered to be completed and a virtual circuit is discarded. At the sending end, TCP divides the whole message into smaller units known as segment, and each segment contains a sequence number which is required for reordering the frames to form an original message.
3.Internet Layer
The Internet layer,also called the network layer, defines the protocols which are responsible for logical transmission of data over the entire network. The main protocols at this layer are: Internet Protocol (IP), Address Resolution Protocol (ARP), Reverse Address Resolution Protocol (RARP), Internet Control Message Protocol ( ICMP), and Internet Group Management Protocol (IGMP).
4. Network Access Layer
The Network Access Layer is the layer in the TCP/IP model at which data is transmitted and received across the physical network.A network interface device, usually a line card, adaptor or port is used to connect the physical wires or fibers to the computer so that it can communicate with other computers. TCP/IP is designed to be independent of the network access method, frame format, and medium. In other word, it is independent from any specific network technology. In this way, TCP/IP can be used to connect different network types, such as Ethernet, Token Ring, X.25, Frame Relay, and Asynchronous Transfer Mode (ATM).
Additionally,you can refer this awesome video to get a clear picture of OSI Model, which is explained by taking analogy.
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