TCP/IP Layers

Last week I attended an interview at Gainsight and interviewer asked me to explain difference between TCP and UDP. TCP is a connection oriented protocol that provides three way handshake. UDP is a connectionless protocol.

As per above figure TCP/IP layer approach has only 4 layers. Presentation and session layer are not there in TCP/IP. Network Interface layer combines Data Link layer and Physical layer.

  1. Application Layer

Application layer defines TCP/IP application protocol and how programs interact with Transport layer to use network. FTP(File Transfer protocol), SMTP(Simple Mail Transfer Protocol), Telnet, SSH, HTTP(Hyper Text Transfer protocol) are protocols of Application Layer.

2. Transport Layer

Transport layer comes in between of Application and Internet layers. The purpose of Transport layer is to permit devices on the source and destination to continue conversation. TCP(Transmission Control Protocol) and UDP(user Datagram protocol) are the protocols of Transport layer. Because TCP is connection oriented it ensures the delivery of packets in order. In UDP packets delivery is not in order. in UDP sender sends the packets and forget about it. In TCP for every packet reached to receiver, sender will get a acknowledgement of packet.

3. Internet Layer

Internet Layer creates the data packets known as IP datagrams, which contains source and destination IP address. It is also responsible for routing of IP address. IP(Internet protocol), ICMP(Internet Control Message Protocol), ARP(Address Resolution Protocol), IGMP(Internet Group Management Protocol) are the protocols of Internet layer.

4. Network Interface Layer

This layer is used to convert data into digital signals or analog signal, light signals(fiber optics), radio signals(Wi-Fi) so that to transfer data coaxial cable, twisted pair cable, fiber optics cable can be used. Ethernet, Token Ring, Frame relay are the protocols of network Interface layer.

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