tcp/ip model view

There are four layers in TCP/IP model.


1. Application Layer


2. Transport Layer


3. Internet Layer


4. Network Access Layer






Application Layer (AL):


• Application Layer (AL), contains those protocols which provides services to users.


• Web browsing, e-mail, encryption, session establishment all these things happen in application Layer which uses protocols such as,


• HTTP, SMTP, DNS, TELNET, FTP, NFS, DFS, IMAP4, POP3, NNTP, SSH, SSL, GOPHER.


• Application Layer (AL), defines network application services like file transfer, network management.


• Identification of services is done using port numbers. Ports are nothing but socket i.e. entry & exit point to the layer.


• Application layer, Presentation layer, Session layer of OSI model


• Responsible for converting data into standard format ex: ASCII, JPEG, MIDI, MP3.


• Encoding-decoding, encryption-decryption, compression, NFS, RPC (remote procedure code).






Transport Layer (TL):


• Two important protocols are used in Transport layer (TL). They are TCP and UDP


• Transport layer (TL), deals with actual manipulation of data and prepares it for delivery through network.


• If data is too large for the single frame, then TL breaks it into smaller pieces and assigns sequence number.


• It ensures that all the data is received in the right order than it was sent.


• TL is responsible for ensuring data is sent and received successfully.


• TL is responsible for verifying delivery of packets.


• Identification services, sequencing, flow control, error correction, segmentation, reassembling is done here.






Internet Layer (IL):


• Internet layer (IL), deals with, finding the way to the destination.


• Internet layer (IL) defines, IP addressing, routing, switching.


• It determines where the data should go on the physical network.


• It is responsible for routing each packet to its destination.


• Defines network address.


• Protocols that are used in this layer are routing protocol-OSPF, RIP, IGRP, EIGRP Routed protocols-IP, IPX, Appletac. And DDP (datagram delivery protocol), ICMP, IPSec.


• This layer is also known as network layer in OSI model.


• IL provides best path to the data to reach destination.


• Device working in this layer is Router.






Network Access Layer:


• It is responsible for putting frames (packets) on the wire.


• Responsible for setting bits & bytes, electrical signals and impulses back and forth across the wire (coaxial or twisted pair).


• Deals with wire, connectors, signals, pulses, modems, fiber optic cable (in for of light).


• “Doors between worlds” connecting physical aspect of network (cables & Digital pulses).


• Describes specifications for topology.


• Devices used here are- HUB, Switch, Repeater, Bridges, and NIC.


• MAC – it talks about physical address


• LLC – it talks about wan protocols like ppp, hdlc, and frame relay.