This is a suite of communication protocols with four layers which was developed by the DoD (Department of Defence) in the 1960s. It is named after the two main protocols (TCP/IP)that are used in the model .The four layers in the TCP/IP protocol suite are Host-to- Network Layer ,Internet Layer ,Transport Layer and Application Layer .
TCP/IP Model specify the way of connection of specific computer and the internet and the way of transmitting data between them. The purpose of this model is to allow communication over large distances
Functions of the TCP IP model happen in four layers, using specific protocols. Each layer in TCP/IP model has a specific function to perform and All these four layers work cooperatively to send data from one layer to another.
- Host to network Layer
- Internet Layer
- Transport Layer
- Application Layer
Host-to- Network Layer
Host-to- Network Layer is the lowest layer of this TCP/IP model .The Physical layer and Data Link layer of OSI reference model are combined here as the Network layer . It explain how the data should be sent physically through the network .This layer transmit the data between two devices on the same network ..The functions carried out by this layer are encapsulating the IP datagram into frames transmitted by the network and mapping of IP addresses into physical addresses . Ethernet, token ring, FDDI, X.25, frame relay are the protocols used by this layer .A network in TCP/IP internetwork can be LAN or VAN .
This is the second layer of the TCP/IP model and IT is named as network layer . send the packets from any network, and they arrive at the destination irrespective of the route they take is identified as the main task of the Internet layer .There have some functionalities and Protocol in this layer
IP Protocol -this is the most important part of the TCP/IP model .It has following responsibilities .
- IP Addressing
- Host-to-host communication
- Data Encapsulation and Formatting
- Fragmentation and Reassembly
ARP stands for Address Resolution Protocol and the physical address will be found from IP address in this layer .The two terms of ARP protocol are ARP request and ARP reply .
- ARP request -ARP request is sent to the network when sender wants to know the physical addresses of the device .
- ARP reply — Every device connected to the network will accept the ARP request and then those devices process the request, but only recipient identify the IP address and sends ARP reply which includes its physical address. The physical address is added to its cache memory and to the datagram header by the recipient .
Internet Control Message Protocol (ICMP) ,notifications about datagram problems back to the sender ,is sent by hosts or routers using this mechanism .A datagram transmit from router-to-router until it finds its destination .sometimes router is unable to route the data. because of some reasons such as disabled links, a device is on fire or network congestion . in such situations the sender will be informed that the datagram is undeliverable using this ICMP protocol .Reporting the problems is the main responsibility of ICMP protocol . the sender has the responsibility of correct those problems .
ICMP protocol has two terms as ICMP Test and ICMP Reply
- ICMP Test — test the reachability of the destination
- ICMP Reply -test the responsiveness of the destination
This transport layer has to concern about reliability of the data ,control the flow of data and responsible about correction of data .User Datagram protocol and Transmission control protocol are the protocols using in this layer .
User Datagram Protocol (UDP) — user datagram protocol gives a connectionless service with end to end transmission . This is identified as unreliable protocol because it doesn’t specify the error it discovers .
Transmission Control Protocol (TCP) — TCP provides a full transport services to applications .the virtual circuit which is created by the TCP, between sender and receiver is active for the transmission duration .
This is the topmost layer of the TCP/IP model . It handles the high level protocols and representation issues . the interaction between user and the application handled by this layer .the layer allows one application to communicate with another application layer by sending its data to the transport layer .
the main protocols used in this layer are -
- HTTP: data(plain text, audio, video ) over the world wide web are accessed by using this HTTP(Hypertext transfer protocol ) protocol .
- SNMP: SNMP stands for Simple Network Management Protocol . It act as a framework to manage devices on the internet .
- SMTP: SMTP stands for Simple mail transfer protocol .this protocol is used to send data through emails .
- DNS: DNS stands for Domain Name System .this protocol maps names with the IP addresses
- TELNET :the connection between the local computer and the remote computer is established using this protocol .
- FTP:FTP stands for File Transfer Protocol .this protocol is uses to transmit files between computers
Advantages of TCP/IP model
- TCP/IP model is independent from operating system .
- The client server architecture of the TCP/IP model is highly scalable .
- It supports number of routing protocols such as Routing Information Protocol and Router Discovery Protocol .
- It helps to establish a connection between two computers which has two different types
Disadvantages of TCP/IP model
- The set up and managing process of TCP model is complicated.
- This model has a higher overhead than Internet Packet Exchange
- The transport layer of this model does not assure the delivery of packets
- TCP model does not allow to replace protocols easily
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