The purpose of each layer in TCP/IP protocol suite is briefly discussed here.
Physical Layer:
There is no specific or dedicated protocol for physical layer in TCP/IP model.
This layer is responsible for actual transmission of data for one device to another. The unit of transmission is bits.
In addition to this, responsibility of physical layer is similar to that in OSI model but mostly depends on the underlying technologies.
Data Link Layer:
The packet received from network layer, is framed which becomes the unit of communication at DLL.
Framing involves encapsulation of data by adding header and trailer to it.
Header include the information about source and destination addresses, which play important role in identification and authentication of correct packet.
Network Layer:
At Network layer, TCP/IP supports Internet Protocol (IP) as a transmission mechanism.
Datagram is the unit of transmission used at network layer.
The major difference between network layer and physical and DLL is that communication in network layer is end-to-end whereas it is node-to-node in physical and DLL.
Transport Layer:
Network layer is responsible for sending datagrams to destination and transport layer is responsible for sending entire message (aka segment) to destination.
A segment may contain one/more datagrams.
Transport layer in TCP/IP is represented by two protocols-
1. UDP aka User Datagram Protocol which provides connection-less service
2. TCP aka Transmission Control Protocol which provides reliable connection-oriented service.
Since Internet may assign different routes to datagrams, the packets received at the destination may arrive out-of-order or may get lost.
Application Layer:
This layer is equivalent to Session, Presentation and Application layers in OSI reference model.
This is the layer where user actually interacts with the system and perform desired tasks.
Various protocols including e-mail services, file transfer, accessing World Wide Web etc. are defined at this layer and the number is increasing with the growing need.
Like transport and network layers, this layer is also an end-to-end layer.
Physical Layer:
There is no specific or dedicated protocol for physical layer in TCP/IP model.
This layer is responsible for actual transmission of data for one device to another. The unit of transmission is bits.
In addition to this, responsibility of physical layer is similar to that in OSI model but mostly depends on the underlying technologies.
Data Link Layer:
The packet received from network layer, is framed which becomes the unit of communication at DLL.
Framing involves encapsulation of data by adding header and trailer to it.
Header include the information about source and destination addresses, which play important role in identification and authentication of correct packet.
Network Layer:
At Network layer, TCP/IP supports Internet Protocol (IP) as a transmission mechanism.
Datagram is the unit of transmission used at network layer.
The major difference between network layer and physical and DLL is that communication in network layer is end-to-end whereas it is node-to-node in physical and DLL.
Transport Layer:
Network layer is responsible for sending datagrams to destination and transport layer is responsible for sending entire message (aka segment) to destination.
A segment may contain one/more datagrams.
Transport layer in TCP/IP is represented by two protocols-
1. UDP aka User Datagram Protocol which provides connection-less service
2. TCP aka Transmission Control Protocol which provides reliable connection-oriented service.
Since Internet may assign different routes to datagrams, the packets received at the destination may arrive out-of-order or may get lost.
Application Layer:
This layer is equivalent to Session, Presentation and Application layers in OSI reference model.
This is the layer where user actually interacts with the system and perform desired tasks.
Various protocols including e-mail services, file transfer, accessing World Wide Web etc. are defined at this layer and the number is increasing with the growing need.
Like transport and network layers, this layer is also an end-to-end layer.
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