PROTOCOLS

Set of rules.

TCP/IP is the universal layered protocol .

OSI(open system interconncet) :-

Osi was developed  by international organization  for standization (iso) and introduced in 1984.

It is a layered architecture (consists seven layers).

Each layer defines a set of functions .which takes part in data communication.

APPLICATION LAYER

 Application layer is responsible for providing an interface for the users to interact with application services.

Ex:-HTTP(web browser),FTP,SMTP(email),telnet etc,

PRESENTATION:-

It is responsible for defining a standard format to the data. It deals with data presentation.

The major functions described at this layer are encoding and decoding.

Ex:- ASCII,EBCDIC(text)

JPEG,GIF,TIFF(graphics)

MIDI,WAV(voice)

MPEG,DAT,AVI(vedio)

And also doing

Encryption to decryption.

Compression and decompression.

SESSION LAYER:-

It is responsible for establishing , maintaining and terminating the connection/sessions.

Session ID is used to identify a session or inter action.

Ex:-

RPCà remote procedure call.

SQLàstructured aqery  language  .

ASPà apple talk session protocall.

TRANSPORT LAYER:-

it provides data delivery mechanism between the applications in the network.

The major function described at the transport layers are

·         Identification of service

·         Multiplexing and demultiplexing

·         Segmentation.

·         Sequencing and reassembling

·         Error control

·         Flow control

IDENTIFICATION OF SERVICE

Identification of a service is done using port numbers.

Port is a logical communication channel.

Total no of ports—0-65535

Reserved ports—1-49151

Open ports –49152-65535

Protocols which take care of data transfer at transport layers are

TCP and UDP

TCP	UDP
Transfer control protocol	User datagram protocol
Provide ack	Doesn’t provide ack
Reliable communication	Unreliable communication
Slower data transfer	Faster data transfer
Protocol no is 6	Protocol no is 17
Ex http,ftp,smtp	Ex dns,dhcp,tftp

NETWORK LAYER:-

It provides logical addressing & path determines(routing)

The protocols that works in this layers are

IP,IPX,Apple talk,etc..

Routed protocols used to carry user data between hosts.

Routing protocols

RIP,OSPF,EIGRP

Routing protocol performs path determination (routing).

DATA LINK LAYER:-

Data link layers are divided into two sub layers.

MAC

Media access control it provides reliable transit of data across a physical link.

It is also provides error detection using CRC(cyclic redundancy check ).

Ex:- Ethernet ,token ring etc..

LLC

Logical link control

It provides communication with network layer.

PHYSICAL LAYER:-

It defines the electrical, mechanical and functional specification for communication between the network devices.

The functions described at these layers are

Encoding/decoding.

It is the process of converting the binary data into signals based on the type of media.

Copper media:-electrical signals of different voltage levels.

Fiber media:-light pulses of different  wave lengthes.

Wireless media:- radio frequency waves.

Layer	Name	Data Unit	Main Function
7	Application Layer	Message	It provides the means for the users to access information on the network using an application.
6	Presentation Layer	Message	This layer deals with syntax and semantics of the data exchanged between two devices.
5	Session Layer	Message	Negotiation of the establishment and termination of connections (sessions).
4	Transport layer	Message	Efficient and cost-effective transportation of data across the network.
3	Network Layer	Packet	Routing of data packets within the network and across multiple networks.
2	Data Link Layer	Frame	Provision of a reliable communication line to the network layer.
1	Physical layer	Bit	Transmission of raw data bits over communication lines.

 Diffence b/w OSI and TCP/IP:-