Communication Communication NetworkNetworkProtocolsProtocols

----Krishna Priyanka ----Krishna Priyanka

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~ Given a Network Architecture, some rules and standards must be

set up to govern the communication i.e.; communication protocols.

~ Ensures secure, fast and error-free data delivery.

Division of protocols:

~ Connection-oriented and connectionless

~ Circuit-switching and Packet-Switching

~ Virtual circuit and datagram

Circuit and Packet SwitchingCircuit and Packet Switching

Protocol Hierarchies:

~ Most networks are organized as stack of layers, each one built upon

the one below it.

~ Number of layers, Name, Content and Function of each layer varies

from network to network.

Reference Models:Reference Models:

1. OSI Reference Model

2. TCP/IP Reference Model

OSI Reference ModelThe OSI model has seven layers. The principles that were applied to arrive at the seven layers can be briefly summarized as follows: 1. A layer should be created where a different abstraction is needed. 2. Each layer should perform a well-defined function. 3. The function of each layer should be chosen with an eye toward defining internationally standardized protocols. 4. The layer boundaries should be chosen to minimize the information flow across the interfaces. 5. The number of layers should be large enough that distinct functions need not be thrown together in the same layer out of necessity and small enough that the architecture does not become unwieldy.

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The Physical Layer

~ The physical layer is concerned with transmitting of raw bits over a communication channel.

Definition of Hardware Specifications

Encoding and Signaling

Data Transmission and Reception

Topology and Physical Network Design

The data link layer

~ Link Layer~ DLL = Logical Link Layer +

Media Access Control

Data Framing

Addressing

Error Detection and handling

The Network Layer

The network layer is the lowest one The network layer is the lowest one in the OSI model that is concerned in the OSI model that is concerned with actually getting data from one with actually getting data from one computer to another even if it is on computer to another even if it is on a remote network; in contrast, the a remote network; in contrast, the

data link layer only deals with data link layer only deals with devices that are local to each other.devices that are local to each other.

Logical Addressing

Routing

Datagram Encapsulation

Fragmentation and Reassembly

Error handling and Diagnostics

The Transport Layer

~Accepts data from above and splits into smaller units

~ Determines what type of service to provide to the session layer.

~ Primary goal is create reliable ~ Primary goal is create reliable end to end communication.end to end communication.

~ The OSI protocol suite ~ The OSI protocol suite implements two types of services at implements two types of services at

the transport layer: connection-the transport layer: connection-oriented transport service and oriented transport service and

connectionless transport service. connectionless transport service.

The Session LayerSession service provides four basic services to

SS-users.

Establishes and terminates connections between SS-users and synchronizes the data exchange

between them. Performs various negotiations for the use of session layer tokens, which the SS-user must

possess to begin communicating. Inserts synchronization points in transmitted data that allow the session to be recovered in

the event of errors or interruptions. Enables SS-users to interrupt a session and

resume it later at a specific point.

The Presentation Layer

the presentation layer is charged with taking care of any issues that might arise where data sent from

one system needs to be viewed in a different way by the other system. It

also takes care of any special processing that must be done to

data from the time an application tries to send it until the time it is

sent over the network.

Translation

Compression

Encryption

The Application Layer

The application layer contains a variety of protocols that are commonly needed by users.

One widely-usedapplication protocol is HTTP (HyperText

Transfer Protocol), which is the basis for the World Wide Web. When a

browser wants a Web page, it sends the name of the page it wants to the server using HTTP. The

server thensends the page back. Other application

protocols are used for file transfer, electronic mail, and network news.

TCP/IP Reference Model

The host-network layer

The Internet Layer

The Transport Layer

The Application Layer

Comparison

OSI vs TCP/IP

References

Andrew S. Tenenbaum ,Computer Networks ,4th edition. Pearson Education, 2003

http://www.tcpipguide.com/free/t_TCPIPInternetArchitectureandProtocolSuite.htm

Jim Kurose, Keith Ross, Computer Networking: A Top Down Approach Featuring the Internet, 3rd edition.

Addison-Wesley, July 2004.