Communication and computer networks

Presented by: Rabail Hyder ali.

Outlines

A brief history Introduction Computer networks

Wide area network Local/Metropolitan area network

Allocation of resources Challenges and issues

A BRIEF HISTORY:

smoke signals

Beating of drum

INTRODUCTION A typical communication system consist of following parts:

INFORMATION

Analog Digital

Transmission of the information can be analog or digital .therefore we have four possibilities:1. Analog information transmitted as an analog signal.

2. Analog information transmitted as a digital signal.

3. Digital information transmitted as an analog signal.

4. Digital information transmitted as a digital signal

When a signal carrying information is transmitted, it looses its energy and strength and gathers some interference (noise) as it propagates away from the

transmitter.

BOOSTED / AMPLIFIED

Boost energy and strength of a signal, it must be amplified (in case of analog signals)

rebuilt (in case of digital signals)

MAJOR ISSUE

NOISE AMPLIFICATION in Analog Signal

Why Digital Signal is preferred over Analog Signal in communication?

• FILTERED OUT of noise in Digital Signal• processing of information for error detection and correction, applying

encryption and decryption techniques to sensitive information.

COMPUTER NETWORKS

Interconnection of computers. The interconnection forms a facility that provides reliable and efficient

means of communication among users and other devices.

Computer networks are also referred to as computer communication networks.

Interconnection among computers may be via wired or wireless transmission medium

Two broad categories1. Wide area networks2. Local/metropolitan area networks

(a) A typical WAN. (b) A typical local/metropolitan area network. (c) A typical local/metropolitan area communication ring network

• Users will be sharing the transmission link to exchanging their information.

Users will also share• the processing power of the computers.• buffering capacity to store the information.• and any other resources that are connected to the computer network.

• The information from one user to another may need to pass through several switching nodes and transmission links before reaching its destination.

• If one path is not available, not feasible, or not functional, some other path may be used

• Exchange of Large Quantity of Information via a Packets of information.

TRANSPORTION OF NFORMATION :Major aspects are

Addressing mechanism to identify users. Addressing mechanism for information packets to identify their source and destination Establishing a connection between sender and receiver and maintaining it Choosing a path or a route to carry the information from a sender to a receiver Implementing a selected route or path. Checking information packets. Encryption and decryption of information Controlling the flow of information. Informing the sender. Billing for the use of resources Ensuring that different computers running different applications and operating systems can

exchange information Preparing information appropriately for transmission .

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OSI (open system interconnection) ModelThe International Organization for Standardization (ISO) established the

Open Systems Interconnection (OSI) Reference Model

Each layer deals with a particular aspect of network communication.

WIDE AREA COMPUTER NETWORKS: A WAN consist of switching nodes and transmission links. Layout of the switching nodes and transmission links is based on the traffic pattern and

expected volume of traffic flow from one site to another site. When a user is ready to transmit information

1. Connection oriented service

2. connectionless service

TRAFFIC MANAGEMENT IN WANREACTIVE TECHNIQUES (in late 1960 and early 1970)

WINDOW SCHEME

OPTICAL FIBER

BISDNs (Broadband Integrated Services Digital Networks)

Transmit voice, video and data at the same time over fiber optic telephone lines. Broadband ISDN can support data rates of 1.5 million bits per second (bps)

Asynchronous transfer mode (ATM) is expected to be used as a transfer mechanism in BISDNs where information is transmitted into the form of the cell

LOCAL & METROPOLITAN AREA NETWORK

LOCAL AREA NETWORK Limited geographical scope(few kilometers) Limited to building or an organization

METROPOLITAN AREA NETWORK Large transmission area (150 km) High data rates TRANSMISSION IN LOCAL & METROPOLITAN AREA NETWORKS

CATAGORIES OF MAC(medium access control)PROTOCOL

Controlled Access Protocols. Contention based protocols.

CONTROLLED ACCESS PROTOCOLS.• Users take TURNS.• Only one user is allowed to transmit info. at a time. CONTENTION BASED ACCESS PROTOCOLS• Don't take turns.• User makes own decision to transmit information.• Example: carrier sense multiple access with collision detection (CSMA/CD)

WIRELESS AND MOBILE COMMUNICATION NETWORKS

The devices used for wireless communication require certain features

Low power consumption Light weight worldwide communication ability. Access to a communication network is wireless so that the end users remain free to move.

LIMITATIONS Range of wireless communication is always limited. Range of user mobility is also limited.

To overcome this limitations: A geographical region is divided into smaller regions called CELLS.

• Each cell has a fixed communication device that serves all mobile devices within that cell.

• As a mobile Device moves out of one cell and into another cell, service of that connection is transferred from one cell to another. This is called the handoff process.

• Low power consumptions.

RESOURCE ALLOCATION TECHNIQUESTwo approaches for allocation of resources among the users. Static Allocation of resources Dynamic allocation of resources

STATIC ALLOCATION OF RESOURCES• Quantity of resources is allocated to each user.• If user doesn't use his allocated resources , no one else can

DYNAMIC ALLOCATION OF RESOURCES

• Desired quantity of resources is allocated to users on the basis of their demands and for the duration of their need.

• Once the need is satisfied, the allocation is retrieved.

• Someone else can use these resources if needed.

CHALLENGES AND ISSUES

Propagation Delay (the time for a signal to propagate from one end to another)

Integrations of different services in the same networks & Each type of service has its own requirements to achieving a desired level of quality of service

Maintaining security and integrity of information.

THANK YOU