Communication and computer networks

Communication and computer networks

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  Communication and computer networks Presentedby: Rabail Hyder ali.
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  Outlines  A briefhistory  Introduction  Computer networks  Wide area network  Local/Metropolitan area network  Allocation of resources  Challenges and issues
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  A BRIEF HISTORY:
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  smoke signals Beating ofdrum
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  INTRODUCTION  A typicalcommunication system consist of following parts:
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  INFORMATION  Analog  Digital
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   Transmission ofthe 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
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  Why Digital Signalis 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.
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  COMPUTER NETWORKS  Interconnectionof 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 categories 1. Wide area networks 2. Local/metropolitan area networks
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  (a) A typicalWAN. (b) A typical local/metropolitan area network. (c) A typical local/metropolitan area communication ring network
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  • Users willbe 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.
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  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 systeminterconnection) Model The International Organization for Standardization (ISO) established the Open Systems Interconnection (OSI) Reference Model Each layer deals with a particular aspect of network communication.
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  WIDE AREA COMPUTERNETWORKS:  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
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  TRAFFIC MANAGEMENT INWAN REACTIVE TECHNIQUES (in late 1960 and early 1970) WINDOW SCHEME OPTICAL FIBER
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  BISDNs (Broadband IntegratedServices 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
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  LOCAL & METROPOLITANAREA 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
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   CATAGORIES OFMAC(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)
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  WIRELESS AND MOBILECOMMUNICATION 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.
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  To overcome thislimitations:  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.
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  RESOURCE ALLOCATION TECHNIQUES Twoapproaches 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.
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  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.
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  THANK YOU