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Network Programming CSC- 341

Network Programming CSC- 341. Instructor: Junaid Tariq, Lecturer, Department of Computer Science. Lecture. 3. Computer Networks. Network Components. Physical Media Interconnecting Devices Computers Networking Software Applications. Introduction to Computer Networks.

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Network Programming CSC- 341

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  1. Network ProgrammingCSC- 341 Instructor: Junaid Tariq, Lecturer, Department of Computer Science

  2. Lecture 3 Computer Networks

  3. Network Components Physical Media Interconnecting Devices Computers Networking Software Applications

  4. Introduction to Computer Networks Networking Media • Networking media can be defined simply as the means by which signals (data) are sent from one computer to another (either by cable or wireless means). • Wide variety of transmission links: • Copper Twisted pair • Coaxial Cable • Optical Fiber • Wireless media

  5. Introduction to Compute Networks Networking Devices • HUB, Switches, Routers, Wireless Access Points, Modems etc.

  6. Introduction to Computer Networks Computers: Clients and Servers • In a client/server network arrangement, network services are located in a dedicated computer whose only function is to respond to the requests of clients. • The server contains the file, print services, application, security, and other services in a central computer that is continuously available to respond to client requests.

  7. Applications • E-mail • Searchable Data (Web Sites) • E-Commerce • News Groups • Internet Telephony (VoIP) • Video Conferencing • Chat Groups • Instant Messengers • Internet Radio

  8. Addressing and Routing • Address: byte-string that identifies a node • usually unique • Routing: forwarding decisions • process of determining how to forward messages to the destination node based on its address • Types of addresses • unicast: node-specific • broadcast: all nodes on the network • multicast: some subset of nodes on the network

  9. Wrap-up • A network can be constructed from nesting of networks • An address is required for each node that is reachable on the network • Address is used to route messages toward appropriate destination

  10. OSI Model

  11. LAYERED TASKS We use the concept of layers in our daily life. As an example, let us consider two friends who communicate through postal mail. The process of sending a letter to a friend would be complex if there were no services available from the post office.

  12. Layered Tasks • Sender, Receiver and Carrier

  13. Layered Tasks • Hierarchy • Higher Layer • Middle Layer • Lower Layer • Services • The Each layer uses the services of the layer immediately below it.

  14. Class Activity Tell any example of layer from daily life.

  15. ticket (complain) baggage (claim) gates (unload) runway landing airplane routing ticket (purchase) baggage (check) gates (load) runway takeoff airplane routing airplane routing Organization of air travel Although this course is about network programming (and not about networking in general), an understanding of a complete network model is essential.

  16. ticket (complain) baggage (claim) gates (unload) runway landing airplane routing ticket (purchase) baggage (check) gates (load) runway takeoff airplane routing airplane routing Organization of air travel: a different view Layers: each layer implements a service • via its own internal-layer actions • relying on services provided by layer below

  17. airplane routing airplane routing airplane routing Distributed implementation of layer functionality ticket (complain) baggage (claim) gates (unload) runway landing airplane routing ticket (purchase) baggage (check) gates (load) runway takeoff airplane routing arriving airport Departing airport intermediate air traffic sites

  18. THE OSI MODEL Established in 1947, the International Standards Organization (ISO) is a multinational body dedicated to worldwide agreement on international standards. An ISO standard that covers all aspects of network communications is the Open Systems Interconnection (OSI) model. It was first introduced in the late 1970s. ISO is the organization.OSI is the model.

  19. Layered Architecture • The OSI model is composed of seven layers ; • Physical (layer1), Data link (layer2), Network (layer3) Transport (layer4), Session (layer5), Presentation (layer6), Application (layer7) • Layer • Designer identified which networking functions had related uses and collected those functions into discrete groups that became the layers. • The OSI model allows complete interoperability between layers. • The Each layer uses the services of the layer immediately below it.

  20. Layered Architecture (cont’d) Figure 2.2Seven layers of the OSI model All People Seem To Need Data Processing

  21. Peer-to-peer Processes • Layer x on one machine communicates with layer x on another machine - called Peer-to-Peer Processes. • Interfaces between Layers • Each interface defines what information and services a layer must provide for the layer above it. • Well defined interfaces and layer functions provide modularity to a network • Organizations of the layers • Network support layers : Layers 1, 2, 3 • User support layer : Layer 5, 6, 7 • It allows interoperability among unrelated software systems • Transport layer (Layer 4) : links the two subgroups

  22. OSI Architecture

  23. Peer-to-peer Processes (cont’d) Figure 2.3The interaction between layers in the OSI model

  24. Peer-to-peer Processes (cont’d) Figure 2.4An exchange using the OSI model • The data portion of a packet at level N-1 carries the whole packet from level N. – The concept is called encapsulation.

  25. LAYERS IN THE OSI MODEL In this section we briefly describe the functions of each layer in the OSI model. Topics discussed in this section: Physical LayerData Link Layer Network Layer Transport Layer Session Layer Presentation Layer Application Layer

  26. OSI Model Physical Layer

  27. Physical Layer • Physical layer coordinates the functions required transmit a bit stream over a physical medium. • The physical layer is responsible for movements of individual bits from one hop (node) to the next.

  28. Physical Layer • Physical layer is concerned with the following: (deal with the mechanical and electrical specification of the primary connections: cable, connector) • Physical characteristics of interfaces and medium • Representation of bits • Data rate : transmission rate • Synchronization of bits • Line configuration • Physical topology • Transmission mode

  29. OSI Model Data Link Layer

  30. Data Link Layer • The data link layer is responsible for moving frames from one hop (node) to the next.

  31. Data Link Layer • Major duties • Framing • Physical addressing • Flow control • Error control • Access control

  32. Data Link Layer • Hop-to-hop (node-to-node) delivery

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