Computer Science Overview Chap4-Networking and the Internet (2)

1. Computer Science OverviewChap4-Networking and the Internet (2) JainShing Wu

2. Networking Topology • The layout of the interconnections of the nodes of a computer network • Types • Bus • Star • Token ring • Mesh

3. Bus Network • A set of clients are connected via a shared communications line • Ethernet • Advantage • Easy to setup • Disadvantage • Reconfiguration, fault isolation and installation of new devices tends to be difficult • A fault along the shared communication line stops all transmissions in the network

4. BUS Network

5. Star Network • Consists of one central switch, hub or computer to which all other nodes are connected • Client and Server

6. Star Network • Advantage • Better performance • Isolation of devices • Benefits from centralization • Easy to detect faults and to remove parts • No disruptions to the network when connecting or removing devices • Installation and configuration is easy • Disadvantage • High dependence of the system on the functioning of the central hub • Failure of the central hub renders the network inoperable

7. Star Network

8. Token Ring • Each node connects to exactly two other nodes, forming a ring • Fiber Distributed Data Interface (FDDI)

9. Token Ring

10. Mesh Network • Each node captures and disseminates its own data, but also serve as a relay for other nodes • Mobile ad hoc networks (MANET)

11. Mesh Network

12. Ethernet • Computer networking technologies for local area networks (LANs) • Ethernet was commercially introduced in 1980 and standardized in 1985 as IEEE 802.3 • Several wiring and signaling variants of the OSI physical layer in use with Ethernet

13. Ethernet • The original 10BASE5 Ethernet used coaxial cable as a shared medium

14. Ethernet • Hub • Bridge • Switch • Router

15. Ethernet Hub • A device for connecting multiple Ethernet devices together and making them act as a single network segment • Multiple input/output (I/O) ports

16. Bridge • Network equipment to allow two or more communication networks, or two or more network segments

17. Switch • Operate at one or more layers of the OSI model including data link and network • Operates simultaneously at more than one of these layers

18. Switch

19. Router • A device that • Forwards data packets between computer networks • Creating an overlay internetwork • Connected to two or more data lines from different networks

20. Router • Reads the address information in the packet to determine its ultimate destination • Using information in its routing table or routing policy, it directs the packet to the next network on its journey

21. Router

22. Internet Protocol Suite • A set of communications protocols used for the Internet and similar networks • OSI seven layers • Known as • Transmission Control Protocol (TCP) • Internet Protocol (IP)

23. OSI Seven Layers

24. Physical Layer • Defines electrical and physical specifications for devices • Defines the relationship between a device and a transmission medium • Copper cable • Fiber optical cable • Includes the layout of pins, Voltages, line impedance, cable specifications, signal timing, hubs, repeaters, network adapters, host bus adapters

25. Data Link Layer • Provides the functional and procedural means to transfer data between network entities • Detect possibly errors that may occur in the physical layer • Intended for • Unicasts • Multicasts • Broadcasts

26. Network Layer • Provides the functional and procedural means of transferring variable length data sequences from host (source) to host (destination) • Maintains the quality of service (QoS) requested by the transport layer • Performs • Network routing functions • Fragmentation and reassembly • Report delivery errors

27. Network Layer • Divided into three sub-layers: • Subnetwork access –considers protocols that deal with the interface to networks • Subnetwork-dependent convergence – when it is necessary to bring the level of a transit network up to the level of networks on either side • Subnetwork-independent convergence – handles transfer across multiple networks

28. Transport Layer • Provides transparent transfer of data between end users • Provides reliable data transfer services to the upper layers • Controls the reliability of a given link through flow control, segmentation/desegmentation, and error control

29. Session Layer • Controls the dialogues (connections) between computers • Establishes, manages and terminates the connections between the local and remote application

30. Presentation Layer • Establishes context between application-layer entities • Provides a mapping between the application-layer entities that may use different syntax and semantics • Presentation service data units are encapsulated into session protocol data units, and passed down the stack

31. Application Layer • Is the OSI layer closest to the end user • Both the OSI application layer and the user interact directly with the software application • Identify communication partners, determine resource availability, and Synchronizing communication

32. Transmission Control Protocol (TCP) • One of the core protocols of the Internet Protocol Suite • The protocol used by major Internet applications • Provides reliable, ordered delivery of a stream of octets from a program on one computer to another program on another computer

33. Transmission Control Protocol (TCP) • The protocol corresponds to the transport layer • Provides a communication service at an intermediate level between an application program and the Internet Protocol (IP)

34. Transmission Control Protocol (TCP) • Detect the problem • IP packets can be lost, duplicated, or delivered out of order • Requests retransmission of lost data • Rearranges out-of-order data • Helps minimize network congestion • A reliable stream delivery service that guarantees all bytes received identical with bytes sent and in the correct order

35. Internet Protocol (IP) • Aprincipal communications protocol used for relaying datagrams (network packets) across an internetwork • It is the primary protocol that establishes the Internet • Deliver datagrams from the source host to the destination host based on the addresses

36. Internet Protocol (IP) • The primary protocol in the network layer • Address hosts and route datagrams (packets)

37. Internet Protocol (IP) • Datagram construction • Each datagram has two components, header and payload • Header • Source IP address, Destination IP address, and other meta-data needed to route and deliver the datagram • Payload • the data to be transported • This process of nesting data payloads in a packet with a header is called encapsulation

38. Internet Protocol (IP) • IP address and routing algorithms • IP Addressing refers to • How end hosts are assigned IP addresses • How subnetworks of IP host addresses are divided and grouped • Routing algorithms • Routing is performed by all hosts, but most importantly by routers • Routing algorithms decide how to move datagrams among networks

39. Network Application • Email • WWW • telnet • ftp • Net TV

40. Question?