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Chapter Goals

Chapter Goals. Compare and contrast bus, ring, and star network topologies Describe packet routing across local and wide area networks Describe the CSMA/CD media access control protocol Describe network hardware devices, including network interface units, routers, and switches.

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Chapter Goals

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  1. Chapter Goals • Compare and contrast bus, ring, and star network topologies • Describe packet routing across local and wide area networks • Describe the CSMA/CD media access control protocol • Describe network hardware devices, including network interface units, routers, and switches Systems Architecture, Fifth Edition

  2. Chapter Goals (continued) • Describe the OSI network model, the TCP/IP protocol suite, and IEEE network standards Systems Architecture, Fifth Edition

  3. Systems Architecture, Fifth Edition

  4. Network Topology • Spatial organization of network devices, physical routing of network cabling, and flow of messages from one network node to another • Can be physical or logical • Three types – star, bus, ring – differentiated by • Length and routing of network cable • Type of node connections • Data transfer performance • Susceptibility of network to failure Systems Architecture, Fifth Edition

  5. Network Topologies Systems Architecture, Fifth Edition

  6. Systems Architecture, Fifth Edition

  7. Systems Architecture, Fifth Edition

  8. Systems Architecture, Fifth Edition

  9. The strengths of two different topologies can be combined by using one topology for physical layout and another for message routing. Systems Architecture, Fifth Edition

  10. Media Access Control • Uses a protocol that specifies rules for accessing a shared transmission medium • Carrier Sense Multiple Access/Collision Detection (CSMA/CD) {Used by Ethernet} • Commonly used in bus networks to detect and recover from collisions • Token passing MAC protocol • Used by ring network topologies Systems Architecture, Fifth Edition

  11. CSMA/CD Protocol • Process • Node listens for an idle state, transmits a packet, and listens for a collision • If a collision is detected, node retransmits after waiting a random waiting period • Primary advantage: simplicity • Primary disadvantage: potentially inefficient use of data transfer capacity Systems Architecture, Fifth Edition

  12. Systems Architecture, Fifth Edition

  13. Addressing and Routing • How messages sent by end nodes find their way through transmission lines and central nodes to their ultimate destination • Local area networks (LANs) • Interconnected to form WANs • Wide area networks (WANs) Systems Architecture, Fifth Edition

  14. Addressing: Ethernet Address • What is an Ethernet Address? Ethernet address, also called MAC address, is a 48-bit number used to uniquely identify each computer in a network. The address is usually written in hexadecimal form (e.g. 006097981E6B). Systems Architecture, Fifth Edition

  15. Addressing: Ethernet Address • Physical Address, MAC Address or Ethernet Address are the same. • Check by • Click Start->Run->cmd • Type IPCONFIG /ALL and then press Enter • “Physical Address” is shown Systems Architecture, Fifth Edition

  16. Addressing: Ethernet Address Ethernet LAN: • Source computer sends message in a FRAME • Ethernet is “Broadcast” so all devices connected to the hub, receive the FRAME • Only the computer that has the correct source address accepts the FRAME Systems Architecture, Fifth Edition

  17. Connecting two LAN segments • Bridges decide to forward (or not) Frames from one segment to another • Routing tables are maintained in the bridge • Bridges always forward broadcast Frames Systems Architecture, Fifth Edition

  18. LANs can be interconnected by using network devices: hubs, brdges, switches, & routers. Systems Architecture, Fifth Edition

  19. Network Hardware Systems Architecture, Fifth Edition

  20. Hubs • Connect nodes to form a LAN • Most are Ethernet devices • Combine separate point-to-point connections between nodes and the hub into a single shared transmission medium by repeating all incoming packets to every connection point • Low-cost alternative for home and small office networks Systems Architecture, Fifth Edition

  21. Bridges • Connect two networks or network segments and copy packets between them • Look at source addresses and update internal tables of node addresses on each network segment • Common uses • Construct a virtual LAN from two separate LANs • Divide a network into segments in order to minimize congestion Systems Architecture, Fifth Edition

  22. Routers • Intelligently route and forward packets among two or more networks • Forward packets based on information other than destination address • Build internal “map” of the network; constantly scan it to monitor traffic patterns and network node changes Systems Architecture, Fifth Edition

  23. Switches • High-speed devices that create virtual LANs on a per-packet basis • Each input connection is treated as a separate LAN • Dramatically increase network performance • Connection decisions made by hardware are based only on destination address • Each virtual LAN has only one sending and one receiving node; eliminates congestion Systems Architecture, Fifth Edition

  24. Network Symbols Systems Architecture, Fifth Edition

  25. OSI Network Layers • Open System Interconnection (OSI) model • ISO conceptual model that divides network architecture into seven layers • Each layer uses services of layer below and is unaware of other layer’s implementations • Uses: • General model of networks • Framework for comparing networks • Architectural roadmap that enhances interoperability among network architectures and products Systems Architecture, Fifth Edition

  26. Systems Architecture, Fifth Edition

  27. Application Layer • Network service request and response • Contains programs that make and respond to high-level requests for network services • End-user network utilities • Network services embedded in the OS • Network service providers Systems Architecture, Fifth Edition

  28. Presentation Layer • Converts and formats data • Ensures correct interpretation of transmitted data • Encryption and decryption • Compression and decompression • Converting data between EBCDIC and ASCII • Font substitution • Primarily used by applications that format data for user display Systems Architecture, Fifth Edition

  29. Session Layer • Negotiates and implements high-level protocol parameters (timeout, half or full duplex, synchronization, quality of service) • Establishes and manages communication sessions • Monitors communication to detect and resolve problems that arise once protocol has been established Systems Architecture, Fifth Edition

  30. Transport Layer • Formats messages into packets suitable for transmission over the network • Places messages within a packet data area and adds header/trailer information (network addresses, error detection data, packet sequencing data) • Gives packets to network layer for delivery • Examines packets for errors; requests retransmission if necessary (when receiving packets) Systems Architecture, Fifth Edition

  31. Network Layer • Routes packets to their proper destination • Those within central node interact with one another to exchange routing information and update internal routing tables Systems Architecture, Fifth Edition

  32. Data Link Layer • Transmits packets and bits • Interface between network software and hardware Systems Architecture, Fifth Edition

  33. Physical Layer • Transmits bit streams • Where communication between devices actually takes place • Includes hardware devices that encode and decode bit streams and the transmission lines that transport them Systems Architecture, Fifth Edition

  34. TCP/IP • The core Internet protocol suite • Delivers most services associated with the Internet • File transfer via FTP • Remote login via Telnet protocol • Electronic mail distribution via SMTP • Access to Web pages via HTTP • Predates and corresponds poorly to OSI model Systems Architecture, Fifth Edition

  35. Internet Protocol • Provides connectionless packet transport across LANs and WANs • Translates datagrams into format suitable for transport by physical network • IP layer can divide datagram into smaller units and transmit them individually • Attaches header information to each unit, including its sequence in the datagram Systems Architecture, Fifth Edition

  36. IP (continued) • Assumes datagram will traverse multiple networks via nodes called gateways • Determines transmission routes via related protocols (ICMP, RIP) • IP nodes • Identified by unique 32-bit address (nnn.nnn.nnn.nnn) • Periodically exchange routing information to keep tables current Systems Architecture, Fifth Edition

  37. Only the IP layer is implemented within the gateways. Systems Architecture, Fifth Edition

  38. Transmission Control Protocol • Provides connection-oriented packet transport to higher-level Internet service protocols, including HTTP, FTP, and Telnet • Provides framework to check for lost messages; explicitly establishes connection with intended recipient before transmitting messages • Performs connection management functions (verifying receipt, verifying data integrity, controlling message flow, securing message content) Systems Architecture, Fifth Edition

  39. TCP (continued) • Sender and recipient TCP layers maintain information about one another (message routes, errors encountered, transmission delays, status of ongoing data transfers) • Uses positive acknowledgment protocol to ensure data delivery • Establishes connections through a port and an socket Systems Architecture, Fifth Edition

  40. Network Standards • IEEE 802 standards • Describe network hardware, transmission media, transmission methods, and protocols • Help ensure compatibility among products from competing vendors • Developed by committees whose membership is drawn from industry, government, and academia • Ethernet standard (802.3) - very successful Systems Architecture, Fifth Edition

  41. Systems Architecture, Fifth Edition

  42. Systems Architecture, Fifth Edition

  43. Summary • Network topology • Addressing and routing • Media access control • Network hardware • OSI network layers • Network standards Systems Architecture, Fifth Edition

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