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Network Topologies

Network Topologies

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Network Topologies

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  1. Network Topologies

  2. Objectives • Describe the basic and hybrid LAN physical topologies, their uses, advantages, and disadvantages • Describe a variety of enterprise-wide and WAN physical topologies, their uses, advantages, and disadvantages • Compare the different types of switching used in data transmission • Understand the transmission methods, or logical topologies, underlying Ethernet, Token Ring, LocalTalk, and FDDI networks

  3. Simple Physical Topologies • Physical topology • Physical layout of a network • A Bus topology consists of a single cable—called a bus— connecting all nodes on a network without intervening connectivity devices

  4. Advantages of Bus Topology • Works well for small networks • Relatively inexpensive to implement • Easy to add to it

  5. Disadvantages ofBus Topology • Management costs can be high • Potential for congestion with network traffic

  6. Simple Physical Topologies • Ring topology • Each node is connected to the two nearest nodes so the entire network forms a circle • One method for passing data on ring networks is token passing • Active topology • Each workstation transmits data

  7. Advantages of Ring Topology • Easier to manage; easier to locate a defective node or cable problem • Well-suited for transmitting signals over long distances on a LAN • Handles high-volume network traffic • Enables reliable communication

  8. Disadvantages ofRing Topology • Expensive • Requires more cable and network equipment at the start • Not used as widely as bus topology • Fewer equipment options • Fewer options for expansion to high-speed communication

  9. Simple Physical Topologies • Star topology • Every node on the network is connected through a central device

  10. Advantages of Star Topology • Good option for modern networks • Low startup costs • Easy to manage • Offers opportunities for expansion • Most popular topology in use; wide variety of equipment available

  11. Disadvantages ofStar Topology • Hub is a single point of failure • Requires more cable than the bus

  12. Hybrid Physical Topologies • Hybrid topology • Complex combination of the simple physical topologies • Star-wired ring • Star-wired topologies use physical layout of a star in conjunction with token ring-passing data transmission method

  13. Hybrid Physical Topologies • Star-wired bus • In a star-wired bus topology, groups of workstations are star-connected to hubs and then networked via a single bus

  14. Hybrid Physical Topologies • Daisy-Chained • A Daisy chain is linked series of devices

  15. Hybrid Physical Topologies • Hierarchical hybrid topology • Uses layers to separate devices by priority or function

  16. Enterprise-Wide Topologies • Enterprise • An entire organization • Backbone networks • Serial backbone • Distributed backbone • Collapsed backbone • Parallel backbone

  17. Enterprise-Wide Topologies • Serial backbone • Two or more hubs connected to each other by a single cable • Distributed backbone • Hubs connected to a series of central hubs or routers in a hierarchy

  18. Enterprise-Wide Topologies • Collapsed backbone • Uses a router or switch as the single central connection point for multiple subnetworks

  19. Enterprise-Wide Topologies • Parallel Backbone • Collapsed backbone arrangement that consists of more than one connection from central router or switch to each network segment

  20. Enterprise-Wide Topologies • Mesh networks • Routers are interconnected with other routers, with at least two pathways connecting each router

  21. Wide Area Network (WAN) Topologies • Peer-to-peer topology • WAN with single interconnection points for each location • Dedicated circuits • Continuous physical or logical connections between two access points that are leased from a communication provider

  22. Wide Area Network (WAN) Topologies • Ring WAN topology • Each site is connected to two other sites so that entire WAN forms a ring pattern

  23. Wide Area Network (WAN) Topologies • Star WAN topology • Single site acts as the central connection point for several other points

  24. Wide Area Network (WAN) Topologies • Mesh WAN topology • Many directly interconnected locations forming a complex mesh

  25. Logical Topologies • Refers to the way in which data are transmitted between nodes • Describes the way: • Data are packaged in frames • Electrical pulses are sent over network’s physical media • Logical topology may also be called network transport system

  26. Switching • Component of network’s logical topology that determines how connections are created between nodes • Circuit switching • Connection is established between two network nodes before they begin transmitting data • Message switching • Establishes connection between two devices, transfers information to second device, and then breaks connection • Packet switching • Breaks data into packets before they are transmitted

  27. Ethernet • Carrier Sense Multiple Access with Collision Detection (CSMA/CD) • The access method used in Ethernet • Collision • In Ethernet networks, the interference of one network node’s data transmission with another network node’s data transmission • Jamming • Part of CSMA/CD in which, upon detection of collision, station issues special 32-bit sequence to indicate to all nodes on Ethernet segment that its previously transmitted frame has suffered a collision and should be considered faulty

  28. Ethernet CSMA/CD process

  29. Ethernet • On an Ethernet network, an individual network segment is known as a collision domain • Portion of network in which collisions will occur if two nodes transmit data at same time • Data propagation delay • Length of time data take to travel from one point on the segment to another point

  30. Ethernet • Demand priority • Method for data transmission used by 100BaseVG Ethernet networks • Demand priority requires an intelligent hub CSMA/CD versus demand priority

  31. Ethernet • Traditional Ethernet LANs, called shared Ethernet, supply fixed amount of bandwidth that must be shared by all devices on a segment • Switch • Device that can separate network segments into smaller segments, with each segment being independent of the others and supporting its own traffic • Switched Ethernet • Newer Ethernet model that enables multiple nodes to simultaneously transmit and receive data over logical network segments

  32. Ethernet A switched Ethernet network

  33. Ethernet • Gigabit Ethernet • 1 Gigabit Ethernet • Ethernet standard for networks that achieve 1-Gbps maximum throughput • 10 Gigabit Ethernet • Standard currently being defined by IEEE 802.3ae committee • Will allow 10-Gbps throughput • Will include full-duplexing and multimode fiber requirements

  34. Design Considerations for Ethernet Networks • Cabling • Connectivity devices • Number of stations • Speed • Scalability • Topology

  35. LocalTalk • Logical topology designed by Apple Computer, Inc. • Uses a transmission method called Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) • A teleconnector is a transceiver used on a LocalTalk network • Macintosh version of TCP/IP is called MacTCP

  36. Token Ring • Token Ring networks use the token passing routine and a star-ring hybrid physical topology • The 100-Mbps Token Ring standard is known as High-Speed Token Ring (HSTR) • On a Token Ring network, one workstation, called the active monitor, acts as the controller for token passing

  37. Token Ring • Multistation Access Unit (MAU) • Regenerates signals Interconnected Token Ring MAUs

  38. Token Ring • Control Access Unit (CAU) • Connectivity device used on a Token Ring network • Lobe Attachment Module (LAM) • Device that attaches to a CAU to expand the capacity of that device

  39. Token Ring • Token Ring networks with STP cabling may use a type 1 IBM connector • A DB-9 connector is another type of connector found on STP Token Ring networks Type 1 IBM and DB-9 Token Ring connectors

  40. Token Ring • Media filter • Device that enables two types of cables or connectors to be linked • Token Ring media filter • Enables DB-9 cable and type 1 IBM cable to be connected A Token Ring media filter

  41. Design Considerations for Token Ring Networks • Cabling • Connectivity devices • Number of stations • Speed • Scalability • Topology

  42. Fiber Distributed Data Interface (FDDI) • Logical topology whose standard was originally specified by ANSI in mid-1980s and later refined by ISO

  43. Asynchronous Transfer Mode (ATM) • Logical topology that relies on a fixed packet size to achieve data transfer rates up to 9953 Mbps • The fixed packet in ATM is called a cell • A unique aspect of ATM technology is that it relies on virtual circuits

  44. Asynchronous Transfer Mode (ATM) • ATM uses circuit switching, which allows ATM to guarantee a specific quality of service (QOS) • ATM technology can be integrated with Ethernet or Token Ring networks through the use of LAN Emulation (LANE)