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Network Topolog



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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 of Bus 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 of Ring 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 of Star 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. Ethernet
    • Padding
      • Bytes added to data portion of an Ethernet frame to make sure this field is at least 46 bytes in size
    • Ethernet frame types:
      • IEEE 802.3 (“Ethernet 802.2” or “LLC”)
      • Novell proprietary 802.3 frame (or “Ethernet 802.3”)
      • Ethernet II frame
      • IEEE 802.3 SNAP frame
  • 35. IEEE 802.3 (“Ethernet 802.2” or “LLC”)
    • Default frame type for versions 4.x and higher of Novell NetWare network operating system
      • Sometimes called LLC frame
      • In Novell’s lexicon, this frame is called Ethernet 802.2 frame
    An IEEE 802.3 frame
  • 36. IEEE 802.3 (“Ethernet 802.2” or “LLC”)
    • Service Access Point (SAP)
      • Identifies node or internal process that uses LLC protocol
    • Frame Check Sequence (FCS)
      • This field ensures that data are received just as they were sent
    • Cyclical Redundancy Check (CRC)
      • Algorithm used by FCS field in Ethernet frames
  • 37. Novell Proprietary 802.3 (or “Ethernet 802.3”)
    • Original NetWare frame type
    • Also called:
      • 802.3 Raw
      • Ethernet 802.3 frame
    A Novell proprietary 802.3 frame
  • 38. Ethernet II
    • Original Ethernet frame type developed by DEC, Intel and Xerox, before IEEE began to standardize Ethernet
    An Ethernet II frame
  • 39. IEEE 802.3 SNAP
    • Adaptation of IEEE 802.3 and Ethernet II
    • SNAP stands for Sub-Network Access Protocol
    An IEEE 802.3 SNAP frame
  • 40. Understanding Frame Types
    • Learning about networks is analogous to learning a foreign language, with the frame type being the language’s syntax
      • Just as you may know the Japanese word for go but how to use it in a sentence, you may know all about the IPX/SPX protocol but not how devices handle it
    • Autosense
      • Feature of modern NICs that enables a NIC to automatically sense what types of frames are running on a network and set itself to that specification
  • 41. Design Considerations for Ethernet Networks
    • Cabling
    • Connectivity devices
    • Number of stations
    • Speed
    • Scalability
    • Topology
  • 42. 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
  • 43. 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
  • 44. Token Ring
    • Multistation Access Unit (MAU)
      • Regenerates signals
    Interconnected Token Ring MAUs
  • 45. 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
  • 46. 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
  • 47. 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
  • 48. Token Ring
    • Token Ring switching
      • Like Ethernet networks, Token Ring networks can take advantage of switching to better utilize limited bandwidth
    • Token Ring frames
      • IEEE 802.5 Token Ring frame
      • IBM Token Ring frame
    An IBM Token Ring frame
  • 49. Design Considerations for Token Ring Networks
    • Cabling
    • Connectivity devices
    • Number of stations
    • Speed
    • Scalability
    • Topology
  • 50. Fiber Distributed Data Interface (FDDI)
    • Logical topology whose standard was originally specified by ANSI in mid-1980s and later refined by ISO
  • 51. 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
  • 52. 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)