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Basic Concepts

Basic Concepts. Link: Physical pathway between devices Line Configuration: Attachment of communications devices to a link Point-to-point (dedicated link between 2 devices) Multipoint (more than 2 devices can use) Link ≠ wire. Topology. Mesh. Star. Tree. Bus. Ring.

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Basic Concepts

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  1. Basic Concepts • Link: Physical pathway between devices • Line Configuration:Attachment of communications devices to a link • Point-to-point (dedicated link between 2 devices) • Multipoint(more than 2 devices can use) • Link ≠ wire EE 766 Computer Interfacing and Protocols

  2. Topology Mesh Star Tree Bus Ring Topology of Networks • Topology defines logical or physical arrangement of links in a network • Transmission control: • Peer-to-peer: All devices equal • Primary-secondary: One device controls traffic while others transmit through primary EE 766 Computer Interfacing and Protocols

  3. Hub Topologies • Mesh: • Dedicated point-to-point links to every other device • n(n-1)/2 links, n-1 interfaces per device • Star: • Point-to-point link only to a central controller • n links, 1 interface per device EE 766 Computer Interfacing and Protocols

  4. Hub Hub Hub Topologies • Tree: • Star with secondary hubs • Hierarchical structure • Bus: • Multipoint connection • Devices connected to the backbone over taps and drop lines EE 766 Computer Interfacing and Protocols

  5. Topologies • Ring: • Point-to-point lines between two neighbors only • Physical or logical organization • Hybrid topologies EE 766 Computer Interfacing and Protocols

  6. Comparison of Topologies • Mesh: • Pros • Parallelism in communication Higher capacity Robustness • High security (privacy) • Easy fault identification and isolation • Cons • High interface and device cost • Hard to install/reconfigure • Limited expandability EE 766 Computer Interfacing and Protocols

  7. Comparison of Topologies • Star: • Pros • Easy installation/reconfiguration • 1 interface/host needed (cheap) • Robustness  Link failures affect only 1 host • Relatively easy fault isolation • Cons • Traffic goes over a bottleneck Single point of failure  Diminishing capacity/node • Limited expandability EE 766 Computer Interfacing and Protocols

  8. Comparison of Topologies • Tree: • Pros and cons similar to star topologies • Additional Pros • Hierarchical Structure  Prioritization and isolation of traffic Better expandability • Additional Cons • More central nodes with lower vitality • Link failures affect entire subtrees EE 766 Computer Interfacing and Protocols

  9. Comparison of Topologies • Bus: • Pros • Very easy installation • Can be used to connect other subnetworks • Cons • Difficult fault isolation • Single point of failure (consider reflections) • Hard to reconfigure • Diminishing capacity/node • Decreasing signal strength with additional taps • Bus length limited (signal strength and bus access) EE 766 Computer Interfacing and Protocols

  10. Comparison of Topologies • Ring: • Pros • Easy installation/reconfiguration (move only 2 connections) • Easy fault isolation • Cons • Unbalanced delay due to unidirectional nature • Link or node failures affect the entire topology(can be resolved with 2 rings or automatically closing switches) EE 766 Computer Interfacing and Protocols

  11. First Later Transmission Mode • Direction of signal flow on link • Simplex (one directional) • Keyboards, monitors, TV broadcast… • Half Duplex (one direction at a time) • Walkie-Talkies, CB radios EE 766 Computer Interfacing and Protocols

  12. Transmission Mode • (Full) Duplex (bidirectional) • Either sharing the same line or utilizing two simplex connections • Telephone network EE 766 Computer Interfacing and Protocols

  13. Categories of Networks • Local Area Networks • Limited geographic area (up to few km) • Privately owned and operated • Single type of topology • Metropolitan Area Networks • Extends over an entire city • Stand-alone or interconnection of LANs • Public or private • Wide Area Networks • Long distance communications • Public and private components • If entirely owned by a single company  Enterprise EE 766 Computer Interfacing and Protocols

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