LAN Topologies and Standards Networks and Protocols Prepared by: TGK First Prepared on: Last Modified on: Quality checked by: Copyright 2009 Asia Pacific Institute of Information Technology

Networks and Protocols LAN Topologies and Standards Slide 2 of 27 Topic & Structure of the lesson LAN Topologies (Bus, Star, Ring, Mesh, and Tree) Characteristics of Topologies LAN Standards (IEEE 802.x Series)

Networks and Protocols LAN Topologies and Standards Slide 3 of 27 Learning Outcomes At the end of this module, YOU should be able to: Explain the WAN technologies – Cellular Network, Satellite Network, and Wireless Network

Networks and Protocols LAN Topologies and Standards Slide 4 of 27 Key Terms you must be able to use If you have mastered this topic, you should be able to use the following terms correctly in your assignments and exams: Bus Topology Star Topology Ring Topology Mesh Topology Tree Topology Characteristics of Topologies LAN Standards

Networks and Protocols LAN Topologies and Standards Slide 5 of 27 Main Teaching Points Communication pattern Expansion of networks Physical outlook of networks Logical operations of networks Network components and connectivity Medium access control and techniques IEEE 802 standards committee and working groups

Networks and Protocols LAN Topologies and Standards Slide 6 of 27 Bus Topology Connected in a row along a single cable, trunk, backbone or segment Communication on a bus Sending the signal Signal propagates along cable(s) A terminator absorbs the signal at the end Only one computer can access wire at any one time The more PC’s attached, more traffic generated Bus is a PASSIVE topology PC only listens for traffic

Networks and Protocols LAN Topologies and Standards Slide 7 of 27 Signal bounce occurs if ends of bus not terminated Terminators attached to each end. Every cable end must be attached to something Generally a 50 Ohm resistor is used as terminator LAN expansion - bus topology Barrel connector Repeater - boosts signal (regenerate/amplify) Bus Topology

Networks and Protocols LAN Topologies and Standards Slide 8 of 27 Bus Topology Data sent to all computers, but only destination accepts 02608c133456

Networks and Protocols LAN Topologies and Standards Slide 9 of 27 Bus Topology Terminators absorb ‘free’ signals

Networks and Protocols LAN Topologies and Standards Slide 10 of 27 Bus Topology Unplugged cable not terminated will take down the network

Networks and Protocols LAN Topologies and Standards Slide 11 of 27 Bus Topology Connectors can be used to combine cable segments Weakened signal Regenerated signal Repeater

Networks and Protocols LAN Topologies and Standards Slide 12 of 27 Bus Topology CSMA/CD (Contention Method) - Carrier Sense Multiple Access /Collision Detection: also called listen-before talk used with bus topology part of Ethernet standard 802.3

Networks and Protocols LAN Topologies and Standards Slide 13 of 27 Star Topology Each segment attached to centralized component, called a Hub If the hub fails, the network goes down The hub is the central connector; not the central controller Simple Star topology:

Networks and Protocols LAN Topologies and Standards Slide 14 of 27 Star Topology Hub is the central point in a Star topology Hub 02608c133456

Networks and Protocols LAN Topologies and Standards Slide 15 of 27 Ring Topology Signal travels around a ring Travels in one direction Signal boosted (regenerated) by each computer as signal passes through (computer acts as repeater) Generally uses Token Passing Simple ring network showing logical ring:

Networks and Protocols LAN Topologies and Standards Slide 16 of 27 Ring Topology A computer grabs the token and passes it around the ring: Data IEEE standard for ring access protocol allows priority levels to be set for tokens and messages. (Problem - one station with high priority messages can monopolize network)

Networks and Protocols LAN Topologies and Standards Slide 17 of 27 Ring Topology FDDI - standard for high speed ring LAN, using optic fiber. Also uses token passing protocol. Some differences to maximize efficiency Multiple tokens can be circulated because station transmits free token immediately after transmits message

Networks and Protocols LAN Topologies and Standards Slide 18 of 27 Mesh Topology The advantages of a mesh topology is that the two nodes are using the entire capacity of the link exclusively In terms of robustness, a mesh topology network can withstand the destruction of anyone of its components without incapacitating the entire network Due to its nature, the mesh network physically prevents any intrusion on the information sent Total number links required:- n(n-1)/2

Networks and Protocols LAN Topologies and Standards Slide 19 of 27 Mesh Topology Due to its nature, the mesh network physically prevents any intrusion on the information sent Total number links required:- n(n-1)/2 To connect all its nodes together, a mesh topology would require n(n-1)/2 wires, or channels

Networks and Protocols LAN Topologies and Standards Slide 20 of 27 Mesh Topology This number increases exponentially when new nodes are added to the network Each node itself would, then, be equipped with n-1 I/O ports to connect itself to the network The disadvantage of the mesh topology is, simply, the amount of cabling itself

Networks and Protocols LAN Topologies and Standards Slide 21 of 27 Tree Topology Addition of new networks to a bus topology would be hard A tree topology, however, is an extension of the bus In a tree, the trunk is usually a high capacity device or connection which facilitates data transmission amongst the branches

Networks and Protocols LAN Topologies and Standards Slide 22 of 27 Tree Topology The advantage of a tree topology is usually that the privacy of transmissions are isolated in a particular branch Also, if a particular branch is incapacitated, the trunk and the other branches may still function The disadvantage is naturally the fault isolation Should a transmission fails to be sent, a fault detection exercise may have to cover the entire distance of the cabling The trunk of the tree must also be properly configured to be robust

Networks and Protocols LAN Topologies and Standards Slide 23 of 27  The physical topology of a network is the layout or actual appearance of the cabling scheme used on a network  The logical topology of a network describes how the data flows through the physical topology  Point-to-point (PTP) topology connects two nodes directly together - Mesh  Multipoint topologies link three or more devices together through a single communication - Star, Bus, Ring, Hybrid Characteristics of Topologies

Networks and Protocols LAN Topologies and Standards Slide 24 of 27 LAN Standards The IEEE 802 Committee IEEE has multiple standards committees LAN standards are set by the IEEE 802 Standards Committee Working Groups of the 802 Standards Committee create individual standards for Ethernet Standards for Token-Ring LAN Standards for Radio and Infrared Wireless LANs Are there others not listed above?...

Networks and Protocols LAN Topologies and Standards Slide 25 of 27 LAN Standards Project 802 produced recommendations covering: Topology, speed, and data link protocol (Bus, Ring, CSMA/CD, Token passing) Medium - coax, twisted pair, fiber optic cable Addressing: (Local access 16 bit address, Unique International 48 bit) The following diagram illustrates where the IEEE 802. standards relates to the ISO - Open Systems Interconnect(OSI) model:

Networks and Protocols LAN Topologies and Standards Slide 26 of 27 PHYSICAL MEDIA CSMA/CD BUS TOPOLOGY RING TOPOLOGY TOKEN BUS BASEBAND/ BROADBAND COAX, UNSHIELDED TWISTED PAIR BROADBAND COAX OPTIC FIBRE TOKEN RING SHIELDED TWISTED PAIR OPTIC FIBRE FDDI (ANSI) LAN Standards

Networks and Protocols LAN Topologies and Standards Slide 27 of 27 Quick Review Question 1.Describe the advantages and disadvantages of the various LAN topologies highlighted. 2.Discuss the importance of the IEEE 802 standards committee towards the networks used today and which do you think is important for the near future.

Networks and Protocols LAN Topologies and Standards Slide 28 of 27 Follow Up Assignment Carry out a research on which LAN topology is most commonly used in LANs today and subsequently, discuss the relationship between the topology you have identified with the efforts of the IEEE 802 standards committee if applicable. Should the chosen topology be of a proprietary standard, you have to discuss the origins of it and the functionality/operations.

Networks and Protocols LAN Topologies and Standards Slide 29 of 27 Summary of Main Teaching Points

Networks and Protocols LAN Topologies and Standards Slide 30 of 27 Q & A Question and Answer Session

Networks and Protocols LAN Topologies and Standards Slide 31 of 27 Topic and Structure of next session Network Protocol Models and Architecture Network Protocols The ISO-OSI Model Comparing TCP/IP Architecture and the OSI Model Next Session