Network Guide to Networks 5th Edition

1
Network Guide to Networks5th Edition

• Chapter 5
• Topologies and Ethernet Standards

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Objectives

• Describe the basic and hybrid LAN physical
  topologies, and their uses, advantages, and
  disadvantages
• Describe the backbone structures that form the
  foundation for most LANs
• Understand the transmission methods underlying
  Ethernet networks
• Compare the different types of switching used in
  data transmission

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Simple Physical Topologies

• Physical topology
• Physical layout of network nodes
• Does not specify
• Device types
• Connectivity methods
• Addressing schemes
• Fundamental shapes
• Bus, ring, star
• Hybrid

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Bus Topology
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Bus Topology

• Single cable connects all network nodes(No
  intervening connectivity devices)
• One shared communication channel
• Physical medium Coaxial cable
• Passive topology
• Node listens for, accepts data
• Uses broadcast to send

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Bus Topology (contd.)

• Advantage relatively inexpensive
• Disadvantages
• Does not scale well
• Difficult to troubleshoot
• Not very fault tolerant

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Ring Topology
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Ring Topology

• Circular network with clockwise data
  transmission
• Active topology
• Workstation participates in data delivery
• Data stops at destination
• Physical medium options
• Twisted pair
• Fiber-optic
• Drawbacks
• Malfunctioning workstation can disable network
• Not flexible or scalable

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Star Topology

• Most popular physical topology
• Most Ethernet networks are based on star topology

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Star Topology

• Node connects through central device
• Physical medium options
• Twisted pair
• Fiber-optic
• Advantages
• Fault tolerance
• Very Scalable

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Logical Topologies

• Describes data transmission between nodes
• Most common bus, ring
• Bus logical topology
• Signals travel from one device to all other
  devices
• May or may not travel through intervening
  connectivity device
• Bus logical topology used by networks with
• Physical bus topology
• Star, star-wired bus topology
• Ethernet

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Logical Topologies (contd.)

• Ring logical topology
• Signals follow circular path
• Ring logical topology used by networks with
• Pure ring topology
• Star-wired ring hybrid physical topology
• Token ring

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Hybrid Physical Topologies

• Pure bus, ring, star topologies rarely exist
  because they are too restrictive
• Hybrid topology are more likely
• Complex combination of simple topologies
• Several options

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Star-Wired Ring

• Combines a star physical topology with a ring
  logical topology
• Benefit stars fault tolerance
• Token Ring (IEEE 802.5) networks use this

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Star-Wired Ring (contd.)
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Star-Wired Bus

• Combines a physical star with a logical bus
• Advantages
• Cover longer distances
• Easily interconnect, isolate different segments
• Drawbacks
• Requires lots of cabling
• Cost of connectivity device(s)
• Hub-based Ethernet networks use this

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Star-Wired Bus (contd.)
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Backbone Networks

• Connects hubs, switches, routers(not end-user
  devices)
• More throughput needed on backbone than to the
  desktops

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Serial Backbone
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Distributed Backbone
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Collapsed Backbone
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Parallel Backbone
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Switching

• Logical network topology component
• Determines connection creation between nodes
• Three methods
• Circuit switching
• Message switching
• Packet switching

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Ethernet

• Developed by Xerox in the 1970s, then improved by
  Digital Equipment Corporation (DEC), Intel, Xerox
  (DIX), and others
• Excellent throughput for reasonable cost makes
  this the most popular LAN technology
• All variations share common access method
  (CSMA/CD)

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CSMA/CD (contd.)
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Ethernet Standards for Copper Cable
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Ethernet Standards for Copper Cable
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Summary of Common Ethernet Standards
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Ethernet Frames