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Data Communications and Computer Networks: A Business User’s Approach Third Edition. Chapter 8: Local Area Networks: Internetworking. Objectives. List the reasons for interconnecting multiple local area network segments and interconnecting local area networks and wide area networks

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chapter 8 local area networks internetworking

Data Communications and

Computer Networks: A

Business User’s Approach

Third Edition

Chapter 8:

Local Area Networks: Internetworking

slide2

Objectives

  • List the reasons for interconnecting multiple local area network segments and interconnecting local area networks and wide area networks
  • Identify the functions and purposes of the various interconnection devices that have been used over time
  • Define a hub and describe the situations in which a hub is used
  • Describe how a transparent bridge learns

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide3

Objectives (continued)

  • Describe what a switch is and how it differs from other devices
  • Describe the types of situations in which using a switch is advantageous
  • Describe what a router is and how it differs from other devices
  • Describe the types of situations in which a router is used

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide4

Introduction

  • Sometimes necessary to connect local area network to another LAN or to wide area network
  • Local area network to local area network connections often performed with bridge-like device
  • Local area network to wide area network connections usually performed with router
  • Switch - can be used to interconnect segments of a local area network

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide5

Why Segment or Internetwork Local

Area Networks?

  • To separate / connect one corporate division with another
  • To connect two LANs with different protocols
  • To connect a LAN to the Internet
  • To break a LAN into segments to relieve traffic congestion
  • To provide a security wall between two different types of users

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide6

Hubs

  • Hub - interconnects two or more workstations into a local area network
  • When workstation transmits to a hub
    • Hub immediately resends data frame out to all connecting links
  • Hub can be managed or unmanaged
    • Managed hub possesses enough processing power that it can be managed from a remote location

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide7

Bridges

  • A bridge (or bridge-like device)
    • Can be used to connect two similar LANs, such as two CSMA/CD LANs
    • Can also be used to connect two closely similar LANs, such as a CSMA/CD LAN and a token ring LAN
    • Examines destination address in a frame
      • Either forwards this frame onto next LAN or does not
    • Examines source address in frame
      • Places this address in a routing table to be used for future routing decisions

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide8

Bridges (continued)

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide9

Transparent Bridge

  • Does not need programming
  • Observes all traffic  builds routing tables
    • This observation is called backward learning
  • Each bridge has two connections (ports)
    • Routing table associated with each port

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide10

Transparent Bridge (continued)

  • Bridge
    • Observes each frame that arrives at port
    • Extracts the source address from the frame
    • Places that address in the port’s routing table
  • Transparent bridge is found with CSMA/CD LANs

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide11

Transparent Bridge (continued)

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide12

Transparent Bridge (continued)

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide13

Transparent Bridge (continued)

  • Transparent bridge can also convert one frame format to another
  • Note that some people / manufacturers call this kind of bridge a gateway or router
  • Bridge
    • Removes headers and trailers from one frame format
    • Inserts (encapsulates) headers and trailers for second frame format

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide14

Remote Bridge

  • Capable of passing data frame from one local area network to another when
    • Two LANs are separated by long distance
    • There is a wide area network connecting the two LANs
  • Remote bridge takes the frame before it leaves the first LAN
    • Encapsulates the WAN headers and trailers
  • When packet arrives at destination remote bridge  that bridge removes the WAN headers and trailers leaving original frame

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide15

Remote Bridge (continued)

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide16

Switches

  • Combination of hub and bridge
  • Can interconnect two or more workstations
  • Like bridge, it observes traffic flow and learns
  • When a frame arrives at a switch, the switch
    • Examines destination address
    • Forwards frame out the one necessary connection
  • Workstations that connect to
    • Hub  on shared segment
    • Switch  on switched segment

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide17

Switches (continued)

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide18

Switches (continued)

  • Backplane of a switch is fast enough to support multiple data transfers at one time
  • A switch that employs cut-through architecture is passing on the frame before the entire frame has arrived at the switch

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide19

Switches (continued)

  • Multiple workstations connected to a switch use dedicated segments
    • Very efficient way to isolate heavy users from the network
  • A switch can allow simultaneous access to multiple servers, or multiple simultaneous connections to a single server

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide20

Switches (continued)

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide21

Isolating Traffic Patterns and Providing

Multiple Access

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide22

Isolating Traffic Patterns and Providing

Multiple Access (continued)

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide23

Isolating Traffic Patterns and Providing

Multiple Access (continued)

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide24

Isolating Traffic Patterns and Providing

Multiple Access (continued)

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide25

Full-Duplex Switches

  • Allows for simultaneous transmission and reception of data to and from a workstation
  • This full duplex connection helps eliminate collisions
  • To support a full duplex connection to a switch, at least two pairs of wires are necessary
    • One for the receive operation
    • One for the transmit operation
  • Most people install four pairs today, so wiring is not problem

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide26

Full-Duplex Switches (continued)

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide27

Network Servers

  • Network servers provide necessary storage for LAN software
  • Usually focal point for network operating system
  • Increasingly, network servers are functioning as bridges, switches, and routers
  • By adding appropriate card, a server can assume multiple functions

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide28

Routers

  • Router - device that connects a LAN to a WAN or a WAN to a WAN
  • Router:
    • Accepts outgoing packet
    • Removes any LAN headers and trailers
    • Encapsulates necessary WAN headers and trailers
  • Because router has to make wide area network routing decisions  router has to dig down into the network layer of the packet to retrieve network destination address

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide29

Routers (continued)

  • Routers are often called “layer 3 devices”
    • Operate at the third layer, or OSI network layer, of the packet
  • Often incorporate firewall functions

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide30

Routers (continued)

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide31

LAN Internetworking in Action:

A Small Office Revisited

  • Recall In Action example from Chapter Seven
  • A small office with 20 workstations in one room and 15 workstations in another room were connected to a server via 100BaseTX
  • One hub was kept in a closet near the 20 workstations while a second hub was near the server

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide32

LAN Internetworking in Action:

A Small Office Revisited (continued)

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide33

LAN Internetworking in Action:

A Small Office Revisited (continued)

  • Now Hannah wants to connect the LAN to the Internet
  • She adds a router next to the server and connects it to the hub
  • She connects the router to a high-speed telephone line such as a T-1 service
  • She will also have to program the router to perform IP addressing and firewall functions

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide34

LAN Internetworking in Action:

A Small Office Revisited (continued)

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide35

LAN Internetworking in Action:

A Small Office Revisited (continued)

  • Now network usage is so high that Hannah must consider segmenting the network
  • She decides to install a database server near the original server and replace both hubs with switches

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide36

LAN Internetworking in Action:

A Small Office Revisited (continued)

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

slide37

Summary

  • Interconnecting multiple LAN segments as well as LANs and WANs
  • Interconnection devices
  • Hubs
  • Transparent bridges
  • Switches
  • Routers

Data Communications & Computer Networks: A Business User\'s Approach, Third Edition

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