Chapter 8 local area networks internetworking
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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

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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


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

  • 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


Chapter 8 local area networks internetworking

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


Chapter 8 local area networks internetworking

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


Chapter 8 local area networks internetworking

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


Chapter 8 local area networks internetworking

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


Chapter 8 local area networks internetworking

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


Chapter 8 local area networks internetworking

Bridges (continued)

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


Chapter 8 local area networks internetworking

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


Chapter 8 local area networks internetworking

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


Chapter 8 local area networks internetworking

Transparent Bridge (continued)

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


Chapter 8 local area networks internetworking

Transparent Bridge (continued)

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


Chapter 8 local area networks internetworking

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


Chapter 8 local area networks internetworking

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


Chapter 8 local area networks internetworking

Remote Bridge (continued)

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


Chapter 8 local area networks internetworking

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


Chapter 8 local area networks internetworking

Switches (continued)

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


Chapter 8 local area networks internetworking

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


Chapter 8 local area networks internetworking

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


Chapter 8 local area networks internetworking

Switches (continued)

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


Chapter 8 local area networks internetworking

Isolating Traffic Patterns and Providing

Multiple Access

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


Chapter 8 local area networks internetworking

Isolating Traffic Patterns and Providing

Multiple Access (continued)

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


Chapter 8 local area networks internetworking

Isolating Traffic Patterns and Providing

Multiple Access (continued)

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


Chapter 8 local area networks internetworking

Isolating Traffic Patterns and Providing

Multiple Access (continued)

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


Chapter 8 local area networks internetworking

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


Chapter 8 local area networks internetworking

Full-Duplex Switches (continued)

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


Chapter 8 local area networks internetworking

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


Chapter 8 local area networks internetworking

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


Chapter 8 local area networks internetworking

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


Chapter 8 local area networks internetworking

Routers (continued)

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


Chapter 8 local area networks internetworking

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


Chapter 8 local area networks internetworking

LAN Internetworking in Action:

A Small Office Revisited (continued)

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


Chapter 8 local area networks internetworking

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


Chapter 8 local area networks internetworking

LAN Internetworking in Action:

A Small Office Revisited (continued)

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


Chapter 8 local area networks internetworking

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


Chapter 8 local area networks internetworking

LAN Internetworking in Action:

A Small Office Revisited (continued)

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


Chapter 8 local area networks internetworking

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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