Institute of Technology Sligo - Dept of Computing

Wrapping The PackageWrapping The Package

Devices & Data EncapsulationDevices & Data Encapsulation

Paul Flynn

Institute of Technology Sligo - Dept of Computing

Evolution of LAN DevicesEvolution of LAN Devices

NICs, Repeaters, & HubsNICs, Repeaters, & Hubs

BridgesBridges

SwitchesSwitches

RoutersRouters

Institute of Technology Sligo - Dept of Computing

NIC SpecificsNIC Specifics

NICs provide hosts with access to NICs provide hosts with access to media by using a MAC address.media by using a MAC address.

MAC stands for Media Access ControlMAC stands for Media Access Control

NICs operate at NICs operate at Layer 2Layer 2 !! !!

Institute of Technology Sligo - Dept of Computing

NICs, Repeaters, & HubsNICs, Repeaters, & Hubs

To connect two computers, you must...To connect two computers, you must... Install a NIC card in each.Install a NIC card in each.

The First LAN

NICNIC

NIC NIC

Attach computers using a crossover cableYou will make a crossover cable in Ch. 5

Institute of Technology Sligo - Dept of Computing

NICs, Repeaters, & HubsNICs, Repeaters, & Hubs

Repeaters can be used to increase the

distance

What’s the maximum distance for Cat 5 cable?

100 meters or approx. 300 feetSo what can we use if this

distance is greater than 100 meters?

NIC NIC

Repeaters amplify and retime signals

Institute of Technology Sligo - Dept of Computing

NICs, Repeaters, & HubsNICs, Repeaters, & Hubs

NIC NIC

NIC NIC

Using repeaters was fine as long as a business only needed two computers

networked.What if a business

wanted a third computer attached?

Or a fourth? What device would they

need?

Institute of Technology Sligo - Dept of Computing

NICs, Repeaters, & HubsNICs, Repeaters, & Hubs

NIC NIC

NIC NIC

A multi-port repeater! Also called a...

Hub

Institute of Technology Sligo - Dept of Computing

A Dilemma!A Dilemma!

NIC NIC

NIC NIC

As businesses expanded their networks, they began to cascade hubs.

Institute of Technology Sligo - Dept of Computing

What’s The Problem?What’s The Problem?

1)1) Hubs share bandwidth between all Hubs share bandwidth between all attached devices.attached devices.

2)2) Hubs are stupid, Layer 1 devices. Hubs are stupid, Layer 1 devices. They cannot filter traffic.They cannot filter traffic.

3)3) Most LANs use a “broadcast Most LANs use a “broadcast topology,” so every device sees every topology,” so every device sees every packet sent down the media.packet sent down the media.

Let’s take a look at how broadcasting works

Institute of Technology Sligo - Dept of Computing

BroadcastsBroadcasts In this picture, all hubs forward all traffic to all devices.

Institute of Technology Sligo - Dept of Computing

So, if Host 1 wants ping Host 2, all hosts see the ping. This is what we mean by a broadcast topology

BroadcastsBroadcasts

21

The red arrows show that all hosts receive the ping request. Only Host 2 will respond.

Institute of Technology Sligo - Dept of Computing

What’s The Solution?What’s The Solution?

We need a smarter hub!We need a smarter hub!

What’s a “smarter hub” called?What’s a “smarter hub” called?

A Bridge! A Bridge!

Bridges filter network traffic based on Bridges filter network traffic based on MAC addresses.MAC addresses.

Let’s take a look at how this works.Let’s take a look at how this works.

Institute of Technology Sligo - Dept of Computing

BridgeBridgeTo lessen the amount of LAN traffic, businesses began to uses bridges to filter frames based on MAC addresses.

Institute of Technology Sligo - Dept of Computing

BridgeBridgeNow, if Host 1 pings Host 2, only the hosts on that LAN segment see the ping. The bridges stop the ping.

21

Institute of Technology Sligo - Dept of Computing

SwitchSwitchA switch (also know as a multi-port bridge), can effectively replace these four bridges.

Institute of Technology Sligo - Dept of Computing

SwitchSwitch Another benefit of a switch is that each LAN segment gets dedicated bandwidth.

The Cloud

10 Mbps10 Mbps

10 Mbps

10 Mbps

10 Mbps

Institute of Technology Sligo - Dept of Computing

Since a switch is a multi-port bridge, we know it will stop local pings from traveling to other network segments.

SwitchSwitch

121

But a switch cannot stop a ping destined for a different LAN segment from traveling to all other LAN segments.

Institute of Technology Sligo - Dept of Computing

SwitchSwitch

16

1

For example, Host 1 pings Host 16. Since Host 16 is on another LAN segment, the switch will flood the ping request out all ports.

What device will solve this problem?

Institute of Technology Sligo - Dept of Computing

RouterRouter

1

16

1

Routers filter traffic based on IP addresses. The IP address tells the router which LAN segment the ping belongs to.

Institute of Technology Sligo - Dept of Computing

Devices Function At LayersDevices Function At Layers

Know These!

Institute of Technology Sligo - Dept of Computing

Devices Function At LayersDevices Function At Layers

Also know that each device not only works at its layer, but all layers below it.

Institute of Technology Sligo - Dept of Computing

Devices Function At LayersDevices Function At Layers

For example, a router is a layer 3 device but also uses MAC addresses (layer 2) and repeats the signal (layer 1)

Institute of Technology Sligo - Dept of Computing

Devices Function At LayersDevices Function At Layers

At what layers do these two

operate?

The Cloud

ALL 7 LAYERS!!

One last bit of information from Chapter 3

Institute of Technology Sligo - Dept of Computing

Good

LuckOn

TheTest!!