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
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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.
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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