evolution of networking devices devices & data encapsulation
TRANSCRIPT
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Evolution of Networking Devices
Devices & Data Encapsulation
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Evolution of LAN Devices
NICs, Repeaters, & Hubs
Bridges
Switches
Routers
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NIC Specifics
NICs provide hosts with access to media by using a MAC address.
MAC stands for Media Access Control
NICs operate at Layer 2 !!
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NICs, Repeaters, & Hubs
To connect two computers, you must...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
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NICs, Repeaters, & HubsRepeaters 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
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NICs, 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?
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NICs, Repeaters, & Hubs
NIC NIC
NIC NIC
A multi-port repeater! Also called a...
Hub
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A Dilemma!
NIC NIC
NIC NIC
As businesses expanded their networks, they began to cascade hubs.
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What’s The Problem?
1) Hubs share bandwidth between all attached devices.
2) Hubs are stupid, Layer 1 devices. They cannot filter traffic.
3) Most LANs use a “broadcast topology,” so every device sees every packet sent down the media.
Let’s take a look at how broadcasting works
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BroadcastsIn this picture, all hubs forward all traffic to all devices.
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So, if Host 1 wants ping Host 2, all hosts see the ping. This is what we mean by a broadcast topology
Broadcasts
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The red arrows show that all hosts receive the ping request. Only Host 2 will respond.
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What’s The Solution?
We need a smarter hub!
What’s a “smarter hub” called?
A Bridge!
Bridges filter network traffic based on MAC addresses.
Let’s take a look at how this works.
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BridgeTo lessen the amount of LAN traffic, businesses began to uses bridges to filter frames based on MAC addresses.
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BridgeNow, 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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SwitchA switch (also know as a multi-port bridge), can effectively replace these four bridges.
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SwitchAnother benefit of a switch is that each LAN segment gets dedicated bandwidth.
The Cloud
10 Mbps10 Mbps
10 Mbps
10 Mbps
10 Mbps
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Since a switch is a multi-port bridge, we know it will stop local pings from traveling to other network segments.
Switch
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But a switch cannot stop a ping destined for a different LAN segment from traveling to all other LAN segments.
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Switch
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?
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Router
1
16
1
Routers filter traffic based on IP addresses. The IP address tells the router which LAN segment the ping belongs to.
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Devices Function At Layers
Know These!
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Devices Function At Layers
Also know that each device not only works at its layer, but all layers below it.
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Devices 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)
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Devices Function At Layers
At what layers do these two
operate?
The Cloud
ALL 7 LAYERS!!
One last bit of information from Chapter 3