CIS131 Chapter 04

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Contents 1 Summary - How to Build a Local (Network) Roadway 2 Driving Bits Across the Network Roadway 2.1 What's a Local Area Network? 2.2 Transmitting Bits Across the Local Network Roadway 2.3 Driving Bits Across a Wire 2.4 The Need for a Two-Lane (Network) Road 2.5 The Equivalent of Asphalt: Cables 2.6 Painting the Lines on the Road: Connectors 2.7 EIA/TIA 568a and 568b Patterns 2.8 Driving in the Right Lane (Pair) on the Road 3 Sharing the Local Roadway: Ethernet Hubs 4 Dirt Roads Versus the DOT 5 My House 6 Corporate Network 7 Non Conductive Media (Wireless)

Summary - How to Build a Local (Network) Roadway

In this chapter we will look at how computers communicate binary using electricity, looking at the popular LAN media cables and connectors. We will also look at the difference between a straight through cable verses a cross over cable, and talk about an Ethernet hub.

Driving Bits Across the Network Roadway

The network is the road that brings people to their destination. As a network person you are responsible for maintaining this roadway.

What's a Local Area Network?

In Chapter 1 we defined a network by listing its characteristics. A LAN is a network where the devices are relatively close together. We looked at a simple network that had two computers, a server, a printer and a hub/switch. This is a pretty simple network, but as a LAN grows it becomes more complex. Each of the the devices is connected to a centralized device. The connection is made with some sort of cable. The cable is the road that the data travels over to get to it's destination. When you go to class your destination is ACC, when you are traveling on the network, your destination would be a server.

Transmitting Bits Across the Local Network Roadway

In Chapter 3 we learned that data is really a bunch of binary digits. If we are moving data from one computer to another that data is really a bunch of bits that needs to be sent over a wire.

Driving Bits Across a Wire

Both sides need to agree which encoding standard will be used for communication. They could decide +-10 volts represents a 1 and +-5 volts represents a 0. They also need to agree on the length of time they will stay at a particular voltage. For example if a computer decide to transmit a particular voltage for .1 seconds it would send 10 bits per second. If the receiving computer thought it was receiving data a 1/20th of a second it would have thought it received 20 bits in a second instead of 10. A common encoding standard prevents problems like this from happening.

The Need for a Two-Lane (Network) Road

If both computers sent data over the same wire their would be problems, so they can use two cables, one to send and one to receive.

The Equivalent of Asphalt: Cables

Below as a table that shows the different types of copper cables that we use and some characteristics of each. In the next section we will get to look at them.

'* IBM has their own specifications for these cables IBM Type 1 = Cat. 4; IBM Type 3 = CAT. 2
'** Not a standard yet

Let's take a look at some of these and other types of cables.

Phone Cable - This is a flat (non-twisted) four wire cable.	RJ-11 - Used for phone cable RJ = Registered Jack	Category V Cable - Twisted cable with four pair, Unshielded Twisted Pair (UTP). This one is plenum.
Category V Cable - This one is Shielded Twisted Pair (STP)	Category VI - Twisted cable with four pair, Notice the plastic divider to keep the four pair separate.	Category VI MT Cable - Flat cable with four twisted pair. See another solution for higher speeds.

Painting the Lines on the Road: Connectors

RJ-45 - Used for CAT III, IV, V and VI cable	RJ-45 - With a molded boot and CAT V cable	RJ-45 - Without a molded boot. (notice the color pattern - EIA/TIA 568b)
Fiber - The top is an SC Type end; the lower is ST type end.	RG-58 (Coaxial Cable) - With BNC (Bayonet Neill-Concelman) connector, T and terminator.	Keystone Jack - Notice this is color coded for the EIA/TIA 568b pattern EIA/TIA 568a and 568b Patterns

EIA/TIA 568a and 568b Patterns

Driving in the Right Lane (Pair) on the Road

Cables 1 and 2 send the data and 3 and 6 receive data. If you have a cable that uses the same wiring pattern it is a straight-through cable. This is relying on a switch or a hub to change the pin out. If you are hooking two computers directly together you have to send data that is transmitted on pin 1 to pin 3 and from 2 to 6. This cable would have the 568A on one end and a 568b on the other, this is called a cross-over cable.

Sharing the Local Roadway: Ethernet Hubs

This is not a new concept to us at this point, but if you need to have more then two devices talking to each other you wouldn't hook each device to each other. In this case a hub can be used, a hub will take a signal from one cable and repeat it down all the other cables.

Dirt Roads Versus the DOT

At home we use dirt roads, we hook our computers to the hub directly. Everything works and our cables are tucked away nice and neat so no one trips over them. In the real world we wouldn't do it this way we would have structured wiring that can be performed by an electrician or the wiring person. This cable would be terminated at both ends and contain no electronic components. Then the network guy would install the hubs/switches and configure them. We are now going to look at two networks that have structured wiring. One only has copper, and the other uses fiber.

My House

Below are pictures taken of my home network. This network is a small one and should be easy to understand. We will be following a CAT V cable from a PC to the switch and all the steps in between.

We start at the computer. The Category V cable is circled.	The cable then goes to the wall jack. The wall jack's cable runs to the basement.	All the cables run through the basement and end up at the patch panel.
The patch panel has cable coming from all over the house going into the top. Then out of the bottom comes the cables to the switch.	Close up of wall mount patch panel. Note the color patterns, even though they are not in the 568b order this is a 568b patch panel. The wires are rearranged to make it easy to punch down.	Here you can see the cables go from the wall mount patch panel to the switch (bottom box). The switch connects to the router (top box) and the router plugs into the cable modem. (box to the left.)
The switch connects all the PC's in the house together. The switch connects to the router which connects to the cable modem.	A close up of the switch. The lights tell you information about the client hooked to it, I.e. speed, transmission mode. etc...	Here we can see the cable plugs the cable modem into the router and the router into the switch. The third cable goes to another switch.
This is the upstairs switch that has the server plugged into as well as the WAP (Wireless Access Point) 802.11b	Also connected to the upstairs switch is the Jet Direct box which turns my printer into a network printer.	Here is a map of the whole network so you can see how everything is connected. This diagram omits keystone jacks and patch panels.

Corporate Network

Below is a group of pictures from a large network that uses fiber. The pictures show two separate ways to convert copper to fiber. Click on the picture to see the full image.

We start with the back of a rack mount patch panel. Remember all the computers in the surrounding area are coming to the patch panel(s).	Here is the front of the patch panel (bottom). The ports on the patch panel plug into the hub. Each hub is plugged into the switch (top). The switch converts to fiber and sends the signal to the center closet.	The fiber comes out of the switch and plugs into this wall mount fiber patch panel. The fiber then runs to the center closet.
Here we see where the fiber comes to within the center closet. This is a rack mount fiber patch panel.	The fiber goes to the fiber transceiver (both orange [fiber] and yellow [cat V] cable is plugged into this) The Cat V then plugs in to the switch. This is how each location talks to each other. (Note: Below is a hub and patch panel that is where the local computers plug into.)	Here is a diagram that shows the path from a client to the server in this network

Non Conductive Media (Wireless)

We should also discuss wireless at this point. A wireless network is one that uses radio wave to transmit data. A wireless node can run in one of two modes.

• Ad Hoc Mode - In Ad hoc mode two nodes talk to each other directly. This is a point to point connection.
• Infrastructure Mode - In this mode all nodes talk to each other through a centralized Wireless Access Point (WAP). This is a point to multipoint configuration, the WAP acts like a hub.

The following table outlines the differences between the different wireless standards that are available.

'*Some speeds can go higher with vendor specific features
'**Ranges can be extended with special antennas
The antennas come in two different types as well.

• Omni - Point to multipoint, 360 degree coverage, low distance point to point.
• Yagi - Point to point, directional antenna, less coverage, higher distances.