Networking Overview Frank Schneemann This short PowerPoint Presentation is designed to give you a general overview of how networks are, most likely, set-up.

Networking OverviewFrank Schneemann

This short PowerPoint Presentation is designed to give you a general overview of how networks are,

most likely, set-up in your school.

Network Theory

Learning networks in one lesson is a daunting task. Still, it is important for administrators to have at least a basic understanding of how networks work. After you study the online tutorial on networks, the PowerPoints and notes below, you should have a basic understanding of how networks work and how they can be used in the educational environment. Any time you connect at least two computers together, you have a computer network. Computer networks allow you to share information and devices. A classroom of the 21st century is no longer a classroom bounded by 4 walls. Networks enable the teacher to expand their classroom to include the class next door, the entire school, the entire district or even the world. The Internet is a network of networks around the world that is built on the same basic principles as the small computer network in your class.

Without communications, there is no education and computer networks enhance our communication. Suppose you are teaching a unit in basic Spanish. How much more rewarding is it to include students from another class at your school in the dialogue between students? Why not dialogue with students from Spain or Mexico City? Networks make that possible.

Types of Networks

• Computer networks that cover a small geographic area, like a classroom or building, are called LAN's (Local Area Networks).

• Networks that cover a large geographic area are called WAN's (Wide Area Networks)

• Networks that cover a city are sometimes called MAN's (Metropolitan Area Networks)

• Networks that are interconnected with other networks all over the world are called the Internet.

• The key device that allows us to connect networks is the router. We will discuss routers in more detail in a later lesson.

Networks allow us to share devices as well. Suppose you have one printer and ten computers. You can attach the printer to one of the computers and share it with all other computers. In fact you can use any printer in the school district to print as long as that printer is shared. There are many other things that you can share. You can share CD ROM's, documents, programs, faxes, connections to the internet, scanners, hard drives, floppy drives, Zip drives; and the list goes on.

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Network Interface Card NIC

But before you can connect two or more computers together to form a network, you must install an important piece of equipment, in each computer, called a Network Interface Card (NIC)

Each NIC has a unique number installed on a memory chip at the factory when the card is manufactured. No two network cards have the same number. This number becomes the address of your computer on the network. We call this number the MAC address or Media Access Control address.

Having an address on the network allows other users to find you on the network and communicate with you.

ARP Table

Not only does your network card have it's own address but it is constantly broadcasting that address to all of the other computers on the LAN. In turn, each computer on the LAN maintains a table that lists the names and MAC addresses of each computer on the local area network. The table is called an ARP table (Address Resolution Protocol)..

When computer X wants to send information to computer Y it simply looks in its ARP table for the address

Peer to Peer Networks

The basic difference between a peer to peer network and a server based network is control. In a peer to peer network each computer is equal. Each computer keeps its own programs and no one computer has control over other computers. You can share information, printers and other devices in a peer to peer network but otherwise all computers are equal

Server Based Network

In a server based network the server exercises some control. A server can control who has access to the network and what things each user on the network can do. A server can also hold programs that it can share with other users. You could install one copy of Microsoft Word on a server and everyone on the network could share it. You could also set up a mail system on a server so everyone can have an email account

A server can be any computer on the network that is running server software such as Microsoft Windows 2000 server. There is also a version of Windows 2000 called, "2000 Professional" that is used as a workstation operating system

School Infratructures

The following graphics show how networks on most K12 schools are organized. The following definitions might be helpful in understanding the graphics

RouterUsed to connect different networks together

Hubs and SwitchesUsed to connect individual classroom computers to the backbone cabling

POP (Point of Presence) Where the internet or outside networks like district offices come into the schoolMDF (Main Distribution Facility)The main wire facility or closet where the main network devices are kept. Most of the time the POP is located here. May be a separate room or just a rack on the library or main officeIDF (Intermediate Distribution Facility)Every building in the school should have an IDF. It is a room or may be just a rack in some room in the building. The IDF’s are connected to the MDF with “backbone” cabling or wiring. The IDF sends wires out to each classroom, called drops, where a hub or switch is connected. The individual classroom computers connect into the hubs or switches.

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Wireless LAN’s

Today many schools are using wireless LAN’s (Local Area Networks). The graphic below shows how wireless LAN’s are most likely set up in a classroom or in your home

The wireless access point is connected to the rest of the school with wires. But, once inside the classroom it be becomes wireless. Computers communicate with the access point with radio waves

Physical Address

• The first address is called the MAC address (Media Access Control)

• The MAC address is on the network card and is burned on at the factory that made the NIC.

• No two MAC address can be the same.

IP Address

• The second address is called an IP address.

• The IP Address is a logical address assigned by the network administrator.

• It is entered into the computer when you set the computer up for the network.

Network Addressing

Every computer on a network has two addresses

192.168.2.100 03 0a 00 3e 71

192.168.2.232 92 62 02 9e 69

192.168.2.322 7f a7 f2 4d 72

• Below are the logical IP addresses and physical MAC addresses of each computer on the network

• The physical MAC address is a 24 bit hexadecimal number

• The logical IP address is a 4 byte number (32 bits long).

Two Addresses for each computer on this small network

How the network keeps track of IP addresses and MAC addresses

Every computer on the network has an ARP table in the memory of its network card to keep track of the physical MAC address and IP address

Below is an actual ARP table from my computer. My IP address is 192.168.2.2

It contains the IP Address on the left and the physical (MAC) address on the right of every computer on the network

Checking your own ARP Table

To check your own ARP table follow the steps below

• Click the Start Button on the bottom of the screen

• Click the Run button

• Type the word, Command, and a box will open up

• Type arp –a (arp space -a)

• Your ARP table should show

Every time you try to communicate with another computer on the network, the address is added to your ARP table

Static vs Dynamic Addressing

There are two ways to assign an IP address to a computer.

1. Static Addressing - You can enter them by hand into each computer. This is not the preferred method because it is tedious and open to many errors in entering the numbers and keeping track of addresses.

2. Dynamic Addressing - Allow a server, called a DHCP server to enter them for you.

How DHCP Servers Work

• You install the server and give it a bank of available IP addresses

• Every time a computer comes on line it is assigned a new address by the DHCP server

Three Basic Types of Network Topology(topology means the layout)

• Bus

• Star

• Token Ring

BUS ETHERNET NETWORK

Computers connected in a row using coaxial cable

BUS ETHERNET

In the illustration above, computer E sends a packet of information to computer B.

In a BUS Network every computer on the network receives the information but only computer B accepts it because it has the right address.

This type of network is called ETHERNET.

STAR ETHERNET NETWORK

A STAR network performs the same as a BUS network except the computers are connected to a central port, such as a hub or switch

STAR ETHERNET

In a STAR ETHERNET network, every computer gets each packet sent on the network but only the destination computer accepts the packet

Hubs and Switches can be connected together in a “Distributed Star Network”

STAR Ethernet NETWORK

Token Ring Networks

In a TOKEN RING network, a token circles around the network and you have to wait grab the token before you can transmit.

Only the destination computer gets the packet

TOKEN RING HUB

T

A TOKEN RING HUB looks like a physical star but inside the hub the token circles from computer to computer and you must grab the token to send a message..

Network Cables

Coaxial Cable

Twisted Pair (Cat 5)

Fiber Optic

BUS ETHERNET NETWORK USING COAX

Computers connected in a row using coaxial cable

CAT5

CABLE

RJ45 Connector

CAT 5 is the most popular

type of network cable

FIBER OPTIC CABLE

How computers think and communicate.

Computers do not use words or letters to communicate and think. Computers are like calculators, they only understand numbers.

When a computer wants to process information the information is converted into numbers. Computers use the BINARY NUMBER SYSTEM

Binary Numbers

• The decimal number system has 10 numbers 0 1 2 3 4 5 6 7 8 9 • The binary number system has only 2 numbers 0 and 1• Computers do not understand decimal numbers, they only

understand binary 1’s and 0’s• An individual binary number (1 or 0) is called a bit• A group of 8 bits are called a byte.• Every character on your keyboard has a binary number associated

with it consisting of 8 bits or 1 byte. • Any number that can be expressed in decimal can also be expressed

in binary. • In binary the value of a number (1or 0) depends on its position in the

byte.• Example: to the computer a capital A is the number

• 65 decimal or• 01000001 binary

• Every other character on your keyboard has some number assiciated with it

Try This!

• Open MS Word

• In MS Word, hold down the ALT key and press 65 on the number keypad

• What happens?

• Try ALT and other numbers on the keypad.

• These are the decimal equivalents of the binary numbers associated with each key.

• Each number you press on the keypad is equal to 1 byte

• There is a table called, ASCII, which shows which byte represents which keyboard character.

• Click here for web ASCII code pages

Turning letters into pulses of electricity on the network wire

When you sit at your computer writing an email, you are typing letters that must be turned into 1’s and 0’s. The 1’s and 0’s are called bits. These bits are turned into pulses of electricity on the wires of the network. One way is for a 3 volt bit = 1 and 0 volt bit = 0

It is important that these bits have some order and structure, otherwise the bits of your email will just blend with the bits from other emails and you will have network confusion on the wires. Where does your message end and another message start ???

Your questions are welcome

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