Understanding Understanding NetworkingNetworking

Joe CiceroJoe CiceroNortheast Wisconsin Technical CollegeNortheast Wisconsin Technical College

Presentation PurposePresentation Purpose

The purpose of this presentation is to The purpose of this presentation is to give the learner a VERY BASIC give the learner a VERY BASIC understanding of TCP /IP networking.understanding of TCP /IP networking.

What we will cover…What we will cover… The NIC or Network Interface CardThe NIC or Network Interface Card TCP/IP or Transmission Control Protocol Internet ProtocolTCP/IP or Transmission Control Protocol Internet Protocol IP or Internet Protocol AddressingIP or Internet Protocol Addressing What a Gateway isWhat a Gateway is Internet Addresses vs. Private IP AddressesInternet Addresses vs. Private IP Addresses NAT or Network Address TranslationNAT or Network Address Translation DNS or Domain Name ServiceDNS or Domain Name Service DHCP or Dynamic Host Configuration Protocol vs. Static DHCP or Dynamic Host Configuration Protocol vs. Static

AddressingAddressing Special IP Addresses – 169, 127Special IP Addresses – 169, 127 Cross-over cablesCross-over cables HubsHubs SwitchesSwitches WirelessWireless Ad hoc vs. InfrastructureAd hoc vs. Infrastructure

The Network Interface CardThe Network Interface Card

Since most of us have a phone, we will use Since most of us have a phone, we will use it to describe what is needed and how it to describe what is needed and how things work on a network.things work on a network.

The network interface card or NIC is like The network interface card or NIC is like your phone. Your phone allows you to your phone. Your phone allows you to connect to the telephone network.connect to the telephone network.

The NIC is the physical device that enables The NIC is the physical device that enables the computer to connect to a computer the computer to connect to a computer network.network.

Language / ProtocolLanguage / Protocol

We all speak some language to We all speak some language to communicate with someone on the other communicate with someone on the other end of our phone. If we call someone who end of our phone. If we call someone who doesn’t speak our language and we don’t doesn’t speak our language and we don’t speak their language it is impossible to speak their language it is impossible to communicate with them.communicate with them.

OneOne “language”, we call it a protocol, our “language”, we call it a protocol, our computer uses to “speak” to other computer uses to “speak” to other computers is Transmission Control computers is Transmission Control Protocol Internet Protocol or TCP IP.Protocol Internet Protocol or TCP IP.

The IP addressThe IP address You have a phone number. You are the only one You have a phone number. You are the only one

with this number. If two individuals had the same with this number. If two individuals had the same phone number the system wouldn’t work phone number the system wouldn’t work correctly. Would a caller get a busy signal if only correctly. Would a caller get a busy signal if only one of the numbers was in use? Would both one of the numbers was in use? Would both phones ring if neither was in use or would phones ring if neither was in use or would neither?neither?

Each computer connected to a network has an Each computer connected to a network has an Internet Protocol (IP) address. There can be only Internet Protocol (IP) address. There can be only one address per computer on the network. If one address per computer on the network. If more than one computer has the same address more than one computer has the same address the computer turned on first will “answer calls” the computer turned on first will “answer calls” for that IP and the other will not.for that IP and the other will not.

To view your active IP Addressing information on a Windows computer you should always type “ipconfig /all” at the command prompt!

NOTE: Viewing it in the Internet Protocol (TCP/IP) Properties box DOES NOT GUARANTEE an active IP!

GatewaysGateways You don’t have to dial an area code when you call You don’t have to dial an area code when you call

someone in your area, your phone can directly someone in your area, your phone can directly communicate with other phones in your area. If communicate with other phones in your area. If you want to dial outside of your area you have to you want to dial outside of your area you have to dial in an area code or country code etc.dial in an area code or country code etc.

Computers on the same network can Computers on the same network can communicate directly with other computers on communicate directly with other computers on their network. If computers need to communicate their network. If computers need to communicate with a computer outside of the network they use with a computer outside of the network they use a gateway. The gateway is “aware” of other a gateway. The gateway is “aware” of other networks and “routes” the traffic to them.networks and “routes” the traffic to them.

How many IP addresses are there?How many IP addresses are there?

Just like there is a limited number of phone Just like there is a limited number of phone numbers, there is a limited number of IP numbers, there is a limited number of IP addresses.addresses.

Most computers currently are using IP version 4 Most computers currently are using IP version 4 (IPv4) which only has 4,294,967,296 possible (IPv4) which only has 4,294,967,296 possible unique addresses. However, many are reserved unique addresses. However, many are reserved for special purposes, such as private networks for special purposes, such as private networks (~18 million addresses). This reduces the (~18 million addresses). This reduces the number of addresses that can be allocated as number of addresses that can be allocated as public Internet addresses.public Internet addresses.

THERE EVENTUALLY WILL BE A SHORTAGE OF THERE EVENTUALLY WILL BE A SHORTAGE OF IPv4 ADDRESSESIPv4 ADDRESSES

InternetInternetvs. vs.

Private Network AddressesPrivate Network Addresses

As the previous slide said there are As the previous slide said there are private addresses that you can use private addresses that you can use on private networks (NOT THE on private networks (NOT THE INTERNET). These addresses will INTERNET). These addresses will work on your network but won’t work work on your network but won’t work on the Internet.on the Internet.

They are:They are:• 10.0.0.0 – 10.255.255.255 16,777,216 single class 10.0.0.0 – 10.255.255.255 16,777,216 single class

AA• 172.16.0.0 – 172.31.255.255 1,048,57 class B172.16.0.0 – 172.31.255.255 1,048,57 class B• 169.254.0.0 – 169.254.255.255 65,536 class B169.254.0.0 – 169.254.255.255 65,536 class B• 192.168.0.0 – 192.168.255.255 65,536 class C192.168.0.0 – 192.168.255.255 65,536 class C

What do/did we do about the What do/did we do about the shortage?shortage?

NAT or Network Address Translation was the NAT or Network Address Translation was the “patch” for the shortage. Every device on the “patch” for the shortage. Every device on the Internet has to have an individual address.Internet has to have an individual address.

Every device on your network has to have an Every device on your network has to have an individual address.individual address.

If you have a device BETWEEN your network and If you have a device BETWEEN your network and the Internet that understands how to the Internet that understands how to communicate with your network and has a valid communicate with your network and has a valid Internet address, every computer doesn’t need a Internet address, every computer doesn’t need a valid Internet address. If you think about it, just valid Internet address. If you think about it, just at NWTC, that saves thousands of IP addresses.at NWTC, that saves thousands of IP addresses.

One device, multiple purposesOne device, multiple purposes

Sometimes your NAT device is also Sometimes your NAT device is also your gateway, router, firewall, etc.your gateway, router, firewall, etc.

IP Address / Domain Name IP Address / Domain Name RelationshipRelationship

So we know that every computer on the So we know that every computer on the Internet has to have an address that is Internet has to have an address that is unique. Why can I type a name in Internet unique. Why can I type a name in Internet Explorer to get to a website?Explorer to get to a website?

Humans would have a hard time Humans would have a hard time remembering tons of numbers so there is remembering tons of numbers so there is this great thing called a domain name this great thing called a domain name server that associates numbers like server that associates numbers like 72.14.203.99 with names like 72.14.203.99 with names like www.google.comwww.google.com. Type either one into . Type either one into your browser and you will go to the same your browser and you will go to the same place.place.

DNS – Domain Name ServerDNS – Domain Name Server

If you type the Preferred DNS server If you type the Preferred DNS server number incorrectly you will NOT be number incorrectly you will NOT be able to use a Domain name but you able to use a Domain name but you will still be able to use an IP address!will still be able to use an IP address!

DHCP vs. Static AddressesDHCP vs. Static Addresses

OK, OK, The phone company gives me OK, OK, The phone company gives me my phone number, and I’ve never had my phone number, and I’ve never had to type any numbers into my computer to type any numbers into my computer and it works – what’s the deal?and it works – what’s the deal?

There is this thing called DHCP or There is this thing called DHCP or Dynamic Host Configuration Protocol. Dynamic Host Configuration Protocol. If your computer is setup to use it AND If your computer is setup to use it AND there is another computer setup to there is another computer setup to give out addresses, you don’t have to give out addresses, you don’t have to do anything.do anything.

Statically Assigned AddressStatically Assigned Address

No DHCP, No Static, and I still have an No DHCP, No Static, and I still have an address!address!

Joe, you must be wrong. I have a computer that Joe, you must be wrong. I have a computer that isn’t connected to a network and therefore can’t isn’t connected to a network and therefore can’t be getting an address from a DHCP server, I be getting an address from a DHCP server, I didn’t set an address and yet…by magic, it has an didn’t set an address and yet…by magic, it has an address!address!

When your Windows-based computer (configured When your Windows-based computer (configured for DHCP) is initializing, it broadcasts three or for DHCP) is initializing, it broadcasts three or more "discover" messages. If a DHCP server does more "discover" messages. If a DHCP server does not respond after several discover messages are not respond after several discover messages are broadcast, the Windows computer assigns itself a broadcast, the Windows computer assigns itself a Class B 169.254.0.0 address. Class B 169.254.0.0 address.

Who is 127.0.0.1?Who is 127.0.0.1?

At home I’m on a 192.168.1.0 network. I At home I’m on a 192.168.1.0 network. I disconnected my router and pinged disconnected my router and pinged 127.0.0.1 and got a response! Is there an 127.0.0.1 and got a response! Is there an invisible computer on my network?invisible computer on my network?

127.0.0.1 is the standard IP address used 127.0.0.1 is the standard IP address used for a loopback network connection. This for a loopback network connection. This means that if you try to connect to means that if you try to connect to 127.0.0.1, you are immediately 127.0.0.1, you are immediately looped looped backback to your own machine. to your own machine.

In other words, 127.0.0.1 is In other words, 127.0.0.1 is youyou!!

Other Special IP AddressesOther Special IP Addresses

An IP Address that ends in a zero An IP Address that ends in a zero denotes the “network”. You cannot denotes the “network”. You cannot assign a computer to the address assign a computer to the address xxx.yyy.zzz.0xxx.yyy.zzz.0

Typically an IP Address that ends in Typically an IP Address that ends in 255 denotes the “broadcast” 255 denotes the “broadcast” address. You should not assign a address. You should not assign a computer xxx.yyy.zzz.255computer xxx.yyy.zzz.255

Cross-over cablesCross-over cables Your phone at home may have a “phone cord” Your phone at home may have a “phone cord”

just like a computer using a wired network has a just like a computer using a wired network has a data cable. Sometimes these are referred to as a data cable. Sometimes these are referred to as a drop cord or patch cord.drop cord or patch cord.

The computer sends data on some of the wires The computer sends data on some of the wires and receives data on some of the wires.and receives data on some of the wires.

In order to connect two computers directly In order to connect two computers directly together (no other equipment in-between them), together (no other equipment in-between them), you need a “cross-over” cable. This cable you need a “cross-over” cable. This cable switches the wires on the end of the cables switches the wires on the end of the cables allowing to computers to communicate.allowing to computers to communicate.

HubsHubs

Another way for you to connect two or Another way for you to connect two or more computers together is through a more computers together is through a “hub”. “hub”.

When a “packet” of information is sent to When a “packet” of information is sent to a hub it retransmits the “packet” to ALL a hub it retransmits the “packet” to ALL computers connected to it. Only the computers connected to it. Only the computer that is at the correct address computer that is at the correct address answers. Hubs are not used much answers. Hubs are not used much anymore because of the increased “traffic” anymore because of the increased “traffic” on the network due to the way they work!on the network due to the way they work!

SwitchesSwitches Another way for you to connect two or Another way for you to connect two or

more computers together is through a more computers together is through a “switch”. “switch”.

A switch keeps track of every computer A switch keeps track of every computer connected to it and where it is plugged connected to it and where it is plugged into on the switch. When a “packet” of into on the switch. When a “packet” of information is sent to a switch, it information is sent to a switch, it retransmits the “packet” to the computer retransmits the “packet” to the computer the “packet” is for. Switches were more the “packet” is for. Switches were more expensive than hubs but are cheap now expensive than hubs but are cheap now and are used more often due to the way and are used more often due to the way they work!they work!

Wireless NetworkingWireless Networking

You may have a cordless phone or a You may have a cordless phone or a cell phone that uses radio waves to cell phone that uses radio waves to communicate with other phones. communicate with other phones.

We can use radio waves with We can use radio waves with computers too. This is called computers too. This is called wireless networking. wireless networking.

Ad hoc vs. InfrastructureAd hoc vs. Infrastructure

Just like we need to have a special cable Just like we need to have a special cable made to make two computers made to make two computers communicate without a hub or switch, we communicate without a hub or switch, we may need to make special setting changes may need to make special setting changes to make two or more computers to make two or more computers communicate without an access point.communicate without an access point.