Local area

networks

What does LAN stand for? Local Area Network.A LAN supplies networking capability to a group of computers close to each other. A LAN is useful for sharing resources - like the S drive or the H drive where our files are at school. A LAN can be connected by wireless or a cable.

WHAT IS A LAN?

WHAT IS A MAN? What does a MAN stand for? Metropolitan

Area Network. An example of a MAN is a network that connects companies together in different city.

New York Los Angeles

WHAT IS A WAN? WAN stands for wide area network. WAN is a

network that connects you to the world. The biggest example of this is the World Wide Web.

WHERE CAN YOU FIND LANS? Some of the places you can have a LAN are

at home e.g. a PC connected to a laptop and even a printer.

Another place is at school. In the classroom T5 we have 15-20 computers connected by cable.

Businesses could also use LANs because everyone will need to access the same thing like work files or printing.

WHAT ARE LANS USED FOR? Sharing resources such as network drives to

share files, printers and internet. I haven’t used them but other students also

share games on the LAN. Teachers have an application called Kamar

that is shared on the LAN.

RESOURCES I CAN ACCESS ON OUR LAN?

At school we use the network for: H drive – this is a network drive where I save my

personal work to. S drive – this is a network drive where I get some

of my work from the teachers e.g. ICT Websites – we use wikispaces in ICT to get out

work. This connection is shared on the LAN across all of our PCs at school.

Printing - I’ve printed out assessments to our printer in the library that is shared on the LAN.

COMPONENTS THAT CAN BE CONNECTED TO A LAN?

Devices with network interface cards can be potentially connected to a LAN. Some of these are:

Modems or routers – connect PCs to the internet. Hub or Switch – these connect multiple PCs and/or

devices e.g. printer together. Splits one port into many. PC or Laptop – these are the same function on a LAN

e.g. allows us to type up our assignments, access the resources. But the laptop is more portable. I can carry it around.

Fileserver – A server shares resources on a LAN, in this case its serving files. Our school server is THSDC.

COMPONENTS THAT CAN BE CONNECTED TO A LAN…

Printers – Need to have a network interface card. Most printers at home don’t have this, they have USB. Our school printers do.Network Attached Storage – Also needs a network interface card, but to store files on. Mobile Devices – Generally these will connect wirelessly, an example is a cellphone that can connect wirelessly to the internet if it has the password.

LAN ARCHITECTURESPeer to Peer vs Client/Server – These

are two main types of local area networks.

PEER TO PEER A peer to peer handle up to 10 computers any more than 10 it starts to slow down. Peer to peer means every computer is equal with each other. It is mainly used for small businesses or at home because there may be a need to share the internet as an example, but rarely between more than 5 machines.

CLIENT/SERVERThe main difference is each computer has a set role, they’re not equal. A servers role is to share resources.A clients role is to request resources.You normally find this type of LAN in schools or businesses because there are too many PCs to share one resource.

CHARACTERISTICS OF A PEER TO PEER VS CLIENT/SERVER:

A PEER TO PEERCost: A peer to peer is the least expensive to run. For example you can setup a home network for less than??? ADSL router/modem+ 2 computers + switchPerformance: It works fine with a small amount of computers – like what you could have at home - but the more you add, the slower it will get.Size: It connect up to 5-10 computers.Security: A peer to peer only has the basic features that come with the operating system, for example, XP only allows you to make file shares read only.

CLIENT/SERVERCost: A client/server is more expensive to run than peer to peer. For example you can set it up at school or a business.Performance: Client/server has a high performance, better to use at school or in big businesses then at home. Size: A client/server connects up to 15-25 computer. Security: Windows server operating systems are the server alternative to XP clients. This has something called Active Directory that allows an administrator to assign permissions at a user level. Far more secure for large networks.

WHAT NETWORK COMPONENTS ARE BEST?Peer to peer Can be used in both Client/server

Hub PCs Switch

Modem/router Laptop Fileserver

Mobile devices Network storage

Wireless devices Network attached storage

Printer Fiber Optic Cable

Cables Router

HUB VS SWITCHBoth these devices do the same thing – splits the number of ports into “many” e.g. four.Also, connects devices you want to share resources e.g. printer.But how efficiently each does that differs. Anything connected to a hub is treated as “one”. Whereas a switch can send only to the device that needs the information.This hub in the picture can connect up to four devices on this network.For example, a computer and printer could be connected.This is best for a peer to peer network because it can only take up to 4 devices and is not as clever as a switch.

MODEM VS ROUTER

Is a better alternative to a hub, its more intelligent and efficient at connecting devices.You can connect more.Its faster and more secure.When you use a switch, you create a LAN.Switches are good for client/server LANs because it can have 24 or 48 ports i.e. devices.When you use a router, you connect two LANs or it can be used to connect users to the internet.

PC/LAPTOP VS SERVERBoth these devices do the same thing – splits the number of ports into “many” e.g. four.Also, connects devices you want to share resources e.g. printer.But how efficiently each does that differs. Anything connected to a hub is treated as “one”. Whereas a switch can send only to the device that needs the information.This hub in the picture can connect up to four devices on this network.For example, a computer and printer could be connected.This is best for a peer to peer network because it can only take up to 4 devices and is not as clever as a switch.

CAT5 VS FIBER CABLESBoth these devices do the same thing – splits the number of ports into “many” e.g. four.Also, connects devices you want to share resources e.g. printer.But how efficiently each does that differs. Anything connected to a hub is treated as “one”. Whereas a switch can send only to the device that needs the information.This hub in the picture can connect up to four devices on this network.For example, a computer and printer could be connected.This is best for a peer to peer network because it can only take up to 4 devices and is not as clever as a switch.

ADVANTAGES & DISADVANTAGES OF CABLING

CoxialCat5 – most commonly used at home and in the work place because ? Reliable; Secure ; Fiber

SpeedDistanceInterferenceCost

DATA TRANSMISSIONSThis means how fast devices can operate.There are 3 types:Simplex transmission: This means the data flows in one direction only. To where it is being sent to.Half- duplex transmission: Data can flow both ways but not at the same time because the data will crush.Full- duplex transmission: The data can flow both ways with out data crushing. It means the data can be sent and receive at the same time.

The preferred mode is the full- duplex transmission because the data can flow both ways with out crushing or loosing data.

LAN TOPOLOGIESBus

RingStar

Hybrid

WHAT ARE THEY? Star: Many businesses and home networks use the

star topology. A star network features a central connection point called a "hub" that may be an actual hub or a switch. The advantage: New computers can be easily added, Cable layouts are easy to modify. The disadvantages: The disadvantages: Uses a large amount of cable, If the centralized point fails, the network fails.

Bus: Bus networks use a common backbone to connect all devices. The backbone is a high capacity communications medium that joins networks and central network devices on the same floor in a building. The advantage: Is it uses least amount of cable, Is easy to extend. The disadvantages: Hardware bugs are difficult to isolate, Cable break can affect many users.

Ring: In a ring network, every device has exactly two neighbors for communication purposes (5). All messages travel through a ring in the same direction. The advantage: Networks can cover greater distances, Performance is even despite many users. The disadvantages: Expanding the system can be costly, Network reconfiguration disrupts operation.

Hybrid: it’s a combination of all topologies.

Model/protocol Acronym Definition Why is it important?

OSI Open Systems Interconnection

A standard that says how information should be sent across 7 layers.

Because it specifies how information is sent and received between two devices on the network.

TCP/IP Transmission Control Protocol/Internet Protocol

For a computer at home to connect to the internet, this protocol would be the “language” they use. To establish connectivity,

Because it makes sure that data is not only transmitted to the right place, but is error free as well.

Model/protocol Acronym Definition Why is it important

DHCP Dynamic Host Configuration Protocol

A service that automatically gives a unique number to any network device that requests to be connected.

Its important on a client/server Lan more than p2p because of how many devices it has to manage. The more devices, the more complex the network is

NAT network address translation

It translates one IP address to be “seen” on the network as another address.

Because it gives your LAN better security. For example, a public IP address from the internet could be different to a private one so any hackers only knew the public not private because it is NAT’d.

ICMP Internet Control Message Protocol

Necessary on an IP network, this is a troubleshooting utility.

It helps you know if a device is connected to the LAN or not, e.g. the ping command

IP ADDRESSING An IP address is a unique number given to any

network device, similar to your address at home for mail to get delivered to.

It is four numbers separated by dots, looks sort of like this - xxx.xxx.xxx.xxx and the numbers can range from 0-255

On a LAN, its made up of the following parts: Network – like a postal address, all devices on the

same network will have this half the same (i.e. first 3 lots of numbers xxx.xxx.xxx).

Host – like your house # and/or street, all devices will be unique to this part (4th set of digits)

IP ADDRESSING… There are 5 different classes. Class A – E

and each class is reserved for specific purposes. We use class C addresses between 192.0.0.0 through 223.255.255.0

CONNECTION TECHNOLOGIESWired vs wireless? Why choose to use it at home i.e. convenience, no messy cables etc.

Why use it at work, wireless is less reliable. You need stable constant access to resources. For example Thursday last week the entire school had no internet access. Unpredictable disconnections.