lan networks

Networking

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WALT: Networking Fundamentals

Know about: What a network is Network standards Different types of networks What’s required to connect to a network Advantages and disadvantages of being

connected to a network


What is a Network?

Two or more computers connected together to share resources and information


What is a Network?

Computers connected to network can be any type of computer

– Each computer could be configured with different operating system

– No restrictions other than having network software understand rules and language needed to recognize computer type and operating system


Where the Personal Computer Fits

PC most commonly used tool to connect to network– Microprocessor chip is “brains”

of PC– Communicates with other

components of PC via internal connecting device called “bus”

– To communicate with external devices, PC needs interface card

To connect PC to network, need interface card for type of network, suitable cable, and appropriate software


Networking Standards

When two or more computers interconnected to communicate and share resources, you have a network

Protocols are rules governing type of cables, interface cards, and electrical signal format

Also govern how information flows between computers on network called transport protocols:– indicates how computer needs to send information over

network – how receiving computer checks that information was

received correctly– how sending computer must address information so it

goes to correct destination computer Application level protocols determine how program on one

computer communicates with program on another computer


Peer-to-Peer Networks

Inexpensive and easy to put together Ideal for home and small office networks Called peer-to-peer because all computers have equal

authority Protocols included in Microsoft Windows 95/98/ME but

several proprietary peer-to-peer network systems available also

Windows NT (or higher) has network component built in with more complex protocols to connect computers


Client - Server Networks

Typical on large networks where one computer (network server) dedicated to controlling network traffic and managing resources

Provides better performance and security as server controls who can access what resources and when

Also called central server as all files stored here Server can be any type of computer with server software

installed, and users clearly identified with access rights Client computer can be any type of computer with network

card and appropriate software to connect to server

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Topologies - Structure

Star– All the network devices connected to a central computer which

is often used as the file server

Ring– Each of the devices on the network is connected in a ring or a

loop. (Each machine has a connection to the one previous and the one after it in the loop)

Bus– Each of the devices is connected directly to a main

communications line, called a bus

MESH– All the computers connected to each other

Click here to view animations on topologies

http://www.teach-ict.com/gcse_new/networks/topologies/theory_topologies.htm

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Figure 8-5

Star Network Topology

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Star: Advantages and Disadvantages

Advantages of a Star– If one cable fails the other stations are not affected

– Consistent performance even under heavy use

– Reliable market proven system

– No problems with collisions of data since each station has its own cable to the server

– Easy to add new stations without disrupting the network

Disadvantages of a Star– May be costly to install because of the cable lengths

required

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Bus Network Topology

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Bus: Advantages and Disadvantages

Advantages of a Bus– Easy and inexpensive to install as it requires the

least amount of cable of the network types

– Easy to add more stations without disrupting the network

Disadvantages of a Bus– The whole network goes down if the main cable fails

at any point

– Cable failure is difficult to isolate

– Network performance degrades under a heavy load

– Information can be transmitted in either direction and occasionally there is data collision.

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Figure 8-7

Ring Network Topology

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Ring: Advantages and Disadvantages

Advantages of a Ring– No dependence on a central computer or file server and

each node controls communication to and from itself

– Transmission around the network is one way only

– High data transmission rates are possible

Disadvantages of a Ring– If one node breaks down transmission is disrupted

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Mesh Network Topology

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Mesh: Advantages and Disadvantages

Advantages of a MESH– Communication is not disrupted– Alternative routes to node points/machines– Security – packages can arrive/be sent via many

different routes– Backup – with multiple connections it is easier to

distribute the data in case of disaster Disadvantages of a MESH

– Cost• of cables required to link machines together• Of machines – similar spec machines required at

each location to be able to take over– Difficult to install and reconfigure


LANs and WANs

Difference lies in who is responsible for cabling

– LAN network stays within building

– WAN if network crosses public street and uses publicly-supplied cabling for part of network

When computer or LAN connected to another computer or LAN in another city or country, public portion of WAN represented schematically by “cloud”


Connecting to a Network

Standard network devices facilitate putting network together

Cabling comes in standard lengths complete with appropriate connectors

Which options, devices, or software you use depends on needs and requirements for network

Variety of connection or cabling options available to access information to or from network

– Newer connection types allow the data to be transferred between computer and network to flow much faster


Connection/Cabling Options

Coaxial Wire with center wire surrounded with insulation and then grounded cover of braided wire.

Fiber Optics Made up of bundled glass or plastic fibers (threads) to transmit data.

Broadband Single wire that can handle multiple paths or channels

Wireless Work with radio frequencies for data transmission.

Infrared Wireless option works with infrared light waves to transmit data.


The Network Interface Card (NIC)

To connect to network, PC must have network interface card (NIC)

Each NIC has unique number or address and connector appropriate for type of cabling chosen

Come in variety of styles and models appropriate for computer type being connected to network


The Hub Connect PCs together to

form network

– Cable from NIC in each PC connects to port on hub

– Cable from hub required to connect to network

Relatively inexpensive to purchase and install

Main disadvantage of hub is all users connected to hub share equal maximum transfer speed


Network Segments

If network has two or more network interface cards, each card considered a segment

Segments allow network traffic to flow faster, depending on which devices are used to manage amount of requests at network


The Bridge

Connects network segments to handle network requests

Do not analyze or re-route messages which makes receiving information faster

Will not re-route or re-transmit information if anything is wrong with connection at either end until first transmission received completely


The Router

Work similar to bridges except examine destination address of information and pass it on appropriate segments only

Bridges may be faster than routers but will not check information coming in

When installing wireless router to network, be sure to set up encryption security options to prevent unauthorized access from external sources using connection


The Switch

Works similar to hub except that each user connected to switch has access to full bandwidth

Can also be used to join network segments


The Firewall

Can be physical device or specialized software installed to prevent any unauthorized external access into any network connected to Internet

Designed to check any messages that travel through network and ensure it matches specified security requirements set up by company


Benefits of Networking

Networking does not make individual workstations faster or more powerful!

Benefits of networking fall into two main categories:

– Communication

– Sharing of resources


Communicating

To send information generated on stand-alone PC requires manual process whereas users on network send information electronically

Messages can be stored on network and are not lost if recipient isn’t available when messages sent or received

Many communication software allows users to instantly message someone else without using e‑mail – “Real time interaction”– Multiple users can participate in same conversation– Some limitations but can be minor issues in

exchange for ability to communicate with each other in real time


Sharing Devices

Some devices can be expensive to set up on every PC and networking allows devices to be shared

– Can be cost savings for capital expenditures as well as productivity time for technical support or maintenance

Connecting devices shared by multiple users via network allows Network Administrator to perform updates or troubleshoot problems from server location


Sharing Information

In network environment, files or folders on any disk can be set up to be shared

Whenever group of people want to share information, referred to as workgroup– Group of users who share business documents

transfer or save files to common network– Common network becomes centralized server

wherein server has control over which files are accessed and which users can use those files

Extremely helpful to network administrator for setting up rights or performing maintenance for workgroups


Using Dedicated Servers Network

– Control network traffic and security– May perform same tasks and contain same information

as file or database server File

– High speed, high capacity hard drive, usually to handle back-up needs

Web– Stores information in web format and information

accessed with browser for company intranets Mail

– Manages high volume of internal and external e-mail Database

– Generally used in complex database applications where many users need to access data at same time


Disadvantages of Networking

Dependency Big disadvantage in that organization’s activities

depend on network to be up and running

– If network fails, users lose access to information and ability to communicate electronically

– In some instances can work from local drive, but if company’s information stored and shared from server, cost of downtime may be more expensive in long term



Expensive For installation and maintenance If network complex with many users, additional

need and expense to employ network administrator

Need “disaster and recovery” plan, not just for theft or security breach, but also power outages or potential hardware failure

Setting up or upgrading a network server should always be discussed with network administrator or consultant who specializes in networks prior to making any decisions



Security Risk

Every person who logs into server has valid login id, and set up according to company’s standards

Every person who logs into server has valid password

When setting up new user, ensure name and information about user entered correctly

Audit each user to ensure access rights to programs and files are same

Requests received for access rights must have signature from corresponding manager

Delete users who no longer work for company

Do not ever give out passwords



Staff who work with network administrator should have own login id and password set up

Firewall set up for Internet connection that has been set up to check user id when sending or receiving messages

If access authorized for users outside network, ensure firewall checks these user ids when request received to access network from remote location

Restrict any users from being able to delete files from any folder on any network drives

Antivirus program installed on server is current and has latest protection files

Perform maintenance checks periodically as well to see what activities may have occurred

Encourage users to have latest updates of Windows on local computers



Loss of Autonomy or Privacy Obliged to work in network environment Privacy may be concern for confidential material “Private” drive set up on network for personal or

confidential files but network administrator can still see these files

If share computer, even though they log in with their own id, they can still see files on local

General business rules dictate that anything you work on a company computer belongs to the company, even though you may work on it on your own time



Viruses Vulnerable to virus attacks Some viruses, called worm viruses, specifically

target servers New viruses being created every day and it

becomes more prudent to read screen carefully before automatically opening message or clicking highlighted button on screen

All antivirus programs provide a feature to automatically detect in “real time”

Remember to run scan of computer on frequent basis and check for updates

lan networks

Technology