Network FundamentalsNetwork Fundamentals

Network DefinitionNetwork Definition

Two or more computers Two or more computers connected together to connected together to share information (e.g., share information (e.g., files) or resources (e.g., files) or resources (e.g., printers)printers)

Network ServicesNetwork Services File Services – Allows multiple users File Services – Allows multiple users

access to sets of files for distribution access to sets of files for distribution or collaboration.or collaboration.

Print Services – Allows multiple users Print Services – Allows multiple users to connect to, and use, centralized to connect to, and use, centralized printers.printers.

Mail Services (including IM) – A Mail Services (including IM) – A server on the network acts as an E-server on the network acts as an E-mail server, receiving all E-mail for mail server, receiving all E-mail for the domain.the domain.

Network ServicesNetwork Services

Directory and Name Services – Directory and Name Services – Enables users to connect to Enables users to connect to particular files and devices without particular files and devices without knowing the physical location of the knowing the physical location of the resource.resource.

The InternetThe Internet

A network of networksA network of networks The Internet itself is nothing more The Internet itself is nothing more

than a set of facilities that connect than a set of facilities that connect separate, little networks together separate, little networks together into one gigantic network. into one gigantic network.

The Internet doesn't provide the The Internet doesn't provide the information you're looking for, one of information you're looking for, one of the smaller networks does.the smaller networks does.

Network AdministrationNetwork Administration

Setting up user accounts and servicesSetting up user accounts and services Monitoring network performanceMonitoring network performance Repairing network failuresRepairing network failures Enforcing securityEnforcing security Providing fault tolerance (backing up)Providing fault tolerance (backing up)

Network Modes of TransmissionNetwork Modes of Transmission

Simplex – One direction onlySimplex – One direction only• Over the air televisionOver the air television• Burglar, Fire AlarmsBurglar, Fire Alarms

Half-Duplex – One direction at a timeHalf-Duplex – One direction at a time• Two-way radiosTwo-way radios

Full-Duplex – Transmit & Receive at Full-Duplex – Transmit & Receive at the same time. Network connections the same time. Network connections allow full-duplex transmission.allow full-duplex transmission.

Types of NetworksTypes of Networks Peer-To-PeerPeer-To-Peer

• All computers are equal partnersAll computers are equal partners• Each user responsible for access to Each user responsible for access to

resources on his/her computerresources on his/her computer• Each workstation acts as either a server Each workstation acts as either a server

or a client in each transactionor a client in each transaction• Easy to install and operateEasy to install and operate• No extra equipment or softwareNo extra equipment or software• Because each person controls access, Because each person controls access,

network security can be a problem.network security can be a problem.

Types of NetworksTypes of Networks

Client-ServerClient-Server• Centralized administration of resourcesCentralized administration of resources• Users must authenticate themselves to Users must authenticate themselves to

use network resourcesuse network resources• Server is equipped to handle requests Server is equipped to handle requests

from multiple users at the same timefrom multiple users at the same time• There is a cost for ease of administration There is a cost for ease of administration

(software, hardware, a trained staff)(software, hardware, a trained staff)

Types of NetworksTypes of Networks

Local Area Network (LAN)Local Area Network (LAN)• Computers connected over a relatively Computers connected over a relatively

small geographic area (a home, an small geographic area (a home, an office, a building or a campus).office, a building or a campus).

Wide Area Network (WAN)Wide Area Network (WAN)• Designed to work over a larger area Designed to work over a larger area

than a LAN, across a city, state, country than a LAN, across a city, state, country or the planet.or the planet.

• Use either a circuit-switched or packet-Use either a circuit-switched or packet-switched network.switched network.

Connecting a Computer to a Connecting a Computer to a NetworkNetwork

Network Interface Card (NIC)Network Interface Card (NIC)• Different cards for different types of Different cards for different types of

network (Ethernet or Token Ring) and network (Ethernet or Token Ring) and for different types of media.for different types of media.

• Each card has a particular Media Access Each card has a particular Media Access Control (MAC) address to uniquely Control (MAC) address to uniquely identify it.identify it.

• Each card is programmed with a TCP/IP Each card is programmed with a TCP/IP address so that other computers can address so that other computers can connect to it.connect to it.

TCP/IP AddressTCP/IP Address

Four series of numbers from 0 – 255Four series of numbers from 0 – 255 Every network-connected device has Every network-connected device has

to have a unique address.to have a unique address. There are only 4.3 Billion addresses There are only 4.3 Billion addresses

available.available.

Dynamic Host Configuration Dynamic Host Configuration Protocol (DHCP)Protocol (DHCP)

On large networks, you can run into On large networks, you can run into problems if you let everyone problems if you let everyone administer their own IP addresses.administer their own IP addresses.

DHCP centralizes the administration DHCP centralizes the administration of IP addresses on the network.of IP addresses on the network.

A DHCP server doles out unique IP’s A DHCP server doles out unique IP’s to requesting computers.to requesting computers.

The IP is The IP is leasedleased to the device for a to the device for a specified period of time (72 hours).specified period of time (72 hours).

Domain Name SystemDomain Name System

When a network is connected to the When a network is connected to the Internet, it’s difficult to remember Internet, it’s difficult to remember the IPs of all the computers you want the IPs of all the computers you want to connect to.to connect to.

Hosts are identified by human-Hosts are identified by human-friendly names (www.nku.edu, friendly names (www.nku.edu, support.microsoft.com).support.microsoft.com).

A DNS server translates the name A DNS server translates the name into the IP address.into the IP address.

Physical Network CharacteristicsPhysical Network Characteristics

Network TopologiesNetwork Topologies Networking MediaNetworking Media Common Network DevicesCommon Network Devices

Network TopologiesNetwork Topologies Star – Each device is connected to a Star – Each device is connected to a

centralized point, like spokes in a centralized point, like spokes in a wheel.wheel.

Extended Star – Additional Extended Star – Additional networking devices added to some networking devices added to some spokes. Typical in schools, large spokes. Typical in schools, large corporations.corporations.

Bus – Single cable running from Bus – Single cable running from server. All workstations connect to server. All workstations connect to cable.cable.

Network TopologiesNetwork Topologies

Ring – Devices connected in a circle. Ring – Devices connected in a circle. A signal (token) is passed from A signal (token) is passed from device to device, and only the device device to device, and only the device with the token may transmit.with the token may transmit.

Double Ring – Two complete circles. Double Ring – Two complete circles. Provides for fault tolerance. If one Provides for fault tolerance. If one circle gets broken, the other takes circle gets broken, the other takes over.over.

Networking MediaNetworking Media Coaxial CableCoaxial Cable

• Similar to video cableSimilar to video cable• Maximum speed is 100 MB/sMaximum speed is 100 MB/s• Maximum run is 500 meters.Maximum run is 500 meters.

Networking MediaNetworking Media Shielded Twisted PairShielded Twisted Pair

• Pairs of wires are twisted together and Pairs of wires are twisted together and have a foil shield around them for noise have a foil shield around them for noise and interference cancellation.and interference cancellation.

Networking MediaNetworking Media Unshielded Twisted Pair (UTP)Unshielded Twisted Pair (UTP)

• The most common LAN cabling.The most common LAN cabling.• Category 3 used for telephone service.Category 3 used for telephone service.• Categories 5, 5e, 6 used for networks.Categories 5, 5e, 6 used for networks.• Rely solely on twisting for interference Rely solely on twisting for interference

cancellation.cancellation.

Networking MediaNetworking Media Fiber Optic CableFiber Optic Cable

• Transmits beams of light instead of Transmits beams of light instead of electrical impulses.electrical impulses.

• Much higher bandwidth, less subject to Much higher bandwidth, less subject to electrical interference.electrical interference.

• Much more expensive to deal with.Much more expensive to deal with.

Networking MediaNetworking Media

When any kind of wiring is going to When any kind of wiring is going to be too expensive, wireless be too expensive, wireless connections are the answer.connections are the answer.• Wireless connections come with a whole Wireless connections come with a whole

new set of security concerns.new set of security concerns.• Home wireless routers and equipment Home wireless routers and equipment

should not be used in a commercial should not be used in a commercial environment.environment.

Network DevicesNetwork Devices HubsHubs

• Connect multiple network clients Connect multiple network clients together.together.

• Not very smart, send everything to Not very smart, send everything to everyone.everyone.

Network DevicesNetwork Devices

SwitchesSwitches• Similar to a hub, but intelligent.Similar to a hub, but intelligent.• Switches know the IP addresses of the Switches know the IP addresses of the

devices attached to it, and send the devices attached to it, and send the message only to the correct device.message only to the correct device.

Bridges – connect segments of a Bridges – connect segments of a network together.network together.

Routers – connect different types of Routers – connect different types of networks together, like LAN to WAN.networks together, like LAN to WAN.

Network UtilitiesNetwork Utilities ping – Test connectivity to another ping – Test connectivity to another

computer.computer. arp – Displays mapping between IP arp – Displays mapping between IP

addresses and MACs.addresses and MACs. nslookup – Displays IP address for a nslookup – Displays IP address for a

given host name.given host name. netstat – Displays information about netstat – Displays information about

active network connections.active network connections. ipconfig – Displays TCP/IP ipconfig – Displays TCP/IP

configuration information.configuration information.

Connecting to the InternetConnecting to the Internet

DialupDialup DSLDSL CableCable SatelliteSatellite

Connecting to the InternetConnecting to the Internet

DialupDialup• Not always onNot always on• Customer does not get an IP addressCustomer does not get an IP address• Ties up the phone line.Ties up the phone line.• Communicates with ISP via low speed Communicates with ISP via low speed

modem.modem.• ISP groups many low speed connections ISP groups many low speed connections

together for transmission to the together for transmission to the internet.internet.

Connecting to the InternetConnecting to the Internet

Digital Subscriber Line (DSL)Digital Subscriber Line (DSL)• High speed connection using telephone High speed connection using telephone

lines.lines.• Generally, customer must be within Generally, customer must be within

18,000 feet of a telco central office.18,000 feet of a telco central office.• Customer becomes a remote computer Customer becomes a remote computer

on the ISP's network, and does get an IP on the ISP's network, and does get an IP address.address.

Connecting to the InternetConnecting to the Internet

Cable Cable • Generally, anyone who has cable TV Generally, anyone who has cable TV

service can get cable high speed service can get cable high speed internet, but not all cable companies internet, but not all cable companies provide service.provide service.

• Like DSL, always on, customer becomes Like DSL, always on, customer becomes a remote computer on ISP's network, a remote computer on ISP's network, gets an IP address.gets an IP address.

• All customers in your neighborhood All customers in your neighborhood share the same bandwidth.share the same bandwidth.

Connecting to the InternetConnecting to the Internet

SatelliteSatellite• Provided by satellite TV companies.Provided by satellite TV companies.• Good for people in rural areas who can't Good for people in rural areas who can't

get cable or DSL service.get cable or DSL service.• Because satellite TV is really one way Because satellite TV is really one way

service, extra stuff has to be added to service, extra stuff has to be added to make service 2-way. Upload speeds are make service 2-way. Upload speeds are one tenth of download speeds.one tenth of download speeds.

• ExpensiveExpensive