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15 June 2008

IT_Chapter_9A

Network Definition

Set of technologies that connects computers

Allows communication and collaboration between users

The Uses of a Network

Simultaneous access to data

Data files are shared

Access can be limited

Shared files stored on a server

Software can be shared

Site licenses

Network versions

Application servers

Shared peripheral device

Printers and faxes are common shares

Reduces the cost per user

Devices can be connected to the network

Print servers control network printing

Manage the print queue

Personal communication

Email

Instantaneous communication

Conferencing

Tele conferencing

Videoconferencing

Audio-conferencing

Data-conferencing

Voice over IP

Phone communication over network wires

Easier data backup

Backup copies data to removable media

Server data backed up in one step

Common Network Types

Local Area Network (LAN)

Contains printers, servers and computers

Systems are close to each other

Contained in one office or building

Organizations often have several LANS

Wide Area Networks (WAN)

Two or more LANs connected

Over a large geographic area

Typically use public or leased lines

Phone lines

Satellite

The Internet is a WAN

Hybrid Network Types

Campus Area Networks (CAN)

A LAN in one large geographic area

Resources related to the same organization

Each department shares the LAN

Metropolitan Area Network (MAN)

Large network that connects different organizations

Shares regional resources

A network provider sells time

Home Area Network (HAN)

Small scale network

Connects computers and entertainment appliances

Found mainly in the home

Personal Area Network (PAN)

Very small scale network

Range is less than 2 meters

Cell phones, PDAs, MP3 players

How Networks Are Structured

Server based network

Node is any network device

Servers control what the node accesses

Users gain access by logging in

Server is the most important computer

Client/Server network

Nodes and servers share data roles

Nodes are called clients

Servers are used to control access

Database software

Access to data controlled by server

Server is the most important computer

Peer to peer networks (P2PN)

All nodes are equal

Nodes access resources on other nodes

Each node controls its own resources

Most modern OS allow P2PN

Distributing computing is a form

Kazaa

Network Topologies

Topology

Logical layout of wires and equipment

Choice affects

Network performance

Network size

Network collision detection

Several different types

Packets

Pieces of data transmitted over a network

Packets are created by sending node

Data is reassembled by receiving node

Packet header

Sending and receiving address

Packet payload

Number and size of data

Actual data

Packet error control

Bus topology

Also called linear bus

One wire connects all nodes

Terminator ends the wires

Advantages

Easy to setup

Small amount of wire

Disadvantages

Slow

Easy to crash

Star topology

All nodes connect to a hub

Packets sent to hub

Hub sends packet to destination

Advantages

Easy to setup

One cable can not crash network

Disadvantages

One hub crashing downs entire network

Uses lots of cable

Most common topology

Ring topology

Nodes connected in a circle

Tokens used to transmit data

Nodes must wait for token to send

Advantages

Time to send data is known

No data collisions

Disadvantages

Slow

Lots of cable

Mesh topology

All computers connected together

Internet is a mesh network

Advantage

Data will always be delivered

Disadvantages

Lots of cable

Hard to setup

Network Media

Links that connect nodes

Choice impacts

Speed

Security

Size

Wire Based Media

Twisted-pair cabling

Most common LAN cable

Called Cat5 or 100BaseT

Four pairs of copper cable twisted

May be shielded from interference

Speeds range from
1 Mbps to 1,000 Mbps

Coaxial cable

Similar to cable TV wire

One wire runs through cable

Shielded from interference

Speeds up to 10 Mbps

Nearly obsolete

Wire Based Media

Fiber-optic cable

Data is transmitted with light pulses

Glass strand instead of cable

Immune to interference

Very secure

Hard to work with

Speeds up to
100 Gbps

Data transmitted through the air

LANs use radio waves

WANs use microwave signals

Easy to setup

Difficult to secure

Network Hardware

Network interface cards

Network adapter

Connects node to the media

Unique Machine Access Code (MAC)

Network linking devices

Connect nodes in the network

Cable runs from node to device

Crossover cable connects two computers

Hubs

Center of a star network

All nodes receive transmitted packets

Slow and insecure

Switches

Replacement for hubs

Only intended node receives transmission

Fast and secure

Bridge

Connects two or more LANs together

Packets sent to remote LAN cross

Other packets do not cross

Segments the network on MAC addresses

Router

Connects two or more LANs together

Packets sent to remote LAN cross

Network is segmented by IP address

Connect internal networks to the Internet

Need configured before installation

Gateway

Connects two dissimilar networks

Connects coax to twisted pair

Most gateways contained in other devices

Network Cabling

Cabling specifications

Bandwidth measures cable speed

Typically measured in Mbps

Maximum cable length

Connector describes the type of plug

Ethernet

Very popular cabling technology

10 Base T, 10Base2, 10Base5

Maximum bandwidth 10 Mbps

Maximum distances100 to 500 meters

Fast Ethernet

Newer version of Ethernet

Bandwidth is 100 Mbps

Uses Cat5 or greater cable

Sometimes called 100Base T

Requires a switch

Gigabit Ethernet

High bandwidth version of Ethernet

1 to 10 Gbps

Cat 5 or fiber optic cable

Video applications

Token ring

Uses shielded twisted pair cabling

Bandwidth between 10 and 25 Mbps

Uses a multiple access unit (MAU)

Popular in manufacturing and finance

Network Protocols

Language of the network

Rules of communication

Error resolution

Defines collision and collision recovery

Size of packet

Naming rules for computers

TCP/IP

Transmission Control Protocol/Internet Protocol

Most popular protocol

Machines assigned a name of 4 numbers

IP address

209.8.166.179 is the White House’s web site

Dynamic Host Configuration Protocol

Simplifies assignment of IP addresses

Required for Internet access

IPX/SPX

Internet Packet Exchange/Sequenced Packet Exchange

Older protocol

Associated with Novell Netware

Replaced by TCP/IP

NetBEUI

Network BIOS Extended User Interface

Used by Windows to name computers

Transmission details handled by TCP/IP

Token ring

Popular in manufacturing and finance

Nodes communicate when they have the token

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