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