chapter7 computer networks

Networks

Chapter 7

Learning Objectives:

List four major benefits of connecting computers to form a network.

Define the terms LAN, WAN, and MAN.

List the three types of networks.

Name the three physical topologies used to build networks.

Benefits of a Network:

Allows simultaneous access to critical programs and data.

Allows people to share peripheral devices, such as printers and scanners.

Streamlines personal communication with email.

Makes the backup process easier.

SHARED DATA, PROGRAMS AND BACKUPS

Networking in a word: efficiency

Network Setup:

• LAN (Local Area Network)

• WAN (Wide Area Network)

• MAN (Metropolitan Area Network)

Local Area NetworkLAN

• A network of computers located relatively near

each other and connected by a cable.

Wide Area NetworkWAN

• Two or more LANs connected together, generally

across a wide geographical area using high-speed or

dedicated telephone line.

Metropolitan Area NetworkMAN

• Similar to a WAN network but is confined to a

single city or metropolitan area.

Node - individual computers attached to a network.

Intranet:

Extranets:

Network Types:

Server Network

Peer-to-Peer Network

Server Network:

• File Server– used to store and forward (send) files from and

to computers (nodes) on the network.

• Client/Server– individual computers (nodes) share the

processing and storage workload with a central server.

Peer-to-Peer Network:

• Simple Peer-to-Peer– all nodes on the network have equal

relationship to all others, and all have similar types of software.

• Distributed Computing– enables users to draw on the processing power

of other computers in the network.

Topology - the physical layout of the cables that connect the nodes of the network.

Network Topologies:

• Bus topology

• Star topology

• Ring topology

Bus topology - a single node to which all the network nodes and peripheral devices are attached.

Bus: a single path connects all devices.

A broken path can bring down all connected devices.

BUS

Star topology - places a hub in the center of the network nodes. Groups of data are routed through the central hub to their destinations.

Star: the hub is in the center of the network nodes.

The entire network goes down only if the hub is lost.

Ring topology - connects the nodes of the network in a circular chain in which each node is connected to the next.

Ring: each node is chained to the next.

If a connection is lost, the entire network goes down.

Network Media - refers to the wires, cables, and other means by which data travels from its source to its destination.

Network Media:

• Twisted-pair wire

• Coaxial cable

• Fiber-optic cable

• Wireless links

Twisted-pair Cable:

Coaxial Cable:

Fiber-optic Cable:

Wireless media:

Protocols

Network Protocol - a set of standards for communication.

• TCP/IP

• IPX/SPX

• NetBEUI

TCP/IP

IPX/SPX

NetBEUI

Network Technologies:

• Ethernet• Fast Ethernet• Token Ring• ARCnet

Ethernet:

Ethernet is the most widely-installed local area network ( LAN) technology. Specified in a standard, IEEE 802.3, Ethernet was originally developed by Xerox from an earlier specification called Alohanet (for the Palo Alto Research Center Aloha network) and then developed further by Xerox, DEC, and Intel.

An Ethernet LAN typically uses coaxial cable or special grades of twisted pair wires. Ethernet is also used in wireless LANs.

The most commonly installed Ethernet systems are called 10BASE-T and provide transmission speeds up to 10 Mbps.

Devices are connected to the cable and compete for access using a Carrier Sense Multiple Access with Collision Detection (CSMA/CD ) protocol.

Fats Ethernet:

Fast Ethernet is a local area network (LAN) transmission standard that provides a data rate of 100 megabits per second (referred to as "100BASE-T"). Workstations with existing 10 megabit per second (10BASE-T) Ethernet Card can be connected to a Fast Ethernet network. (The 100 megabits per second is a shared data rate; input to each workstation is constrained by the 10 Mbps card.)

Gigabit Ethernet:

Gigabit Ethernet, a transmission technology based on the Ethernet frame format and protocol used in local area networks (LANs), provides a data rate of 1 billion bits per second (one gigabit). Gigabit Ethernet is defined in the IEEE 802.3 standard and is currently being used as the backbone in many enterprise networks.

Token Ring:

A Token Ring network is a local area network (LAN) in which all computers are connected in a ring or star topology and a bit- or token-passing scheme is used in order to prevent the collision of data between two computers that want to send messages at the same time. The Token Ring protocol is the second most widely-used protocol on local area networks after Ethernet.

ARCNET

ARCNET is a widely-installed local area network (LAN) technology that uses a token-bus scheme for managing line sharing among the workstations and other devices connected on the LAN.

The LAN server continuously circulates empty message frames on a bus(a line in which every message goes through every device on the line and a device uses only those with its address).

When a device wants to send a message, it inserts a "token" (this can be as simple as setting a token bit to 1) in an empty frame in which it also inserts the message. When the destination device or LAN server reads the message, it resets the token to 0 so that the frame can be reused by any other device.

The scheme is very efficient when traffic increases since all devices are afforded the same opportunity to use the shared network.

Network Operating System (NOS) - the group of programs that manages the resources on the network.

Network Operating System Software:

• Microsoft Windows NT Server• Banyan VINES• AppleShare• Artisoft LANtastic

Modem - (short for modulator-demodulator). Used to translate digital signals into analog signals that can travel over standard phone lines.

Modem

Digital Phone Lines:

ISDN

T1

T3

ATM

ISDN(Integrated Services Digital Network)

ISDN (Integrated Services Digital Network) is a standard for digital transmission over ordinary telephone copper wire as well as over other media.

Home and business users who install an ISDN adapter (in place of a telephone modem) receive Web pages at up to 128 Kbps compared with the maximum 56 Kbps rate of a modem connection.

ISDN requires adapters at both ends of the transmission so your access provider also needs an ISDN adapter.

In many areas where DSL and cable modem service are now offered, ISDN is no longer as popular an option as it was formerly.

T1

Multimedia Network - a network that enables artists to store, retrieve, and share data with other users.