NETWORK Topologies An Introduction. What is a Network? Several computers linked together by a cable. Allows users to share resources. Allows the rapid.

NETWORKTopologies

An Introduction

What is a Network?

• Several computers linked together by a cable.

• Allows users to share resources.

• Allows the rapid transfer of data.

• Allows users to communicate with each other.

Local Area Networks

• LANs are usually found on a single site.

• May be single building, room or floor.

• There are four main LAN topologies (maps).

Bus Network

S tation 1S tation 5S tation 3

S tation 2 S tation 4 S tation 6

T erm inator

Bus Network

• Several stations are connected to a single cable.• Terminators are used to stop data “falling off”.

• Advantages of a Linear Bus Topology– Easy to connect a computer or peripheral to a linear bus.

– Requires less cable length than a star topology.

• Disadvantages of a Linear Bus Topology– Entire network shuts down if there is a break in the main cable. – Difficult to identify the problem if the entire network shuts

down.

Star Network – Central Hub

Workstation 1

Workstation 2

Workstation 3Workstation 4

Workstation 5Central Hub

Star Network• Stations are directly connected to a central hub.• Data on a star network passes through the hub before

continuing to its destination• Advantages of a Star Topology

– Easy to install and wire.

– No disruptions to the network when connecting or removing devices.

– Easy to detect faults and to remove parts.

• Disadvantages of a Star Topology– Requires more cable length than a linear topology.

– If the hub or concentrator fails, nodes attached are disabled.

– More expensive than linear bus topologies because of the cost of the hub.

Ring Network

S tation 1S tation 2

S tation 3

S tation 4

S tation 5

S tation 6

P rin ter

Ring Network• Cable forms an endless loop.• Stations are directly connected to this loop.• Data flows in one direction around ring.• Topology is commonly implemented as token ring

• Advantages of a Ring Topology– Each node in the network is able to purify and amplify the

data signal before sending it to the next node.– More stations can easily be added.– Individual workstations can be isolated from the ring.

• Disadvantages of a Ring Topology– A break in the ring causes the entire network to fail.

Mesh NetworkS tation 1

S tation 2

P rin ter

S tation 3

S tation 4

S tation 5

Mesh Network• Each station is connected to every other station.• Mesh topology's are used in critical connection of

host computers (typically telephone exchanges).

• Advantages of a Mesh Topology– Any failure of one computer allows all others to continue,

as they have alternative paths to other computers.– Alternate paths allow each computer to balance the load

to other computer systems in the network by using more than one of the connection paths available.

• Disadvantages of a Mesh Topology– Difficult to add more stations.

Topology ComparisonFeatures Bus

topologyStar

topologyRing

topologyMesh

topology

Expense Low Medium High High

Reliability Good Excellent Good Excellent

Geographically coverage ability

Poor Good Excellent Good

Troubleshooting ease Poor Excellent Good Poor

Network Card - NIC

• Purpose of NIC is to physically connect computer into network

Can have an RJ-45 connector port, a BNC connector port or both.

BNC port

RJ-45 port

Peer–Peer Network• Allow users to share

resources and files located on their computers.

• They do not have a file server or a centralized management source

• All computers are considered equal; they all have the same abilities to use the resources available on the network.

Designed primarily for small to Designed primarily for small to medium local area networks.medium local area networks.

Peer-Peer Network

• Advantages of a peer-to-peer network:– Less initial expense. No need for a dedicated server. – An operating system (such as Windows 95) already in

place may only need to be reconfigured for peer-to-peer operations.

• Disadvantages of a peer-to-peer network:– Decentralized. No central repository for files and

applications. – Security. Does not provide the security available on a

client/server network.

Client-Server Network

• Allow the network to centralize functions and applications in one or more dedicated file servers

• The file servers become

the heart of the system, providing access to resources and providing security.

• Individual workstations (clients) have access to the resources available on the file servers.

The network operating system provides the mechanism to integrate all the components of the network. Novell Netware and Windows NT Server are examples of client/server network operating systems.

Client-Server Network• Advantages of a client/server network:

– Centralized. Resources and data security are controlled through the server. – Scalability. Any or all elements can be replaced individually as needs

increase. – Flexibility. New technology can be easily integrated into system. – Interoperability. All components (client/network/server) work together. – Accessibility. Server can be accessed remotely and across multiple

platforms.

• Disadvantages of a client/server network:– Expense. Requires initial investment in dedicated server. – Maintenance. Large networks will require a staff to ensure efficient

operation. – Dependence. When server goes down, operations will cease across the

network.

NETWORKTopologies

The End