Download Network Hardware

Computer communication
Networks
Specification Requirements
Candidates should be able to:
• describe the hardware needed to connect
stand-alone computers into a local area
network, including hub/switches, wireless
access points
• explain the different roles of computers in
a client-server and a peer-to-peer network
• describe, using diagrams or otherwise, the
ring, bus and star network topologies
Network Hardware
Network interface card:
• A network adapter such as a network
interface card (NIC) is needed to connect
computers and other peripherals to a
network, either by cable or wirelessly.
Each connected device is allocated an IP
address to uniquely identify it on
a TCP/IP network.
Network Hardware
• Terminator
– Device attached to the end of bus network
– Prevents signals from bouncing
Network Hardware
• Repeaters
– Signals can lost integrity, become attenuated
over long distances
– Repeaters clean the signal up, then sends it
on.
Network Hardware
• Hubs
– Effectively repeaters
– Sends signal to all devices connected to it
– Only intended receiver will process it
– Used in star networks
– Not good for large networks – collisions
– Whole network goes down if Hub is broken
Network Hardware
• Bridges
– Connects different network segments together
– Can speed up a networks performance
– Only sends on to different segments,
determined by reading MAC address
– If not different segment then packet is
discarded clearing up traffic.
Network Hardware
• Switches
– High Speed Bridge
– Has a dedicated CPU
– Intelligently determines route of packet to
destination
Network Hardware
• Twisted pair Cables
– are the most common and is often called
Ethernet cabling. Category 5 (Cat5) twistedpair cables can carry 100Mb per second over
distances of up to 100 metres.
Network Hardware
• Coaxial cable
– is better at resisting electrical interference so
it can be installed over longer lengths, but it is
not as flexible.
Network Hardware
• Fibre Optic Cable
– has a central glass core and transmits signals
using light at extremely high speeds over
huge distances. It can be used outside
buildings but it is significantly more expensive
to purchase and install.
Network Types
Client Server
•
On a client-server network there are two types of computers with two
distinct roles. One or more server computers have the role of
controlling access to shared resources like files and printers. Multiple
client computers are then connected to the server computers and
these are where the user works.
•
The user typically logs onto a client computer which then connects to
the server, verifies the user and then allows them access to the files
and software stored on the server that they have permission to access.
•
All the data is stored on the servers, which generally have far greater
security controls than the client computers. Since data storage is
centralised, security is easier to manage, updates to the data are
far easier to administer and it is far easier to backup the data
centrally.
•
Some servers may have a more specialised role such as a print server,
dedicated to controlling access to shared printers on the network and
queuing print jobs in the order that they were sent by the users.
Network Types
Peer to Peer
•
In a peer-to-peer network computers are simply linked together,
either using cables and a hub or wirelessly.
•
Such networks do not have computers with particular roles, instead,
each computer can simultaneously act as both a client and a server,
and each has equivalent responsibilities and status.
•
This means that any computer on the network can load information
from the hard disk of any other computer and a computer on the
network can use any printer connected to any other computer.
•
A peer-to-peer network will be cheaper to set up and, provided there
are only a small number of computers, will be easier to manage than
server based networks.
•
However they are less secure and peer-to-peer networks are used
mainly by home users and small companies who do not have the
necessary technical staff to maintain a client-server network.
Network Types
Peer to Peer Vs Client Server
Peer to Peer
Client Server
No network wide security
Central control of security.
Soon become unworkable
Easier to supervise network performance
Machines slow down when being accessed
by others
Easier to perform software upgrades
Machines holding data being accessed can be Faster performance – fewer data collisions
restarted
Difficult to keep track of who has what
information
Client machines freed up
Backup becomes complicated
Easier to perform back-ups
Expensive to set up and good expertise
required
Infrastructure may be required.
Server failures have more impact
Network Hardware
• Servers
– Application Servers
• DBMS Systems and other software
– Communication Servers
• Entry point to network for external users
– File and Print Servers
• Stores of data and access to printers
– Mail Servers
• Access to email.
– Web servers
• Allows intranets
• Contains devices such as webcams, routers etc.