1. Computer Communication & Networks
Introduction to Networking
Made by:
Sidra !

2. What is a Network?
A network consists of 2 or more computers
connected together, and they can communicate
and share resources

3. Why Networking?
• Sharing information — i.e. data
communication
• Do you prefer these?
• Or this?

4. • Sharing hardware or software
• E.g. print document
• Centralize administration and support
• E.g. Internet-based, so everyone can access the same administrative
or support application from their PCs

5. How many kinds of Networks?
• Depending on one’s perspective, we can
classify networks in different ways
• Based on transmission media: Wired (UTP, coaxial cables, fiber-
optic cables) and Wireless
• Based on network size: LAN and WAN (and MAN)
• Based on management method: Peer-to-peer and Client/Server
• Based on topology (connectivity): Bus, Star, Ring …

6. LAN - Local Area Network
• Local Area Network (LAN)
• Small network, short distance
• A room, a floor, a building
• Limited by no. of computers and distance covered
• Usually one kind of technology throughout the LAN
• Serve a department within an organization
• Examples:
• Network inside the Student Computer Room
• Network inside your home

7. WAN – Wide Area Network
• A network that uses long-range telecommunication links to connect
2 or more LANs/computers housed in different places far apart.
• Towns, states, countries
• Examples:
• Network of our Campus
• Internet Your home
USA
WAN
Campus

8. MAN - Metropolitan Area Network
 Larger than a LAN and smaller than a WAN
- example: campus-wide network
- multi-access network
 Technologies:
 coaxial cable
 microwave

9. Network Management Method
Peer to Peer Network
• Peer-to-peer network is also called workgroup
• No hierarchy among computers all are equal
• No administrator responsible for the network
Peer-to-peer

10. Network Management Method
• Advantages of peer-to-peer networks:
• Low cost
• Simple to configure
• User has full accessibility of the computer
• Disadvantages of peer-to-peer networks:
• May have duplication in resources
• Difficult to uphold security policy
• Difficult to handle uneven loading
• Where peer-to-peer network is appropriate:
• 10 or less users
• No specialized services required
• Security is not an issue
• Only limited growth in the foreseeable future

11. Network Management Method
Clients and Servers
• Network Clients (Workstation)
• Computers that request network resources or services
• Network Servers
• Computers that manage and provide network resources and services to
clients
• Usually have more processing power, memory and hard disk space
than clients
• Run Network Operating System that can manage not only data, but
also users, groups, security, and applications on the network
• Servers often have a more stringent requirement on its performance
and reliability

12. Network Management Method
• Advantages of client/server networks
• Facilitate resource sharing – centrally administrate and control
• Facilitate system backup and improve fault tolerance
• Enhance security – only administrator can have access to Server
• Support more users – difficult to achieve with peer-to-peer
networks
• Disadvantages of client/server networks
• High cost for Servers
• Need expert to configure the network
• Introduce a single point of failure to the system

13. Topology ― 3 basic types
• Bus Topology
• Simple and low-cost
• A single cable called a trunk (backbone, segment)
• Only one computer can send messages at a time
• Passive topology - computer only listen for, not regenerate data

14. Topology ― 3 basic types
 Advantages of a bus topology:
 uses less cable compared to other physical topologies like star
 works well for small networks
 does not need a central device, such as a hub, switch, or router
 Disadvantages of a bus topology:
 slower access to the network and less bandwidth due to the
sharing of the same cable by all devices
 challenging to identify and isolate problems
 break at any point in the bus cable can disable the entire bus
network

15. Topology ― 3 basic types
Star Topology
• Each computer has a cable connected to a single point
• More cabling, hence higher cost
• All signals transmission through the hub; if down, entire
network down
• Depending on the intelligence of hub, two or more computers
may send message at the same time
Hub

16. Topology ― 3 basic types
 Advantages of a Star Topology:
 upgradeable, flexible, and reliable
 easy to design and install
 diagnosing problems relatively easy
 allows for more throughput than any other topology
 Disadvantages of a Star Topology:
 requires a lot of cable to connect computers .
 expensive to build because of the additional cost of cables
and devices

17. Topology ― 3 basic types
• Ring Topology
• Every computer serves as Ack T T
a repeater to boost signals T
• Typical way to send data:
T dat T dat
• Token passing
a a
• only the computer who
gets the token can send T
data T
T Ack
• Disadvantages T Ack
dat
• Difficult to add computers a
• More expensive T
• If one computer fails, whole network fails T Ack

18. Network Devices: Repeaters
 A repeater receives the
signal, regenerates it, and
passes it on.
 Repeaters are used mainly
at the edges of networks to
extend the wire so more
workstations can be added.

19. Network Devices: Hubs
 Using a hub changes the
network topology from a linear
bus, where each device plugs
directly into the wire, to a star.
 Hubs come in three basic types:
 Passive
 Active
 Intelligent

20. Network Devices: Bridges
 Bridges operate at the data link
layer of the OSI model.
 The function of the bridge is to
make intelligent decisions about
whether or not to pass signals
on to the next segment of a
network.
 When a bridge sees a frame on
the network, it looks at the
destination MAC address and
compares it.

21. Network Devices: Switches
 Switches learn certain
information about the data
packets that they receive from
computers on the network.
 They use this information to build
forwarding tables to determine
the destination of data sent by
one computer to another on the
network.
 They help segment a network
and reduce network traffic
congestion.

22. Network Devices: Routers
 Routers operate at the Network
layer of the OSI model.
 They are slower than bridges and
switches but make "smart"
decisions on how to route
packets.
 Routers are capable of
segmenting the network.