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.
