This document discusses computer networks and networking concepts. It defines what a computer network is and different types of networks like LAN, MAN, and WAN. It then covers network topologies, describing physical topologies like bus, star, ring, mesh, tree and hybrid topologies. It also discusses common networking devices like routers, switches, hubs, bridges and others. Finally, it covers some common networking cables used like coaxial cable, Ethernet cable and optical fiber cable.

1. Network Topology And
Devices

2. NETWORK
 A Computer Network, or simply a Network, is a collection
of computers and other hardware interconnected by
communication channels that allow sharing of resources and
information. A network is a group of devices connected to
each other.
 Networks may be classified into a wide variety of
characteristics, such as the medium used to transport the
data, communications protocol used, scale, topology,
benefit, and organizational scope.

3. NETWORK CLASSIFICATION
 A local area network (LAN) is a computer network that
interconnects computers in a limited area such as a home,
school, computer laboratory, or office building using network
media.
 A metropolitan area network (MAN) are high speed
networks that connects LAN’s in a metropolitan area.
Managed by a consortium of users or a single network
provider.
 A Wide Area Network (WAN) is a network that covers a
broad area i.e. any telecommunications network that links
across metropolitan, regional, or national boundaries.

4. NETWORK TOPOLOGY
Network topology is the arrangement of the various elements
(links, nodes, etc.) of a computer or a biological
network. Essentially it is the topological structure of a network
and may be depicted physically or logically. Topologies are
either:
 Physical
 Logical

5. TYPES OF PHYSICAL TOPOLOGY
 Point to
Point
 Bus
 Star
 Ring
 Mesh
 Tree
 Hybrid

6. POINT TO POINT
Point-to-Point topology is a point-to-point communication
channel that appears to the user to be permanently
associated with the two endpoints. A tin can telephone is the
best example.

7. BUS
All computers and devices are connected to single cable or
BUS. It consists of a main run of cable with a terminator at
each end. It is popular on LANs as they are inexpensive
and easy to install.

8. STAR
In local area networks with a star topology, each network host is
connected to a central hub with a point-to-point connection. In Star
topology every node is connected to central node called hub or switch.

9. RING
A network topology that is set up in a circular fashion in which
data travels around the ring in one direction and each device
on the right acts as a repeater to keep the signal strong as it
travels. Each device incorporates a receiver for the incoming
signal and a transmitter to send the data on to the next device
in the ring.

10. MESH
In mesh topology each computer is connected to each other by
separate cables. There is a point tom point connection
between each node.
This type of topology is generally used in military area.

11. TREE
The type of network topology in which a central 'root' node (the top level of
the hierarchy) is connected to one or more other nodes that are one level
lower in the hierarchy (i.e., the second level) with a point-to-point link
between each of the second level nodes and the top level central 'root'
node

12. HYBRID
Hybrid networks use a combination of any two or more
topologies in such a way that the resulting network does
not exhibit one of the standard topologies.

13. ADVANTAGES AND DISADVANTAGES OF
THE 4 MOST COMMONLY USED
NETWORK TOPOLOGIES

14. BUS TOPOLOGY
Advantages
 Easy to connect a computer or peripheral to a linear bus.
 Requires less cables than any other topologies.
 Doesn’t requires any specialized network equipment.
Disadvantages
 Difficult to trouble shoot.
 Network disruption when more computers are added to
it.
 A break in the cable will prevent all systems from
accessing the network.

15. RING TOPOLOGY
Advantages
 Cable faults are easily located making trouble shooting
easier
 Ring networks are moderately easily to install.
Disadvantages
 Expansion to the network can cause network disruption
 A single break in the cable can disrupt the entire network

16. MESH TOPOLOGY
Advantages
 Provides redundant path between the devices
 Network can be expanded without any inconvenience to
current user.
Disadvantages
 Requires more cables than any other toplology
 Complicated implementations

17. STAR TOPOLOGY
ADVANTAGES
 Easy to install and wire.
 Security can be implemented in the hub/switch.
 Easy to detect faults and remove parts.
DISADVANTAGES
 Requires more cable length.
 If the hub or concentrator fails nodes attached are
disabled
 More expansive due to he cost of concentrators
associated with it.

18. NETWORKING DEVICES
Networking devices typically refers to hardware that facilitates
the use of a computer network. Computer networking
devices are units that mediate data in a computer
network. Some of the networking devices are:
 Gateway
 Router
 Switch
 Bridge
 Hub
 Repeater
 Multiplexer
 Modem

19. GATEWAY
A device sitting at a network node for
interfacing with another network that uses
different protocols.

20. ROUTER
A specialized network device that determines
the next network point to which it can forward a
data packet towards the destination of the
packet.

21. SWITCH
A device that allocates traffic from one network
segment to certain lines (intended destinations)
which connect the segment to another network
segment.

22. BRIDGE
A device that connects multiple network
segments along the data link layer.

23. HUB
A device connects multiple Ethernet segments together
making them act as a single segment. When using a hub,
every attached device shares the same broadcast domain and
the same collision domain. Therefore, only
one computer connected to the hub is able to transmit at a
time.

24. REPEATER
A device to amplify or regenerate digital signals
received while sending them from one part of a
network into another.

25. MULTIPLEXER
A device that combines several electrical
signals into a single signal.

26. MODEM
A device that modulates an analog "carrier" signal (such as
sound), to encode digital information, and that also
demodulates such a carrier signal to decode the transmitted
information, as a computer communicating with another
computer over the telephone network.

27. BROUTER
Brouters are a combination of router and bridge. A
Brouter transmits two types of traffic at the exact same
time: bridged traffic and routed traffic.

28. NETWORK INTERFACE CARD
Network Interface Card, or NIC is a hardware card installed
in a computer so it can communicate on a network. The
network adapter provides one or more ports for the network
cable to connect to, and it transmits and receives data onto
the network cable.
Network Card Wireless LAN Card

29. TRANSCEIVERS
Transceiver short for transmitter-receiver, a device that both
transmits and receives analog or digital signals. The term is
used most frequently to describe the component in local-area
networks that actually applies signals onto the network wire and
detects signals passing through the wire. For many LANs, the
transceiver is built into the network interface card.

30. FIREWALL
Firewall is a piece of hardware and/or software which
functions in a networked environment to prevent some
communications forbidden by the security policy, analogous
to the function of firewalls in building construction.

31. PROXIES
 A proxy device acts as a firewall by responding to input
packets (connection requests, for example) in the manner of
an application, whilst blocking other packets.
 A proxy server acts as an intermediary for requests
from clients seeking resources from other servers. A client
connects to the proxy server, requesting some service, such as
a file, connection, web page, or other resource available from a
different server and the proxy server evaluates the request as
a way to simplify and control their complexity

32. NETWORKING CABLES
Networking cables are used to connect one network
device to other network devices or to connect two or more
computers to share a printer, scanner etc. Different types
of network cables like Coaxial cable, Optical fibre cable
etc.
Optical fibre
Ethernet cable
Coaxial cable