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MICHAEL ANTHONY ANYEBE GROUP 4 2308-1203-0187
CNW 101 ASSIGNMENT INFORMATICS Page 1
ROUTER
Routers are networking devices used to extend or segment networks by forwarding
packets from one logical network to another. Routers are most often used in large
internetworks that use the TCP/IP protocol suite and for connecting TCP/IP hosts and
local area networks (LANs) to the Internet using dedicated leased lines.
ADVANTAGES OF ROUTER
 Routers have advanced features that allow you to implement quality of services
using querying or traffic shaping, filtering traffic using access control lists
(ACLs), or protecting traffic using encryption.
 A router contains broadcasts and multicasts, when a broadcast or multicast is
received on an interface, it is not forwarded to another interface, by default.
 Routers are better at connecting different layers to technologies together such
Ethernet and token ring or FDDI and serial, without any conversion issues.
 Router can change packets on the same interface using virtual LANs (VLANS).
 Routers are commonly used to solve broadcast problems.
DISADVANTAGES OF ROUTER
 Router is more expensive than Hub, Bridge & Switch.
 Router only work with routable protocol.
 Routing updates consume bandwidth.
Increase latency due to greater degree of packet filtering.
 Router is one cannot configure a particular port.

FUNCTIONS OF ROUTER
The function of a router is to manage the paths along which information is forwarded
within a network. They are necessary to facilitate communication between computers and
the Internet.
Internet data is transferred through the TCP/IP networking protocols that are designed to
communicate data. When it is transmitted, the data is split into fragments called packets.
A router is designed to direct these packets to the correct destination along the best
possible route, hence the name, router.
Routers range in size from the small ones we have in our homes and that are available
from computer shops and from Internet Service Providers, to absolutely huge models that
manage huge flows of data between computer networks and throughout the Internet. The
smaller, home-based models make it possible to share one Internet connection between a
few computers on the network, and this enables more than one person to use it, whereas
the larger ones are far more intricate and have many multi-function routing devices.
Routers come in two basic types: Dynamic and static. The dynamic comes already
programmed to manage data traffic across the network, which is managed by a routing
protocol, whereas a static router needs to be manually configured by a network
administrator who programs all of the necessary routes that are needed for data packets.
Essential services and utilities can be integrated into a network so that it is more secure
and responds more efficiently. For example, a router can be made to incorporate a
security feature such as a firewall for added protection against viruses and other nastiest
that have the ability to destroy computers and enable hackers to gather our personal
information. It is also possible to increase network function by integrating services such
as IP voice, or video capability.
SWITCH
Switches are a special type of hub that offers an additional layer of intelligence to basic,
physical-layer repeater hubs. A switch must be able to read the MAC address of each
frame it receives.

ADVANTAGES OF SWITCH
 Reduces the number of Broadcast domains.
 Supports VLAN's which can help in Logical segmentation ports physical ports
splitting up the broadcast domain.
 Intelligent device compared to Hub's which can make use of CAM table for Port to
MAC mapping
 Compared to Bridges, Switches are more H/w oriented therefore operations are less
CPU intense Basic operations.
 The cost to number of ports ratio is best for a cheaper cost you get switches with
more number of ports available than Routers.
DISADVANTAGES OF SWITCH
 Not as good as a router in limiting Broadcasts
 Communication between VLAN's need inter VLAN routing Router, but these
days there are a number of Multilayer switches available in the market.
 Handling Multicast packets needs quite a bit of configuration & proper designing.
 At times switches when in Promiscuous mode is a opening for Security attacks
spoofing ip address or capturing Ethernet Frames using ethereal.
FUNCTIONS OF SWITCH
LEARNING FUNCTIONS
Learning is the process of obtaining the MAC address of connected devices. When a
frame reaches into the port of a switch, the switch reads the MAC address of the source
device from frame and compares it to its MAC address table also known as CAM
Content Addressable Memory table). If the switch cannot find a corresponding entry
in MAC address table, the switch will add the address to the table with the port
number via the frame arrived.
FORWARDING FUNCTION
Forwarding is the process of passing network traffic a device connected to one port of a
Network Switch to another device connected to another port on the switch. When
a Layer 2 frame reaches a port on the Network Switch the switch reads the source MAC
address of the frame as a part of learning function, and it also reads the destination MAC

address also as a part of forwarding function. The destination MAC address is important
to determine the port number which the destination device is connected.
PREVENTING LAYER 2 SWITCHING LOOP
In practical Local Area Networking, redundant links are created to avoid complete
network failure in an event of failure in one link. Redundant links can cause layer 2
switching loops and broadcast storms. It is the function of a network switch to prevent
layer 2 switching loops and broadcast storms.
REPEATER
A digital device that amplifies, reshapes, retimes, or performs a combination of any of
these functions on a digital input signal for retransmission.
ADVANTAGE OF REPEATER
 Makes it easy to expand a network over a large distance.
 Connection between various types of media example fibre optic, UTF, coaxial
cable is possible.
DISADVANTAGE OF REPEATER
 Traffic cannot be filtered to ease congestion.
 A repeater cannot work across multiple network architectures.
FUNCTIONS OF REPEATER
A repeater is used to amplify signals carried by a network. The function of a repeater is to
receive incoming signals or a packet of data, regenerate the signals to their original
strength and retransmit them. When a repeater amplifies the electric signals in a network,

they allow transmissions to travel a greater distance. For a repeater to work, both network
segments must be identical.
Repeaters are used to lengthen individual network segments to form a large extended
network.
Repeaters are used to boost signals in coaxial and twisted pair cable and in optical
fiber lines. An electrical signal in a cable gets weaker the further it travels, due to energy
dissipated in conductor resistance and dielectric losses. Similarly a light signal traveling
through an optical fiber suffers attenuation due to scattering and absorption. In long cable
runs, repeaters are used to periodically regenerate and strengthen the signal.
BRIDGE
BRIDGE: This is device filters data traffic at a network boundary. Bridges reduce the
amount of traffic on a LAN by dividing it into two segments.
ADAVANTAGES OF BRIDGE
 Bridges are self configuring.
 Primitive bridges are often inexpensive.
 Reduce size of collision domain by micro segmentation in non switched
networks.
 Transparent to protocols above the MAC layer.
 Allows the introduction of management performance information and access
control.
 LANs interconnected are separate and physical constraints such as number of
stations, repeaters and segment length.

DISADVANTAGES OF BRIDGE
 Does not limit the scope of broadcasts.
 Does not scale to extremely large networks.
 Buffering introduces store and forward delays - on average traffic destined for
bridge will be related to the number of stations on the rest of the LAN.
 Bridging of different MAC protocols introduces errors.
 Because bridges do more than repeaters by viewing MAC addresses, the extra
processing makes them slower than repeaters.
 Bridges are more expensive than repeaters.
FUNCTIONS OF BRIDGE
Collision
A network connects a number of computers together with one cable. The data passed
over the cable is an electronic pulse that travels the length of the wire. More than one
message pulsing on the cable would merge and interfere with each other. Only one device
can transmit at any one time. If a network connects a large number of computers, each
would have to wait a long time to get a turn applying data to the line. The main reason for
segmenting networks is to reduce the number of devices connected to the same wire and
thus reduce the wait time for transmission. A network bridge unites these segments.
Installation
Bridges operate with MAC addresses. On being introduced to a network, the bridge
learns the MAC addresses of the devices on each segment to which it connects. It then
keeps a table of these locations. The MAC address is the physical address of a computer
and is hard-coded onto the computer's network adapter.
Operation
Once the bridge has compiled its filtering table it operates by listening to the data packets
traveling on each segment. If it receives a data packet where the source and destination
addresses are on the same segment, it ignores it. This is called ''filtering." If the source
and destination of the packet are on different segments, it passes the packet through to the
segment containing the destination computer.

GATEWAY
A gateway is a device used to connect networks using different protocols. Gateways
operate at the network layer of the OSI model. In order to communicate with a host on
another network, an IP host must be configured with a route to the destination network. If
a configuration route is not found, the host uses the gateway (default IP router) to
transmit the traffic to the destination host.
FUNCTIONS OF GATEWAY
 A gateway can be implemented in software, hardware and some time as a
mixture of together. There are lots of equipment’s and techniques which
are being processed such as voice and data communication.
 The gateways are the best option to achieve the multimedia
communications between dissimilar networks because every network has
different protocol and characteristics.
 Gateways are also a key mechanism of any telephony communications.
Gateway is offering bridge between telephone network and internet.
 For real time communication gateway supporting audio conversion and
carry out extinction and call setup. Gateway also controls the processing
information across the network which contains information about to set up
the actual end to end call.
 A network gateway work like a firewall and filters packets. It also
separates corporate network as intranet from a public network.
 A gateway may also install on a stand-alone device. A gateway performs
as the interface between local and wide area protocols such as TCP/IP on
the Internet.
 A gateway supervises its client devices, gather their data and execute other
task. Gateway devices allow net client to access a variety of computer
networks.

 Gateway is also offering on-line services exclusive of having a preceding
service agreement or a continuing association with the service supplier.
ADVANTAGES OF GATE WAY
 Low maintenance and installing cost.
 Reliable routing experience.
 Multiple numbers of connections is possible unlike usage of general purpose
computers.
DISADVANATAGES OF GATEWAY
 Troubleshooting is hard.
 Easily be overload and slow down communication.
References

 James, F.K., Keith, W.R.(2010),Computer Networking A Top-Down
Approach, Pearson Education Inc., U S A.
 Peterson, L.L., Davie, B.S., (2007), Computer Networks A systems Approach,
Elsevier, Inc., California, USA.
 Groth, D., (2002), Network+, Sybex, Inc., Alameda, California, USA.
 Sosinsky, B., (2009), Networking Bible, Wiley Publishing, Inc., Indianapolis,
Indiana, USA.
 Gallo, M.A., Hancock, W.M.,(2002), Networking Explained, Butterworth-
Heinemann, Woburn, Massachusetts, USA.
 wikipedia.com, google.com, time.com, bbc.com, twitter.com.

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