SEM VI Computer Networks laboratory

Experiment No.: Date:

Title: Study of various Hardware and Software Network components.

Aim: To study various components in computer communication networks.

Learning objectives: At the end of this experiment, students will able to

 Identify and Define essential components of networks.
 Distinguish between the various interfacing components and
the network layers in which they are working.

Theory:
A system that carries a commodity between 2 or more entities is called a network.
There are so many networks in our daily life like transport network, electrical network,
computer network…etc. So a computer network is a network consists of devices (often
referred to as nodes) connected by media links. Computer networks share common devices,
functions, and features including servers, clients, transmission media, shared data, and other
hardware and software resources. A detailed description of those hardware and software
devices is given below.
Servers - Servers are computers that hold shared files, programs, and the network operating
system. Servers provide access to network resources to all the users of the network. There are
many different kinds of servers, and one server can provide several functions. For example,
there are file servers, print servers, mail servers, communication servers, database servers,
print servers, fax servers and web servers, to name a few.
Clients - Clients are computers that access and use the network and shared network resources.
Client computers are basically the customers (users) of the network, as they request and receive
services from the servers

Transmission Media - Transmission media are the facilities used to interconnect

computers in a network, such as twisted-pair wire, coaxial cable, and optical fiber cable.
Transmission media are sometimes called channels, links or lines.
Hub-Hubs are used to build a LAN by connecting different computers in a star/hierarchal
network topology, the most common type on LANs now a day. A hub is a very simple (or dumb)
device, once it gets bits of data sent from computer A to B, it does not check the destination,
instead, it forwards that signal to all other computers (B, C, D…) within the network. B will then
pick it up while other nodes discard it. This amplify that the traffic is shared. There are mainly
two types of hubs:

 Passive: The signal is forwarded as it is (so it doesn’t need power supply).

SEM VI Computer Networks laboratory

 Active: The signal is amplified, so they work as repeaters. In fact they have been called
multiport repeaters. (use power supply)
Hubs can be connected to other hubs using an uplink port to extend the network. Hubs work on
the physical layer (lowest layer). That’s the reason they can’t deal with addressing or data
filtering.

Switch-Switches on the other hand are more advanced. Instead of broadcasting the frames
everywhere, a switch actually checks for the destination MAC address and forward it to the
relevant port to reach that computer only. This way, switches reduce traffic and divide the
collision domain into segments, this is very sufficient for busy LANs and it also protects
frames from being sniffed by other computers sharing the same segment. They build a table
of which MAC address belongs to which segment. If a destination MAC address is not in the
table it forwards to all segments except the source segment. If the destination is same as the
source, frame is discarded. Switches have built-in hardware chips solely designed to perform
switching capabilities, therefore they are fast and come with many ports. Sometimes they are
referred to as intelligent bridges or multiport bridges. Different speed levels are supported.
They can be 10 Mb/s, 100 Mb/s, 1 Gb/s or more.
Bridge-Bridges are used to extend networks by maintaining signals and traffic. They are on
the data link layer so in principle they are capable to do what switches do like data filtering
and separating the collision domain, but they are less advanced. They are known to be used to
extend distance capabilities of networks. In a comparison with switches, they are slower
because they use software to perform switching. They do not control broadcast domains and
usually come with less number of ports.
Routers-They are used to connect different LANs or a LAN with a WAN (e.g. the internet).
Routers control both collision domains and broadcast domains. If the packet’s destination is
on a different network, a router is used to pass it the right way, so without routers the internet
could not functions. They use NAT (Network Address Translation) in conjunction with IP
Masquerading to provide the internet to multiple nodes in the LAN under a single IP address.
Now a day, routers come with hub or switch technology to connect computers directly. They
work on the network layer so they can filter data based on IP addresses. They have route
tables to store network addresses and forward packets to the right port.
Gateways-They are very intelligent devices or else can be a computer running the
appropriate software to connect and translate data between networks with different protocols
or architecture, so their work is much more complex than a normal router. For instance,
allowing communication between TCP/IP clients and IPX/SPX or AppleTalk. Gateways
operate at the network layer and above, but most of them at the application layer. The term
Gateway is used to refer to routers in some articles so beware. In this case, the router has
SEM VI Computer Networks laboratory

gateway software. And Default Gateway is used to refer to the node (e.g. router) connecting
the LAN to the outside (e.g. internet).
Repeaters- They are simple devices that work at the physical layer of the OSI. They
regenerate signals (active hubs does that too).There is an important rule to obey while using
repeaters/hubs to extend a local network and is called the 5-4-3 rule or the IEEE way. The
rule forces that in a single collision domain there shouldn’t be more than 5 segments, 4
repeaters between any two hosts in the network and only 3 of the segments can be populated
(contain user connections).This rule ensures that a signal sent over the network will reach
every part of it within an acceptable length of time. If the network is bigger, the collision
domain can be divided into two parts or more using a switch or a bridge.
Modem- It is a contraction of the terms modulator and demodulator. Modems perform a
simple function: They translate digital signals from a computer into analog signals that can
travel across conventional phone lines. The modem modulates the signal at the sending end
and demodulates at the receiving end. Modems provide a relatively slow method of
communication. In fact, the fastest modem available on the market today has a maximum
speed of 56kbps, compare that to the speed of a 10Mbps network connection, and it is found
that the modem is approximately 180 times slower. That makes modems okay for browsing
web pages or occasionally downloading small files but wholly unsuitable for downloading
large files. As a result, many people prefer to use other remote access methods, including
ISDN and DSL access.

Network Interface card— They are sometimes called NIC—are the mechanisms by
which computers connect to a network. NICs come in all shapes and sizes, and they come in
prices to suit all budgets. The NIC prepares (formats) and sends data, receives data, and
controls data flow between the computer and the network. On the transmit side, the NIC
passes frames of data on to the physical layer, which transmits the data to the physical link.
On the receiver's side, the NIC processes bits received from the physical layer and processes
the message based on its contents

Wireless access points-This referred to as either WAPs or wireless APs, are a transmitter
and receiver (transceiver) device used for wireless LAN (WLAN) radio signals. A WAP is
typically a separate network device with a built-in antenna, transmitter, and adapter. WAPs
use the wireless infrastructure network mode to provide a connection point between WLANs
and a wired Ethernet LAN. WAPs also typically have several ports allowing a way to expand
the network to support additional clients. Depending on the size of the network, one or more
WAPs may be required. Additional WAPs are used to allow access to more wireless clients
and to expand the range of the wireless network. Each WAP is limited by a transmission
SEM VI Computer Networks laboratory

range; the distance a client can be from a WAP and still get a useable signal. The actual
distance depends on the wireless standard being used and the obstructions and environmental
conditions between the client and the WAP.

Firewalls-Today, firewalls are an essential part of a network’s design. A firewall is a

networking device, either hardware or software based, that controls access to your
organization’s network. This controlled access is designed to protect data and resources from
outside threat. To do this, firewalls are typically placed at entry/exit points of a network. For
example, a firewall might be placed between an internal network and the Internet. After the
firewall is in place, it can control access in and out of that point. Although firewalls typically
protect internal networks from public networks, they are also used to control access between
specific network segments within a network.

Conclusion: