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Assignment # 02:
Solve the following:
Question # 52:
In a class A subnet, we know the IP address of one of the hosts and the mask as given
below:
IP Address: 25.34.12.56
Mask: 255.255.0.0
What is the first address (Network Address)?
Solution:
We can also write:
IP = 00011001.00100010.00001100.00111000
Mask = 11111111.11111111.00000000.00000000
Perform AND operation of IP & Mask we get.
00011001.00100010.00001100.00111000
11111111.11111111.00000000.00000000
00011001.00100010.00000000.00000000 25.34.0.0
So the network address is:
Network Address: 25.34.0.0
Question # 53:
In a class B subnet, we know the IP address of one of the hosts and the mask as given
below:
IP Address: 125.134.112.66
Mask: 255.255.224.0
What is the first address (Network Address)?
Solution:
We can also write:

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IP = 01111101.10000110.01110000.01000010
Mask = 11111111.11111111.11100000.00000000
Perform AND operation of IP & Mask we get.
01111101.10000110.01110000.01000010
11111111.11111111.11100000.00000000
01111101.10000110.01100000.00000000 125.134.96.0
So the network address is:
Network Address: 125.134.96.0
Question # 54:
In a class C subnet, we know the IP address of one of the hosts and the mask as given
below:
IP Address: 192.44.82.16
Mask: 255.255.255.192
What is the first address (Network Address)?
Solution:
We can also write:
IP = 11000000.00101100.01010010.00010000
Mask = 11111111.11111111.11111111.11000000
Perform AND operation of IP & Mask we get.
11000000.00101100.01010010.00010000
11111111.11111111.11111111.11000000
11000000.00101100.01010010.00000000 192.44.82.0
So the network address is:
Network Address: 192.44.82.0

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Define the following terms:
Hub:
Hub is common connection point for devices in a network. Hubs are commonly used to
connect segments of a LAN. A hub contains multiple ports. When a packet arrives at one port, it
is copied to the other ports so that all segments of the LAN can see all packets.
A passive hub serves simply as a conduit for the data, enabling it to go from one device (or
segment) to another. So-called intelligent hubs include additional features that enable an
administrator to monitor the traffic passing through the hub and to configure each port in the
hub. Intelligent hubs are also called manageable hubs.
A third type of hub, called a switching hub, actually reads the destination address of each packet
and then forwards the packet to the correct port.
Figure 1: Hub Representation:
Switch:
A network switch is a small hardware device that joins multiple computers together within
one local area network (LAN). Technically, network switches operate at layer two (Data Link
Layer) of the OSI model.
Network switches appear nearly identical to network hubs, but a switch generally contains more
intelligence (and a slightly higher price tag) than a hub. Unlike hubs, network switches are
capable of inspecting data packets as they are received, determining the source and destination
device of each packet, and forwarding them appropriately. By delivering messages only to the
connected device intended, a network switch conserves network bandwidth and offers generally
better performance than a hub.
As with hubs, Ethernet implementations of network switches are the most common. Mainstream
Ethernet network switches support either 10/100Mbps Fast Ethernet or Gigabit Ethernet
(10/100/1000) standards.
Different models of network switches support differing numbers of connected devices. Most
consumer-grade network switches provide either four or eight connections for Ethernet devices.
Switches can be connected to each other, a so-called daisy chaining method to add progressively

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Router:
Routers are small physical devices that join multiple networks together. Technically, a router is a
Layer 3 gateway device, meaning that it connects two or more networks and that the router
operates at the network layer of the OSI model.
Home networks typically use a wireless or wired Internet Protocol (IP) router, IP being the most
common OSI network layer protocol. An IP router such as a DSL or cable modem
broadband joins the home's local area network (LAN) to the wide-area network (WAN) of the
Internet.
By maintaining configuration information in a piece of storage called the routing table, wired or
wireless routers also have the ability to filter traffic, either incoming or outgoing, based on the IP
addresses of senders and receivers. Some routers allow a network administrator to update the
routing table from a Web browser interface. Broadband routers combine the functions of a router
with those of a network switch and a firewall in a single unit.
Figure 3: Router Example.
Figure 2: Switch & Hub Difference.

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Modem:
A modem modulates outgoing digital signals from a computer or other digital device to
analog signals for a conventional copper twisted pair telephone line and demodulates the
incoming analog signal and converts it to a digital signal for the digital device.
In recent years, the 2400 bits per second modem that could carry e-mail has become obsolete.
14.4 Kbps and 28.8 Kbps modems were temporary landing places on the way to the much
higher bandwidth devices and carriers of tomorrow. From early 1998, most new personal
computers came with 56 Kbps modems. By comparison, using a digital Integrated Services
Digital Network adapter instead of a conventional modem, the same telephone wire can now
carry up to 128 Kbps. With Digital Subscriber Line (DSL) systems, now being deployed in a
number of communities, bandwidth on twisted-pair can be in the megabit range.
Figure 4: Modem Demonstration.
Host:
A network host is a computer connected to a computer network. A network host may offer
information resources, services, and applications to users or other nodes on the network. A
network host is a network node that is assigned a network layer host address.
Computers participating in networks that use the Internet Protocol Suite may also be called IP
hosts. Specifically, computers participating in the Internet are called Internet hosts, sometimes
Internet nodes. Internet hosts and other IP hosts have one or more IP addresses assigned to their
network interfaces. The addresses are configured either manually by an administrator,
automatically at start-up by means of the Dynamic Host Configuration Protocol (DHCP), or
by stateless address auto configuration methods.
Every network host is a physical network node (i.e. a network device), but not every physical
network node is a host. Network devices such as modems, hubs and network switches are not
assigned host addresses (except sometimes for administrative purposes), and are consequently
not considered as network hosts. Devices such as network printers and hardware routers have IP

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addresses, but since they are not general-purpose computers, they are sometimes not considered
as hosts.
Network hosts that participate in applications that use the client-server model of computing are
classified as server or client systems. Network hosts may also function as nodes in peer-to-peer
applications, in which all nodes share and consume resources in an equipotent manner.
Server:
A network server is a computer designed to process requests and deliver data to other (client)
computers over a local network or the Internet.
Network servers typically are configured with additional processing, memory and storage
capacity to handle the load of servicing clients. Common types of network servers include:
Web servers
proxy servers
FTP servers
Online game servers
Numerous systems use this client / server networking model including Web sites and email
services. An alternative model, peer-to-peer networking enables all computers to act as either a
server or client as needed.
Figure 5: Server & Host/Client Representation.

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Question:
What is fundamental difference between the circuit switching and packet switching?
Tabulate their advantages and disadvantages.
Packet Switching Vs Circuit Switching:
Packet-switched and circuit-switched networks use two different technologies for sending
messages and data from one point to another.
Each has their advantages and disadvantages depending on what we are trying to do.
Packet Switching Circuit Switching
1. In packet-based networks, the message
gets broken into small data packets.
These packets are sent out from the
computer and they travel around the
network seeking out the most efficient
route to travel as circuits become
available. This does not necessarily
mean that they seek out the shortest
route.
2. Each packet may go a different route
from the others.
3. Each packet is sent with a ‘header
addresses. This tells it where its final
destination is, so it knows where to go.
4. The header address also describes the
sequence for reassembly at the
destination computer so that the packets
are put back into the correct order.
5. One packet also contains details of how
many packets should be arriving so that
the recipient computer knows if one
packet has failed to turn up.
6. If a packet fails to arrive, the recipient
computer sends a message back to the
computer which originally sent the data,
asking for the missing packet to be resent
7. Message is broken up into segments
(packets).
8. Each packet carries the identification of
the intended recipient, data used to assist
in data correction and the position of the
1. Circuit switching was designed in 1878
in order to send telephone calls down a
dedicated channel. This channel
remained open and in use throughout the
whole call and could not be used by any
other data or phone calls.
2. There are three phases in circuit
switching:
Establish
Transfer
Disconnect
3. The telephone message is sent in one go,
it is not broken up. The message arrives
in the same order that it was originally
sent.
4. In modern circuit-switched networks,
electronic signals pass through several
switches before a connection is
established.
5. During a call, no other network traffic
can use those switches.
6. The resources remain dedicated to the
circuit during the entire data transfer and
the entire message follows the same path.
7. Circuit switching can be analogue or
digital
8. With the expanded use of the Internet for
voice and video, analysts predict a
gradual shift away from circuit-switched
networks.

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packet in the sequence.
9. Each packet is treated individually by the
switching centre and may be sent to the
destination by a totally different route to
all the others.
10. It is easier to double the capacity of a
packet switched network than a circuit
network –
11. Advantages:
Circuit is dedicated to the call – no
interference, no sharing
Guaranteed the full bandwidth for
the duration of the call
Guaranteed Quality of Service
12. Dis-Advantages.
Under heavy use there can be a
delay
Data packets can get lost or become
corrupted
Protocols are needed for a reliable
transfer
Not so good for some types data
streams e.g real-time video streams
can lose frames due to the way
packets arrive out of sequence.
9. A circuit-switched network is excellent
for data that needs a constant link from
end-to-end. For example real-time video.
10. A circuit network is heavily dependent on
the number of channel available.
11. It is expensive to expand a circuit
switching system.
12. Advantages:
Security
Bandwidth used to full potential
Devices of different speeds can
communicate
Not affected by line failure (re-
diverts signal)
Availability – do not have to wait
for a direct connection to become
available
During a crisis or disaster, when the
public telephone network might
stop working, e-mails and texts can
still be sent via packet switching
13. Dis-Advantages.
Inefficient – the equipment may be
unused for a lot of the call, if no
data is being sent, the dedicated line
still remains open
Takes a relatively long time to set
up the circuit
During a crisis or disaster, the
network may become unstable or
unavailable.
It was primarily developed for
voice traffic rather than data traffic.