Computer Networks

This document provides information on various topics related to Computer Networks such as OSI model, TCP, UDP, IP addressing, routing protocols, and more. It includes explanations, examples, and comparisons to help understand the concepts better. The document also mentions the different types of assignments and their solutions available on Desklib for Computer Networks.

Running Head: COMPUTER NETWORKS 0 | P a g e
Computer Networks
Individual Task
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1.a Open Systems Interconnect (OSI) model is having seven layers, which are application,
session, presentation, transport, network, data link and physical layer. Host A is sending a
request to the Hub-B for accessing a webpage form the Server F. Host A and Hub B are
connected with physical layer technology, which is Ethernet. Hub-B accepts the request at
physical layer, and forwards it to the Router-C. therefore, these devices are at different layers of
the OSI model, such as Hub-B is at data link layer, Router-C is ate Network Layer, Router-D at
Network Layer, Switch-E at data link layer.
1.b Message size is 2000 bytes. Header size is 200 bytes for each layer. Therefore, total header
size is 1200 bytes. Total size of header and message is 3200 bytes.
So, (1200/3200)*100 = 37.5 %

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1.c Encapsulation is process in which message is added some bytes for information about the
data and protocols for the understanding the control and data flow. Each layer is having
separated work, such as network layer is used for the node-to-node delivery of the packet.
Therefore, each layer is adding the header in the main message for understand about the packet.
It is like postal services.
1.d client-server model is having a centralized computer, which manage all the other systems.
Client-server model is stable, as it is responding clients for their request. Client-server model is
more scalable, as new client is easily added in the system. Security is high in the Client server
model as it is having access controls for each client separated. Performance of client-server
model is high, as server is dedicated for all the clients. Backup feature is so important for the
safety of the data. It is better in the client-server network model.
1. e a network is required proper addressing of the computer systems. Computer systems are
connected than they are required IP addresses for each system. So, according to choose address
for networking, such as 192.168.10.1 for group of 254 computer systems with a subnet mask,
which is 255.255.255.0. It is also possible by the DHCP.

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Source: (study-ccna.com, 2018)
TCP is having 3-way handshake in which host send a request to the server. Than server send a
response with acknowledgement. In the end, host send the acknowledgement of the connection
establishment to the server as shown in below figure.
Source: (study-ccna.com, 2018)
For closing the connection host send a request as FIN as shown in the below figure.
Source: (study-ccna.com, 2018)

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2.b TCP is reliable protocol as it is taking acknowledgement of the packet. Few features make it
more reliable. TCP is providing reliable data transfer. It uses sequence number for the segments.
It provides flow control and error control, which makes it more reliable. It is having connection-
oriented service. TCP is more flexible than other protocols. It is sending data in the ordered way.
It retransmits the lost packets. It is also discarding duplicate packets.
1. TCP is reliable protocol and UDP is unreliable protocol
2. TCP is having sequencing of segments and acknowledgements but UDP is not having it.
2.d i Data in the first segment is 1910-1010 = 900
2.d ii Acknowledgement number is 1010
2.d.iii The value of rwnd = 3500-1000 = 2500.
Host B can receive only 2500 bytes of data before overflowing its buffer. Host B advertises this
value in its next segment to A.

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Routing protocols are needed for the transfer data from a dedicated route with a proper security.
It is specifies about the communication between the routers for distributing data and selecting
routes for data transfer (FS.COM, 2018). Routing Information Protocol (RIP) is follows the
distance vector routing protocol and Open Shortest Path First is follows link state routing
protocol. RIP is having slow convergence and OSPF is having fast convergence. RIP uses
Bellman-ford algorithm for routing and OSPF uses Dijkstra’s algorithm for routing
(techdifferences.com, 2017).

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IPv4 is these three basic characteristics, which are as:
Connectionless: it is not establishing any connection before sending packets.
Unreliable: it provides best effort and it is not uses overhead for packet delivery.
Media Independent: it operates independently for carrying the data through the medium.

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Time to live is 8-bit field in the IPv4 version. It indicates the maximum number of hops in the
network, where datagram can take reach. If, value of time-to-live is equal to zero than packet is
discarded from the network. It is used for avoiding looping.
Type of service is 8 bits field in the IPv4 version. It is used for the Quality of Services (QoS).
i. Address class is C
ii. Subnet mask is 255.255.255.224
iii. 3 bits used for the managing the network from the host-id

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iv. These are following ranges of the IP addresses for the desired network:
All networks are having 30 hosts.
v. Total number of subnet hosts are 8
vi. Number of usable hosts are 30
vii. 192.168.10.1 - 192.168.10.30
Smaller LAN are more efficient comparatively a larger LAN in an organization. It is also helpful
for the extending the network. Smaller LAN’s are having less congestion. It is helpful to short
out the isolated network problems. Implementation of security is better in the smaller LAN.

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i. _ _ 1 _ 0 1 1 _ 0 1 0
Position 1 is having number of one’s in even number at the position 1,3,5,7,9,11, so it is 0
parity
Position 2 is having number of one’s in odd number at the position 2, 3,6,7,10,11 so it is
1 parity
Position 4 is having number of one’s in even at the position 4,5,6,7 so it is having 0 as
parity
Position 8 is having number of one’s in odd number at the position 8, 9,10,11,12 so it is 1
parity
ii. Bit stream transmitted to the channel is 01100111010.
iii. It is a good method for the one-bit error check code and it is based on the even and odd
parity.
iv. It is one-bit error correcting code so if number of bits change more than one than it is
failed to discover the error at the destination.
Frame check Sequence (FCS) is used for the error detection. There are different methods for the
error correction in the frame, such as hamming code, Cyclic Redundancy Check (CRC). There
are different standard for checking of the frame and data in the frame, such as CRC-32.
There is a different command according to the operating system. As an example, in windows arp
–a is a command to locate MAC address of the device. These are the steps for finding MAC
address (Mitchell, 2018).
First, ping the system by using ping command.

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Source: Author
i. Ping is a command for checking availability of the destination computer system. It is
used for checking communication path between the different systems in a network
(Fisher , 2018).
ii. tracert is a command for the finding path of a packet by which it transfers from source to
destination.
iii. route print command is used to view and manipulate the IP routing table.

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i. Bridge is the best device to connecting LAN of different buildings. Bridge is having a
good quality to forwarding of the packet in a selective manner.
ii. Switches are the best way to linking LAN segments in a building to control broadcast
traffic.
Spanning Tree Protocol (STP) is blocking the redundant links in a network for avoiding looping
problem.

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Source: (Yadav, 2018)
Application layer is providing interface to the network functions.
Presentation layer is converting machine independent data to machine independent data, where
bits become data.
Session layer is managing the logical connections between the applications.
Transport layer is providing end-to-end reliability of the packet delivery.
Network layer is responsible for the Intra and Inter networking as well as routing.

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Data link layer is providing a reliable direct point-to-point connection.
Physical layer is providing connection to all the nodes with the help of different types of media.
Encapsulation is process in which message is added some bytes for information about the data
and protocols for the understanding the control and data flow. Each layer is having separated
work, such as network layer is used for the node-to-node delivery of the packet. So, each layer is
adding the header in the main message for understand about the packet. It is like postal services.
Open Systems Interconnect (OSI) model is having seven layers, which are application, session,
presentation, transport, network, data link and physical layer. Host A is sending a request to the
Hub-B for accessing a webpage form the Server F. Host A and Hub B are connected with
physical layer technology, which is Ethernet. Hub-B accepts the request at physical layer, and
forwards it to the Router-C. therefore, these devices are at different layers of the OSI model,
such as Hub-B is at data link layer, Router-C is ate Network Layer, Router-D at Network Layer,
Switch-E at data link layer.

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1. HTTP
2. SMTP
3. Email Server 1
4. SMTP
5. Email server 2
6. POP/IMAP
7. HTTP
TCP is having sequencing of the segments and acknowledgements. Destination is arranging the
segments according to the sequence numbers and if any segment is lost. Source will be
retransmitting that packet. Therefore, it is more reliable as compared to UDP.
TCP takes into account the level of congestion in the network.
Congestion level determines the amount of data sent by a sender.

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It is not supporting broadcasting in the network.
It is using connection-oriented protocols, so congestion control is easy.
These are the basic difference between the TCP and UDP:
Source: Author
UDP is used in the different application, such as DHCP, DNS, SNMP, TFTP, VoIP and IPTV.
As an example, Skype is not required retransmission of the packets. If picture is little bit blur
than it is not a big issue for the clients (Stallings, 2007).

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i. Data in the first segment is 1110 – 110= 1000 bytes
ii. Acknowledgement number is 110
iii. 4000-2000 =2000
Host B can receive only 2000 bytes of data before overflowing its buffer. Host B
advertises this value in its next segment to A (Lammle, 2011).
Source: Author

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i. Type of service is an 8 bits field in the IPv4 version. It is used for the Quality of Services
(QoS).
ii. Time to live is an 8-bit field in the IPv4 version. It indicates the maximum number of
hops in the network, where datagram can take reach. If, value of time-to-live is equal to
zero than packet is discarded from the network. It is used for avoiding looping.
iii. Protocol is the set of rules for communication between the different devices in the
network. It is used for the data and control access of the devices (Kenneth C. Mansfield
& Antonakos, 2009).

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i. Address class is C
ii. Subnet mask is 255.255.255.224
iii. 3 bits used for the managing the network from the host-id
iv. These are following ranges of the IP addresses for the desired network:
All networks are having 30 hosts.
v. Total number of subnet hosts are 8
vi. Number of usable hosts are 30
vii. 192.168.10.1 - 192.168.10.30

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Smaller LAN are more efficient comparatively a larger LAN in an organization. It is also helpful
for the extending the network. Smaller LAN’s are having less congestion. It is helpful to short
out the isolated network problems. Implementation of security is better in the smaller LAN
(Henderson, 2003).
Frame check Sequence (FCS) is used for the error detection. There are different methods for the
error correction in the frame, such as hamming code, Cyclic Redundancy Check (CRC). There
are different standard for checking of the frame and data in the frame, such as CRC-32
(Forouzan, 2007).
i. _ _ 1 _ 0 1 1 _ 0 1 0

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Position 1 is having number of one’s in even number at the position 1,3,5,7,9,11, so it is 1
parity
Position 2 is having number of one’s in odd number at the position 2, 3,6,7,10,11 so it is
0 parity
Position 4 is having number of one’s in even at the position 4,5,6,7 so it is 1 parity
Position 8 is having number of one’s in odd number at the position 8, 9,10,11,12 so it is 0
parity
ii. Bit stream transmitted to the channel is 10110110010.
iii. It is a good method for the one-bit error check code and it is based on the even and odd
parity.
iv. It is one-bit error correcting code so if number of bits change more than one than it is
failed to discover the error at the destination.
Interface: W26
IP address Physical Address Type
W24 6287 Dynamic
W25 2566 Dynamic
W27 4959 Dynamic

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i. Bridge is the best device to connecting LAN of different buildings. Bridge is having a
good quality to forwarding of the packet in a selective manner.
ii. Switches are the best way to linking LAN segments in a building to control broadcast
traffic (Dye, et al., 2007).
Hubs are not intelligent device, but switches are intelligent. Switches are having virtual paths for
the data forwarding separately. Hub is using flooding for the packet transmission. Therefore,
congestion in the network is so high (Blanchet , 2010).

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Source: Author
Spanning Tree Protocol (STP) is blocking the redundant links in a network for avoiding looping
problem.
References
Blanchet , M., 2010. IP network node and middleware for establishing connectivity to both the
IPv4 and IPv6 networks.. Washington, Patent No. 7,657,642.
Dye, M., McDonald, R. & Rufi, A., 2007. Network Fundamentals, CCNA Exploration
Companion Guide. Indianapolis: Cisco press..
Fisher , T., 2018. Ping Command. [Online]
Available at: https://www.lifewire.com/ping-command-2618099
[Accessed 28 December 2018].
Forouzan, A. B., 2007. Data communications & networking. 8th ed. New Delhi: Tata McGraw-
Hill Education.
FS.COM, 2018. RIP vs OSPF: What Is the Difference?. [Online]
Available at: https://community.fs.com/blog/rip-vs-ospf-what-is-the-difference.html
[Accessed 28 December 2018].
Henderson, T. R., 2003. Host mobility for IP networks: a comparison. IEEE network, 17(6), pp.
18-26.
Kenneth C. Mansfield, J. & Antonakos, J. L., 2009. Computer Networking for LANS to WANS:
Hardware, Software and Security. 1 ed. Bostan(MA): Cengage Learning.
Lammle, T., 2011. CCNA Cisco Certified Network Associate Deluxe Study Guide. indiana: John
Wiley & Sons.

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Mitchell, . B., 2018. How to Use an IP Address to Find a MAC Address. [Online]
Available at: https://www.lifewire.com/find-a-mac-address-using-an-ip-address-818132
[Accessed 28 December 2018].
Stallings, W., 2007. Data and computer communications. 8th ed. New delhi: Pearson Education
India.
techdifferences.com, 2017. Difference Between RIP and OSPF. [Online]
Available at: https://techdifferences.com/difference-between-rip-and-ospf.html
[Accessed 28 December 2018].
Yadav, V., 2018. Learning the OSI Model. [Online]
Available at: https://codeburst.io/learning-the-osi-model-32b48cc55bdd
[Accessed 28 December 2018].