INF350 Computer Networks Assignment Solution: October 2016, Detailed

This document presents a comprehensive solution to an INF350 Computer Networks assignment. It begins by defining a communication network and its core components, relating these concepts to general systems theory. The solution then explores methods to enhance the throughput of communication channels and emphasizes the significance of communication networking standards. The assignment further delves into the comparison of the OSI and TCP/IP network reference models, elucidating their relationship to networking communication standards. Additionally, the solution explains the 802.3 standard, including calculations related to bit length in the original standard. Finally, the document addresses a problem concerning the fraction of network bandwidth occupied by headers in a multi-layered protocol hierarchy. The solution includes all calculations and references used to arrive at the answers.

infm 350 computer networks assignment
STUDENT NAME:
22 OCTOBER, 2016

1. Define “communications network” and discuss such a network’s component parts.
Relate these networks to general systems theory.
Answer: the communication network can be defined as an inter-connection of the devices in
which multiple devices which are connected to each other through the network send or
receive messages to or from each other. Its components are client, server and the connection
media. The server is the one which provides responses to the client queries and the client is
the machine from which the query is sent. For example a local computer is client and Google
acts as a server to answer the questions. The connection media are the wires and devices like
router, ISP etc. through which the message travels from client to the server. All these
together form a communication network. The network can be at a small scale like a LAN or
even at a global network like World Wide Web which is the interconnection of the smaller
networks, which form a larger network at the global level. The servers may be present
anywhere in the network and the message is sent to them for via the connection media and
then the servers responses back which are again sent back via connection media. In simple
language we call then source and destination devices. These devices send message to the
communication network, which follows certain rules to send the message through layer by
layer of the network and then to the destination device. Same process is followed when
message travels back from destination to the source. The network has multiple
communication layers and different devices work on different layers.
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2. The speed of digital signals through various communications media is limited by the laws
of physics. Discuss some of the methods used to increase the throughput of
communications channels.
Answer:
3. Describe and discuss the importance of communications networking standards.
Answer: as the word standard describes a set of rules of guidelines, the same way
communications networking standards are certain rules and guidelines that have designed
for the network and device that run on it. They are important because when the messages
travel from different layers of the network from one network to the other, and from one
device to the other, it is necessary for it to follow certain rules so that the message is
correctly delivered. Thus all layers work together following these standards all together.
As we see that technology is changing, thus to keep up with it, the network is required to
follow these standards. For example to send an image to receive one, http standard must
be followed.
4. Define and compare the OSI and TCP/IP network reference models. How are these
models related to networking communications standards?
Answer: OSI and TCP/IP are both different models that have been designed for
communication over the network. They have a framework in which certain rules have been
defined for the device communication and access over the different layers through which the data
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travels. These are used in network communication standard because they provide layered
architecture and rules for data transfer from one layer to the other. On these network layers
defined in them, the network standards applied. In simple words we can say that, since the data is
sent via devices and devices have to follow certain standards and the devices work on different
layers of the model, hence they are connected to the networking standards.
OSI(Open System Interconnection) TCP/IP(Transmission Control Protocol /
Internet Protocol)
It has a framework which follows a protocol
independent standard.
TCP/IP model framework is based on standard
protocols. These are the protocols on which
Internet has developed
It’s like a communication gateway between
the network and end user.
It rather acts as a communication protocol
The delivery of packets is done and
guaranteed by transport layer.
The transport layer does not guarantees the
packet delivery but is still considered reliable
It has a separate Presentation layer and
Session layer.
No separate Presentation layer or Session layer.
Network layer provides both connection
oriented service usually but can also provide
connectionless service.
Network layer provides connectionless service.
There is a problem related to fitting the
protocols in to the layers
Since based on protocols, hence no such
problem.
Protocols can be easily replaced with the
technological changes.
Replacement of the protocol is not easy.
Services, interfaces and protocols are
defined clearly and are distinct to each other.
Services, interfaces and protocols are not
separate due to protocol dependence.
It is made up of 7 layers It is made up of 4 layers
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5. What does the 802.3 standard describe? How long was a bit in the original 802.3
standard in meters? Use a transmission speed of 10 Mbps and assume the propagation
speed in coax is 2/3 the speed of light in a vacuum. (Source: Tanenbaum and Wetherall)
Show and explain all your work.
Answer: the 802.3 standard is the specification of Ethernet in the network. In other words we
can say that it can be considered as a system which is used for physical communication in the
network. The bit used to be 1m long in the original 802.3 standard.
The speed of light in coax = 200,000 km/sec
= 200 meters/μsec.
Given speed = 10 Mbps
 At 10 Mbps, time to transmit 1 bit = 0.1 μsec to transmit a bit.
 0.1 * 200 = 20
 Length of bit = 20 meters.
6. (5 points) A system has an n-layer protocol hierarchy. Applications generate messages
of length M bytes. At each of the layers, an h-byte header is added. What fraction of the
network bandwidth is filled with headers? (Source: Tanenbaum and Wetherall) Show
and explain all your work.
Answer:
According to the question,
Message length = M bytes
Header length = h bytes
Protocol layers = n
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 No. of Header bytes per packet = nh
Therefore, Total bytes per packet = message length + header bytes = (M+nh)
We know that Fraction of something is = fractional part / total
 Fraction of bandwidth filled with headers = header size / total size
= nh/(M+nh)
References
Anonymous. (n.d.). Network Standards (Data Communications and Networking). Retrieved from
what-when-how.com: http://what-when-how.com/data-communications-and-
networking/network-standards-data-communications-and-networking/
Burke, J. (2015). What is the difference between OSI model and TCP/IP other than the number
of layers? Retrieved from searchnetworking.techtarget.com:
http://searchnetworking.techtarget.com/answer/What-is-the-difference-between-OSI-
model-and-TCP-IP-other-than-the-number-of-layers
TANENBAUM, A. S. (2011). COMPUTER NETWORKS. Amsterdam, The Netherlands:
Prentice Hall.
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