Networks

This document discusses the use of Transmission Control Protocol (TCP) for packet tracking between two end hosts. It also explains the concept of selective acknowledgement in TCP transmission. Additionally, it provides an overview of Cascading Style Sheets (CSS) and its three types: inline, internal, and external.

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Question 1
Transmission Control Protocol (TCP) uses sequence and acknowledgment number to maintain
the packet tracking between two end hosts. It is a way to maintain record of the data in the
network. All the packets have delivered to both the end successfully. Sometimes, few packets are
missing in the network because of the fault in the network or anything else. Below diagram is
shows TCP connection between client and server (Certiology, 2018).
Source: ( Stretch, 2010)
In above diagram, client sends request to the server then server sends desired packets to the
clients as per request. In between, server sends four segments to the client. In addition, client is
missing segment -2 because of network issues. Therefore, it sends an AcK-1 to the server to
informing about segment loss (Cisco, 20018). However, server already sends segment-3 and
segment-4. Client does not accept the segment-3 and segment -4, as it is missing segment-2.
Client again sends an Ack-1 to the server then server sends all the remaining segments (Dye, et
al., 2007).

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It is a not proper way of data transfer. Therefore, selective acknowledgement concept is applied
for data transfer as shows in below diagram.
Source: ( Stretch, 2010)
In above diagram, Selective Acknowledgement (Sack) working process is showing with different
steps. It reduces the traffic of the network, as well as unnecessary retransmissions of the
segments. According to this approach, it is not necessary to sends all the packets again, as
previous segment is lost in the network (Forouzan, 2007). It is a way to reduces segment
retransmissions. If any segment is lost in the network then a Sack is send with an
acknowledgement packet. Therefore, no need to retransmission of packet, as they already
receives segments by client. It requires retransmission of selected lost segment to the client
( Stretch, 2010).
Selective acknowledgement is beneficial for handling flow control and congestion control. TCP
is used this thing to reduce retransmission rate of segments. Segments are losses because of
network faults. Therefore, it is not necessary to resend the already sends packets (Gapiński,
2014).
There are many packets, which are lost because of faulty internetworking devices. Therefore, it
is not necessary to send all those packet, which are sends after the lost packet. In network,

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different types of issues are occurred, such as attenuation, distortion, and noise. There are many
things in the network, which creates an issue for data transfer (Velte & Velte, 2013). Therefore,
it is big task to reduce packet losses. A basic task reduces data losses in the network and
increases the efficiency of the network. Computer networks are having many things to transfer
data from one source to destination. Mainly media is the reason for data losses, as data loss rate
is high in wireless media, because of medium and technology as compared to wired media
( Stallings, 2018).
TCP transmission is having best way to data transfer. However, it is uses connection-oriented
approach for data transfer. It is measured that, TCP is more reliable then UDP data transmission.
Data loss is a different thing but remedy after data loss is very important in data transfer
(Mitchell, 2018). Data communication is highly required in the present era with high efficiency
and security of data. Therefore, data losses are not tolerable in the data transmission (Sunshine,
2013). It is a common thing that, if any segment is already send to the client then it is not
necessary to resend it. Selective acknowledgement provides low rates of retransmission in the
TCP transmission of segments (Kenneth C. Mansfield & Antonakos, 2009).
Reliable transmission is requiring for data transmission and it is a way to handle packet loss in
data transfer. TCP transmission is reliable because of connection-oriented approach. Selective
acknowledgement approach is best way to reduce retransmission on already sends packets.
TCP transmission is best way to data transmission. Selective acknowledgement is best thing to
reduce the unnecessary transmission of the rest segment in the network. It improves the
performance of the channel as well as efficiency of the network. Traffic is also reducing in the
communication channel from the selective acknowledgement technique. It is a way to identify
the selected segment to resend to the receiver.
Data communication is not easy to maintain all the operation of the data transfer. Therefore, it is
necessary to improve the efficiency of the network through reduce unnecessary traffic of the
communication channel. It is necessary to reduce network faults because of traffic and technical
problems. However, physical damage is a huge issue in front of communication medium.

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Question 2
a. As per given details, it is mention in the table that nine subnet mark has been created. All
the details are based on the concept of networks (Hogg & Vyncke, 2008). It is based on
the network and host ids. There are many things to manage in deciding subnet marks
(Lammle, 2011). Subnet mask is based on the number of bits (Goldstein, 2017). Given
data is provided in the table.
Subnet mask Subnet mask in binary Number of
subnets
Number
of hosts
255.255.255.0 11111111 11111111 11111111 00000000 20 = 1 28 –2 =254
255.255.255.128 11111111 11111111 11111111 10000000 21 = 2 27 –2 =126
255.255.255.192 11111111 11111111 11111111 11000000 22 = 4 26 –2 =62
255.255.255.224 11111111 11111111 11111111 11100000 23 = 8 25 –2 =30
255.255.255.240 11111111 11111111 11111111 11110000 24 = 16 24 –2 =14
255.255.255.248 11111111 11111111 11111111 11111000 25 = 32 23 –2 =6
255.255.255.252 11111111 11111111 11111111 11111100 26 = 64 22 –2 =2
255.255.255.254 11111111 11111111 11111111 11111110 27 = 128 21 –2 =0
255.255.255.255 11111111 11111111 11111111 11111111 28 = 256 20 –2 =0
b. Nine-subnet mask has founded in the part (a). We can use seven subnets for creating
networks with hosts of different quantities. It is based on the number of bits. Class C is
having 8 bit for hosts (Darwich, 2011). Therefore, we can generate different subnet
masks. It is a way to create different subnets based on the requirement of the host
(Kivisaari, 2000).
c. In case of IPv6, 2 addresses are deducted because of zero is a network address and 255 is
broadcast address. Therefore, we cannot assign these addresses to the host. Every
network is having all zeros and all ones (Goldstein, 2017). Therefore, it is necessary to

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avoid those addresses to avoid ambiguity in the network. It is necessity to secure both the
addresses as they are having a special purpose in IPv4 configuration (Kivisaari, 2000).
d. CIDR notation for the 201.168.67.0 IP address is 201.168.67.0/25. In Classless Inter-
Domain Routing, mention number of bits after the IP address, such as 201.168.67.0/25.
Here, 25 is number of bits for network id. It is used for creating number of networks
(Tanenbaum, 2014). It is a type of super netting and it borrows bits from the network id.
There are many advantages of the CIDR, such as managing network with desired host’s
requirements. There is a best way to solve issues of classful addressing.

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Question 3
a.
Cascading Style Sheets (CSS) has created to decorate web pages through different types of
changes, such as colors, styles, and many others. It is a common term in the website designing,
as well as on the World Wide Web (WWW).
Hypertext Markup Language (HTML) uses for creation of web pages. This is a standard way to
design a website with fonts, hyperlinks, background colors, and graphic doodads. It is lengthy
process to decorate a website. CSS make it very easy to decorate a website. It provides different
things in separate files as well as in the file also for better understanding (Kumar, 2018).
CSS has divided in three types, which are as:
i. Inline CSS
ii. Internal CSS
iii. External CSS
Source: (Kumar, 2018)
Cascading Style Sheet is famous and popular think that is used in the web designing. It uses to
set the style in web pages that contain HTML elements. CSS is best for the web designing. It sets

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different things of a web page, such as, the font-family, color, font-size, background color and
many other things of a web page (Meinecke, 2018).
Inline CSS: it contains the CSS property in the body section attached with element.
Example:
<!DOCTYPE html>
<html>
<head>
<title>Inline Cascading Style Sheet web page </title>
</head>
<body>
<p style = "color:#009900;
font-size:50px;
font-style:italic;
text-align:center;">
MyExample Cascading Style Sheet </p>
</body>
</html>
Internal or Embedded CSS: it is used for single HTML document must be styled uniquely. It is
known as document level CSS. It is set within the HTML file in the head section.
Example:
<!DOCTYPE html>

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<html>
<head>
<title>Internal Cascading Style Sheet web page </title>
<style>
.main {
text-align:center;
}
.GFG {
color:#009900;
font-size:50px;
font-weight:bold;
}
.geeks {
font-style:bold;
font-size:20px;
}
</style>
</head>
<body>
<div class = "main">
<div class ="ME">MyExample Cascading Style Sheet </div>

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<div class ="me">A computer science portal for geeks</p>
</div>
</body>
</html>
External CSS: it contains separate Cascading Style Sheet file that contains only style property
with the help of tag attributes. All the CSS property should be written in a separate file with the
extension of .css. It should be linked to the HTML document using link tag. All style can be set
only once and that will be applied across web pages ( Kyrnin, 2019).
example.css
body {
background-color:powderblue;
}
.main {
text-align:center;
}
.GFG {
color:#009900;
font-size:50px;
font-weight:bold;
}
#me {
font-style:bold;
font-size:20px;
}
Below is the HTML file that is making use of the created external style sheet
 Link tag is used to link the external style sheet with the html webpage.

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 href attribute is used to specify the location of the external style sheet file.
<!DOCTYPE html>
<html>
<head>
<link rel="stylesheet" href="geeks.css"/>
</head>
<body>
<div class = "main">
<div class ="ME">MyExapmle</div>
<div id ="me"> Webpage for computer geeks </p>
</div>
</body>
</html>
There are many things to require changes to decorate a web page. It is necessary to manage
different things with the help of the external file. Most of the files are uses inline CSS. It is also
providing a better way to change all the stuff as per the requirement.
Here is an example of external CSS
<!DOCTYPE html>
<html>
<head>

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<link rel="stylesheet" type="text/css" href="mystyle.css">
</head>
<body>
<h1>Answer 3</h1>
<p> JokesCWK2-2018-19.html </p>
</body>
</html>
Here is external mystyle.css file code
body {
background-color: lightblue;
}
h1 {
color: navy;
margin-left: 20px;
}
Here is an example of inline CSS
<!DOCTYPE html>
<html>
<head>
<style>
body {

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background-color: linen;
}
h1 {
color: maroon;
margin-left: 40px;
}
</style>
</head>
<body>
<h1>Solution 3</h1>
<p>This is a JokesCWK2-2018-19.html file </p>
</body>
</html>
Here is an example of mixed CSS.
<!DOCTYPE html>
<html>
<head>
<link rel="stylesheet" type="text/css" href="mystyle.css">

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<style>
h1 {
color: orange;
}
</style>
</head>
<body>
<h1>JokesCWK2-2018-19.html</h1>
<p>The style of this document is a combination of an external stylesheet, and internal style</p>
</body>
</html>
<!DOCTYPE html>
<html>
<body>
<h1 style="color:blue;margin-left:30px;">JokesCWK2-2018-19.html</h1>
<p>example of inline CSS.</p>
</body>

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</html>
Here is an example of multiple styles.
<!DOCTYPE html>
<html>
<head>
<link rel="stylesheet" type="text/css" href="mystyle.css">
<style>
body {background-color: linen;}
</style>
</head>
<body style="background-color: lightcyan">
<h1>Multiple Styles Will Cascade into One Web page </h1>
<p>In this example, the background color is set inline, in an internal stylesheet, and in an
external stylesheet.</p>
<p>Try experimenting by removing styles to see how the cascading stylesheets work. (try
removing the inline first, then the internal, then the external)</p>
</body>
</html>

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b.
Inline CSS has the highest priority, as it is present in the web page itself then comes Internal or
document level followed by External CSS. External CSS has the least priority. A web page can
have different type of the CSS (Bakke, 2011). This order is followed, if a page is having different
types of CSS:
 Highest priority CSS is override all the CSS, as inline CSS has highest priority.
 Second is document level CSS or internal CSS that is override the external CSS.
 External CSS has applied if there is no internal and inline CSS is present in the web page.
Cascading Style Sheet is uses to make a web page better in looking wise. It makes required
changes based on the client requests as well as programmer and designer creativity. It is not
necessary to create webpage but it provides a different look of a page with creativity and
innovative things. There are many inbuilt templates are available in the market with latest
Cascading Style Sheet. It is a best process to make a webpage interactive with minor changes in
the Cascading Style Sheet.

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Question 4
Softwares are combinations of different programs. It is having source code that is based on the
particular language. Patents may have been created to secure innovation as well as to help
encourage them. However, they are regularly hindering it. Many small and big companies have
bought too many patents for different products and services to shake down companies.
They all are race of patents of their softwares and any other thing to taken competitive advantage
but it is not a proper used of this facility. It is a way to limit competition and it will provide
access to new tools, innovations, and knowledge.
Small business and individual inventors are also creating impossible things, which are requiring
patent system work in their favor. It is a defense from giant arsenals and litigation budgets.
Patent system is useful for the development and sharing of new technologies.
The U. S. Patent Office has decided about the patents distribution. They will provide patents only
granted to genuine inventions. In case of software patents, The U. S. Patent office has been
issued patents to basic technologies, such as:
1. Real-time, multiple-player games
2. Streaming of audio and video though the Internet
3. Look up barcodes using a network
4. All VoIP systems
All of these are serving as huge technologies in the field of computer science technology.
Multinational companies are having innovative innovation in their softwares as well as
processing of the project. However, there are many bad patents, such as patent on hyperlinks.
Many small business and individual innovators has created different things in their working
process but they are not as important as much they were required (Goldmann, 2010).
There is a lengthy battle between patent office and innovators for assigning process of patents. In
addition, there are many bad patents, which are facing troublesome lawsuits, licensing fees, as
well as stifled innovation (EFF, 2018).

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Patent office makes pressure on small businesses, individual innovators, and nonprofits in many
terms. They can take an amount between $5000 and $ 20,000 per patents to provide patent.
Small businesses are starting their processing, such as necessary paperwork. Patent litigation is
not a cheap process, as it is an arduous and expensive process for small businesses.
Many of innovators are already abandoning the system of patents, such as Free and Open Source
Software (FOSS) movement. There are many things, which are not requiring any protection. A
fear is always there to someone take patents for other work. Therefore, it is necessary to have a
record for the software work processes. Many of the software inventors are thinking that anyone
can attempt to patent the same technology. There are many things to require patents but it is not
necessary to patent all the things, which are not requiring any type of security. Therefore, Defend
Innovation has launched by the EFF.
Softwares are having a source code that is a pure code of a person or individual innovator. In
addition, a person or team is having a source code that is different from others. That code is also
generated through some types of software, which are also having patents. It is not necessary to
provide protection to every source code. It is a way to stop knowledge sharing processes.
Therefore, open sources technology is providing its source code to everyone without any cost.
Patent office has taken action against it already that they will provide protection only those
technologies, which is really having a good stuff. It is a way to stop bad patents and it reduces
unnecessary traffic in the field of patents. EFF has started a process to stop bad patents. There
are many organizations, which are providing their source code to change and innovate new
things based on the knowledge. They are also having societies for such types of work in which
individual innovators are sharing their personal knowledge with everyone. It is a way to handle
different things, without any fight.
EFF has provided their best efforts to stop patents for nonsense things. Patent means a valuable
thing in front of whole world. It is necessary to provide protection to software code but not
everyone that are not having a level. Most of the companies are having their patents to secure
their innovations. Therefore, it is not necessary to secure new things that are based on those
patents in the software field ( Samuels, 2013).

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