Network and Security: Layers, Multiplexing, and Error Control Mechanisms

This article provides an overview of network security, including the different layers such as the application, internet, and physical layers. It also covers multiplexing mechanisms, error control, and other topics such as routers, MAC addresses, Ethernet headers, TCP window size, and cellular networks.

NETWORK AND SECURITY
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Introduction
Network security are the procedures and practices aimed towards the protection of a network and
its data from malicious and unauthorized access. The activities protected against include access to
data, modification of the data and misuse of the data such as deletion of part or whole of the data
and network control mechanisms such as denial of service. Network security involves policies and
practices managed through the responsibility of a network admin. The network access is controlled;
identification procedures are utilized such as log in credentials or a passphrase. The network is
categorized into several layers, application, internet and the physical layer discussed in the text.
Application layer.
The application layer provides the interface from which the users can access the services provided
by the network such as web browsing, email services and social media. The application layer if
formed by platform specific applications that have the ability to establish and utilize connections via
the network, the applications are installed on the devices, phones and computers. There are
different architectures of the application layer:
The server-client architecture: the server authenticates the client and allows the client access
information contained within the server such as storage or computing. The client uses the
application layer to access the server.
Peer-peer architecture: in this model of connection, either device connected can provide
information to the other and therefore act in the capacity of the server or client depending on the
direction of data transfer.
In a more categorical classification, the application layer can be described as host-based or cloud-
based. Web browsers and emails are used to illustrate examples of the application layer.
Internet layer:
In this layer, the address resolution protocol defines the MAC address of the devices that are
connected to the network. In the attempt to illustrate the address resolution protocol, the following
commands are used:
The arp-a is used to view the cache in the address resolution protocol.
Since the ip is the true address of an entry into the network, the command arp-d ip is used to delete
an entry.
The command arp-d* is used to delete all the entries in the address resolution protocol.
Reviewing the data link, the commands were demonstrated on a computer running on the Linux
platform. The network layer is used for the transmission of data and communication between the
devices connected. The ipv4 and ipv6 are used in the network layer.
Physical layer.
The physical layer is the connection in an existing network of the connected devices. The layer is
defined by the Manchester encoding, multiplexing, transmission media and the data flow of Analog
or digital data.

Analog data can be converted into digital data and transmitted to digital computers for processing
or storage.
The transition of bits in the periods represent binary values in the Manchester encoding.
The flow of data in the network is allowed through three different mechanisms, full duplex, simplex
and half duplex. The full duplex data flow involves the transmission of data in either directions of the
network at the same time, half duplex allows for data to be send in either direction but one direction
at ago while the simplex only permits the flow of data in one direction.
Multiplexing is the process where the data channels is divided into multi data channels to allow
faster transmission of the data. The process involves splitting frequency, wavelength and time into
frequency, wavelength and time multiplexing respectively.
The transmission media is the physical environment through which data transmission within the
network is carried from one device to another. The media includes cables, air and vacuum. The
different media are coaxial cables, microwaves and radio waves, optic cables etc.
Topic 4.
Question 5.
The multiplexing mechanisms in the LCC sublayer within a multipoint network provides the error
control mechanism through provision of repetitive requests automatically with the flow control and
management.
Question 7.
To be able to connect to different physical networks, routers are made with several network
interface data cards that help in the reduction of the redundancy in the network and data. In the
event that one NIC is corrupted, the other functions in its place to reduce data redundancy.
Question 19.
During the internet connection, the MAC address is successfully mapped with the internet protocol,
and an entry, that is new, is added to the address resolution protocol. The addition of entries is
dynamic to allow static entries to be added. The MAC address, using a predetermined time, can be
removed from the address resolution protocol using a set time depending on the disconnection
status of the network.
Question 20.
The header of the Ethernet is modified following the addition of a new address on the router to send
the data packets to the new destination.
Topic 6.
Question 5.
Located from 0 to 65535, storing port number destinations are counted and therefore one is added
to the maximum value 65535 to determine the number of bits to be used as storing port destination
number 65536.
Question 8.

A new port is allocated when a new tab is opened on the web browser and a network connection is
attempted each time. Because the data packets are labelled specifically for each port, the data is not
interrupted nor modified.
Question 14.
The handshake process is carried in 3 steps.
The steps are:
The client attempts a connection to the server via the network.
The server acknowledges the connection by giving a feedback.
The client acknowledges the response from the server.
Question 15.
The TCP window size field implements the flow control. The client specifies the maximum byte that
can be received without acknowledgment, the receiver meanwhile slows or stops data sending
through delaying the acknowledgement.
Topic 8.
Question 5.
Type 1 virtualization products are found on the firmware while type 2 products are located on the
operating system.
Question 8.
1G cellular networks supported only voice and had a frequency of 30Hz.
2G networks allowed switching between voice and data with the support of voice, data, short
messaging and multimedia messaging.
3G supports high data speeds basing on the CDMA technology.
4G allows very high data transfer speeds and mostly utilizes the LTE technology based on IP.
Question 9.
To distribute the cellular network over a wide geographical area, cells are used.
The mobile switching centre controls and manages the network interfaces and telephone services
allocation to the public.
Base station is the network’s communication point that is fixed.
Question 10.
The mobile switching centre manages and controls the user devices allowing them to shift from one
cell to another. The base station then receives the new traffic after changing from one cell to the
other.