Networking and Security: Overview of OSI and TCP/IP Models

This report discusses computer networking, OSI and TCP/IP models, and their layers. It also covers topics such as Wireshark, virtualization, and network hardware.

A
Report
On
Networking and Security

Introduction
Computer Networking is a type of telecommunication network that incorporates a linked
network of various computing devices and is also a medium to share resources. This report
wholly discusses about how the connectivity is made among computing devices and systems.
It also includes a brief overview of layers of OSI model and TCP/IP referencing model that
makes this connectivity possible.
Lecture-1
This lecture describes how the data is transmitted over any network, starting from number
system which enables any computer to understand the inputs and translate the values to give
the desired output. There are four number system that are used in networking.
a. Decimal number system with base 10, it represents quantities and addresses IPv4
protocol. (Mirkovic, Dietrich, Dittrich, & Reiher, 2004, p.7).
b. Binary number system represents how the data is stored into the system and it can be
used to examine bits in data.
c. Hexadecimal number system addresses IPv6 protocols and represents relatively larger
quantities. Basically it is a shorthand way to write large binary numbers.
d. Octal number system is used for modifying Linux permissions.
Wireshark is a Protocol Analyser and thusly can catch the parallel information that
comprised arrange movement and after that dissect and show that information in approaches
to enable us to comprehend it. Wireshark is use all through the systems administration
industry as isn't just vital to us, yet in addition to arrange engineers around the world.
Virtualization supports server farms around the world. We are just worried about its
utilization as a work area client; anyway its venture into industry is significant.
Lecture-2
In this, operation of basic networking hardware like NIC, Hubs, Switches and routers is
discussed. In Circuit Switched systems a committed channel is set up before information
being sent. (Shin, 2010) The best case of a circuit exchanged system is the Plain Old
Telephone System (POTS) as utilized in numerous organizations and homes. Once the

circuit is set up, you and the individual on the opposite end of the phone successfully have a
wire interfacing the two phones for the span of the phone call. This course anyway is
basically worried about Packet Switched systems. Example of packet switched network is
ARPANET. It stands for Advanced Research Projects Agency Network. It incorporates both
packet switching and TCP/IP protocols. Earlier Interface Message Processors (IMPs) were
used to connect to network and nowadays routers fulfil the need.
Packet Switching is done in offices using Wifi, cables in homes, larger networks like
business or university networks using optical fibre. This devices are interconnected by NIC
cards, routers, network hubs etc. The data transmission over the network is based on two
network models i.e. OSI and TCP/IP model. These models can handle small packets of data.
For large amount of data transmission it has to be fragmented (at the beginning) and
reassembly at the destination. The transmission of data is described by these two network
models.
Lecture 3
OSI and TCP/IP referencing model is a virtual model that shows how the data is transmitted
over network. These two models have different number of layers. OSI has seven layers
whereas TCP/IP has 4 layers. (Hidalgo, Siu, Nemunaitis, Rizzo, Hammond, Takimoto,
Ferrante, 2001, p.7).
Application layer is common in both models. This layer is the user interface and enables user
to get access to interact with thousands of services and devices over the internet and on local
network. It has categories of interaction:
a. Client/server architecture- In this client request services from the server like a web client
request web pages from web servers.
b. Peer to peer architectures- In this, each machine in the system can go about as both a
server and a customer (at the same time if required). All machines (peers) can share
assets (document and printers) and can likewise get to any mutual asset.
c. Host based architectures- Each system has mainframe connected to terminals and this
mainframe performed all the processing.
d. Cloud based architecture- It can supply a scope of administrations to associations
including the processing stage, working frameworks and programming.

Lecture 4-
Data link layer is a network interface layer. The Data Layer only communicates with devices
on its local network. There are two sub layers of data link layer i.e. logical link layer (LLC)
and Media access control (MAC). LLC is the upper interface layer which allows IPv4, IPv6,
IPX and other transaction concurrently whereas MAC sends traffic to the network media and
receives traffic from the network media. Network Interface card have a 48 bit MAC address
and this address is used for communication. NIC cards are smart devices as it inspects every
packet on the local network. Media Access Control is worried about mediating access to the
system. In controlled access just a single station can transmit at once. Gadgets needing to
transmit must sit tight. Token Ring and FDDI are two cases that utilization this kind of
media get to control. This lecture involves other terms such as CSMA/CD, CSMA/CA and
ARP.
CSMA/CD- Carrier Sense Multiple Access with Collision Detection. This is the Media
Access Protocol utilized by Ethernet. Ethernet is the most broadly utilized Data Link strategy
for associating PCs and different gadgets to a network. This media get to technique enables
various PCs to all utilization a typical system media. One issue is that crashes can happen
when two machines attempt to send an Ethernet bundle at the same time.
CSMA/CA- Carrier Sense Multiple Access with Collision Avoidance. From multiple points
of view this Data Link convention works comparably to CSMA/CD anyway the stations
attempt to keep away from crashes by saving the system media. Before transmitting an
information outline a station can send a Request to send casing to the Wireless Access Point.
The Access Point sends a Clear to Send (CTS) edge to the remote network. The CTS holds
the system for the asking for station for a predefined time of time. The asking for station
sends the edge without dread of an impact.
ARP- System Operating Systems (like Windows and Linux) keep up a table in RAM (called
the ARP store) that contains the IP Address and MAC address of machines that have been
reached as of late.

Lecture 5
Address resolution protocol (ARP) decides the MAC address of a machine on the
neighbourhood connects with a particular IP address. It communicates message getting some
information about the IP address proprietor and if the framework reacts, MAC address is
known and is gone into ARP cache. (Zimmermann, 1980, p.7).
The Internet (Network) layer conveys arrange movement starting with one host then onto the
next. The two hosts are frequently isolated by long separations. It has a part of Sending the
bundle to the neighborhood switch and let it handle the remote conveyance of system
movement. Every gadget on an IP network requires an IP address. There are two sorts of IP
address: IPv4 and IPv6 respectively.
Network Address Translation (NAT) - The PCs (has) on most home systems utilized private
IP addresses (assigned by the DHCP server in the switch). Home system switches utilize
NAT to give Internet access to those hosts. (Fall, & Stevens, 2011, p.7).
DNS (Domain Name System) - Name goals of Internet names is dealt with by DNS. Name
goals is the way toward looking into the IP address of an Internet name, or for invert queries,
deciding the host name of a specific IP address.
Lecture 6
The transport layer terms is discussed in this lecture. It keeps up the exchange of information
bundles between the layers. Application regularly share expansive stream of information and
this layers breaks vast pieces of information into little measured fragments so the switches
can deal with them thus numerous applications can gain admittance to the system (this is
called multiplexing). At the goal, the divided information must be reassembled by the
vehicle layer once again into the organization sent by the sending application. This is called
reassembly. Reassembly may likewise include reordering in situations where bundles were
conveyed out of request. Transport layer has two conventions:
Client Datagram Protocol (UDP) gives essential transport administrations to arrange
applications. The UDP header determines the source and goal port numbers, the length of the
UDP header (in bytes) and a checksum. In UDP correspondences no checking is done to
guarantee parcels arrive securely. TCP is an association arranged convention. It ensures
dependable and all together conveyance of information from sender to recipient.

Lecture 7
The first layer of both the models is physical layer. The data is transmitted over the network
in the form of analog and digital signals. Frameworks can likewise be classified by the
manner in which information streams between gadgets. Simplex framework can just send
information one way. Half-duplex framework permit information stream in both directions.
But just one way at any one time. (Forouzan & Fegan, 2002, p.7). Full duplex permits
information stream in the two bearings simultaneously. Further multiplexing is discussed as
it is an important part of physical layer. Multiplexing is utilized to isolate up an interchanges
channel so the channel can transmit numerous discussions at the one time. There are many
transmission media for transfer of data in physical layer that are unshielded twisted pair,
shielded twisted pair, coaxial cable, optical fibre etc.

References
Mirkovic, J., Dietrich, S., Dittrich, D., & Reiher, P. (2004). Internet Denial of Service: Attack and
Defense Mechanisms (Radia Perlman Computer Networking and Security).
Shin, D. H. (2010). The effects of trust, security and privacy in social networking: A security-
based approach to understand the pattern of adoption. Interacting with
computers, 22(5), 428-438.
Hidalgo, M., Siu, L. L., Nemunaitis, J., Rizzo, J., Hammond, L. A., Takimoto, C., ... & Ferrante,
K. (2001). Phase I and pharmacologic study of OSI-774, an epidermal growth factor
receptor tyrosine kinase inhibitor, in patients with advanced solid
malignancies. Journal of clinical oncology, 19(13), 3267-3279.
Zimmermann, H. (1980). OSI reference model--The ISO model of architecture for open
systems interconnection. IEEE Transactions on communications, 28(4), 425-432.
Fall, K. R., & Stevens, W. R. (2011). TCP/IP illustrated, volume 1: The protocols. addison-
Wesley.
Forouzan, B. A., & Fegan, S. C. (2002). TCP/IP protocol suite. McGraw-Hill Higher Education.