OSI Layers

This report discusses the OSI layers, specifically the data link layer and error control, as well as the transport layer and mobile and cloud networks. It covers topics such as framing, error detection, and correction, as well as the functions and protocols of the transport layer. The report also explores the challenges faced by mobile networks and the integration of cellular networks and cloud computing.

Running Head: OSI LAYERS 0
OSI Layers
Report
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OSI Layers 1
Table of Contents
Data link layer..................................................................................................................................2
Framing:.......................................................................................................................................2
Error Control:...............................................................................................................................3
Transport Layer...............................................................................................................................9
Mobile and Cloud network............................................................................................................16
Cloud-Based RAN:....................................................................................................................17
Reference.......................................................................................................................................19

OSI Layers 2
Data link layer
It was designed for error free transmission between different nodes in a network. It is
second layer of Open system Interconnection (OSI) model (Chen, Hsu, & Cheng, 2014). This
layer breaks the datagrams and converts them into frames, which are ready for transfer into the
network. It is called framing. It has two main functions, which are as:
1. Providing reliable data transfer
2. Flow control
Framing:
Physical layer is used for transferring bits without any structure. The responsibility of the
data link layers creates and recognizes frame boundaries. It is a process, in which adding of bits
in the beginning and end of the frame for recognition. It used four methods for framing, which
are widely used are:
1. Character count
2. Character stuffing
3. Bit stuffing
4. Physical layer coding violations
All these methods are used for frame transmission.
Character Count: It is using a header field in which mention number of characters in the frame.
Destination node is checked this field and separate that frame. It is used for finding end of the
frame. It is having a huge disadvantage that if header is missing because of transmissions then no

OSI Layers 3
one can find end of the frame. Therefore, this method is rarely used for data transmission
(Cowley, 2012).
Character Stuffing: This method is used American Standard Code for Informational
Interchange (ASCII) character sequence in starting and ending of the frame. This method is used
for overcomes the disadvantages of character count method. It used Data Link Escape (DLE)
STX and DLE ETX in starting and ending of frame. If destination is missing the synchronization
bits then it is used DLE STX and DLE ETX for finding the frame. However, it is having an
insertion and deletion time for stuffing of character (Dye, McDonald, & Rufi, 2007).
Bit stuffing: this is third method of framing. It allows data frame to contain arbitrary number of
bits, which is a character code. It is inserted in the starting and ending of the frame. It is also
known as flag byte in a frame such as 01111110. This is a way to send and receive frames
between different nodes in a network (Forouzan, 2007).
Physical layer coding violations: This is a method to encode and decode the bits using some
redundancy, such as Cyclic Redundancy Check (CRC), CRC-16 and CRC-32. It is used for
marking frame boundaries (Kenneth C. Mansfield & Antonakos, 2009).
Error Control:
Physical layer is not providing any grantee for error free transmission. The DLL is
responsible for error detection as well as error correction in data transfer between different
nodes. Most of the network model is using checksum for error control. Checksum is a compute
bit, which are used to find error in the frame. Checksums are having two types, which are error
detecting, and error detecting and correcting (Mitchell, 2018).
These are few methods of error detection:

OSI Layers 4
Source: (Forouzan, 2007)
Parity Bit: It is a simple method for error detection in the frame during data transmission in
network. The parity bit is selected behalf of number of zeros or ones.
Source: (Forouzan, 2007)
Assume that sender wants to send data, which are as mention below in ASCII code as
1110111 1101111 1110010 1101100 1100100
After calculation of parity bit these bits are sent to the channel
11101110 11011110 11100100 11011000 11001001

OSI Layers 5
1. Receiver receive these bits without any error
11101110 11011110 11100100 11011000 11001001
At the receiver end, parity bit is checked of each character and it comes up with even numbers
(6, 6, 4, 4, 4). The data are accepted.
2. Receiver receive the bits with error during data transmission
11111110 11011110 11101100 11011000 11001001
The receiver check the parity of each character and it comes up with even and odd numbers (7, 6,
5, 4, 4). It is showing that the data is corrupted during the transmission.
Source: (Forouzan, 2007)
In case of Two-dimensional parity check row and column, parities are added according to each
row 1’s as shown in above diagram.
Checksum: In case of checksum, sender and receiver both are following few steps for
transmission and receiving the data as shown in below figure.

OSI Layers 6
Source: (Forouzan, 2007)
Source: (Forouzan, 2007)
Cyclic Redundancy Check: It is standard code for data transmission. There are few steps for
sending data as shown in below diagram. Data is added with n bits, divisor and remainder part. It
is create a CRC code of n bits (Tanenbaum, 2014).
Source: (Forouzan, 2007)

OSI Layers 7
Source: (Forouzan, 2007)
Source: (Forouzan, 2007)
CRC is most useful data sending techniques and it is providing better result from all other
techniques. However, it is more complex than other technique but it is better than others for data
transmission (Sunshine, 2013).

OSI Layers 8
Transport Layer
It is providing service to upper layer, which is application layer and lower layer, which is
network layer. It is a fourth layer of OSI model. It gives service to the application layer as well
as it receives services from the network layer as shown in below figure. Transport layer is
having their position between application layer and network layer.
Source: (Forouzan, 2007)
Transport layer is having different functions, which are packetizing, addressing, connection
control and reliability.
Source: (Forouzan, 2007)

OSI Layers 9
It provides process-to-process delivery of segments.
Source: (Forouzan, 2007)
Process-to-process delivery is shows in above diagram. Different layers are providing
different services. Data link layer provides node-to-node delivery of frames. It is also responsible
for error control. Network layer is liable for delivery of packet at host-to-host. In computer
system, different processes are initialized for accessing data from other node. Therefore,
transport layer is providing services to delivery of segment to all the processes.
Source: (Forouzan, 2007)
Above diagram is showing that process in which processes are transferring data using
multiplexing and demultiplexing.

OSI Layers 10
Source: (Forouzan, 2007)
Above diagram is showing a connection making between two different nodes. Host A is
sending a connection request to the Host B. Host B is deciding to permit that connection or not.
Same process is applicable for Host B, if it is required a connection to data transfer (Stallings,
2007).
Below figure is showing connection termination process. Termini nation required a
connection release request from node than they send an acknowledgement. This process is repeat
for the entire host for connection termination.
Source: (Forouzan, 2007)
Transport layer is also provides error control. Data link layer is proving error control at
the physical layer and data link layer as we discussed above. Transport layer is providing
segment management using different approaches for proper data transfer (Forouzan, 2007).

OSI Layers 11
Source: (Forouzan, 2007)
Transport layer is used two protocols for data transfers, which are as:
1. User Datagram Protocol
2. Transmission Control Protocol
Both protocols are working in different style as per the requirement of different layers.
UDP is not reliable for their services. Therefore, it is used in video conferencing. However, TCP
is reliable and it is used in mailing system and other secure applications.
User Datagram Protocol (UDP):
It is a layer-4 protocol, which provides connectionless services. It is better for fast
services with data losses.
Source: (Forouzan, 2007)

OSI Layers 12
UDP is an appropriate protocol for those applications, which are provide flow and error
control. UDP is mostly preferred by many applications, such as Skype.
Transmission Control Protocol:
TCP is uses Connection-oriented concept for data transmission in network. TCP is
reliable protocol because of it use connection-oriented data transfer between different nodes. All
the segments are having a proper connection id. Therefore, each segment monitored by sender.
They are having a specific path for sending the data. TCP is providing numbering to all
segments. It is start from any random number. It defines a number to the first segment of
message. This number is used for acknowledgement field. The acknowledgment number is
cumulative. Different parts of TCP header are showing in below diagram (Kenneth C. Mansfield
& Antonakos, 2009).
Source: (Forouzan, 2007)
TCP header is having different fields for managing data transfer. All fields are having a
specific purpose, such as checksum is used for error control. Source and destination address is
included in the header of TCP. TCP header is using different headers for providing many
services to the network. Description of different headers is showing in below diagram.

OSI Layers 13
Source: (Forouzan, 2007)
TCP connection is having different stages as shows in below diagram.
Client sends a SYN signal to the server for connection establishment. Server sends
acknowledgment to the client for ensuring a secure connection. Same as connection release is
required a FIN request for closing the connection. Transport layer is used multiplexing for data
transfer. Multiplexing is having two types.
Source: (Forouzan, 2007)

OSI Layers 14
Frequency Division Multiplexing (FDM): it uses different frequencies for data transmission. It
is an analog multiplexing technique, which combines signals. Data is send with a channel. All
the data is marge, combine with a signal, and sent it with a carrier frequency.
Source: (Forouzan, 2007)
Wavelength Division Frequency (WDM): it is used different frequencies for data transfer
using optical fiber cable. It is an analog multiplexing technique, which is combine optical
signals. It combines all the signals and transfers all the data with the help of optical fiber cable as
shows in above diagram.
Source: (Forouzan, 2007)
Time Division Multiplexing (TDM): it is a technique, which use same frequency for data
transfer in different time slots. It is a digital multiplexing technique, which is combine data.
Source: (Forouzan, 2007)

OSI Layers 15
Mobile and Cloud network
In present era, many things are completely based on telecommunication systems. Cellular
networks are facing many problems because of increasing ration of mobile users. It increases
traffic in an unmatched rate, which has an impact on the reliable cellular network services. From
last decades, mobile operators are facing many challenges to fulfill user’s requirements, which
are based on new technologies, such as Long Term Evolution (LTE) (Ceselli, Premoli, & Secci,
2017).
LTE is used for helping of Radio Access Network (RAN) for increasing the capacity. It
may be because of older technologies and hardware components. However, current system are
facing high traffic problem during peak hours. It is highly dynamic and unpredictable. In this
situation, it is difficult to manage components in a distributive way. It is based on real time
demand and capacity of hardware components will manage according to that requirements. In
addition, during non-peak hours resources are not optimized in a proper way. It is wastage of
resources, such as energy, bandwidth and many more. It is also directly affecting operational
expenses of mobile operators (Dinh, Lee, Niyato, & Wang, 2013).
All those reason are handling by the virtualization of cellular networks and cloud
computing. It can be seen as a solution of managing mobile networks. In addition, Cloud
computing services does not support mobile ecosystem and cloud computing services. Cloud
computing is having different purposes (Sanaei, Abolfazli, Gani, & Buyya, 2014). Mobile
Virtual Network Operator (MVNO) can adopt different models except the radio spectrum
license. MVNO outsource different process, such as marketing and selling. Cloud computing is
ready to optimized all the things and it is a betterment of networks (Atzori, Iera, & Morabito,
2010).

OSI Layers 16
Virtualization is a process, which is influence on technical and business innovations. The
Mobile Cloud Networking (MCN) project is focusing on the integration of cellular network and
cloud computing using network function virtualization. MCN is an EU-funded research project.
MCN project will investigate different things, which are mobile network, decentralized
commuting, smart storage and LTE (Karagiannis, Jamakovic, Edmonds, & Parada, 2014).
Source: (Karagiannis, Jamakovic, Edmonds, & Parada, 2014)
Mobile networks are having different things to manage but during peak hours; it faced
many challenges, which are needed by all the
Cloud-Based RAN:
It is a concept for managing cellular network by cloud computing services. The Mobile
Cloud Network project enables mobile networks to enterprises and mobile devices users. MVNO
is design service platforms, which include core network and cloud computing. It provides access
to all users for mobile network and cloud services. It is possible through Radio Access Network-
as-a-Service (RANaaS). It merged all the things at a same place for different services. It faces
different challenges, which are associated with the realization of this technology. Main challenge
is that how to provide all these service, which follow infrastructure sharing, pay-as-you-go,
elasticity and on-demand cloud computing service. It is a complex process for efficiently allocate

OSI Layers 17
resources for different service. It is also facing optimization issues for load balancing (Chen &
Zhao, 2012).
Source: (Karagiannis, Jamakovic, Edmonds, & Parada, 2014)
Source: (Karagiannis, Jamakovic, Edmonds, & Parada, 2014)

OSI Layers 18
Mobile networks are uses cloud computing in different applications. Mobile devices are
based on the cloud computing. Cellular network is core network and it uses different concept of
cloud computing to manage networking. It is a distributed system and it uses virtualization
concept for managing cellular network (Fernando, Loke, & Rahayu, 2013).
All the users are access their network from cellular network and they also get all those
facilities, which are they used by cloud computing. It will provide different services, such as (IP
multimedia subsystem as a service, Digital Signage Service as a Service and Information
Centric Networking/Content Delivery Network as a Service. These services are making it
different and excellent in upcoming time (Miettinen & Nurminen, 2010).
Cloud service providers are researching on visualization of cellular network and cloud
computing services. IBM, Microsoft, Google and Amazon are providing different services in
present market to different clients at a huge level, such as Netflix uses Amazon Web Services.
All the cloud vendors are highly interested to develop such types of projects, which can merge
both technologies ( Evans, 2017)

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Reference
Evans, B. (2017). The Top 5 Cloud-Computing Vendors: #1 Microsoft, #2 Amazon, #3 IBM, #4
Salesforce, #5 SAP. Retrieved September 18, 2018, from
https://www.forbes.com/sites/bobevans1/2017/11/07/the-top-5-cloud-computing-
vendors-1-microsoft-2-amazon-3-ibm-4-salesforce-5-sap/#4adccb5f6f2e
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Science & Business Media.
Dinh, H., Lee, C., Niyato, D., & Wang, P. (2013). A survey of mobile cloud computing:
architecture, applications, and approaches. Wireless communications and mobile

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computing, 13(18), 1587-1611.
Dye, M., McDonald, R., & Rufi, A. (2007). Network Fundamentals, CCNA Exploration
Companion Guide. Indianapolis, USA: Cisco press.
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Stallings, W. (2007). Data and computer communications (8th ed.). New delhi: Pearson
Education India.

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Sunshine, C. (2013). Computer network architectures and protocols. New Jersy: Springer
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Tanenbaum, A. S. (2014). Computer networks. Harlow, Essex: Pearson.