A Comparative Evaluation of OSI and TCP/IP Models: P. Ravali
A Comparative Evaluation of OSI and TCP/IP Models: P. Ravali
A Comparative Evaluation of OSI and TCP/IP Models: P. Ravali
Abstract: Networking can be done in a layered manner. To reduce design complexities, network designers organize protocols. Every layer
follows a protocol to communicate with the client and the server end systems. There is a piece of layer n in each of the network entities.
These pieces communicate with each other by exchanging messages. These messages are called as layer-n protocol data units [n-PDU]. All
the processes required for effective communication are addressed and are divided into logical groups called layers. When a communication
system is designed in this manner, it is known as layered architecture. The OSI model is a set of guidelines that network designers used to
create and implement application that run on a network. It also provides a framework for creating and implementing networking standards,
devices, and internetworking schemes. This paper explains the differences between the TCP/IP Model and OSI Reference Model, which
comprises of seven layers and five different layers respectively. Each layer has its own responsibilities. The TCP/IP reference model is a solid
foundation for all of the communication tasks on the Internet.
1. Introduction
A collection of autonomous computers interconnected by a
single technology is called as computer networks. Computer
devices use communication languages known as network
protocols. These protocols describe how a computer
communicates with other computers at the bit and byte level.
It tells us the rules and conventions between network devices.
Protocols generally use packet switching techniques to send
and receive data in the form of packets [1].
Network protocols include mechanisms for devices to identify
and make connections with each other, as well as formatting
rules that specify how data is packaged into messages sent and
received.
Some
protocols
also
support
message
acknowledgement and data compression designed for reliable
and/or high-performance network communication. These
protocols are layered on top of each other.
At the time the Internet was developed, layering had proven to
be a successful design approach for both compiler and
operating system [3]. This gave rise to the concept of layered
protocols which nowadays form the basis of protocol design
[4].The purpose of each layer is to provide services to the
higher layers. Each layer acts as a virtual machine to the layer
above it. This concept can be commonly known as
information hiding, abstract data types, data encapsulation,
object-oriented programming. The rudimentary idea is to
provide service to its users but keep the details of its internal
state and algorithms hidden.
A network protocol is necessary since it allows two data
communication devices to communicate with each other.
Communication systems establish communications by sending
and receiving data. In general, much of the following should
be undertaken:
Data formats for data exchange where digital bit strings are
exchanged.
Address mapping.
Address formats for data exchange to identify both senders
and receivers address.
Routing using internetworking.
Detection of transmission errors is necessary on networks
which cannot assure error-free operation.
Loss of information-timeouts and retries.
Sequence control when long bit stings are lost, delayed or
chosen different routes.
Flow control when senders transmission is faster than
receivers.
Direction of information flow needs to be addressed if
transmission flows in only one direction.
Acknowledgements for correct reception of packets for
connection-oriented communication.
To implement a networking protocol, the protocol software
modules are interfaced with a framework implemented on the
machine's operating system [2]. Systems typically do not use a
single protocol to handle a transmission. Instead they use a set
of cooperating protocols, sometimes called a protocol family
or protocol suite. Some of the best known protocols are:
IPX/SPX, AX.25, AppleTalk and TCP/IP.
Protocols are layered in modern designs. Layering is a design
principle which divides the protocol design into number of
smaller parts, each of which accomplishes a particular subtask, and interacts with the other parts of the protocol only in a
small number of well-defined ways [5]. The advantages of
layered protocols is that the methods of passing information
from one layer to another are specified clearly as part of the
protocol suite, and changes within a protocol layer are
prevented from affecting the other layers. Since they are
divided into different functional layers, assigning protocols to
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15. Comparison
Models
between
OSI
and
TCP/IP
TCP/IP
Application Layer
Transport Layer
Internet Layer
Physical Layer
Link Layer
Figure 4: OSI and TCP/IP Model [25].
There are seven layers in the OSI Model, only four in the
TCP/IP Model. This is because TCP/IP assumes that
applications will take care of everything beyond the Transport
Layer. The TCP/IP Model also squashes the OSIs Physical
and Data Link Layers together into the Network Access Layer
[26]. The basic differences between the OSI and TCP/IP
models are shown above in figure 4.
The Open Systems Interconnection (OSI) model is a standard
"reference model" created by the International Organization
for Standardization (ISO) to describe how the different
software and hardware components involved in a network
communication should divide labor and interact with one
another. It defines a seven-layer set of functional elements,
ranging from the physical interconnections at Layer 1 (also
known as the physical layer, or PHY interface) all the way up
to Layer 7, the application layer.
The Transmission Control Protocol (TCP) and the Internet
Protocol (IP) are two of the network standards that define the
Internet. IP defines how computers can get data to each other
over a routed, interconnected set of networks. TCP defines
how applications can create reliable channels of
communication across such a network. Basically, IP defines
addressing and routing, while TCP defines how to have a
conversation across the link without garbling or losing data.
TCP/IP grew out of research by the U.S. Dept. of Defense and
is based on a loose rather than a strict approach to layering.
Many other key Internet protocols, such as the Hypertext
Transfer Protocol (HTTP), the basic protocol of the Web, and
the Simple Mail Transfer Protocol (SMTP), the core email
transfer protocol, are built on top of TCP. The User Datagram
Protocol (UDP), a companion to TCP, sacrifices the
519
OSI
Reference model
This is a theoretical model
Has 7 layers
Considered a reference tool
Stricter boundaries for the
protocols
Vertical approach
16. Conclusion
In this paper an attempt has been made to explain the
differences in TCP/IP and OSI models. OSI model is an
architecture which gives an idea how packets transfer over the
network during any communication. The Transmission
Control Protocol / Internet Protocol (TCP/IP) was created by
the Department of Defense (DoD) to make sure and protect
dataintegrity, and also maintained communications in the time
of disastrous war. However, if designed and deployed properly
according to standard, a TCP/IP network can be a truly
reliable and flexible one Efficiency and feasibility. The OSI
norms tend to be prescriptive (for instance the "layer N" must
go through "all layers below it"), whereas the TCP/IP
protocols are descriptive, and leave a maximum of freedom for
the implementers. One of the advantages of the TCP/IP
approach is that each particular implementation can use
operating system-dependent features, generally resulting in a
greater efficiency (fewer CPU cycles, more throughput for
similar functions), while still ensuring "interoperability" with
other.
The TCP/IP and OSI architecture models both employ all
connection and connectionless models at transport layer.
However, the internet architecture refers to the two models in
TCP/IP as simply connections and data grams. But the OSI
reference model, with its penchant for precise terminology,
uses the terms connection-mode and connection-oriented for
the connection model and the term connectionless-mode for
the connectionless model TCP/IP is the older of the two
approaches to data communications and is well established
throughout the world. The OSI model, however, is a proven
concept that is used in all other data communications
References
[1] http://compnetworking.about.com/od/networkprotocols/g/
protocols.htm
[2] Marsden 1986, Section 6.1 - Why are standards
necessary? pp. 64-65, uses BSC as an example to show
the need for both standard protocols and a standard
framework.
[3] Comer 2000, Sect. 11.2 - The Need for Multiple
Protocols, pp. 177, explains this by drawing analogies
between computer communication and programming
languages.
[4] Sect. 11.10 - The Disadvantage of Layering, pp. 192,
states: layering forms the basis for protocol design.
[5] http://en.wikipedia.org/wiki/Internetwork_protocol
[6] American Psychological Association (APA): Protocol
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[14] http://searchnetworking.techtarget.com/definition/OSI
[15] http://www.webopedia.com/quick_ref/OSI_Layers.asp
Updated March 11, 2014 / Posted September 24, 1999, by
Vangie Beal.
[16] Andrew S. Tanenbaum in Computer networks, pp. 41
[2008].
[17] http://searchnetworking.techtarget.com/definition/TCP-IP
Posted by Margaret Rouse WhatIs.com
[18] http://en.kioskea.net/faq/1855-the-tcp-ip-model Published
by-aakai1056-Latest update by deri58, November 2014.
[19] http://www.omnisecu.com/tcpip/tcpip-model.php
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[20] http://www.omnisecu.com/tcpip/tcpip-model.php
Published by: Jajish Thomason.
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