osi model

1. The history of communication is a fascinating journey that spans
the entire existence of humanity. From ancient forms of
non-verbal communication to the sophisticated technologies of the
modern era, the evolution of communication has played a pivotal
role in shaping human civilization.
The earliest human communication likely involved gestures, facial
expressions, and body language. As communities grew more
complex, spoken language developed, allowing for more nuanced
and precise communication. The invention of writing systems,
such as cuneiform in Mesopotamia and hieroglyphics in Egypt,
marked a significant leap forward, enabling the recording and
preservation of information.
Communication is undoubtedly one of the most brilliant
discoveries of mankind. It is the foundation of human connection,
collaboration, and progress. The ability to convey thoughts, ideas,
and emotions has allowed societies to flourish, facilitating the
exchange of knowledge, culture, and innovation. While other
discoveries and inventions have also been monumental, the
impact of communication on shaping the human experience is
unparalleled.
Communication

2. Protocol Wars
A long-running debate in computer science known as the
Protocol Wars occurred from the 1970s to the 1990s when
engineers, organizations and nations became polarized over the
issue of which communication protocol would result in the best
and most robust computer networks. This culminated in the
Internet–OSI Standards War in the 1980s and early 1990s,
which was ultimately "won" by the Internet protocol suite
(TCP/IP) by the mid-1990s and has since resulted in most other
protocols disappearing.
The pioneers of packet switching technology built computer
networks to research and provide data communications in the
late 1960s and early 1970s. As more networks emerged in the
mid to late 1970s, the debate about interface standards was
described as a "battle for access standards". An international
collaboration between several national postal, telegraph and
telephone (PTT) providers and commercial operators agreed to
the X.25 standard in 1976, which was adopted on public data
networks providing global coverage. Separately, proprietary
data communication protocols also emerged, most notably
IBM's Systems Network Architecture and Digital Equipment
Corporation's DECnet.
The United States Department of Defense developed and
tested TCP/IP during the 1970s in collaboration with

3. universities and researchers in the United States, United
Kingdom and France. IPv4 was released in 1981 and the DoD
made it standard for all military computer networking. By 1984,
an international reference model known as the OSI model had
been agreed upon, with which TCP/IP was not compatible.
Many governments in Europe – particularly France, West
Germany, the United Kingdom and the European Economic
Community – and also the United States Department of
Commerce mandated compliance with the OSI model and the
US Department of Defense planned to transition away from
TCP/IP to OSI.
Meanwhile, the development of a complete Internet protocol
suite by 1989, and partnerships with the telecommunication
and computer industry to incorporate TCP/IP software into
various operating systems laid the foundation for the
widespread adoption of TCP/IP as a comprehensive protocol
suite. While OSI developed its networking standards in the late
1980s, TCP/IP came into widespread use on multi-vendor
networks for internetworking and as the core component of
the emerging Internet.

4. 1
OSI MODEL
Abdelbasset Benghina

5. History:
Early Networking:
In the 1960s and 1970s, various computer networks started to emerge, but
they often used proprietary protocols specific to the hardware and software
of each vendor.
Different network technologies, such as ARPANET (precursor to the
internet), Ethernet, and X.25, were in use. These early networks relied on
their own communication protocols and couldn't easily interoperate.
The concept of intercommunication protocols, as described by the OSI
(Open Systems Interconnection) model, began to take shape in the late
1970s and early 1980s. It marked a significant milestone in the history of
computer networking and the development of standardized communication
protocols.

6. 2
Introduction
 Open Systems Interconnection Basic Reference Model (OSI
Reference Model or OSI Model) is an abstract description for
layered communications and computer network protocol design. It
was developed as part of the Open Systems Interconnection
(OSI) initiative. In its most basic form, it divides network
architecture into seven layers which, from top to bottom, are the
Application, Presentation, Session, Transport, Network, Data-Link,
and Physical Layers. It is therefore often referred to as the OSI
Seven Layer Model.

7. 3
SESSION
NETWORK
DATA LINK
PHYSICAL
TRANSPORT
APPLICATION
PRESENTATION
SESSION
NETWORK
DATA LINK
PHYSICAL
TRANSPORT
APPLICATION
PRESENTATION
MIDDLE LAYER
HIGHER LAYER
Hop to Hop
Source to Destination
Physical Medium
Application to Application
Application to Application
Application to Application
Hop to Hop
Source to Destination
Rou ter
Switch
Hub and Repeater
Process to Process
LOWER LAYER
OSI Model's 7 Layers

8. 4
Host and Media Layer

9. OSI Layers
Application
Presentation
Session
Transport
Network
Data Link
Physical
TCP/IP Suit
Application
Presentation
Session
Transport
Network
Data Link
Physical
Activities
IP, ARP/RARP, ICMP, IGMP,
SCTP, TCP, UDP, Sockets and
Telnet, FTP, SMTP, HTTP, DNS, SNMP,
IEEE 802 Standards, TR, FDDI, PPP,
Medium, Coax, Fiber, 10base, Wireless
etc…
Logical address
Ports address
Specific address
Physical address
To allow access to network resources
To Translate, encrypt, and compress
data
To establish, manage, and terminate
se ssion
To Provide reliable process-to-process
Message delivery and error recovery
To move packets from source to
destination; to provide internetworking
To organize bits into frames; to provide
Hop-to-hop delivery
To Transmit bits over a medium; to provide
Mechanical and electrical specifications
5
Data, Protocol & Activities

10. 12
Application layer
H7
X.500 FTAM
Data
X.400
Message H7
X.500
Data
FTAM
(Human or Program)
Message
X.400
Application layer
To presentation layer
USER
From presentation layer
Application Layer
USER
(Human or Program)
(user level service)


The application layer is responsible for providing services to the user.
Concerned:




Network virtual terminal (Software)
File transfer, access and management
Mail services
Directory services (access to distributed database sources for global information about various objects
and services)

11. 11
Presentation Layer (dependency)


The presentation layer is responsible for translation, compression and encryption
Concerned:



Translation (interoperability between different encoding
system) Encryption (Privacy schemes)
Compression (data compression)
presentation layer
H6 Data H6 Data presentation layer
To session layer
From application layer
From session layer
To application layer

12. 10
Session Layer
From Presentation layer
(Dialog initiation)


The session layer is responsible for dialog control and synchronization
Concerned:


Dialog Control (Half Duplex/Full duplex)
Synchronization (Synchronization points, process inline within same page)
H5 Data Data Data H5 Data Data Data
Session layer
To transport layer
To Presentation layer
From transport layer
Session layer
Syn Syn Syn Syn Syn Syn

13. 9
Transport Layer
From session layer
(Process to Process)


The transport layer is responsible for the delivery of a message from one process to
another
Concerned:





Service-point addressing (Port address)
Segmentation and reassembly (Sequence number)
Connection control (Connectionless or connection oriented)
Flow control (end to end)
Error Control (Process to Process)
H4 Data H4 Data H4 Data
Segments
H4 Data H4 Data H4
Segments
Data
Transport layer
To network layer
From session layer
From network layer
Transport layer

14. 8
Network Layer (Source to Destination)


The network layer is responsible for the delivery of individual packets from the source
host to the destination host.
Concerned:


Logical addressing (IP Address)
Routing (Source to destination transmission between networks)
H3 Data Packet H3 Data Packet
Network layer
To data link layer
From transport layer
From data link layer
To transport layer
Network layer

15. 7
Data Link Layer (Host to Host)


Data link layer is responsible for moving frames from one hop (Node) to the next.
Concerned:





Framing (stream of bits into manageable data units)
Physical addressing (MAC Address)
Flow Control (mechanism for overwhelming the receiver)
Error Control (trailer, retransmission)
Access Control (defining master device in the same link)
H2 Data T2 H2 Data T2
Data link layer
To physical layer
From network layer To network layer
From physical layer
Data link layer

16. 6
Physical Layer





One of the major function of the physical layer is to move data in the form of electromagnetic signals
across a transmission medium.
Its responsible for movements of individual bits from one hop (Node) to next.
Both data and the signals can be either analog or digital.
Transmission media work by conducting energy along a physical path which can be wired or wireless
Concerned:

Physical characteristics of interface and medium (Transmission medium)

Representation of bits (stream of bits (0s or 1s) with no interpretation and encoded into signals)

Data rate (duration of a bit, which is how long it last)

Synchronization of bits (sender and receivers clock must be synchronized)

Line configuration (Point-to-Point, Point-to-Multipoint)

Physical topology

Transmission mode (Simplex, half duplex, full duplex)
110 10101000000010111 110 10101000000010111
Physical layer
From data link layer To data link layer
Physical layer
Transmission medium