Introduction to TCP/IP and OSI

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23 Οκτ 2013 (πριν από 4 χρόνια και 15 μέρες)

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Introduction to TCP/IP and OSI
model

10/23/2013

1

Mr. Naresh Sharma, http:
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More
OSI

Info


Who made up the
OSI?


It was created by the
International
Organization for
Standardization (ISO)


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The Open System Interconnection
Model (OSI)


The International Standards Organization (ISO) has
developed a universal architecture for computer
communications.


This standard, Known as the
open Systems
Interconnection model, or OSI model.


The purpose of OSI is

to permit communications
among devices made by manufacturers.

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OSI Layers


OSI has seven layers.


Each layer represents a particular function.


It could be, each function is preformed by a
separate piece of hardware or software.


Sometimes, a single program may performed the
functions of several layers.


All layers are necessary for communications to
occur.

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OSI Layers


The ISO
-
OSI model chooses to divided the
function of computer communications into
seven layers, though more or fewer could
have been chosen.

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What is the

OSI Reference Model?


It is a conceptual
framework specifying the
network functions that
occur at each layer


It is a way of picturing
how information travels
through networks.

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OSI Reference Model (standard)


Any application process should
be able to communicate freely
with any any application
process in any other computer
that supports the same
standards…


The
OSI Reference Model

shows how this takes place.

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Mr. Naresh Sharma, http:
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OSI Reference Model


The OSI reference
model describes how
data makes its way
from application
programs through a
network medium to
another application
located on another
computer on a
network

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To accomplish this task data must travel from the
application layer to the physical layer on one
computer across the network media and from the
physical layer to the application layer of another
computer

Computer A

Computer B

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OSI Reference Model Layers


The Application Layer provides services
to application processes (such as
electronic mail, file transfer, and
terminal emulation) that are outside of
the OSI model.


The application layer identifies and establishes the availability of
intended communication partners (and the resources required to
connect with them), synchronizes cooperating applications, and
establishes agreement on procedures for error recovery and
control of data integrity.

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OSI Reference Model


The Presentation Layer ensures that
information sent by the application
layer will be readable by the
application layer of the receiving
system.


The presentation layer is also
concerned with the data structures
used by programs and therefore
negotiates data transfer syntax for the
application layer.

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OSI Reference Model


The Session Layer establishes,
manages, and terminates sessions
between applications and manages
data exchange between presentation
layer entities


(Ensures Interhost communication)



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OSI Reference Model


The Transport Layer is responsible
for reliable network communication
between end nodes.


The transport layer provides
mechanisms for the establishment,
maintenance, and termination of
virtual circuits, transport fault
detection and recover, and
information flow control.

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OSI Reference Model


The Network Layer provides
connectivity and path selection
between two end systems.


The network layer is the layer at
which routing occurs.

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OSI Reference Model


The Data Link Layer provides
reliable transit of data across a
physical link.


The data link layer is concerned
with


physical addressing,


network topology,


line discipline,


error notification,


ordered delivery of frames,


flow control.

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OSI Reference Model


The physical layer defines the
electrical, mechanical, procedural,
and functional specifications for
activating, maintaining, and
deactivating the physical link
between end systems

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OSI Reference Model

Host Layers:

}

Media Layers:

}

Control physical delivery of
messages over a network

Provide accurate data
delivery between computers

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As data moves down through the layers
of the OSI model, headers are added.

Computer A

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Computer B


As data moves up through the layers of the OSI model, headers
are removed.

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OSI Reference Model


There are other models by different vendors


Most vendors use the OSI Model


OSI is conceptual other than tangible


Used to educate how networks function at
each layer

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What does the OSI Model do?


It reduces complexity (from one big problem
to 7 small ones)


It standardizes interfaces


It facilitates modular engineering


It assures interoperable technology


Accelerates evolution


Simplifies teaching & learning

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Review Time!


Divide into two groups


Play Jeopardy


Bonus answer is the layer number

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OSI Layers


The Lowest layer, Known as
physical Layer
or Layer 1,



is responsible for transmission of bits.



Is always implemented by using hardware.


Is encompasses the mechanical, electrical, and
functional interface.


Is the interface to the outside world


using electronic signals as specified by
interface standards.

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OSI Layers


The
Data Link Layer, Or Layer 2,


is responsible for ensuring error
-
free,


reliable transmission of data.


Scrutinizes the bits received to determine if errors
occurred during transmission.


Is able to request retransmission or correction of
any errors using protocols.

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OSI Layers


The
Network Layer, or Layer 3,


is responsible for setting up the appropriate
routing of messages throughout a network


is concerned with he types of switching networks
used to route the data


Note:

Physical, Data Link, and Network layers are usually
referred to as the
lower layers

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OSI Layers


The
Transport Layer, or Layer 4,


is responsible for isolating the function of the
lower layers from the higher layers


is responsible for monitoring the quality of the
communication channel


is responsible for selecting the most cost
efficient communication service.


accepts messages from higher layers, and
breaks them down into messages that can be
accepted by the lower layers

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OSI Layers


The
Session Layer, or Layer 5,


is responsible for terminating the connection


requests a logical connection be established based
on the end user’s request


handles any necessary “log
-
on” and password
procedures.

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Mr. Naresh Sharma, http:
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OSI Layers


The
Presentation Layer, or Layer 6,


provides format and code conversion services


handles any necessary conversion different
character codes; example







ASCII
-
to
-

EBCDIC

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OSI Layers


The Application Layer or Layer 7
,


provides access to the network for the end user


determines the user’s capabilities on the network


some Application Layer software, permit remote
terminal to only access a host computer; other
Application Layer software might also permit file
transfers.

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The TCP/IP Protocol Suite


The TCP/IP Suite


is a collection of protocols originally designed for
use on an network connecting U.S. government
agencies with universities performing research



specifies protocols at various levels of the OSI
model and covers a wide variety of tasks likely to
be performed on an open network

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nareshsir.com

Comparison of ISO
-
OSI Model and the
DOD (TCP/IP) Model

Application


Application


Presentation


Session


Transport


Host
-
to
-
Host


Network


Internet


Data Link


Network Access


Physical





Source:
http://starter.sdsu.edu/remote/demo/osi
-
tcp.html


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Layers


How network hardware and software work
together in layered fashion to make
communication possible



Each layer covers different network activities ,
equipment and protocols.

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10/23/2013

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Mr. Naresh Sharma, http:
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\
nareshsir.com

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Mr. Naresh Sharma, http:
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nareshsir.com

OSI


Open Systems Interconnection


developed by the International Organization
for Standardization (ISO)


has seven layers


is a theoretical system delivered too late!


TCP/IP is the de facto standard

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OSI Layers

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Application

Provides access to the OSI environment for users and also
provides distributed information service

Presentation

Provides independence to the application process from
difference in data representation (syntax)

Session

Provides the control structure for communication between
application; establishes, manages ___ terminates connection
(session) between cooperating applications.

Transport

Provides reliable, transparent transfer data between end
points; provides end
-
to
-
end error recovery and flow control.

network

Provides upper layer with independence from the data
transmission and switching technologies used to connect
systems; responsible for establishing, maintaining, and
terminating connections.

Data Link

Provides for the reliable transfer of information across the
physical link; sends blocks of data (frames) with the necessary
synchronization, error control ,and flow control

Physical

Concerned with transmission of unstructured bit stream over
physical medium; deals with the mechanical, electrical,
functional and procedural characteristics to access the
physical

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Physical


Concerned with transmission of unstructured bit
stream over physical medium


Deals with the mechanical, electrical, functional
and procedural characteristics to access the
physical medium


0,1


Volt, duration, transmission characteristic
directions, connectors pins

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Data Link



Provides for the reliable transfer of information
across the physical link



Sends blocks of data (frames) with the
necessary synchronization, error control and flow
control


Frame, acknowledgment from lost, duplicate


Piggy backing

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Network



Provides upper layer with independence from the
data transmission and switching technologies used
to connect systems


Responsible for establishing, maintaining, and
terminating connections.


Operations of subnet, Packet size


Routing
, congestion control



network
Addressing


Accounting


Broadcast networks

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Transport



Provides reliable, transparent transfer of
data between end points


Provides end
-
to
-
end error recovery and
flow control.


Addressing port, connection management


Distinctive network connection, multiplexing

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Session



Provides the control structure for communication
between applications


Establishes, manages and terminates
connections (sessions) between cooperating
applications.


Dialog management


Token Management



synchronization

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Presentation



Provides independence to the application
processes from difference in data
representation (syntax)


ASCII , Unicode

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Application Layer


Provides access to the OSI environment for users


Provides distributed information services.


Web browsing (http) E
-
Mail (smtp)


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Mr. Naresh Sharma, http:
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Need For
Protocol

Architecture


data exchange can involve complex
procedures, cf. file transfer example


better if task broken into subtasks


implemented separately in layers in stack


each layer provides functions needed to perform
comms for layers above


using functions provided by layers below


peer layers communicate with a protocol

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Key Elements of a Protocol


syntax
-

data format


semantics
-

control info & error handling


timing
-

speed matching & sequencing


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TCP/IP Protocol Architecture


developed by US Defense Advanced Research
Project Agency (DARPA)


for ARPANET packet switched network


used by the global Internet


protocol suite comprises a large collection of
standardized protocols

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Naresh

Sharma, http:
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Simplified Network Architecture

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TCP/IP Layers


no official model but a working one


Application layer


Host
-
to
-
host, or transport layer


Internet layer


Network access layer


Physical layer

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Physical Layer


concerned with physical interface between
computer and network


concerned with issues like:


characteristics of transmission medium


signal levels


data rates


other related matters

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Network Access Layer


exchange of data between an end system and
attached network


concerned with issues like :


destination address provision


invoking specific services like priority


access to & routing data across a network link
between two attached systems


allows layers above to ignore link specifics


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Internet Layer (IP)


routing functions across multiple networks


for systems attached to different networks


using IP protocol


implemented in end systems and routers


routers connect two networks and relays data
between them


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Transport Layer (TCP)


common layer shared by all applications


provides reliable delivery of data


in same order as sent


commonly uses TCP

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Application Layer


provide support for user applications


need a separate module for each type of
application


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OSI v TCP/IP

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TCP/IP Applications


have a number of standard TCP/IP applications
such as


Simple Mail Transfer Protocol (SMTP)


File Transfer Protocol (FTP)


Telnet

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Some TCP/IP Protocols

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