OSI AND TCP/IP MODELS. Outline Introduction OSI Model TCP/IP Model IPv4 vs. IPv6.
Introduction to TCP/IP and OSI model 1/12/20141Mr. Naresh Sharma, http:\\nareshsir.com.
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Transcript of Introduction to TCP/IP and OSI model 1/12/20141Mr. Naresh Sharma, http:\\nareshsir.com.
Introduction to TCP/IP and OSI model
04/10/23 1Mr. Naresh Sharma, http:\\nareshsir.com
More OSI Info
• Who made up the OSI?
• It was created by the International Organization for Standardization (ISO)
04/10/23 2Mr. Naresh Sharma, http:\\nareshsir.com
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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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.04/10/23 11Mr. Naresh Sharma, http:\\nareshsir.com
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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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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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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LayersHow 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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04/10/23 34Mr. Naresh Sharma, http:\\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
04/10/23 37Mr. Naresh Sharma, http:\\nareshsir.com
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 LayerProvides access to the OSI environment for usersProvides distributed information services.Web browsing (http) E-Mail (smtp)
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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 protocol04/10/23 45Mr. Naresh Sharma, http:\\nareshsir.com
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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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
04/10/23 49Mr. Naresh Sharma, http:\\nareshsir.com
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
04/10/23 50Mr. Naresh Sharma, http:\\nareshsir.com
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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04/10/23 56Mr. Naresh Sharma, http:\\nareshsir.com
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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