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Transcript of Slide 3 Networking Concepts Lecture 1 Aedited
8/3/2019 Slide 3 Networking Concepts Lecture 1 Aedited
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Networking
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Content
•
Model of Communication• The OSI Model
• The TCP/IP Model
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MODEL OF COMMUNICATION
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Networking History
• Standalone Device. – Duplication of equipments and resources.
– Inability to communicate efficiently.
– Lack of networking management.
• LAN.
–
Connects devices that are close together.• WAN.
– Interconnects LANs across a large area.
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Analyzing network in layers
What is flowing ?Data
What different forms flow ?Text, Graphic, Video ...
What rules govern flow ?
Standard, Protocol ...
Where does the flow occur ?
Cable, Atmosphere ...
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Communication
• Transmission of information.
• Examples:
– Speaking.
– Smoke signal.
– Body language.
– Morse.
– Telephone.
– Broadcast systems (radio, television).
– Internet
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Communication process
SourceAddress
DestinationAddress
Medium
Packets
Protocols
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Communication characteristics
• Addresses
– Who are the source and the destination of acommunication process?
• Media
– Where is the communication take place?
• Protocols
– How to make the communication processeffectively?
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Communication: Human conversation
• Address – Hello Mr.A, I am B
• Media
– Atmosphere
• Protocol
– Language – Speed
– Handshaking
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Data Communication
• Address
– Source address, Destination address
• Media – Cable, Fiber, Atmosphere
• Protocol
– Format
– Procedure
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Protocol
• Protocol is a set of rules, or anagreement, that determines theformat and transmission of data that
make communication on a networkmore efficient.
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OSI MODEL
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OSI model development
• Researched and developed by the ISO -
I nternational O rganization for S tandardizations.
• 1977: establish a subcommittee todevelop a communications architecture.
• 1984: publish ISO-7498, the Open SystemInterconnection (OSI) reference model.
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OSI model
• The OSI model: a framework within whichnetworking standards can be developed.
– It provided vendors with a set of standards
that ensured greater compatibility and interoperability between the various types of network technologies that were produced by the many companies around the world.
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A layered model
•The communications functions arepartitioned into a hierarchical set oflayers.
•
Each layer performs a related subset ofthe functions required to communicate.
• Each layer relies on the next lower layerto perform more primitive functions andprovides services to the next higherlayer.
The OSI Model define a set of layers and
the services performed by each layer
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Why a layered model?
• Reduces complexity.
•
Standardizes interfaces.• Facilitates modular engineering.
• Ensures interoperable technology.
• Accelerates evolution.
• Simplifies teaching and learning.
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7 layers of the OSI reference model
• Layer 7: Application
• Layer 6: Presentation
•
Layer 5: Session• Layer 4: Transport
• Layer 3: Network
• Layer 2: Data Link
• Layer 1: Physical
•All P eople S eem T o N eed D ata P rocessing
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The Application Layer
• Is the OSI layer that is closest to the user;it provides network services to the user’s
applications. – File transfer
– Electronic mail
– Terminal access
– Word processing
– Intended communication partners
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The Presentation Layer
• Ensures that the information that theapplication layer of one system sends outis readable by the application layer of
another system.
– Format of data
– Data structure
– Data conversion
– Data compression
–
Data encryption
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The Session Layer
• Establishes, manages, and terminatessessions between two communicating
hosts.
– Sessions
– Dialog
– Conversations
– Data exchange
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The Transport Layer
• Provides reliable, transparent transfer ofdata over networks.
– Segments, data stream, datagram
– Connection oriented and connectionless
–
End-to-end flow control – Error detection and recovery
– Segmentation & reassembly
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The Network Layer
• Provides connectivity and path selectionbetween two host systems that may belocated on geographically separated
networks.
– Packets
– Virtual circuits
– Route, routing table, routing protocol
– Logical address
–
Fragmentation
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The Data-Link Layer
• Provides for the reliable transfer of datacross a physical link.
– Frames
– Physical address
– Network topology
–
Line discipline – Synchronization
– Error control
– Flow control
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The Physical Layer
• Transmission of an unstructured bitstream over a physical link between end
systems. – Electrical, mechanical, procedural and
functional specifications
– Physical data rate – Distances
– Physical connector
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Encapsulation
•All communications on a network originate ata source, and are sent to a destination. Theinformation sent on a network is referred to asdata or data packets. If one computer (host A)wants to send data to another computer (hostB), the data must first be packaged through aprocess called encapsulation.
• Encapsulation wraps data with the necessaryprotocol information before network transit.
Therefore, as the data packet moves downthrough the layers of the OSI model, itreceives headers, trailers, and otherinformation.
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Encapsulation example: Air-mail
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Encapsulation example: E-mail
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Encapsulation with the layers
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Steps in order to encapsulate data
• Build the data – As a user sends an e-mail message,its alphanumeric characters are converted to datathat can travel across the internetwork.
• Package the data for end-to-end transport – The datais packaged for internetwork transport. By using
segments, the transport function ensures that themessage hosts at both ends of the e-mail system canreliably communicate.
• Add the network IP address to the header – The datais put into a packet or datagram that contains a
packet header with source and destination logicaladdresses. These addresses help network devicessend the packets across the network along a chosenpath.
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Steps: Cont.
• Add the data link layer header and trailer – Eachnetwork device must put the packet into a frame. Theframe allows connection to the next directly-connected network device on the link. Each device inthe chosen network path requires framing in order forit to connect to the next device.
• Convert to bits for transmission – The frame must beconverted into a pattern of 1s and 0s (bits) fortransmission on the medium. A clocking functionenables the devices to distinguish these bits as theytravel across the medium. The medium on the
physical internetwork can vary along the path used.For example, the e-mail message can originate on aLAN, cross a campus backbone, and go out a WANlink until it reaches its destination on another remoteLAN.
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Protocols
•Is a formal set of rules and conventions that governs how computers exchangeinformation over a network medium.
• Implements the functions of one or moreof the OSI layers.
• A communication protocol is concerned
with exchanging data between two peerlayers.
• Protocol Data Units (PDUs) : Block of
data that a protocol exchange.
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TCP/IP MODEL
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TCP/IP model development
• The late-60s The Defense AdvanceResearch Projects Agency (DARPA)originally developed TransmissionControl Protocol/Internet Protocol (TCP/IP) to interconnect various defensedepartment computer networks.
• The Internet, an International Wide AreaNetwork, uses TCP/IP to connectnetworks across the world.
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4 layers of the TCP/IP model
• Layer 4: Application
• Layer 3: Transport
•
Layer 2: Internet• Layer 1: Network access
It is important to note that some of the layers in the TCP/IP model have the same
name as layers in the OSI model.Do not confuse the layers of the two models.
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The Application Layer
• Handles high-level protocols, issues ofrepresentation, encoding, and dialogcontrol.
• The TCP/IP combines all application-related issues into one layer, andassures this data is properly packaged
for the next layer. – FTP, HTTP, SMNP, DNS ...
– Format of data, data structure, encode …
– Dialog control, session management …
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The Transport Layer
• The transport layer deals with thequality-of-service issues of reliability,flow control, and error correction.
– Segments, data stream, datagram.
– Connection oriented and connectionless.
– Transmission control protocol (TCP).
– User datagram protocol (UDP).
– End-to-end flow control.
–
Error detection and recovery.
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The Internet Layer
• Send source packets from any networkon the internetwork and have them arrive
at the destination independent of the pathand networks they took to get there.
– Packets, Logical addressing.
– Internet Protocol (IP).
– Route , routing table, routing protocol.
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The Network Access layer
• Concerned with all of the issues that anIP packet requires to actually make thephysical link. All the details in the OSI
physical and data link layers.
– Electrical, mechanical, procedural andfunctional specifications.
– Data rate, Distances, Physical connector.
– Frames, physical addressing.
– Synchronization, flow control, error control.
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Comparing TCP/IP with OSI
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Comparing TCP/IP with OSI (cont.)
Similarities:
– Both have layers.
–
Both have application layers, though theyinclude very different services.
– Both have comparable transport andnetwork layers
– Packet-switched technology is assumed.
– Networking professionals need to knowboth.
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Comparing TCP/IP with OSI (cont.)
Differences: – TCP/IP combines the presentation and
session layer issues into its application
layer. – TCP/IP combines the OSI data link and
physical layers into one layer.
–
TCP/IP appears simpler because it hasfewer layers.
– Typically networks aren't built on the OSIprotocol, even though the OSI model is
used as a guide.
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