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.

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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

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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

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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

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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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Slide 3 Networking Concepts Lecture 1 Aedited