chapter 1-intro (2) [compatibility mode]

8/8/2019 Chapter 1-Intro (2) [Compatibility Mode]

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Introduction to Data

Chapter One

Communication

and

OSI Model

Course ObjectivesUpon completion of this Course students should be

able to:o List major technologies in data communication

o Explain the operation and application areas of data

o Appreciate standards that have been defined forconnecting a computer to data circuit terminating

o Explain the operation and application areas ofsome of the alternative methods that can beemployed to detect transmission errors

o Explain the various data communication networksavailable

o Handle communication equipment

Chapter 1: ContentIntroduction to Data Communication and OSI ModelData Communications.

Components

Direction of Data Flow.

Networks.

Network Criteria

Type of Connection.

Topology

Categories of Networks.

The Open Systems Interconnection (OSI) Model

Peer-to-Peer Processes

Functions of Layers

Review QuestionsWhat is networking?

networking is the practice of linking two or more computing devices

together for the purpose of sharing data. Networks are built with a

mix of computer hardware and computer software.

What is data communication?concerns the transmission of digital messages convey to devices external to the

What are components involved in data communication?

Sender, receiver, Message, Medium and protocol

Name directions of data flow?

Simplex, half duplex and full duplex

What is network topology?arrangement or mapping of the elements (links, nodes, etc.) of a network,

especially the physical (real) and logical (virtual) interconnections between nodes

message source

Overview of Data Communications & Networking

Definition

Data information presented in whatever form

the process ofexchanging databy using a

communication device(hardware and software)

Data Communication

The Effectiveness of Data Communication:-

Delivery data reach to thecorrect destination

Accuracy data received is thecorrect data

Timeliness data transmittedwithout delay(real-

time transmission)


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Half-Duplex

Both can send AND receive

BUT

not at the same timeBandwidth?

i.e:- walkie-talkie

Full-Duplex

Both can send AND receive

SIMULTANEOUSLY sharing bandwidth between signal traveling in both direction

i.e:- telephone network

Distributed Processing

Network Criteria

Networks

Physical Structures

Categories of Networks

Distributed Processing

Definition a task isdivided amongmultiple computers, each will have theirown system processing, and at the endresu w e e vere comp e o eac other, so that is where we need aNETWORK.

One workstation is asubsetto anotherworkstation.

Performance i.e:- transmit time, response time

Evaluated by metrics: throughput and delay

Reliability i.e:- frequency of failure, time to recover failure and

network robustness in catastrophe (devastation)

Network Criteria

ecurity Examples:

protect data from unauthorized access (hackers)

Protect data from damage and development

Implement policies and procedure for data recovery

Type of Connection

Point-to-Point

Physical Structures

Multipoint


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Point-to-point

Dedicated link between TWO devices

Multipoint

(Multidrop)

More than 2 devices SHARE a SINGLE link

Capacity of the channel is SHARED spatially/temporally

Physical Topology

Categories of Topology

Definition the way in which a network is laid out physically

Fully Connected Mesh Topology

Every device has a dedicated point-to-point link to every other device

Advantage:-

Carry its own data load

Robust

Privacy and security

Disadvantage:-

Link must be shared by

multiple device

No. of I/O ports

Star Topology

Point-to-point to a central controller

Advantage:-

Easy to install, reconfigure and troubleshoot

Robustness

More suited for larger networks

Easy to expand network

Cabling types can be mixed

Disadvantage:-

Failure of hub cripples

attached stations

More cable required

Bus Topology

Signals go through the cable become weaker and weaker

Explanation:

One long cable as a backbone to link all devices

Nodes connected to the bus c able by drop lines and taps

Drop line connected between devices and main cable

Taps is connector splices into the main cable to create contact with metallic core


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Bus Topology (cont.)

Advantage:-

Ease of installation

Cheapest topology to implement

Failure of one station does not affect others

Less expensive due to less footage of cabling and no network hubsGood for smaller networks not requiring higher speeds

Disadvantage:-

Difficult reconnection and fault isolation

Not meant to be used as a stand-alone solution in a large building

Limited in size and speed

Difficult to troubleshoot

Difficult to administer/troubleshoot

A cable break can disable the entire network; no redundancy

Maintenance costs may be higher in the long run

Performance degrades as additional computers are added

Ring Topology

Passing token to take turn

Dual ring - for line backup

Advantage:-

Ease to install and reconfigure

Can create much larger network using Token Ring

Growth of system has minimal impact on performance

All stations have equal access

Ring Topology (cont.)

Disadvantage:-

Moves, adds and changes of devices can affect the network

Network adapter cards and Multi Access Unit (MAU)'s are much more

expensive than Ethernet cards and hubs

Much slower than an Ethernet network under normal load

Failure of one computer may impact others

Complex

Hybrid Topology

A combination of any two or more networktopology to form complete network

Physical topology refers to the layout of cables, computers and other

peripherals

describes the layout of the network, just like a map showsthe layout of various roads

Logical Topology the method used to pass the information between the

computers

describes how the data is sent across the network

E.g.: how the cars are able to travel (the direction and

speed) at every road on the map.

Categories of Network

The categories of network depends on

its:-

Size

Ownership

Distance cover

Physical architecture

Local Area Network

It is privately owned

i.e:- single office, building, campus


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Local Area Network (cont.) Metropolitan Area Network

To extend over an entire city

i.e:- telecommunication company (telco)

Wide Area Network Network Configuration

Internet

Definition: combination 2 or more network ~known as

Internetwork

is a collection of many separate networks.

A global network connecting millions of computers.More than 100 countries are linked into exchanges ofdata, news and opinions

Is a worldwide system of computer networks severalnetworks which users can communicate each other ifthey have permission to get information from any othercomputer (and sometimes talk directly to users at othercomputers).

Internet History

1960s~Advanced Research Projects Agency (ARPA) ~ interested to find a

way how to connect to others PC so

enable for data sharing and exchanging data.

Reducing cost

eliminating duplication of effort

1967~proposed ARPANET

1969~ARPANET is become realit ARPANET was currently using the Network Control Protocol (NCP) to transfer data among hosts

1972~The first e-mail program was created by Ray Tomlinson of BBN.

1973~proposed protocol Transmission control protocol (TCP)

Encapsulation

Datagram

The function of gateway

Then, split protocol to

TCP ~ responsible for higher level function : segmentation, reassembly and error detection

Internetworking Protocol (IP)~ handle datagram routing


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How Internet today?

Today, the Internet is a public, cooperative, andself-sustaining facility accessible to hundreds ofmillions of people worldwide.

Physically, the Internet uses a portion of the totalresources of the currentl existin ublictelecommunication networks.

Technically, to distinguish the Internet use of a set of protocols called TCP/IP (for

Transmission Control Protocol/Internet Protocol)

Two recent adaptations of Internet technology, theintranet and the extranet, also make use of theTCP/IP protocol.

Internet today

How to connect to Internet?

Internet Service Provider (ISP)

International Service Provider

National Service Provider

Backbone network maintained by specialized company

E.g: Jaring, TMnet, Celcom.net, Maxis Net, iDiGi Internet

Service, Time.Net

Regional Service Provider ~ smaller ISPs that

connected to one or more national ISPs

Local Internet Service Provider

E.g: ISP in a company and can be connected to regional and

national ISP

Protocol and Standard

Protocol = rule

enable two entities to communicate in sending and receivingmessage using a protocol (agreed)

Set of rule that govern data communication

e ne w a , ow an w en o communc a e

3 key elements:

Syntax ~ refers to the structure of format of the data

Semantics ~ refers to meaning of each section of bits

Timing ~ refers to 2 characteristic

When data should be send

How fast data can be sent

e.g:

sender produce: 100Mbps;

receiver can process:1Mbps

overload

Protocol and Standard

Standard Agreed-upon rule

Why? Guideline for manufacturer to create and maintain any

equipment to ensure the connectivity needed in market and

international communication uaran ee ng na ona an n erna ona n eropera y o a a

and telecommunication technology and process

Two categories De facto ~ standard not approved by an organized body but

has adopted as standard through widespread usedEstablished by manufacturer that seek to define the functionality of

new product

De jure ~ standard that has been legislated by an officiallyrecognized body

Standard Organization International Organization for Standardization (ISO)

Multinational body ~ committees from various c ompany

Developing cooperation in the realms of scientific, technological andeconomic activity

International Telecommunication Union-TelecommunicationStandard Sector (ITU-T) Define national standard for telecommunication

American National Standards Institute (ANSI) Prvate and not aff l ated w th U.S federal government

Institute of Electrical and Electronics Engineers (IEEE) Largest professional engineering society

Aims to advance theory, creativity, and product quality in electricalengineering, electronics, radio related to engineering

Oversees development and adoption of international standards forcomputing and communication

Electronic Industries Associated (EIA) Activities include public awareness education and standards development.

Contribution in defining physical connection interfaces and electronicsignaling specification for data communication.


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TCP/IP Model

OSI Model

Layered Tasks

Sender, Receiver, and Carrier

Hierarchy task done in order

Services

it Sender the higher layer uses services of the

middle layer. The middle layer uses services of thelower layer and the lower layer uses services of thecarrier.

Sending a letter Internet Model (Internet Layers)

Peer-to-Peer ProcessesInterfaces between Layers defines whatinformation and services a layer must provide for the layer

above it.

Organization of the Layers

Functions of Layers

Summary of Layers

Internet Layers Peer-to-Peer Processes

At the physical layer, the communication is direct

The processes on each machine that communicate at a given layer

Interfaces enable passing data and network information down through layers at the sender and

receiver

Each interfaces defines information and services must provide by a layer for a layer above it


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An exchange using the Internet model Data exchange using the Internet model (cont..)

Divided to three subgroups:-

Layer 1 (Physical)

Layer 2 (Data Link)

Layer 3 (Network)

Organization of the Layers

Network Support Layers-deals with the physical aspects

of moving data from one device

to another

Layer 4 (Transport)

Layer 5 (Application) User Support Layer-allows interoperability among

unrelated software systems

Transport Layer-links the two subgroups,

-ensures what the lower layers have

transmitted is in a form that the upper

layers can use

Application

Transport

Function of Layers

Data Link

Physical

Physical Layer

The physical layer is responsible for

transmitting individual bits from one node to

the next.

Defines the cable or the physical medium

Physical characteristics of interfaces and media

Defines characteristics of the interface between thedevices and the transmission media

Defines type of transmission medium

Representation of bits

Defines the type of representation (how bits changed to

Physical Layer Major Duties:-

sgnas

Data rate

Defines transmission rate (no. of bits sent each second)-duration of a bit

Synchronization of bits

Synchronized the bit level (receiver clock)


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Source-to-Destination Delivery Example 2In Figure 2.11 we want to send

data from a node with network

address A and physical address 10,

located on one LAN, to a node

with a network address P and

physical address 95, located onanother LAN. Because the two

devices are located on different

networks we cannot use physical

addresses only; the physical

addresses only have local

jurisdiction (control). What we

need here are universal addresses

that can pass through the LAN

boundaries. The network (logical)

addresses have this characteristic.

Transport Layer

The transport layer is responsible for delivery of a message from

one process to another.

Provides end-to-end connection between two devices during

communication by performing sequencing, acknowledgement,checksums, and flow control

Port addressing Gets the entire message to the correct process on that computer

Segmentation and reassembly Enable the transport layer to reassemble the message correctly upon

arrival at the destination

To identify and replace packets that were lost in the transmission

Connection control

Transport Layer Major Duties:-

Connectionless

User Datagram protocol

No end-to-end reliability check

E.g.: DNS update, and SMS

connection-oriented

Transmission Control protocol (TCP)

Guarantees that is receives as it was sent

E.g.: Telnet, FTP, SSH and Telephone conservation (real world)

Flow control

End-to-end flow control

Error control

Transport Layer Major Duties(cont.)

n - o-en error con ro

Ensure the entire message arrives at the

receiving transport layer without error

(damage,lost,duplicate) - retransmission

Reliable process-to-process delivery of a message

Data delivery not only between both computer but also from

specific process on one computer to a specific process on the other.


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Example 3 Application Layer

The application layer is responsible for

providing services to the user.

Mail services

Basis for email forwarding and storage

File transfer and access

Allows user to access files in a remote host (changes/read

data)

Retrieve file from remote computer for use in the local

Application Layer Major Duties:-

computer

Manage or control files in a remote computer locally

Remote log-in

User can log into a remote computer and access theresources of that computer

Accessing the World Wide Web (WWW)

For internet usage

Summary of Duties

OSI Model

Review Session

OSI Layer

Application

Presentation

Session

Transport

Network

Data Link

Physical


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Why a Layered Model? Layers with Function

7 Layers of the OSI Reference Model

The Application (Upper) Layers

Layer 7: Application

Layer 6: Presentation

Layer 5: Session

Layer 4: Transport

Layer 3: Network

Layer 2: Data Link

Layer 1: Physical

The Application (Upper) Layers

Application

User interface

Examples Telnet, HTTP

Presentation

How data is presented

Special processing, such as encryption

Examples ASCII, EMCDIC, JPEG

Session

Keeping different applications data separate

Examples Operating system/application access

scheduling

The Data Flow (Lower) Layers

Transport

Reliable or unreliable delivery

Error correction before transmit

Examples: TCP, UDP, SPX

Network

Provide logical addressing which routers use for path determination

Examples: IP, IPX Data Link

Combines bits into bytes and bytes into frames

Access to media using MAC address

Error detection not correction

Examples: 802.3/802.2, HDLN

Physical

Moves bits between devices

Specifies voltage, wire speed, and pin-out cables

Examples: EIA/TIA-232, V.35

Application think of browsers

Presentation think of common data format

Session think of dialogs and conversations

Transport think of flow control and reliability

The OSI Models

Network think of path selection, routing, andlogical addressing

Data Link think of frames and media accesscontrol

Physical think of signals and media


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chapter 1-intro (2) [compatibility mode]

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