Computer communication networks chapter 1 ppt (vtu odd sem EC)

Computer Communication Networks

Mr. Kunjan D Shinde

Assistant ProfessorDepartment of Electronics and Communication Engineering

PESITM Shivamogga.

213/08/2015 Mr. Kunjan D. Shinde, Asst. Professor, Dept. of E&CE, PESITM Shivamogga.

UNIT 1Network ModelsLayered TaskOSI ModelWorking of

Physical layer, Data link layer, Network layerTransport layer, Session layer, Presentation layerApplication layer

TCP/IP Protocol SuiteWorking of each layers

AddressingPhysical, Logical, Port, and Specific addressing. Acall Last_Class

Telephone and Cable Networks for Data CommunicationTelephone NetworksDial up modemDSLCable TV for data Transmission


Contents Chapter 1


Layered Task


Chapter 1: Network Models




Seven Layers of OSI model

ISO- International Standards Organization. - International Organization for Standardization.

- Established in 1947- Multifunctional body dedicated to worldwide

agreement on international standards.- ISO standard that covers all aspect of Network

Communication is OSI model

OSI – Open System Interconnect Model- 1st introduced in late 1970’s- has 7 ordered layers- Open System is set of protocols that allows two

different system to communicate regardless of their underlying hardware or software

- OSI is not a protocol- purpose is to facilitate communication b/w different

systems without changing its logic of underlying h/w and s/w.

ISO is Organization. OSI is the Model




The Interaction Between layers in the OSI Model




An exchange of data using the OSI model




Physical Layer

Functions of Physical layerPhysical Layer is responsible for movements of individual bits from one hop(node) to the

next.- Physical Characteristics - Data Rate- Synchronization of Bits- Line Configuration- Physical Topology- Transmission Mode




Data Link Layer

Functions of Data Link layerData Link Layer is responsible for moving frames from one hop(node) to the next.

- Framing- Physical Addressing- Flow control- Error Control- Access Control




Hop to Hop Delivery




Network Layer

Functions of Network layerNetwork Layer is responsible for the delivery of individual packets from source to

destination.

- Logical Addressing- Routing




Source to destination Delivery




Transport Layer

Functions of Transport layerTransport Layer is responsible for the delivery of the message from one process to another.

- Service point addressing- Segmentation and Reassembly- Connection control- Flow control- Error control




Reliable Process to process delivery




Session Layer

Functions of Session layerSession Layer is responsible for dialog control and synchronization.

- Dialog control- Synchronization




Presentation Layer

Functions of Presentation layerPresentation Layer is responsible for Translation, compression and encryption.

- Translation- Encryption- Compression




Application Layer

Functions of Application layerApplication Layer is responsible for providing services to the user.

- Network Virtual terminal- File transfer, access, and management- Mail services- Directory Services




Summary of Layers in OSI model




TCP/IP Protocol Suite




Addressing




Physical Addressing

07:01:02:01:2C:4B

A 6-byte (12 hexadecimal digits) physical address.




Logical Addressing




Port Addressing




Port Addressing

753

A 16-bit port address represented as one single number.




Specific Addressing

Specific address is used in some applications which need user friendly addresses.

Example

email: [email protected] used to define the address of the receiver.

URL- Universal Resource LocatorURL- www.pestrust.edu.in/pesitm/

-used to find a document on World Wide Web



Chapter 1: Telephone Networks

The telephone network had its beginnings in the late 1800s and was originally created to provide voice communication.

Need to communicate digital data results in the invention of the dial-up modem

High speed downloading – DSL- Digital Subscriber Line

The entire network, which is referred to as the plain old telephone system (POTS), was originally an analog system using analog signals to transmit voice.

PSTN : Public Switched Telephone Networks

Telephone networks use circuit switching.




Endoffices

Local loop

Trunk

Tandemoffices Regional offices

Trunk

• • •

It has 3 major components 1. Local Loops – Twisted pair cable, END/local central office, BW- 4kHz for voice

083622229542. Trunks – is a transmission media handles Communication b/w offices

3. Switching Offices - to avoid physical link b/w two subscriber, Telephone company has switches.

- A switch connects several local loops or trunks and allows a connection b/w different subscribers.

Major Components of Telephone Networks



Chapter 1: Unit 1

Home workStudy and prepare notes on

1. LATA1. Intra LATA Service2. Inter LATA Service

Point of Presence2. Signaling 1. Study in detail 2. Data Transfer Network and Signaling Network 3. Signaling System Seven (SS7)

Detailed notes on Layers in SS73. Services Provided by telephone Network4. Dial up modem – basic, v.32, v.34, v.90 and v.92

Last Date for Submission : its up to u.. Set a date




Telephone companies developed a new technology when the traditional modems reached their peak data rate, this new technology was DSL- Digital Subscriber Line.

DSL is used to provide higher-speed access to the Internet.

Digital subscriber line (DSL) technology is one of the most promising for supporting high-speed digital communication over the existing local loops.

Variants of DSL are

ADSL -AsymmetricHDSL -High bit rateSDSL -SymmetricVDSL -Very high bit rate xDSL - generally referred as xDSL where x = A, H, S, or V.

Digital Subscriber Line




Some points on ADSL

ADSL- Asymmetric –b’coz it uses a different speed in upstream and downstream.- downstream has higher data rate than upstream

ADSL is an asymmetric communication technology designed for residential users; it is not suitable for businesses.

The existing local loops can handle bandwidths up to 1.1 MHz (data and voice Communication).

ADSL is an adaptive technology. The system uses a data rate based on the condition of the local loop line.

1. Using Existing Local Loops-uses a existing local loops.-new BW was achieved by ADSL, b’coz of change in the filter used by

TC.




Some points on ADSL Cont’d..

2. Adaptive Technology-1.1 MHz is a theoretical bandwidth of Local Loops.- some factors that influence the change in BW property are Distance, Size of the cable, Signaling used and so .on..- Hence these factors need to be taken care, so the Adaptive Technology.Adaptive technology is used to test the conditions of the channel and to find the available BW of the line- Data rate of the ADSL is not fixed, it changes based on the condition and type of local loop cable.

3. Discrete multitone Technique (DMT)-Modulation Technique used by ADSL is DMT.-No predefine way to set the BW and divide among the users (each s/m can decide on its BW division).- typical BW -1.104MHz is divided in to 256 channels.-each channel uses the BW of 4.312kHz




Discrete Multitone technique




Bandwidth Division in ADSL

-Voice - Channel 0- Idle - Channel 1 to 5- Upstream data and Control -Channel 6 to 30 (24 channels), QAM modulation is used and BW is 24*4000*15=1.44Mbps {normal 500kbps b’coz of noise} - Downstream Data and Control - Channel 31 to 255 (24 channels), QAM modulation is used and BW is 224*4000*15=13.4Mbps{normal 8Mbps b’coz of noise}







High-bit-rate digital subscriber line (HDSL): It’s an alternative to T-1 line(1.544 Mbps)

Limitation of T-1 line is it uses alternative mark inversion(AMI) encoding, which is very susceptible to attenuation at high frequencies. Thus the length of T-1 line is limited to 3200ft (1km). Thus there is need of repeater for longer distances.

HDSL uses 2B1Q encoding which is less susceptible to attenuation. Up to a distance of 12000ft(3.86km) a data rate of 1.544Mbps can be achieved without repeaters.

HDSL uses 2 twisted pairs (One pair for each direction) to achieve full-duplex transmission.




Summary




The cable TV network started as a video service provider, but it has moved to the business of Internet access. In this section, we discuss cable TV networks per se; in Section 9.5 we discuss how this network can be used to provide high-speed access to the Internet.




Communication in the traditional cable TV network is unidirectional.




Communication in an HFC cable TV network can be bidirectional.




Cable companies are now competing with telephone companies for the residential customer who wants high-speed data transfer. In this section, we briefly discuss this technology.

BandwidthSharingCM and CMTSData Transmission Schemes: DOCSIS




Downstream data are modulated using the 64-QAM modulation technique.

The theoretical downstream data rateis 30 Mbps. The theoretical upstream data rate

is 12 Mbps.

Upstream data are modulated using the QPSK modulation technique.










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