VoIPVOICE OVER INTRENET

PROTOCOL

Nishikant P. TaksandeIASRI, New Delhi, India

Introduction

VoIP History and Goals.

VoIP Architectures

VoIP Protocols

VoIP Using SIP and H.323

Quality of Service (QoS)

Applications in Agriculture

Case Study: Timbaktu Collective Project

Conclusions

References

Contents

VoIP stands for Voice over Internet protocol

“ VoIP is the ability to make telephone calls over IP-based data networks with a suitable

quality of service and superior cost . ” Also known as

IP telephony Voice over Broadband Internet telephony

VoIP Technology emerged over Public switched Telephone Network(PSTN).

Introduction

PSTN History

Dedicated copper wire

Expensive

Service

Equipment

Based on circuit switched network

Plain Old Telephone Service (POTS)

PSTN

PSTN

Call flow from one phone to another with traditional PSTN network.

Motivation and Origin of VoIP

Demand for Multimedia communication

Demand for integration of Voice and Data networks

Cost Reduction in long distance telephone calls

PSTN network:Users frustrated by poor QoS

Coding/decoding (codec) between analog voice and digital packets

Gateways to PSTN

Goals and Benefits of VoIP Goals

Consolidation of voice, data on a single network

Simplify infrastructure, operations; provide bundled services

Support for intelligent terminals as well as phones

Benefits

Reduced long-distance costs

Some cite this as a large business savings

For residential customers too

Internet

Internet

Voice transmission using internet by VoIP enable phone and computer

Basic VoIP working model

Voice

CODEC:

Analog to Digital

Compress

Create Voice Datagram

Add Header

(RTP, UDP, IP etc)

CODEC:

Digital to Analog

Decompress

Re-Sequence and

Buffer-Delay

Process Header

Voice

analog analog

digital digital

NetworkNetwork

Transmission of Voice over Network

PC to PC.

Phone to Phone Via Internet.

Phone to internet to PSTN.

PSTN to Internet to PSTN.

VoIP Architectures

Phone to Phone

PSTN

Service provider

InternetBB

DSL

Local

branch

LocalDSL

FW

ISP

PSTN to PSTN through Internet

PSTN

Service provider

GW

Local

Main

Exchange ISP

PSTN

GW

Main Main

Main

Exchange

PC to PC

Private service

Internet

DSLDSL

FW

ISP

Broadband phone to Conventional phone abroad

Telephone network

Private service

Internet

DSL

International network

GW

Exc.

PSTNPSTN

FW

ISP

15

VoIP phone to VoIP phone

Private service

Internet

DSL

International network

PSTNPSTN

FW

ISP

VoIP Protocols

SIP (Session Initiation Protocol): The SIP protocol is a standard developed by the Internet Engineering Task Force (IETF) for establishing multimedia sessions such as voice, instant messaging and video

IAX(Inter Asterisk eXchane): The IAX protocol was developed by a team of open-source developers working on the Asterisk project

H.323: The call setup protocol H.323 is standardized by the International Telecommunications Union (ITU). In a VoIP environment, H.323 is a common protocol running on voice gateways to connect the VoIP network to the PSTN.

IMS(IP Multimedia Subsystem): IMS is currently in development and testing phases, and was originally developed as a protocol for carrying 3G telephony data.

VoIP Protocols…

VoIP Protocols and OSI Model

VoIP Using Session Initiation Protocol (SIP)

SIP is protocol used to initiate the session. It is deployed with the main purpose of initiation, modification and termination of multimedia sessions.

SIP Message

The elements participating in a SIP-based system will signal between each other by exchanging SIP messages.SIP messages are text-based messages and have the general structure as shown below:

A start line. One or more header fields. One empty line, followed by an optional body

SIP Elements

Network access element or end point devices: Elements that interact directly with users or servers to establish calls. They are called User Agents (UA).

SIP network core element:

These are intermediate elements participating in

forwarding SIP messages. Proxy server Registration server(Registrar) Redirect server

SIP Proxy Server

It sits between a client application and a real server

SIP Proxy therefore provides a constant location which is always on to responds calls

SIP proxy directly forward SIP messages to user agent client

Registration server is a part of SIP proxy in case of small and medium enterprises

Registration process is realized by REGISTER request to Registrar Server

IP phone

SIP proxy

Computer SIP call trough proxy

RTP

SIP Proxy Server...

Redirect server generate response to request it received by redirecting the client directly to source without passing through itself.

Simple SIP system including two SIP User

Agents (UAs) and one SIP Proxy. Typical SIP model in a small region.

UA 1 UA 2

SIP Proxy

Hub

Simple model of system

Hardware Model of System

1.INVITE

2. TRYING 3. INVITE

4. TRYING 5. RINGING

6. RINGING

7.RING8. 200 (OK)

9. 200 (OK)

10. ACK 11. ACK12.RTP Voice Stream

13.BYE (Hang Op) 14. BYE15. 200 (OK)

16. 200 (OK)

Call flow of system

Call Flow

Simplicity

Scalability

Functional distribution

Benefits Of SIP

SIP PSTN interaction is done by gateways

Messages in each protocol are mapped to other protocol formats

SIP call from a PSTN gateway will not be different from a SIP call from a device.

SIP PSTN Interaction

H.323 was designed to support real-time transfer of audio and video data over packet networks

H.323 involves several different protocols covering specific aspects of Internet telephony.

VoIP Using H.323

G.711: It compresses speech so that to transfer over packet network

H.245: Choose best compression algorithm

Q.931: Establishing connection, providing dial tone, making ringing sound, release connection

H.225: protocol for talking to the gatekeeper by Registration, Admission, Status (RAS) channel

Protocols used in H.323

H.323 Protocol Stack

UDP

H.245(Call Control)

Q.931(Call Signaling)

G.7xx RTCP

k

H.225 (RAS)

RTP

TCP

IP

Data Link Layer

Physical Layer Protocol

H.323 Protocol stack

Terminal On LAN Calling Remote Phone

InternetInternet

PSTNPSTN

Gatekeeper

PCGateways

Phone

Working of H.323

H.323 is bulky, complexly standardized

Not many potentialities to develop in the future

SIP Can add or remove media from the available session

Predicted that SIP is the principal for the development of next generation network (NGN)

Comparing SIP And H.323 Protocol

QoS is challenge for VoIP to grow in future

Latency.

Jitter

Packet loss

Post Dial Delay(PDD)

Bandwidth

Network delay

Poor compression

Signal attenuation

VoIP Quality Of Service (QoS)

Jitter

Loss

Latency

Frequent Network Problem

Representation of Network problems

Integration Of Voice And Data

More bandwidth

Cost Reduction

Video conferencing

Free IP to IP Call

One carrier

Advantage of VoIP

Phone line is down if broadband connection is down

Phone adapter and/or router occasionally must be rebooted

Voice quality degrades if internet connection has latency, jitter or significant packet loss

Disadvantages of VoIP

VoIP by MTNL: Rs.1/min. (International call)

VoIP by Tata indicom : Rs.1/min (International call) [6]

VoIP by Skype: Skype to Skype(PC to PC): Free Call phone and mobile: $0.029

VoIP Call Rates

Application of VoIP

38

Skype uses VoIP

Skype

Most popular VoIP application

Free calls to other Skype users

Cheap calls

Various add-on facilities also available

39

Skype Uses VoIP

Skype as a telephone Skype can be used as a

conventional telephone Particularly useful on laptops

for the traveller Sense of presence – know if

recipient is online Additional features: Integration with Web browser

(sharing browsing) Video Skype

Click to call: Users click on webpage and immediately speak with a customer service representative

The calls are carried over Voice over Internet Protocol.

Allows organisation to monitor when online visitors change from the website visitor to be interactive about their queries.

Can use this concept to make expert system more interactive with farmers.

VoIP for Interactive Website

Application Of VoIP In Agriculture

Providing cheap network communications using (VOIP).

A computer kiosk managed by a farmer at

each village.

farmers are benefited by getting timely market prices, information about fertilizers,

crop varieties.1 million farmers in 10,000+ villages will be benefitted . [1]

Caribbean Farmers Network (CaFAN)

Open Academy for Philippines Agriculture

With the initiative of open academy for Philippine agriculture, three villages get connected by means of VoIP.

This will enable farmers and extension worker in village to have access to agriculture technologies online.

With this VoIP connection farmers can call to research and development centre.

Farmer can access faster internet connection. [5]

Open Academy for Philippines Agriculture

VoIP-based Intra-village Teleconnectivity - Timbaktu Experiment

Intra-village connectivity: a single gateway from a village to an [8]

external telecom network and

extend the reach further within the village

An acceptable solution would ideally be:easy to deploy and maintain;using off-the-shelf components;low on operational expenditure; andlow on power consumption.

Open Academy for Philippines AgricultureAn architecture based on WiFi & Ethernet

Intra-village connectivity

Hardware

Intra-village network

End-user devices

External gateway

Software exchange

Hardware

Gateway Phone adapter

Timbaktu Layout

Village Layout

Call Flow

Call flow between PSTN and VoIP users.

Timbaktu project is very effective in connecting remote village to agricultural market place

Remote villages will not have sufficient PSTN connection

Use of existing line for communication

Laying new intra village network, communication can be done effectively with less input cost

Experimental Results

VoIP sends voice over data networks instead of data over voice network

Internet along with TCP/IP are driving forces for VoIP technology

Ideal for computer based communications

Market for VoIP is established and is rapidly growing

VoIP cuts communication costs and improves efficiency

Needs QoS for acceptable quality

Conclusion

References[1] Carribbean Farmers Network, available online at

http://www.caribbeanfarmers.org.

[2] Davidson, J., Peters, J., Bhatia M., Kalidindi S., Mukharjee S. (2008), Voice over IP Fundamentals, second Edition, Cisco Press, Pearson Education.

[3] Kelly,T.V., VoIP For Dummies (2005), Willy Publishing, available online at http://www.freebookcenter.net/Download/voip_ebooks_download _o.html_VoIP%20Dummies%20(2005).pdf.html .

[4] Lammle,T. (2007), CCNA: Cisco Certified Network Associate study guide, Sixth Edition, Willy India publication.

[5] Open Academy for Philippine Agriculture (2007), 3 remote barangays get connected through VOIP technology, available online at http://www.openacademy.ph/index.php?option=com_content&task=view&id=970&Itemid=276&limit=1&limitstart=0

References…

[6] Tata Indicom, Indiworld-VoIP Service from Tata Indicom. available online at http://www.tataindicom.com/indiworld-voip-service.aspx .

[7] Tanenbaum, A, S. (2006), Computers Networks, Fourth Edition, Pearson Education.

[8] Timbaktu Collective, Timbaktu collective network, available online at

http://www.timbaktu.org/networking.html.

[9] Wikipedia (2006), VoIP terminology, available online at http://en.wikipedia.org/wiki/Category:VoIP_terminology_%26_concepts

THANK YOU