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Transcript of VoIP - seminar at IASRI, New Delhi
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