VOICE OVER INTRENET PROTOCOL Nishikant P. Taksande IASRI, New Delhi, India
ContentsIntroductionVoIP History and Goals.VoIP ArchitecturesVoIP ProtocolsVoIP Using SIP and H.323Quality of Service (QoS)Applications in AgricultureCase Study: Timbaktu Collective ProjectConclusionsReferences
Introduction 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 telephonyVoIP Technology emerged over Public switched TelephoneNetwork(PSTN).
PSTN HistoryDedicated copper wireExpensive Service EquipmentBased on circuit switched network
Plain Old Telephone Service (POTS) PSTNCall flow from onephone to anotherwith traditionalPSTN network.
Motivation and Origin of VoIPDemand for Multimedia communicationDemand for integration of Voice and Data networksCost Reduction in long distance telephone callsPSTN network:Users frustrated by poor QoSCoding/decoding (codec) between analog voice and digitalpacketsGateways to PSTN
Goals and Benefits of VoIPGoals Consolidation of voice, data on a single network Simplify infrastructure, operations; provide bundled services Support for intelligent terminals as well as phonesBenefits Reduced long-distance costs Some cite this as a large business savings For residential customers too
Basic VoIP working model InternetVoice transmissionusing internet by VoIPenable phone andcomputer
Transmission of Voice over NetworkVoice Voice CODEC: CODEC: analoganalog Analog to Digital Digital to Analog Compress Decompress Create Voice Datagram Re-Sequence and Buffer-Delay Add Headerdigital digital (RTP, UDP, IP etc) Process Header Network
VoIP ArchitecturesPC to PC.Phone to Phone Via Internet.Phone to internet to PSTN.PSTN to Internet to PSTN.
Phone to Phone BB Internet PSTN ISP Service provider branch FWLocal Local DSL DSL
PSTN to PSTN through Internet PSTN ExchangePSTN Main Exchange ISP Service Main provider GW Main GW Main Local
PC to PC Internet ISP Private service FWDSL DSL
Broadband phone to Conventional phone abroad International network PSTN InternetTelephone network Exc. ISP Private service GW FW DSL
VoIP phone to VoIP phone International network PSTN Internet ISP Private service FW DSL 15
VoIP ProtocolsSIP (Session Initiation Protocol): The SIP protocol is astandard developed by the Internet Engineering Task Force(IETF) for establishing multimedia sessions such asvoice, instant messaging and videoIAX(Inter Asterisk eXchane): The IAX protocol wasdeveloped by a team of open-source developers working onthe Asterisk project
VoIP Protocols…H.323: The call setup protocol H.323 is standardizedby the International Telecommunications Union (ITU).In a VoIP environment, H.323 is a common protocolrunning on voice gateways to connect the VoIP networkto the PSTN.IMS(IP Multimedia Subsystem): IMS is currently indevelopment and testing phases, and was originallydeveloped as a protocol for carrying 3G telephony data.
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 MessageThe elements participating in a SIP-based system will signalbetween each other by exchanging SIP messages.SIP messages are text-based messages and have the generalstructure as shown below: A start line. One or more header fields. One empty line, followed by an optional body
SIP ElementsNetwork access element or end pointdevices: Elements that interactdirectly with users or servers toestablish 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 ServerIt sits between a client application and a real serverSIP Proxy therefore provides a constant location which isalways on to responds callsSIP proxy directly forward SIP messages to user agentclientRegistration server is a part of SIP proxy in case of smalland medium enterprisesRegistration process is realized by REGISTER requestto Registrar Server
SIP Proxy Server...Redirect server generate response to request it received byredirecting the client directly to source without passingthrough itself. SIP proxy RTP ComputerIP phone SIP call trough proxy
Hardware Model of System Simple SIP system including two SIP User Agents (UAs) and one SIP Proxy. Typical SIP model in a small region. HubUA 1 UA 2 SIP Proxy Simple model of system
Benefits Of SIPSimplicityScalabilityFunctional distribution
SIP PSTN InteractionSIP PSTN interaction is done by gatewaysMessages in each protocol are mapped to otherprotocol formatsSIP call from a PSTN gateway will not bedifferent from a SIP call from a device.
VoIP Using H.323H.323 was designed to support real-time transfer ofaudio and video data over packet networks H.323 involves several different protocols coveringspecific aspects of Internet telephony.
Protocols used in H.323G.711: It compresses speech so that to transfer overpacket networkH.245: Choose best compression algorithmQ.931: Establishing connection, providing dialtone, making ringing sound, release connectionH.225: protocol for talking to the gatekeeper byRegistration, Admission, Status (RAS) channel
H.323 Protocol StackG.7xx RTCP H.225 Q.931 H.245 (RAS) (Call Signaling) (Call Control) RTP UDP TCPk IP Data Link Layer Physical Layer Protocol H.323 Protocol stack
Terminal On LAN Calling Remote Phone PC GatewaysGatekeeper Internet PSTN Phone Working of H.323
Comparing SIP And H.323 ProtocolH.323 is bulky, complexly standardizedNot many potentialities to develop in the futureSIP Can add or remove media from the availablesessionPredicted that SIP is the principal for thedevelopment of next generation network (NGN)
VoIP Quality Of Service (QoS)QoS is challenge for VoIP to grow in future Latency. Jitter Packet loss Post Dial Delay(PDD) Bandwidth Network delay Poor compression Signal attenuation
Frequent Network ProblemJitterLossLatency Representation of Network problems
Advantage of VoIPIntegration Of Voice And DataMore bandwidthCost ReductionVideo conferencingFree IP to IP CallOne carrier
Disadvantages of VoIPPhone line is down if broadband connection is downPhone adapter and/or router occasionally must be rebootedVoice quality degrades if internet connection has latency, jitteror significant packet loss
VoIP Call RatesVoIP by MTNL: Rs.1/min. (International call)VoIP by Tata indicom : Rs.1/min (Internationalcall) VoIP by Skype: Skype to Skype(PC to PC): Free Call phone and mobile: $0.029
Skype uses VoIP Skype Most popular VoIP application Free calls to other Skype users Cheap calls Various add-on facilities also available38
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 Skype39
VoIP for Interactive WebsiteClick to call: Users click onwebpage and immediately speakwith a customer servicerepresentativeThe calls are carried over Voiceover Internet Protocol.Allows organisation to monitorwhen online visitors change fromthe website visitor to beinteractive about their queries.Can use this concept to makeexpert system more interactivewith farmers.
Caribbean Farmers Network (CaFAN)Providing cheap networkcommunications using(VOIP).A computer kioskmanaged by a farmer ateach village.farmers are benefited by getting timelymarket prices, information aboutfertilizers, crop varieties.1 million farmers in 10,000+ villages will be benefitted .
Open Academy for Academy for Philippines Agriculture Open 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. 
VoIP-based Intra-village Teleconnectivity - Timbaktu ExperimentIntra-village connectivity: a single gateway from a village to an external telecom network and extend the reach further within the villageAn acceptable solution would ideally be: easy to deploy and maintain; using off-the-shelf components; low on operational expenditure; and low on power consumption.
An architecture based on WiFi & EthernetOpen Academy for Philippines Agriculture Intra-village connectivity
Call FlowCall flow between PSTN and VoIP users.
Experimental ResultsTimbaktu project is very effective in connecting remotevillage to agricultural market placeRemote villages will not have sufficient PSTN connectionUse of existing line for communicationLaying new intra village network, communication can bedone effectively with less input cost
ConclusionVoIP sends voice over data networks instead of data overvoice networkInternet along with TCP/IP are driving forces for VoIPtechnologyIdeal for computer based communicationsMarket for VoIP is established and is rapidly growingVoIP cuts communication costs and improves efficiencyNeeds QoS for acceptable quality
References Carribbean Farmers Network, available online at http://www.caribbeanfarmers.org. Davidson, J., Peters, J., Bhatia M., Kalidindi S., Mukharjee S. (2008), Voice over IP Fundamentals, second Edition, Cisco Press, Pearson Education. 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 . Lammle,T. (2007), CCNA: Cisco Certified Network Associate study guide, Sixth Edition, Willy India publication. 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… Tata Indicom, Indiworld-VoIP Service from Tata Indicom. available online at http://www.tataindicom.com/indiworld-voip-service.aspx . Tanenbaum, A, S. (2006), Computers Networks, Fourth Edition, Pearson Education. Timbaktu Collective, Timbaktu collective network, available online at http://www.timbaktu.org/networking.html. Wikipedia (2006), VoIP terminology, available online at http://en.wikipedia.org/wiki/Category:VoIP_terminology_%26_concepts