Voice Over IP (VoIP): Internet Telephony

Voice Over IP (VoIP): Internet TelephonyDr. Najla Al-nabhan1VoIP DefinitionThe use of IP networks, namely the LAN and WAN, to carry voice

2Internet TelephonyThe use of the Internet that was originally designed to carry computer data to carry voice A packet switched networkVoice was originally carried over circuit switched networksPSTN3Related IssuesVoice over Frame RelayVoice over ATM4Further EvolutionMedia transmission over IPAudioImageVideo 5VoIP Basic FunctionsSignaling Database servicesMapping addresses (IP to Phone numbers) etc. Call connect and disconnect (bearer control)CODEC operations For encapsulating voice into data packets6Some Codecs

Source: Juniper Networks7VoIP ComponentsServers For processing IP calls and manage interaction with private branch exchange (PBX) etc.End-point devices such as phones Media and VoIP gatewaysIP networkSource: Juniper Networks8A PBX (private branch exchange) is a telephone system within an enterprise that switches calls between enterprise users on local lines while allowing all users to share a certain number of external phone lines.8Overcoming the ChallengesLatencyJitterBandwidthPacket loss ReliabilityScalabilitySecurityFeaturesInteroperabilitySwitch over cost9LatencyLatency is the time taken for a packet to arrive at its destinationPacket switching overheadCongestion Latency may result in voice synchronization problems 10JitterJitter is the delay experienced in receiving a packet when a packet is expected to arrive at the end point at a certain time

11BandwidthWhen bandwidth is shared between voice and computer data, certain bandwidth may have to be allocated for voice communication on a network 12Packet LossPacket loss in unavoidableIt can be minimally tolerated in voice transmissionIt should not, in the first place, distort the audio13ReliabilityBecause the computer network is used, the reliability of the network will have an impact on the telephony serviceIn the analog telephone industry, reliability of 99.999 percent uptime is requiredThe above is known as five ninesVoIP networks can achieve over 98 percent reliability ?14ScalabilityAbility to add more telephony equipment as the company growsNetwork bandwidth and other issues may have an effect on scalability 15SecurityAs VoIP uses the Internet, for example, it is vulnerable to the same type as security risksHackingDenial of serviceEavesdropping 16FeaturesIP telephony need to match and, in the long run, exceed the features provided by the PSTNCall waitingThree way calling etc. 17InteroperabilityIP telephony equipment manufactured by different vendors must be able to talk to each otherStandardized protocols are needed18Migration CostThe cost of migrating from legacy PBX to IP PBX

19Facing the ChallengesMany of the challenges listed have now been addressed by effective network performance management and standardized protocols

20Network Performance ManagementAddresses the following issues:LatencyReliabilitySecurity 21Other TerminologyFXS Foreign Exchange Station)FXO Foreign Exchange Office22FXSA device that connects on one side to an analog equipment and other side to the InternetA simple example is the ATA (Analog Telephone Adapter) that connects an analog phone to the Interent

23FXOAn interface between the PSTN and the local equipment that would also connect to the InternetAn example use would be to have a telephone that connects to the Internet and, at the same time, has a connection to the PSTN as well There are equipment that will automatically switch to the PSTN if for some reason the VoIP connection does not function

24Modes of Internet TelephonyPC-to-PCPC-to-PhonePhone-to-PhoneNote: In the above listing phones can be either analog or digital phones 25Case 1: PC to PC ConnectionMade over the internet for voice connectionSample product:Net2PhoneNetMeetingCalls are free

Vendors of PC to PC ConnectionSkypeEarthlink

26Case 2: PC to Phone ConnectionMade over the Internet for connecting PC to phones Sample Product:Net2PhoneNeed to pay for the calls but they are relatively inexpensive Cheaper compared to phone to phone calls made over the Internet

Vendors Net2Phone27Procedure1. Download Net2Phone FREE software from (download.asp )2. Create a Username and Password3. Select the amount of money you want to add to your account4. Login to the software5. Make PC2Phone calls and send faxes- Net2Phone28Dialing from the PC

29FeaturesPC2PCPC2PhonePC2FaxInstant messaging 30Case 3: Phone to Phone Connection Phone to phone calls are made over the InternetA special phone will connect to a hub or switch on the network31Typical Layout

ATA32Connections

33Analog Telephone Adapter (ATA) ManufacturersCISCOAT&TLinksys34A Note on Implementation ProblemsSome of the adapters may not work properly when used in conjunction with a NATSome vendors may lock the ATA meaning that it would only work with their serviceA fee may have to be paid to unlock the ATA35Soft PhonesSoft phones do not require an ATA for connectionThey connect through the computerIt can be used for example with a notebook computer to facilitate mobility 36Residential Broadband Phone CompaniesVonageAT&T CallVantage VoicePulsePacket8VocalTec37IP Telephony Standards and ProtocolsH.323 ITU standardSIP IETF standardMGCPIETF standardH.248ITU standardMegacoIETF standard

38H.323An ITU recommendation applicable to Packet-based multimedia communications systems. - CISCOH.323 defines a distributed architecture for creating multimedia applications, including VoIP CISCOOlder and more established protocol

39Gateways and GatekeepersGateway equipment performs the task of allowing non-IP equipment to talk to IP equipment Gatekeepers manage the calls within a particular zoneBoth items will be present in a H.323 network40H.323 Components

Source: CISCO41SummaryImplementations based on the three different protocols will be in useAll three will be implemented with IP as the common coreH.323 is an older implementation protocol for VOIP.

Reference: N. Ganesan, Ph.d. 42