Voice Over IP (VoIP): Internet Telephony N. Ganesan, Ph.d.

Chapter Objectives

Chapter Modules

VoIP DefinitionThe use of IP networks, namely the LAN and WAN, to carry voice

Internet 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 networksPSTN

Related IssuesVoice over Frame RelayVoice over ATM

Further EvolutionMedia transmission over IPAudioImageVideo

VoIP Basic FunctionsSignaling Database servicesMapping addresses (IP to Phone numbers) etc. Call connect and disconnect (bearer control)CODEC operations For encapsulating voice into data packets

Some Codecs Source: Juniper Networks

VoIP ComponentsServers For processing IP calls and manage interaction with PBX etc.End-point devices such as phones Media and VoIP gatewaysIP networkSource: Juniper Networks

Overcoming the ChallengesLatencyJitterBandwidthPacket loss ReliabilityScalabilitySecurityFeaturesInteroperabilitySwitch over cost

LatencyLatency is the time taken for a packet to arrive at its destinationPacket switching overheadCongestion Latency may result in voice synchronization problems

JitterJitter is the delay experienced in receiving a packet when a packet is expected to arrive at the end point at a certain time

BandwidthWhen bandwidth is shared between voice and computer data, certain bandwidth may have to be allocated for voice communication on a network

Packet LossPacket loss in unavoidableIt can be minimally tolerated in voice transmissionIt should not, in the first place, distort the audio

ReliabilityBecause 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 ?

ScalabilityAbility to add more telephony equipment as the company growsNetwork bandwidth and other issues may have an effect on scalability

SecurityAs VoIP uses the Internet, for example, it is vulnerable to the same type as security risksHackingDenial of serviceEavesdropping

FeaturesIP telephony need to match and, in the long run, exceed the features provided by the PSTNCall waitingThree way calling etc.

InteroperabilityIP telephony equipment manufactured by different vendors must be able to talk to each otherStandardized protocols are needed

Migration CostThe cost of migrating from legacy PBX to IP PBX

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

Network Performance ManagementAddresses the following issues:LatencyReliabilitySecurity

Standardized ProtocolsInteroperability

Migration PathSource: Avaya

Gateways 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 network

Other TerminologyFXS Foreign Exchange Station)FXO Foreign Exchange Office

FXSA 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

FXOAn 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

Source: QTelNet

Source: QTelNet

Also known as ATA Analog Telephone AdapterSource: QTelNet

Source: QTelNet

Source: QTelNet

Source: QTelNet

Source: QTelNet

Source: QTelNet

Source: QTelNet

Source: QTelNet

Source: QTelNet

Source: QTelNet

Modes of Internet TelephonyPC-to-PCPC-to-PhonePhone-to-PhoneNote: In the above listing phones can be either analog or digital phones

Case 1: PC to PC ConnectionMade over the internet for voice connectionSample product:Net2PhoneNetMeetingCalls are free

VendorsSkypeEarthlink

Case 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

Procedure1. Download our FREE software 2. Create a Username and Password 3. Select the amount of money you want to add to your account 4. Login to the software 5. Make PC2Phone calls and send faxes- Net2Phone

Dialing from the PC

FeaturesPC2PCPC2PhonePC2FaxInstant messaging

VendorsNet2Phone

Case 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 network

Typical LayoutATA

Connections

Vonage Broadband Phone Features

Voicemail Plus Caller ID with Name Call Waiting Call Forwarding 3-Way Calling In-Network Calling Traveling with Vonage Area Code Selection Call Transfer Click-2-Call Call Return (*69) Caller ID Block (*67) Repeat Dialing International Call Block Ring Lists Call Hunt

Analog Telephone Adapter (ATA) ManufacturersCISCOAT&TLinksys

A 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 ATA

Soft 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

Residential Broadband Phone CompaniesVonageAT&T CallVantage VoicePulsePacket8VocalTec

IP Standard Setting BodiesIETFITU

IP Telephony Standards and ProtocolsH.323 ITU standardSIP IETF standardMGCPIETF standardH.248ITU standardMegacoIETF standard

H.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

H.323 ComponentsSource: CISCO

Scope of H.323Source: CISCO

Deployment of H.323 NetworkSource: CISCO

Source: CISCO

Source: CISCO

SIPRelatively newer protocol

Source: CISCO

Source: CISCO

Source: CISCO

Other ProtocolsRTPReal-time Transport ProtocolResponsible for end-to-end delivery of real-time data such as audio and videoRTCPReal-time Transport Control ProtocolThe optional companion protocol to RTP that furnishes information about the quality of data delivered by RTP

SummaryImplementations based on the three different protocols will be in useAll three will be implemented with IP as the common coreH.323 is the older implementation that may give way to SIP Backed by CISCO

Read more on Toms page about locability etc. Read Juniper networks to talk more about VoIP protocols.