Voice Over IP: Issues And Challenges

Voice over IP: Issuesand ChallengesIPRaj JainThe Ohio State UniversityColumbus, OH ate.edu/ jain/Raj JainThe Ohio State University1

OverviewqqqqqqVoice over IP: Why?Sample Products and Services13 Technical Issues4 Other IssuesProtocolsH.323 StandardRaj JainThe Ohio State University2

MarketqqqqInternational VOIP calls could cost 1/5th of normalrates Big share of 18B US to foreign calls. 15B within Europe.500,000 IP telephony users at the end of 1995.15% of all voice calls on IP/Internet by 2000 10M users and 500M in VOIP product sales in1999 [IDC]US VOIP service will grow from 30M in 1998 to 2B in 2004 [Forester Research] 2B in 2001 and 16B by 2004 [Frost & Sullivan]Raj JainThe Ohio State University3

Scenario 1: PC to PCIPNetworkqqqNeed a PC with sound cardIP Telephony software: Cuseeme, Internet Phone, .Video optionalRaj JainThe Ohio State University4

Scenario 2: PC to PhoneIPNetworkPhoneNetworkGatewayqNeed a gateway that connects IP network to phonenetwork (Router to PBX)Raj JainThe Ohio State University5

Scenario 3: Phone to tewayNeed more gateways that connect IP network to phonenetworksThe IP network could be dedicated intra-net or theInternet.The phone networks could be intra-company PBXs orthe carrier switchesRaj JainThe Ohio State University6

AdvantagesqqqqACADBDBCPrivate voice networks require n(n-1) access links.Private data networks require only n access links.Voice has per-minute distance sensitive chargeData has flat time-insensitive distance-insensitvechargeEasy alternate routing More reliabilityNo 64kbps bandwidth limitation Easy to provide high-fidelity voiceRaj JainThe Ohio State University7

ApplicationsqqqqAny voice communication where PC is already used:m Document conferencingm Helpdesk accessm On-line order placementInternational callbacks(many operators use voice over frame relay)Intranet telephonyInternet faxRaj JainThe Ohio State University8

Sample ProductsqqqqqVocalTec Internet Phone: PC to PC.Microsoft NetMeeting: PC to PC. Free.Internet PhoneJACK: ISA card to connect a standardphone to PC. Works with NetMeeting, InternetPhoneetc. Provides compression.Internet LineJACK: Single-line gateway.Micom V/IP Family:m Analog and digital voice interface cardsm PC and/or gatewayRaj JainThe Ohio State University9

Products (Cont)PBXPC wV/IP S/wmGatewayRouterIP NetworkFeatures:q Compressionq Phone number to IP address translation.q Supports RSVP.q Limits number of calls.Raj JainThe Ohio State University10

Products (Cont)qqVocalTec Internet Telephony Gateway:m Similar to Micom V/IPm Interactive voice response system for problemreportingm Allows WWW plug inm Can monitor other gateways and use alternateroutes including PSTNm Sold to Telecom Finland. New Zealand Telecom.Lucent's Internet Telephony Server: Gateway Lucent PathStar Access ServerRaj JainThe Ohio State University11

Products (Cont)qqCISCO 2600 Routers: Voice interface cards (VICs)Reduces one hop.Baynetworks, 3COM, and other router vendors haveannounced product plansPBXRouterIP NetworkPCRaj JainThe Ohio State University12

Sample ServicesqqqqqqIDT Corporation offers Net2Phone, Carrier2Phone,Phone2Phone services.Global Exchange Carrier offers international callsusing VocalTec InternetPhone s/w and gatewaysQuest offers 7.5 /min VOIP Q.talk service in 16cities.ITXC provides infrastructure and management to'Internet Telephone Service Providers (ITSPs)'America On-line offers 9 /min service.AT&T announced 7.5 /min VOIP trials in 9 US cities.Raj JainThe Ohio State University13

Services (Cont)qqqqqOther trials: USA Global link, Delta 3, WorldCom,MCI, U.S. West, Bell Atlantic, Sprint, AT&T/Japan,KDD/Japan, Dacom/Korea, Deutsche Telekom inGermany, France Telecom, Telecom Finland, andNew Zealand Telecom.Level 3 is building a nation wide IP network fortelephony.Bell Canada has formed 'Emergis' division.Bellcore has formed 'Soliant Internet Systems' unitBell Labs has formed 'Elemedia' divisionRaj JainThe Ohio State University14

Technical Issues1. Large Delaym Normal Phone: 10 ms/kmile 30 ms coast-tocoastm G.729: 10 ms to serialize the frame 5 ms lookahead 10 ms computation 25 ms one wayalgorithmic delaym G.723.1 100 ms one-way algorithmic delaym Jitter buffer 40-60 msm Poor implementations 400 ms in the PCm In a survey, 77% users found delay unacceptable.Raj JainThe Ohio State University15

Technical Issues (Cont)2. Delay Jitter: Need priority for voice packets.Shorter packets? IP precedence (TOS) field.3. Frame length: 9 kB at 64 kbps 1.125 sSmaller MTU Fragment large packets4. Lost Packets: Replace lost packets by silence,extrapolate previous waveform5. Echo cancellation: 2-wire to 4-wire.Some FR and IP systems include echo suppressors.PBXThe Ohio State Raj Jain

Technical Issues (Cont)6. Silence suppression7. Address translation: Phone # to IP. Directory servers.8. Telephony signaling: Different PBXs may use differentsignaling methods.9. Bandwidth Reservations: Need RSVP.10. Multiplexing: Subchannel multiplexing Multiple voice calls in one packet.11. Security: Firewalls may not allow incoming IP traffic12. Insecurity of internet13. Voice compression: Load reductionRaj JainThe Ohio State University17

Other Issues1. Per-minute distance-sensitive charge vsflat time-insensitive distance-insensitive charge2. Video requires a bulk of bits but costs little.Voice is expensive. On IP, bits are bits.3. National regulations and government monopolies Many countries forbid voice over IPIn Hungary, Portugal, etc., it is illegal to access a website with VOIP s/w. In USA, Association ofTelecommunications Carriers (ACTA) petitioned FCCto levy universal access charges in ISPs4. Modem traffic can’t get more than 2400 bps.Raj JainThe Ohio State University18

Compression StandardsqqqqG.711: 64 kbps Pulse Code Modulation (PCM)G.721:m 32 kbps Adaptive Differential PCM (ADPCM).m Difference between actual and predicted sample.m Used on international circuitsG.728: 16 kbps Code Excited Linear Prediction(CELP).G.729: 8 kbps Conjugate-Structure Algebraic CodeExcited Linear Prediction (CS-ACELP).Raj JainThe Ohio State University19

Compression (Cont)qG.729A:m A reduced complexity version in Annex A ofG.729.m Supported by AT&T, Lucent, NTT.m Used in simultaneous voice and data (SVD)modems.m Used in Voice over Frame Relay (VFRADs).m 4 kbps with proprietary silence suppression.Raj JainThe Ohio State University20

Compression (Cont)qG.723.1: Dual rates (5.3 and 6.3 kbps).m Packet loss tolerant.m Silence suppression option.m Recommended by International MultimediaTeleconferencing Consortium (IMTC)'s VOIPforum as default for H.323.m Supported by Microsoft, Intel.m Mean opinion score (MOS) of 3.8.4.0 Toll quality.Raj JainThe Ohio State University21

ProtocolsqqqqqqRSVP: Resource Reservation protocol [RFC 2205]RTP: Real-time Transport Protocol.Sequencing, timestamp, payload identification, anddelivery monitoring. [RFC 1889]RTCP: RTP Control Protocol. Provides deliveryfeedback.RTSP: Real-time Streaming Protocol. Allowscontrolling streaming audio/video. [RFC 2326]SIP: Session Initiation Protocol [IETF mmusic]SDP: Session Description Protocol [RFC 2327]Raj JainThe Ohio State University22

Protocols (Cont)qqqqqqSAP: Session Announcement Protocol [IETF mmusic]SCCP: Simple Conference Control Protocol [IETFmmusic]VPIM: Voice Profile for Internet Mail [RFC 1911].Voice messages in email. MIME profile.SCTP: Simple Computer Telephony Protocol. LikeSMTP for mail. [www.phonezone.com]802.1p: Priority over LANs802.1Q: Virtual LANsRaj JainThe Ohio State University23

Protocols (Cont)qqS.100: Standard application programming interfacefor computer telephony.m Endorsed by the Enterprise Computer TelephonyForum.m Will allow applications from different vendors toshare the telephony server resources for switching,routing, and media processing.SCbus: High-speed TDM bus for computer telephony.m Endorsed by ANSI.m Telephony products from Micom, VocalTec, IDTare all based on SCbus.Raj JainThe Ohio State University24

Protocols (Cont)qqInternet Fax Routing standard: Allows routingcommunication among fax servers.H.323 Internet telephony (video conferencing)standardRaj JainThe Ohio State University25

Protocols (Cont)qqqqqqqIPv6: 4-bit priority, 24-bit flow labelIP over ATM: MPOA allows QoS.MPLS: Multiprotcol Label Switching. Will supportQoS. [IETF mpls]ST-II: Stream Protocol V2. Connection oriented IP.IPv5. Provides resource reservations. [RFC 1819]Integrated Services: Guaranteed (CBR) andcontrolled-load (nrt-VBR) services. [RFC 2211 2212]Multicasting: IGMP [RFC 2236]Multicast Routing: MOSPF, DVMRP, PIMRaj JainThe Ohio State University26

Video I/OEquipmentVideoCodecAudio xingTelephony/Conferencing SystemsNetworkInterfaceNetworkRaj JainThe Ohio State University27

Conferencing StandardsNetworkConf. 2,G.728Audio RateskbpsVideoCodecData SharingControl64, 48-6464, 48-64,16H.261,H.263T.120H.24264, T.120H.230,H.242Multiplexing H.221SignalingQ.931H.221Q.931LANH.323 V1/V21996/1998G.711,G.722,G.723.1,G.728, G.72964, 48-64, 16,8, 729H.225.0Q.931H.223-8, 5.3/6.3H.261H.263T.120H.245Raj JainThe Ohio State University28

H.323 ProtocolsqqMultimedia over LANsProvides component descriptions, signalingprocedures, call control, system control, audio/videocodecs, data protocolsAudioControl and ManagementG.711, G.722,H.225.0 H.225.0 H.245H.261G.723.1, G.728,RAS Signaling ControlH.263G.729RTPX.224 Class 0UDPTCPNetwork (IP)Datalink (IEEE 802.3)RTCPVideoDataT.124T.125T.123Raj JainThe Ohio State University29

H.323 NRouterATMThe Ohio State UniversityGatewayMCUH.323ProxyTo InternetRaj Jain30

H.323 TerminalsH.261H.263Audio temControlUserInterfaceRTPH.245 ControlLAN InterfaceVideo I/OEquipmentQ.931 Call SetupRAS GatekeeperInterfaceRaj JainThe Ohio State University31

H.323 TerminalsqqqqqClient end points. PCs.H.245 to negotiate channel usage and capabilities.Q.931 for call signaling and call setup.Registration/Admission/Status (RAS) protocol tocommunicate with gatekeepers.RTP/RTCP for sequencing audio and video packets.Raj JainThe Ohio State University32

H.323 GatewaysqqProvide translation between H.323 and other terminaltypes (PSTN, ISDN, H.324)Not required for communication with H.323 terminalson the same ionand InterworkingISDNTerminalProcessingRaj JainThe Ohio State University33

H.323 GatekeepersqqqqqqqqProvide call control services to registered end points.One gatekeeper can serve multiple LANsAddress translation (LAN-IP)Admission Control: AuthorizationBandwidth management(Limit number of calls on the LAN)Zone Management: Serve all registered users withinits zone of controlForward unanswered callsMay optionally handle Q.931 call controlRaj JainThe Ohio State University34

H.323 MCUsqqqqqMultipoint Control UnitsSupport multipoint conferencesMultipoint controller (MC) determines commoncapabilities.Multipoint processor (MP) mixes, switches, processesmedia streams.MP is optional. Terminals multicast if no MP.MCUMulticastUnicastRaj JainThe Ohio State University35

SIPqqqqqSession Initiation ProtocolAllows locating a callee at different locationsCallee registers different locations with SIP ServerServers can also use finger, rwhois, ldap to find a calleeMessages: Ack, Bye, Invite, Register, Redirection, .LocationXServerJain@cis Jain@acmInvite Jain@cisMoved to Jain@acmInvite Jain@acmAck Jain@acmRaj JainThe Ohio State University36

SummaryqqqqqVoice over IP products and services are being rolled outIdeal for computer-based communicationsIP needs QoS for acceptable qualityA number of working group at IETF are working on itH.323 provides interoperabilityRaj JainThe Ohio State University37

OrganizationsqqqqqqIMTC: International Multimedia TeleconferencingConsortiumVOIP: Founded in 1966 by Cisco, Microsoft,VocalTec, 3Com/USR, Dialogic etc. to augmentH.323. Folded into IMTC.Enterprise Computer Telephony Forum (ECTF),http://www.ectf.orgInternet Fax Routing ForumVoice Profile for Internet Mail (VPIM) Work Groupof EMAVON Coalition, Inc., http://www.von.orgRaj JainThe Ohio State University38