1 © 1999, Cisco Systems, Inc. Course Number Presentation_ID Voice Data Integration Cisco do Brasil Jonio Cavalcanti VoIP Network Design

2 Presentation_ID © 1999, Cisco Systems, Inc. Agenda IntroductionIntroduction Codecs Voice Over Packets Characteristics for VoIP, VoATM and VoFR QoS and Signaling for VoIP Conclusions

3 Presentation_ID © 1999, Cisco Systems, Inc. Agenda IntroductionIntroduction Codecs Voice Over Packets Characteristics for VoIP, VoATM and VoFR QoS and Signaling for VoIP Conclusions

4 Presentation_ID © 1999, Cisco Systems, Inc. VoCoders ( AUDIO CODECS ) Quality often measured using MOS Standards vs Entrepreneurial DTMF tones Language sensitivity

5 Presentation_ID © 1999, Cisco Systems, Inc. Voice Quality: Compression Standards Unacceptable UtilityBusinessToll PCM Quality ADPCM 32 (G.723) LD CELP 16 (G.728) ADPCM 16 (G.726) LPC 4.8 CS-ACELP 8 (G.729) MPMLQ (G.723.1) Bandwidth (kbps)

6 Presentation_ID © 1999, Cisco Systems, Inc. Agenda IntroductionIntroduction Codecs Voice Over Packets Characteristics for VoIP, VoATM and VoFR QoS and Signaling for VoIP Conclusions

7 Presentation_ID © 1999, Cisco Systems, Inc. Route Replacement Branch Office PSTN Main Office T1,E1 QoS WAN (Intranet/Internet) V V V V Telco Switch PBX PBX PBX Voice GW Voice GW

8 Presentation_ID © 1999, Cisco Systems, Inc. VoX Transport PSTN Branch OfficeMain Office Analog/Digital Voice GWs QoS WAN V V V V Telco Switch PBX PBX

9 Presentation_ID © 1999, Cisco Systems, Inc. Enterprise Voice VPN Philadelphia Typical Building PSTN Data Center T1,E1 QoS WAN (Intranet/Internet) V V V V Telco Switch PBX PBX PBX PSTN V V V Phoenix Charlotte Call Comes In Bypass PSTN

10 Presentation_ID © 1999, Cisco Systems, Inc. Dial Plan Design IP QoS WAN 3600A AS5300 PSTN V V 3600B V V NXX 555-xxxx 1111 NXX 556-xxxx 1111 Netmeeting PC NXX 559-xxxx NXX 557-xxxx PBX 7 and 7 digits for Local PSTN 71 and 10 digits for Long Distance to PSTN 7 digits of “on net” Location

11 Presentation_ID © 1999, Cisco Systems, Inc. Agenda IntroductionIntroduction Codecs Voice Over Packets Characteristics for VoIP, VoATM and VoFR QoS and Signaling for VoIP Conclusions

12 Presentation_ID © 1999, Cisco Systems, Inc. VoFR, VoATM, VoIP Quality Cost ($) Quality UnacceptableBusiness Quality Toll Quality CS-ACELP 8 Kbps (G.729) Cellular Utility Quality VoATM (8 Kbps) VoFR VoIP VoATM (PCM/AAL1) InternetIntranet PSTN VOICE VoFR, VoATM, VoIP Quality

13 Presentation_ID © 1999, Cisco Systems, Inc. L3/L2 Transport Characteristics L3—VoIP Flexible—IP is ubiquitous “Soft” form of QoS IP/UDP/RTP overhead (RTP compression) Quickly emerging technology L2—VoFR, VoATM “Hard” Qos Infrastructure can be rigid Better suited for high volume bulk voice

14 Presentation_ID © 1999, Cisco Systems, Inc. Agenda IntroductionIntroduction Codecs Voice Over Packets Characteristics for VoIP, VoATM and VoFR QoS and Signaling for VoIP Conclusions

15 Presentation_ID © 1999, Cisco Systems, Inc. Voice Transport Requirements Background noise Silence suppression Comfort noise Language sensitivity Subjective quality (MOS) MOS Delay and delay variation Echo cancellation Loss Bandwidth Delay VoIP Challenges in the WAN

16 Presentation_ID © 1999, Cisco Systems, Inc. missing packet G.729 vocoder algorithm VoIP (G.729) Is Tolerant of “Occasional” Packet Loss The friendly “retransmission” is of no use in the Voice world… late is as good as never Complex “concealment strategy” in algorithm interpolates lost packets based on context

17 Presentation_ID © 1999, Cisco Systems, Inc. How Does Echo Happen? Echo is due to a reflection Impedance mismatch at the 2w-4w hybrid is the most common reason for echo 2 Wire Local Loop Central Office 2w-4w Hybrid Receive Direction Transmit Direction Rx & Tx Superimposed Echo is always present and as a problem is a function of the echo delay, and the magnitude of the echo Echo is always present and as a problem is a function of the echo delay, and the magnitude of the echo

18 Presentation_ID © 1999, Cisco Systems, Inc. Delay—How Much Is Too Much? Cumulative Transmission Path Delay Time (msec) CB Zone Satellite Quality Fax Relay, Broadcast High Quality Delay Target ITU’s G.114 Recommendation = 0 – 150msec 1-way delay

19 Presentation_ID © 1999, Cisco Systems, Inc. Fixed Delay Components Propagation—six microseconds per kilometer Serialization Processing Coding/compression/decompression/decoding Packetization Processing Delay Propagation Delay Serialization Delay— Buffer to Serial Link

20 Presentation_ID © 1999, Cisco Systems, Inc. Fixed Frame Serialization Delay Matrix Frame Size Link Speed 56kbps 64kbps 128kbps 256kbps 512kbps 768kbps 1536kbs 1 Byte 143us 125us 62.5us 31us 15.5us 10us 5us 64 Bytes 9ms 8ms 4ms 2ms 1ms 640us 320us 18ms 128 Bytes 16ms 8ms 4ms 2ms 1.28ms 640us 36ms 256 Bytes 32ms 16ms 8ms 4ms 2.56ms 1.28ms 72ms 512 Bytes 64ms 32ms 16ms 8ms 5.12ms 2.56ms 144ms 1024 Bytes 128ms 64ms 32ms 16ms 10.24ms 5.12ms 1500 Bytes 46ms 214ms 187ms 93ms 23ms 15mss 7.5ms

21 Presentation_ID © 1999, Cisco Systems, Inc. Variable Delay Components Queuing delay Dejitter buffers Variable packet sizes Dejitter Buffer Queuing Delay

22 Presentation_ID © 1999, Cisco Systems, Inc. Delay Variation—“Jitter” t t Sender Transmits Sink Receives A A B B C C A A B B C C D1D1 D 2 = D 1 Sender Receiver Network D 3 = D 2

23 Presentation_ID © 1999, Cisco Systems, Inc. QoS Networking Tools Congestion Management (WFQ) QoS Signaling (IP Prec / RSVP) Packet Residency (MLPPP/MTU Size Reduction) Bandwidth (RTP Header Compression, Silence Suppression, VAD) Generic Traffic Shaping

24 Presentation_ID © 1999, Cisco Systems, Inc. Presentation Session Transport Network Link Physical G.729(A)/G.723(.1)/G.711 H.323/SIP/SGCP/IPDC RTP/UDP IP MLPPP/FR/ATM AAL1 – – – Voice over IP Protocols Constant - Voice Packets ride on UDP/RTP Variable - Several Signaling Methods

25 Presentation_ID © 1999, Cisco Systems, Inc. ITU H.323 Infrastructure ITU H.323 Infrastructure Intranet Gatekeeper Gateway e H.323 Terminals V - User Interface - Gateway - Video Terminal Telephone Network H.320 (Over ISDN) H.324 (Over POTs) Speech Only (PSTN) Proxy Real-Time Network

26 Presentation_ID © 1999, Cisco Systems, Inc. Agenda IntroductionIntroduction Codecs Voice Over Packets Characteristics for VoIP, VoATM and VoFR QoS and Signaling for VoIP Conclusions