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Abdellatif O. Abdellatif Sudatel Telecom Group

Abdellatif O. Abdellatif Sudatel Telecom Group. Voice Over IP. 1. Why An Organization Would Use IPT. 2. Definition. 3. IP Telephony QoS. 4. How Your Voice Becomes A Packet. 5. MOS. 6. SIP & H.323. Contrast between PSTN and NGN / Smooth Migration. 7.

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Abdellatif O. Abdellatif Sudatel Telecom Group

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  1. Abdellatif O. AbdellatifSudatel Telecom Group

  2. Voice Over IP

  3. 1 Why An Organization Would Use IPT 2 Definition 3 IP Telephony QoS 4 How Your Voice Becomes A Packet 5 MOS 6 SIP & H.323 Contrast between PSTN and NGN / Smooth Migration 7

  4. Why an organization would use IPT Trackable Cost Saving : • Moves, Adds, and Changes (MACS) • Bandwidth and equipment efficiency • Lower cost of transmission • New applications and devices

  5. 1 Why An Organization Would Use IPT 2 Definition 3 IP Telephony QoS 4 How Your Voice Becomes A Packet 5 MOS 6 SIP & H.323 Contrast between PSTN and NGN / Smooth Migration 7

  6. Definition • IP Telephony • Transmission of voice, fax, and related services over packet-switched IP- based networks. • Internet Telephony • Specific sub-set of IP Telephony in which the principal transmission network is the public Internet. • Voice-over-the-Net (VoN); Internet Phone; Net Telephony.

  7. Definition • Voice-over-IP (VoIP) • Specific sub-set of IP Telephony in which the principal transmission network(s) is (are) private, managed IP-based network(s). • Voice-over-DSL (VoDSL)

  8. IP Telephony Instead of using traditional circuit switch systems for voice communications, IP Telephony uses a packet protocol originally designed for data communications Circuit Switched - PSTN Packet Switched– Data Network

  9. PSTN PSTN ISP ISP Internet Modem Modem Configuration Options PC-to-PC USER A USER B USER B Server

  10. ISP IPTP PSaTN PSTN Internet Modem PC-to-Phone IP Telephony Provider Gateway USER A USER B

  11. PSTN PSTN Phone-to-Phone Management IP Network Gateway Gateway Network of IP Telephony Service Provider USER B USER A USER B USER B USER A

  12. Gateways allow PCs to also reach phones Public Switched Telephone Network Initially, PC to PC voice calls over the Internet Gateway IP Network Multimedia PC Multimedia PC Gateway PSTN …or phones to reach phones PSTN

  13. 1 Why An Organization Would Use IPT 2 Definition 3 IP Telephony QoS 4 How Your Voice Becomes A Packet 5 MOS 6 SIP & H.323 Contrast between PSTN and NGN / Smooth Migration 7

  14. Packet loss (%) 10 9 8 Unacceptable for Voice or Fax ITU G.114 Utility Recommendation 7 6 5 4 3 PossiblyTolerable for Voice Operational Target for Voice and Fax 2 1 0 100 200 300 500 Delay (ms) 400 IP Telephony QoS

  15. The Three Current Models OF QOS • Best Effort • Integrated Services (INTSERV ) • Differentiated Services (DIFF SERV)

  16. 6 1 2 3 4 5 6 1 3 5 4 QoS: Delays-1 NetworkDelay • Sender Delay: • Codingdelay • Packetingdelay • Transmission delay … • Receiver Delay: • Decodingdelay • DePacketingdelay • Receiverdelay …   IP Network Loss Packet T T"#T’#T Sender Network Receiver

  17. Delay-2 • Fixed Delay Components • Propagation • Serialization • Processing: (coding, compression, decompression, decoding)

  18. Delay-3 • Variable Delay Components • Queuing delay • Dejitter buffers • Variable packet sizes

  19. 1 Why An Organization Would Use IPT 2 Definition 3 IP Telephony QoS 4 How Your Voice Becomes A Packet 5 MOS 6 SIP & H.323 Contrast between PSTN and NGN / Smooth Migration 7

  20. How Your Voice Becomes A Packet • Voice Encoding : Analog to Digital • The NyquistTheorem • Quantization and Quantization Techniques • Compressing Voice • - compression Techniques • - CODECs

  21. How to Turn Voice Into Bits • The 4 Step Recipe : • Take Many Sample Of The Analog Signal • Calculate A number Representing Each Sample (quantization ) • Convert The Number To Binary • (Optional) compression

  22. The Nyquist Theorem • A tribute to Dr Nyquist • The Nyquist Theorem : “ if you sample a signal in regular intervals at least twice the highest Channel frequency the samples will contain enough information to accurately reconstruct the signal”

  23. The Nyquist Theorem • Some Important Frequencies : The Human Ear : 20-20,000 Hz Human speech : 200- 9,000 Hz Telephone Channels : 300- 3, 400 Hz Nyquist Theorem : 300- 4,000 Hz

  24. Quantization Techniques • Waveform Algorithms ( Encode everything ) • - PCM • - AD PCM • Source Algorithms ( Encode changes ) • - CS- ACELP • - LDCELP

  25. CODECs • Waveform CODECs - G.711 Uses PCM coding and chomps up 64 kbps - G.726 Used AD PCM Coding and eats 32 kbps … or 24 kbps … or 16 kbps

  26. 1 Why An Organization Would Use IPT 2 Definition 3 IP Telephony QoS 4 How Your Voice Becomes A Packet 5 MOS 6 SIP & H.323 Contrast between PSTN and NGN / Smooth Migration 7

  27. Mean opinion score MOS How Good Do They Sounds ? Based On Mean Opinion Score Scale Of 1-5 Toll Quality Is 4,0 MOS

  28. DSP • Digital signal processors are the engines behind a voice network • Perform the following: • - Analog to digital conversion • - conferencing • - Echo cancellation • - Voice activity Detect • - Comfort noise • - Transcoding

  29. 1 Why An Organization Would Use IPT 2 Definition 3 IP Telephony QoS 4 How Your Voice Becomes A Packet 5 MOS 6 SIP & H.323 Contrast between PSTN and NGN / Smooth Migration 7

  30. IP Telephony SignalingProtocols: H.323 Describes terminals and other entities that provide multimedia communications services over Packet Based Networks (PBN) which may not provide a guaranteed Quality of Service. H.323 entities may provide real-time audio, video and/or data communications.

  31. Packet Based Network Circuit Switched Networks H.323 Components Multipoint Control Unit Gatekeeper Gateway Terminal

  32. SIP: Session Initiation Protocol Session Initiation Protocol - An application layer signaling protocol that defines initiation, modification and termination of interactive, multimedia communication sessions between users. IETF RFC 2543 Session Initiation Protocol

  33. SIP Components PSTN Location Server Redirect Server Registrar Server User Agent Gateway Proxy Server Proxy Server SIP Distributed Architecture

  34. Contents 1 Why An Organization Would Use IPT 2 Definition 3 IP Telephony QoS 4 How Your Voice Becomes A Packet 5 MOS SIP & H.323 6 7 Contrast between PSTN and NGN / Smooth Migration

  35. App Server IN NMS Policy Service Packet core network Soft switch Soft switch switch STP AMG SIP Phone IAD PC Phone H.323 Phone Smooth Migration Soft switch Tandem /toll exchange Packet core network LE LE SG ISUP TMG WMG PLMN PSTN

  36. Intelligent Service Server Service Server SoftSwitch IP Core Signaling Module Switching Array SS7 Signaling Gateway CPU User Access Module Trunk Module Trunk Gateway User Access Gateway Trunk Gateway Trunk Gateway Contrast between PSTN and NGN

  37. Final Thoughts • One approach, which is hotly debated in the VoIP market, is to rip out your old PBX, phones and wiring and replace everything with IP phones. That might work in some cases, particularly where the old PBX is long past its expiration date, but it isn't always the best approach.

  38. Consider deploying IP Telephony based on a Phased Approach • Understand the benefits that the technology offers, not just the costs • Have a Plan

  39. References • http://www.protocols.com/papers/voip.htm • http:// communication howstuffworks.com/ip-telephony • http://www.networkmagazine.com/encyclopedia/search?term=IPtelephony • CCNA_voice_cbt_nuggets • CCNP-ngts-VoIP

  40. Thanks!!!

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