1. Introduction Chapter 1

2. Internet Telephony 2 Instructor Ming-Feng Chang, mfchang@csie.nctu.edu.twmfchang@csie.nctu.edu.tw EC 425, 5731812 Textbook “ Carrier Grade Voice over IP. ” D. Collins, 2nd ed., McGraw-Hill, 2003. Additional technique reports and papers Requirements Homework and machine problems25% One mid-term exam 45% One term project 30%

3. Internet Telephony 3 Telephone 1876 Alexander Graham Bell transfered voice over wire for the first time. Direct connection; telephones are sold in pair A B D E F C

4. Internet Telephony 4 Switches As the number of users increases, switching centers are more economical A B D E F C

5. Internet Telephony 5 Digital Switches Took more than 100 years from analog to digital voice transmission Better quality for long distance calls Demands to telephone network become constantly higher World-wide communication network

6. Internet Telephony 6 Mobile Communications Bell Laboratories introduced the idea of cellular communications in 1947 Motorola and Bell Labs in the 60s and early 70s were in a race to design portable devices Dr. Cooper, 2-pound Motorola handset (1973)

7. Internet Telephony 7 The Internet Data Networks since 1960 ’ s ARPA*-Net 1969 Internet since early 1990 ’ s

8. Internet Telephony 8 What is VoIP? Use a LAN and/or WAN to carry voice in the same way as the telephone system. Why? Save costs Improve facilities.

9. Internet Telephony 9 VoIP Gateway The interface between VoIP and PSTN An essential feature for VoIP

10. Internet Telephony 10 Cheap phone-cards/voice carriers

11. Internet Telephony 11 Carrier Grade VoIP Carrier grade and VoIP mutually exclusive A serious alternative with enhanced features Carrier grade The last time when it fails 99.999%, five-nines reliability Verizon network supports 70M voice access lines AT&T serves 300M voice calls a day Short call setup time, high speech quality no perceptible echos, noticeable delay or annoying noises Self-healing, highly scalable and manageable

12. Internet Telephony 12 VoIP Transport voice traffic using IP Voice over the Internet? Interconnected networks Applications: e-mail, file transfer, e-com The greatest challenges Voice quality and bandwidth Control and prioritize the access Internet: best-effort transfer The next generation VoIP != Internet telephony

13. Internet Telephony 13 IP A packet-based protocol Routing on a packet-by-packet base Packet transfer with no guarantees May not receive in order May be lost ore severely delayed TCP/IP Retransmission Assemble the packets in order Congestion control Useful for file-transfers and e-mail

14. Internet Telephony 14 Data and Voice Data traffic Asynchronous – can be delayed Extremely error sensitive Voice traffic Synchronous – the stringent delay requirements More tolerant of errors IP is not for voice VoIP must Match the PSTN Offer new and attractive capabilities at a lower cost

15. Internet Telephony 15 Why VoIP? Why carry voice? Internet support instant access to anything Everything can be done on the net? “ Dot-com guy ” Many new services and applications However, voice services provide more revenues Why use IP for voice? Why try to fix something that is not broken? Circuit-switching is not for datacom IP Equipment cost, integrated access, less bandwidth, and widespread availability

16. Internet Telephony 16 Lower Equipment Cost PSTN switch Proprietary – hardware, OS, applications High operation and management cost Training, support and feature development cost Mainframe computer The IP world Standard hardware and mass-produced Application software is quite separate A horizontal business model IN does not match the openness and flexibility of IP A few highly successful services

17. Internet Telephony 17 Moore ’ s Law Processing power doubles every 18 months Frame10 Router20 ATM 40 Circuit80

18. Internet Telephony 18 Voice/Data Integration Click to talk application Personal communication E-commerce CTI – Computer Telephony Integration Web collaboration Shop on-line with a fried at another location Video conferencing IP-based PBX IP-based call centers

19. Internet Telephony 19 Lower Bandwidth Requirements PSTN G.711 - 64 kbps Human speech bandwidth < 4K Hz The Nyquist Theorem: sample rate twice the bandwidth 8K * 8 bits Sophisticated coders 32kbps, 16kbps, 8kbps, 6.3kbps, 5.3kbps GSM – 13kbps Save more by silence-detection Traditional telephony networks can use coders too But it is difficult So many switches VoIP – two ends of the call negotiate the codec

20. Internet Telephony 20 The Widespread Availability of IP IP LANs and WANs The ubiquitous presence VoFR or VoATM Only for the backbone of the carriers Voice over WLAN Voice over WiFi for now Voice over WiMax could be a real threat for PLMN

21. Internet Telephony 21 The VoIP Market The revenue projection Value-added service

22. Internet Telephony 22 Revenue breakdown VoIP Fax over IP

23. Internet Telephony 23 VoIP Challenges Speech quality Must be as good as PSTN Delay The round-trip delay International calls through satellite – 500-600 ms G.114 – < 300 ms Jitter Delay variation Different routes or queuing times Adjusting to the jitter is difficult Jitter buffers add delay

24. Internet Telephony 24 Packet loss Traditional retransmission cannot meet the real-time requirements Packets must be played in order Speech-coding techniques MOS, Mean Opinion Score >= 4 P.800, but subjective in nature G.71164kbps4.3 G.72632kbps4.0 G.723 (celp)6.3kbps3.8 G.72816kbps3.9 G.7298kbps4.0 GSM13kbps3.7 iLBC13.33/15.2kbps high robustness to packet loss iSAC10-32kbpswideband codec

25. Internet Telephony 25 Network Reliability and Scalability PSTN system fails Five-nines reliability The office computer network fails Today ’ s VoIP solutions Redundancy and load sharing Scalable too – easy to start small and expand Fiber-optic transport, gigabit router, high-speed ATM base

26. Internet Telephony 26 Managing Access and Prioritizing Traffic A single network for a wide range of applications Call admitted if sufficient resources available Different types of traffic are handled in different ways QoS has required huge efforts

27. Internet Telephony 27 VoIP Implementations IP-based PBX solutions A single network Enhanced services

28. Internet Telephony 28 IP voice mail One of the easiest applications Hosted PBX solutions For SOHO Internet and telephony access IP call centers Use the caller ID Automatic call distribution Load the customer ’ s information on the agent ’ s desktop Click to talk

29. Internet Telephony 29

30. Internet Telephony 30 IP user devices VoIP protocols, SIP Integrated functions Telephony, WWW, e-mail, voice mail, address-book WiFi phone

31. Internet Telephony 31 Skype A peer-to-peer VoIP client developed by KaZaa in 2003 Skype can work almost seamlessly across NATs and firewalls has better voice quality than the MSN and Yahoo IM applications encrypts calls end-to-end, and stores user information in a decentralized fashion SkypeOut, SkypeIn

32. Internet Telephony 32 New applications The networks are converging Possible applications Video Phones Conferencing Collaboration Tools Distance Learning / Training Tele-medicine, tele-repair, tele- … On-line gaming Dating Applications Skype is rolling out developer kits and programs to encourage innovation, similar to the wireless industry promoting application development on their platforms

33. Internet Telephony 33 Why Internet Telephony? The business case Integration of voice and data Bandwidth consolidation Tariff arbitrage Universal presence of IP Maturation of technologies The shift to data networks

34. Internet Telephony 34 VoIP Spectrum Traditional Telecomm Segments in transition to VoIP International Low cost calling Internal networks of large carriers Numerous equipment makers, software providers Residential VoIP phone service This area is exploding: Vonage, Packet8, Broadvoice … Office PBX systems Using VoIP inside a company location, and between corporate branches Call Center Instant Messaging Not only the traditional big 3, but newcomers like Skype … Consumer and Business Application Areas Voice applications Wireless Internet applications

35. Internet Telephony 35 Course Overview VoIP and RTP Voice codecs H.323 SIP – simple and flexible MGC and softswitch SS7, UMTS QOS Voice over WLAN P2P IP communications Charging and payments