1. VoIP & Mobile VoIP 97598039 梁紀翔 NETLab

2. Topics • Voice over Internet Protocol • H.323, SIP, Skype • Adoption • Benefits • Challenge • Mobile VoIP • Generic Access Network

3. Voice over Internet Protocol • Family of transmission technologies for delivery of voice communications over IP networks • Talks to other IP phone or PTSN • Use codecs convert analog voice into digital audio stream • Video, text, file, conference, voice mail…etc

4. Common protocols • H.323 (ITU-T) • Session Initiation Protocol (RFC 3261) • Skype (Propritary)

5. H.323 • First VOIP standard (Feb. 1996) • Part of H.32x family • Audio-Video communication on packet network • Call singling & control, multimedia transport & control, bandwidth control for P2P and multipoint conference • Based on Q.931 of ISDN

9. SIP • Application Layer protocol for controlling multimedia communication session over IP • Client-Server HTTP like Text-based control message request/response • Depend on SDP (RFC 2327), RTP

13. Skype • Proprietary P2P model, written by KaZaA developers • Decentralized user directory • AES encrypted

14. Adoptions • Many implementations of H.323 & SIP • Analog Telephone Adapter connects old phone and IP network • Dedicated IP phone • Softphone on PC

15. Benefits • Reducing communication and infrastructure costs • Charged per amount of data not per time • Free/Open-source IP-PBX software integrate legacy phone system ex. Asterisk • Flexibility • Easy to encrypt, location independence • Integration with other services

16. Challenge • QoS • Latency and Jitter • Power failure • Emergency call • Lack of redundancy • Number portability • Security • Fax and other telephony devices

17. Mobile VoIP • Extension of mobility to VoIP network • Mobile device with SIP client ex. fring • High speed IP communication 3.5G, WiFi, WiMax • Some company may block SIP • Use softswitch to bridge SIP and RTP to cell phone network • Handset still use GSM or CDMA

18. Generic Access Network • 3GPP standard to let dual-mode handset to seamlessly roam or handover between WLAN and WAN(GPRS) • GAN Controller • Inside cellular core network, as another base station • When detects WLAN, establish secure IP connection to GAN Controller

19. Questions ?

20. References • VoIP http://en.wikipedia.org/wiki/VoIP • H.323 http://hive.packetizer.com/users/packetizer/papers/h323/h323_protocol_overview.pdf • SIP http://www.cs.columbia.edu/sip/ • Asterik http://www.asterisk.org/ • Skype http://www.skype.com/intl/en/ • GAN http://www.3gpp.org/ftp/Specs/html-info/43318.htm • GAN http://www.3gpp.org/ftp/Specs/html-info/44318.htm • “行動網際網路電話之研製與實現”, 李昆達, 2005 • “H.323 網路電話視訊監控與錄製系統之研製”, 曾致皓, 2008 • “H.323 網路電話音訊監控與錄製系統之研製”, 黃威穎, 2008 • “客製化H.323協定之智慧型網路電話監控與錄音系統”, 蔡家瑞, 2009