Mobile Internet Telephony: Mobility Extension to H.323

1. Mobile Internet Telephony: Mobility Extension to H.323 Adviser: Ho-Ting Wu Speaker: Chih-Hao Tseng

2. Outline • Introduction VoIP • Mobility Issues On H.323 Termainals • Call Signaling Procedure For Mobility Management • Conclusion • Reference

3. Introduction • Voice over IP (VOIP) uses the Internet Protocol (IP) to transmit voice as packets over an IP network • Digital signal processors (DSP) segment the voice signal into frames and store them in voice packets. Here the voice signal is digitized, compressed and converted to IP packets and then transmitted over the IP network. • Internet telephony gateway (ITG) bridges switched circuit phone networks and packet-switched data network.

4. Structure

5. VoIP • Signaling • User Information Translation • Session Establishment • Session Negotiation • agree on a set of media and codecs, add/suppres media, change encoding,… • Media Transport • Real-time Transport Protocol (RTP) • Real-time Transport Control Protocol (RTCP)

6. Sequencing Payload Identification Frame Indication Source Identification Synchronization Transport Address QoS feedback Session control Identification Synchronization RTP & RTCP

7. VoIP Phones

8. Codec

9. Introduction H.323 • ITU-T standard • International Telecommunication Union-Telecommunication Standardization Sector • Provides the technical requirements for voice communication over IP service • Control Protocol • H.225/Q.931 Call Signaling • H.225 (Registration, Admission, Status)RAS Signaling • H.245 Media Control

10. Components of H.323 • Terminal • Endpoint that support H.245, Q.931, RAS, RTP,MCU • Gateway • Connect heterogeneous networks • Gatekeeper • Address Translation • Bandwidth Management

11. RAS Message (1/2)

12. RAS Message (2/2)

13. Protocol Stack

14. RAS Channel 1. ARQ (alias address/bandwidth) 2. ACF (call signaling channel address/bandwidth) 6. ACF Q.931 Call Signaling Channel 5. ARQ 3. Setup 4. Call Proceeding 7. Alerting 8. Connect (H.245 Address) H.245 Control Channel (Logical Channel 0) Master/Slave Determination Capability Exchange OpenLogicChannel (RTCP address) OpenLogicChannelACK (RTP & RTCP address) RTP Stream RTCP Stream RTCP Stream H.323 Call Setup Flow Chart Gatekeeper Terminal Terminal

15. Introduction SIP • Session Initiation Protocol (SIP) • IETF standard • Internet Engineering Task Force • Application layer control protocol for creating, modifying and terminating sessions • Text-encoded protocol • SIP URL • Sip: bob@ntut.edu.tw • Sip: 11025919@ntut.edu.tw • Supporting Protocol • Session Description Protocol (SDP) • Session Announcement Protocol (SAP)

16. Communication Flow Chart

17. Components of SIP Phone • SIP Clients • Proxy Server • acts as both a server and a client for the purpose of making requests on behalf of other clients • forwards client requests to another SIP server or to the final destination • may “fork” requests to multiple servers (“search tree”) • Registrar Server • A server that receives registrations from clients and regarding current locations • Redirect (Location) Server • redirects users to try other SIP server as the next-hop towards destination, and client has to contact it directly

18. (3) tsengii@140.124.181.206 (2) tsengii (4) INVITEtsengii@140.124.181.206 (1) INVITE tsengii (5) 200 OK (6) 200 OK (8) ACK tsengii@140.124.181.206 (7) ACK tsengii@140.124.181.206 Invitation Location(Redirect) server key@140.124.181.217 tsengii Proxy key tsengii@140.124.181.206

19. SIP Message body

20. Compare between H.323 & SIP

21. Supporting Protocols

22. Mobility Issues On H.323 Terminals • Internet Telephony: From stationary to mobile Terminals • System Architecture • Mobility Management

23. abbreviation • POTS: Plain Old Telephone Service • IAM: Initial Address Message • ACM: Address Complete Message • ANM: ANswer Message • REL: RELease

24. POTS phone to H.323 terminal

25. H.323 terminal to POTS phone

26. Internet Telephony: From stationary to mobile Terminals • Static IP to Dynamic IP • Discrete reachability • Portability • Off –line reachability • Continuous reachability • Mobility (encompasses portability) • On-going connection

27. Handoff mechanism • Home agent • Home location register • Foreign agent • Visitor location register • Real-time handshaking

28. System Architecture

29. Mobility Management • 4 core operations: • Registration • Call establishment • Roaming • Handoff

30. Intrazone roaming • A mobile host moves with a zone

31. Interzone roaming • It crosses the boundary to other zones.

32. Call Signaling Procedure For Mobility Management • Registration • Call Establishment • Roaming • Using IP Multicast to Support Mobility

33. Registration • A Gatekeeper may advertise its availability for mobility services (GK active) • Gatekeeper multicasts a new message called Gatekeeper advertisement (GAD) to the respective zone to advertise its availability. • A mobile terminal may solicit the service of a Gatekeeper (terminal active) • A mobile terminal may send a GRQ message to the Gatekeeper well-known discovery multicast address.

34. Call Establishment • A call between a Plain Old Telephone Service (POTS) phone and an H.323 terminal can be made from either direction. • POTS phone to an H.323 cross ITG • An H.323 to a POTS phone cross ITG

35. Call establishment ITG to H.323 terminal

36. Call establishment H.323 terminal to ITG

37. Roaming • Request-to-join • Requesting by the new participants • Only the request-to-join approach is demonstrated. • Invite-to-join • Being invited by the participants of a conference • Invite-to-join can be performed in a similar manner.

38. Call signaling for roaming: intrazone roaming

39. Call signaling for roaming: interzone roaming

40. Using IP Multicast to Support Mobility • D class：224.0.0.0～239.255.255.255：for Multicast • Individual hosts are free to join and leave a multicast group at any time • Sends an Internet Group Management Protocol (IGMP) leave message to the immediately neighboring multicast router to depart the group in the old subnet, and sends a report message to join the group in the new subnet.

41. Call signaling for call establishment with multicasting ITG to H.323

42. Call signaling for call establishment with multicasting H.323 to ITG

43. Call signaling for intrazone roaming with multicasting

44. Call signaling for interzone roaming with multicasting

45. Conclusion(1/2) • Two approaches to mobility: • Using ad hoc multipoint conference expansions • Using IP multicasting to emulate mobility • Since ad hoc multipoint expansion has been defined in H.323, our solution introduces no additional entities to H.323 and requires minimal modifications to the existing H.323 protocol.

46. Conclusion(2/2) • Signal exchange in ITG • Circuit switching to Packet switching • Handoff time delay • Too long to make session disconnected?

47. Reference • “Mobile Internet Telephony : Mobility Extension to H.323”, Wanjiun Liao, Member, IEEE,IEEE Transactions on vehicular technology, vol.50, no.6, November 2001. • OpenH323,” http://www.voxgratia.org/” • OpenH323, “http://www.openh323.org/” • http://life.iiietc.ncu.edu.tw/xms/forum/show.php?id=4125 • 校園網路IPv6 SIP VoIP之建置與推廣, 黃悅民,國立成功大學 工程科學系 教授 • http://www.environmental-studies.de/GSM_Netz/Roaming/R-3/Handover.jpg