SIP-I for Interworking between PSTN and IP Networks Tiina Mustalahti 15.9.2008

1. SIP-I for Interworking between PSTN and IP Networks Tiina Mustalahti 15.9.2008 Supervisor: Jyri Hämäläinen

2. Outline • Objective of the Study • Methodology • IP Multimedia Subsystem • Session Control Protocols • Conclusions

3. Outline • Objective of the Study • Methodology • IP Multimedia Subsystem • Session Control Protocols • Conclusions

4. Objective of the Study • Evaluate the use of SIP-I for interworking between the PSTN and IP networks • Compare SIP-I to the other session control protocols • Study the SIP-I protocol from operators’ point of view

5. Outline • Objective of the Study • Methodology • IP Multimedia Subsystem • Session Control Protocols • Conclusions

6. Methodology • Literature survey • The documents studied included standards, books, figures, guidelines, whitepapers, press releases, and other material • Interviews • The empirical part of the study was collected by conducting interviews (5) with the experts from different operators and the Ericsson organization

7. Outline • Objective of the Study • Methodology • IP Multimedia Subsystem • Session Control Protocols • Conclusions

8. IP Multimedia Subsystem (1/2) • Core Network consists of the following parts: • Circuit Switched domain • Packet Switched domain • IP Multimedia Subsystem (IMS) – along in Release 5 • IMS provides real-time multimedia sessions, such as Voice over IP (VoIP) calls • The main signaling protocol is Session Initiation Protocol (SIP) Anywhere. Anytime. Any device.

9. IP Multimedia Subsystem (2/2)

10. Outline • Objective of the Study • Methodology • IP Multimedia Subsystem • Session Control Protocols • Conclusions

11. Session Control Protocols (1/3) • Session Initiation Protocol (SIP) • SIP is responsible for establishing and managing multimedia sessions, such as VoIP calls • SIP does not provide any method directly interworking with the PSTN network: alternative protocols are needed (BICC, SIP-T and SIP-I) • Bearer Independent Call Control (BICC) • Standardized by ITU-T in 2000 • Based on the signalling protocol used in PSTN, ISUP • SIP for Telephones (SIP-T) • Defined by IETF in 2002 • Extention to SIP for interworking between the IP and PSTN networks • Based on both SIP and ISUP • SIP with encapsulated ISUP (SIP-I) • Standardized by ITU-T in 2004 • Extention to SIP for allowing full interworking with the PSTN network • Based on both SIP and ISUP

12. Session Control Protocols (2/3)

13. Session Control Protocols (3/3) • Comparison between BICC and SIP-T/SIP-I • BICC is more mature than SIP-T and SIP-I • IMS was standardized around SIP: SIP-T and SIP-I considered as longer term solutions than BICC • There does not appear to be any futher plans to modify BICC • Full technical specification of SIP-I will be provided by 3GPP during Release 8 timeframe • BICC cannot be used for interworking between the wireless and wireline domains unlike SIP-T and SIP-I • Comparison between SIP-T and SIP-I • SIP-I is generally accepted as more complete specification than SIP-T

14. Outline • Objective of the Study • Methodology • IP Multimedia Subsystem • Session Control Protocols • Conclusions

15. Conclusions • Benefits relating to SIP-I • Based on both SIP and ISUP protocols • Since IMS was standardized around SIP, SIP-I is considered as a long-term solution • Full technical specification is coming: SIP-I will be considered as an alternative to BICC between two MSC Servers • Retards for the deployment of SIP-I • Migration towards to an all-IP network including new protocols, such as SIP-I, takes always time and money • Most of the operators want to proceed slowly and learn from the IP pioneers • SIP-I still in its early phase • Specifications are general and lack of important details

16. Conclusions • The mobile industry should adopt only one session control protocol • There would not be too many separate interworking cases • Services supported end-to-end without loss of functionalities • SIP-I was found to fit best for this purpose

17. Questions?