CANS: An H.323 Signalling Service Rhodes University Broadband 2 Computer Science Department

Rhodes University/Comp uter Science 03/09/2002 Today’s Presentation Overview H.323 Services –Non-Signalling and Signalling Example (AlarmClock Service) Summary

Rhodes University/Comp uter Science 03/09/2002 Overview H.323 is an IP communications signalling protocol Without services it is simply an ‘ancient telephone’ sitting on an advanced underlying network - waste Services include but not limited to conventional telephone services (CT) IP communications protocol must define mechanisms to create new services

Rhodes University/Comp uter Science 03/09/2002 Signalling vs. Non-signalling Services Non-signalling service is simply an H.323 compliant terminal with embedded “intelligence” –E.g. Reader, MarkReader Signalling service requires information that the protocol itself needs to handle or pass consistently –E.g. Call Transfer SS(H.450.2)

Rhodes University/Comp uter Science 03/09/2002 Non-signalling service Creation Requires limited knowledge of H.323 protocol Can wrap a number of conventional applications within H.323 compliant terminal Can develop powerful applications quickly Very easy to deploy – no additional signalling info

Rhodes University/Comp uter Science 03/09/2002 Signalling Service Creation Requires extensive knowledge of H.323 protocol –Includes knowledge of ASN.1 structures –Extended to other description languages (ABNF) –Release documents to standardise new services –Interoperability Bake-offs for product testing More restrictive as a result of maintaining interoperability – trade-off Interoperability not guaranteed but recovery is

Rhodes University/Comp uter Science 03/09/2002 H.323: Std Signalling Service Mechanisms As of H.323 version 4, there are 3 ways of extending the H.323 protocol messages (H.225) –H Supplementary Services (SS Framework) –H Generic Extensibility Framework (GEF) –Non-Standard Parameters (Property of underlying message description – ASN.1)

Rhodes University/Comp uter Science 03/09/2002 Other Std Service Creation Features Annexes to Recommendation H.323 Example = Annex K – HTTP-Based Control of H.323 Services Allows service providers to provide users with a flexible way of controlling the services they use (using HTTP) AlarmClock service uses Annex K

Rhodes University/Comp uter Science 03/09/2002 Example Service Implemented a service to demonstrate the use of the H.323 service extension mechanisms Made use of both H.450 (SS) and H.460 (GEF) Finally, demonstrate the use of Annex K What does the service do?

Rhodes University/Comp uter Science 03/09/2002 AlarmClock Service A service that enables H.323 users (SoftPhone or Telephone) to request a service (reminder) call at a specified time on a specified device The service (CallBack) call can be made to both SoftPhones & Telephones (extended to include SMS messages using an MGCP SMS Gateway)

Rhodes University/Comp uter Science 03/09/2002 Example Scenario (Setup) H.323 AlarmClock Server H.323 SoftPhone Invoke ReturnError OpenURL(Register.html)

Rhodes University/Comp uter Science 03/09/2002 Example Scenario (CallBack) H.323 AlarmClock Server Initiate H.323 Call via gateway PSTN Telephone user

Rhodes University/Comp uter Science 03/09/2002 ASN.1 Structure (Callback details)

Rhodes University/Comp uter Science 03/09/2002 ACSGW

Rhodes University/Comp uter Science 03/09/2002 GWACS ILLEGAL !!!!!

Rhodes University/Comp uter Science 03/09/2002 GWACSGWACS

Rhodes University/Comp uter Science 03/09/2002 Summary H.323 is flexible Still maintains a high std of interoperability A wealth of really exciting services can be developed using H.323 H.323 is moving forward every day (lots of industry support)

Rhodes University/Comp uter Science 03/09/2002 We also acknowledge the bursary support of the National Research Foundation and Microsoft. This work was undertaken in the Distributed Multimedia Centre of Excellence at Rhodes University with financial support from Telkom, Comparex Africa, Letlapa Mobile Solutions and THRIP.