Mikko Suominen S-38.310 Thesis Seminar on Networking Technology Helsinki University of Technology

1. Enhancing System Capacity and Robustness by Optimizing Software Architecturein a Real-time Multiprocessor Environment Mikko Suominen S-38.310 Thesis Seminar on Networking Technology Helsinki University of Technology 01.06.2004

2. Basic Information • Thesis written at Oy L M Ericsson Ab, Finland • Supervisor: Professor Jorma Jormakka • Instructors: M.Sc. Ilkka Koskinen and M.Sc. Juha Eloranta

3. Contents • Background • Problem Description • Objectives • Scope • UMTS Release 4 Network • Media Gateway • Architecture Tradeoff Analysis Method • Architecture Optimization and Analysis • Conclusion and Future Research

4. Background (1/2) • The Universal Mobile Telecommunications System (UMTS) is a third generation mobile network standard specified by the 3rd Generation Partnership Project (3GPP). • The UMTS has been evolved from the GSM (Global System for Mobile Communications) and the GPRS (General Packet Radio Service) networks. • UMTS specifications are divided into multiple releases. • Each release contains some new functionalities and modifications to the network architecture.

5. Background (2/2) • The UMTS Release 4 network architecture physically separates call control from media and bearer control. • This means that the Mobile Switching Centre (MSC), which handles these tasks in the GSM network, is divided into two separate network elements. • The MSC server handles the call control. • The Media Gateway (MGW) handles the media and the bearer control. • The MSC server controls the MGW via the Gateway Control Protocol (GCP) interface.

6. Problem Description (1/2) • The Ericsson Media Gateway for Mobile Networks (M-MGW) is an existing product that fulfills the specifications for the MGW. • The M-MGW is the real-time multiprocessor system this thesis deals with.

7. Problem Description (2/2) • System properties, such as capacity and robustness, are highly dependent on the software architecture. • The research problem of this thesis is to find and analyze different kinds of distributed software architectures that could enhance the capacity and the robustness of the M-MGW. • The capacity enhancement increases the possible amount of traffic carried through the M-MGW. • The robustness enhancement improves the in-service performance of the M-MGW.

8. Objectives • The purpose of this thesis is to find a number of software architectures that would help to solve the research problem of the thesis. • Every proposed software architecture optimization will be shown to work according to the specifications. • Finally, the proposed architectures will be analyzed in the light of capacity and robustness improvements.

9. Scope • This thesis deals with the UMTS Release 4, because it is the first release containing the physical separation between the MSC server and the MGW functionalities. • Inside the M-MGW, the software architecture optimization scope is limited to the User Plane Control Functions (UPCF), which handles the GCP and controls the actual User Plane. • This thesis presents only architectural level solutions. • More detailed solutions including the implementation have been left to future research.

10. AuC BSC BSS BTS CN CS EIR GGSN GMSC HLR ME MGW MS MSC PSTN RNC RNS SGSN SIM USIM VLR Authentication Centre Base Station Controller Base Station System Base Transceiver Station Core Network Circuit Switched Equipment Identity Register Gateway GPRS Support Node Gateway Mobile Switching Centre Home Location Register Mobile Equipment Media Gateway Mobile Station Mobile Switching Centre Public Switched Telephone Network Radio Network Controller Radio Network Subsystem Serving GPRS Support Node Subscriber Identity Module User Services Identity Module Visitor Location Register UMTSRelease 4Network

11. Media Gateway (1/2) • The fundamental purpose of the MGW is to connect the UMTS Core Network to other networks, such as UTRAN (UMTS Terrestrial Radio Access Network) and ISDN (Integrated Services Digital Network). • The MGW transports traffic between different networks and may support: • media conversion • bearer control • payload processing e.g. with different codecs

12. API CPP GCP MGW Application Programming Interface Connectivity Packet Platform Gateway Control Protocol Media Gateway Media Gateway (2/2) M-MGW Software Architecture

13. Architecture Tradeoff Analysis Method (1/2) • Architecture Tradeoff Analysis Method (ATAM) is a technique for analyzing software architectures. • The ATAM is developed in Software Engineering Institute of Carnegie Mellon University (CMU/SEI). • The purpose of the ATAM is to assess the consequences of architectural decisions in light of quality attribute requirements. • The ATAM process consists of nine steps. • A simplified version of the ATAM is used in this thesis.

14. Architecture Tradeoff Analysis Method (2/2) Quality Attribute Scenario

15. Architecture Optimization and Analysis (1/5) • Capacity enhancement • Increase the possible amount of traffic carried through the M-MGW • UPCF software architecture optimization so that it is able to handle more GCP messages simultaneously • Study, which UPCF tasks can be run in parallel on different processors • Robustness enhancement • Improve the in-service performance of the M-MGW • UPCF software architecture optimization so that its fault tolerance is improved • Study, which UPCF services can be replicated across multiple processors

16. Architecture Optimization and Analysis (2/5) UMTS Originating Call

17. Architecture Optimization and Analysis (3/5) Signaling Connection Failure

18. Architecture Optimization and Analysis (4/5) • Quality attribute scenario 1 • Capacity  Transaction Throughput  Handling Busy Hour Call Attempts • Source of stimulus: MSC server • Stimulus: GCP transaction arrivals during the busy hour • Environment: Normal operation • Artifact: UPCF system area • Response: All arrived GCP transactions can be handled • Response measure: All arrived calls can be established

19. Architecture Optimization and Analysis (5/5) • Quality attribute scenario 2 • Robustness  Software Failure  Handling A Subsystem Crash • Source of stimulus: Subsystem internal to the UPCF • Stimulus: Subsystem crash • Environment: Normal operation • Artifact: UPCF system area • Response: UPCF system area degraded • Response measure: No downtime

20. Conclusion and Future Research (1/2) • Three different architecture enhancements were found. • Enhancement 1 • Easy to implement • Most of the legacy architecture could be re-used • Does not improve the M-MGW capacity or robustness from a single MSC server’s point of view • Enhancement 2 • Improves notably the M-MGW capacity and robustness • Future proof solution (very scalable) • Harder to implement than the first one • Enhancement 3 • Might improve the M-MGW capacity, but not robustness • Can be seen as a further enhancement of the first or the second enhancement

21. Conclusion and Future Research (2/2) • Possible topics for future research: • Testing and simulating the M-MGW software architecture enhancements found in this thesis • Enhancing the user plane functions • Optimizing the usage of the GCP in the M-MGW

22. Thank you for listening! Questions?