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Rev A Mikko Suominen01.06.2004 1
Enhancing System Capacity and Robustness by Optimizing Software Architecture
in a Real-time Multiprocessor Environment
Mikko Suominen
S-38.310 Thesis Seminar on Networking Technology
Helsinki University of Technology
01.06.2004
Rev A Mikko Suominen01.06.2004 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
Rev A Mikko Suominen01.06.2004 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
Rev A Mikko Suominen01.06.2004 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.
Rev A Mikko Suominen01.06.2004 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.
Rev A Mikko Suominen01.06.2004 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.
Rev A Mikko Suominen01.06.2004 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.
Rev A Mikko Suominen01.06.2004 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.
Rev A Mikko Suominen01.06.2004 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.
Rev A Mikko Suominen01.06.2004 10
UMTSRelease 4Network
BSS
BSC
RNS
RNC
CN
Node B Node B
IuPS
Iur
Iub
USIM
ME
MS
Cu
Uu
MSC serverSGSN
Gs
GGSNGMSCserver
GnHLR
Gr
GcC
D
Nc
H
EIR
F Gf
GiPSTN
IuCS
VLRB
Gp
VLR
G
BTSBTS
Um
RNC
Abis
SIM
SIM-ME i/f or
MSC server
B
PSTN
cell
CS-MGWCS-MGW
CS-MGW
AuC
Nb
McMc
Nb
PSTNPSTN
Nc
Mc
AGb
E
BSS
BSC
RNS
RNC
CN
Node B Node B
IuPS
Iur
Iub
USIM
ME
MS
Cu
Uu
MSC serverSGSN
Gs
GGSNGMSCserver
GnHLR
Gr
GcC
D
Nc
H
EIR
F Gf
GiPSTN
IuCS
VLRB
Gp
VLR
G
BTSBTS
Um
RNC
Abis
SIM
SIM-ME i/f or
MSC server
B
PSTN
cell
CS-MGWCS-MGW
CS-MGW
AuC
Nb
McMc
Nb
PSTNPSTN
Nc
Mc
AGb
E
AuCBSCBSSBTSCNCSEIRGGSNGMSCHLRMEMGWMSMSCPSTNRNCRNSSGSNSIMUSIMVLR
Authentication CentreBase Station ControllerBase Station SystemBase Transceiver StationCore NetworkCircuit SwitchedEquipment Identity RegisterGateway GPRS Support NodeGateway Mobile Switching CentreHome Location RegisterMobile EquipmentMedia GatewayMobile StationMobile Switching CentrePublic Switched Telephone NetworkRadio Network ControllerRadio Network SubsystemServing GPRS Support NodeSubscriber Identity ModuleUser Services Identity ModuleVisitor Location Register
Rev A Mikko Suominen01.06.2004 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
Rev A Mikko Suominen01.06.2004 12
Media Gateway (2/2)
MGW
Application
CPP
User Plane Control
FunctionsGCP Termination
Media FramingFunction
Media Stream Function
User Plane Functions
Operationand
Maintenance
Bearer Termination External Bearer Control
Real-time Routing Switching Function Signaling Gateway
Physical Interfaces
API
GCPA
PI
AP
I
API
Signaling Transport Converter
Connection Coordinators
Virtual MGWs
APICPPGCPMGW
Application Programming InterfaceConnectivity Packet PlatformGateway Control ProtocolMedia Gateway
M-MGWSoftwareArchitecture
Rev A Mikko Suominen01.06.2004 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.
Rev A Mikko Suominen01.06.2004 14
Architecture Tradeoff Analysis Method (2/2)
Source ofStimulus
Stimulus
Artifact
Environment
Response
ResponseMeasure
QualityAttributeScenario
Rev A Mikko Suominen01.06.2004 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
Rev A Mikko Suominen01.06.2004 16
Architecture Optimization and Analysis (2/5)
MSC serverRNC MGWUE
SETUP
CALL PROCEEDINGInitial Address
Bearer Information
ADD.request ( CTX$, T$ )
ADD.reply ( CTX1, T2 )
Establish Bearer +Change Through-connection
ADD.request ( CTX1, T$ )
ADD.reply ( CTX1, T1 )
Prepare Bearer +Change Through-connection
RAB ASSIGNMENT REQ
RAB ASSIGNMENT COMPL UP Init
UP Init Ack
Continuity
Address CompleteALERTING
Answer
MOD.request ( CTX1, T1 )
MOD.reply ( CTX1, T1 )
MOD.request ( CTX1, T2 )
MOD.reply ( CTX1, T2 )CONNECT
Change Through-connection +Activate Inter-working Function +Activate Voice Processing Function
Activate Inter-working Function +Activate Voice Processing Function
UMTSOriginatingCall
Rev A Mikko Suominen01.06.2004 17
Architecture Optimization and Analysis (3/5)
SignalingConnectionFailure
MSC server MGW
SEC.request ( MGW Communication Up )
SEC.reply ( MGW Communication Up Ack )
Signaling connection failure
Signaling in service
Rev A Mikko Suominen01.06.2004 18
Architecture Optimization and Analysis (4/5)
• Quality attribute scenario 1– Capacity Transaction Throughput Handling Busy Hour Call Attempts
i. Source of stimulus: MSC serverii. Stimulus: GCP transaction arrivals during the busy houriii. Environment: Normal operationiv. Artifact: UPCF system areav. Response: All arrived GCP transactions can be handledvi. Response measure: All arrived calls can be established
Rev A Mikko Suominen01.06.2004 19
Architecture Optimization and Analysis (5/5)
• Quality attribute scenario 2– Robustness Software Failure Handling A Subsystem Crash
i. Source of stimulus: Subsystem internal to the UPCFii. Stimulus: Subsystem crashiii. Environment: Normal operationiv. Artifact: UPCF system areav. Response: UPCF system area degradedvi. Response measure: No downtime
Rev A Mikko Suominen01.06.2004 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
Rev A Mikko Suominen01.06.2004 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
Rev A Mikko Suominen01.06.2004 22
Thank you for listening!
Questions?