mikko suominen s-38.310 thesis seminar on networking technology helsinki university of technology

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 TechnologyHelsinki University of Technology

01.06.2004


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


Contents

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


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.


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.


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.


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.


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.


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.


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

VLRG

BTSBTS

Um

RNCAbis

SIM

SIM-ME i/f or

MSC serverB

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

VLRG

BTSBTS

Um

RNCAbis

SIM

SIM-ME i/f or

MSC serverB

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


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


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


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.


Architecture Tradeoff Analysis Method (2/2)

Source ofStimulus

Stimulus

Artifact

Environment

Response

ResponseMeasure

QualityAttributeScenario


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


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



SignalingConnectionFailure

MSC server MGW

SEC.request ( MGW Communication Up )

SEC.reply ( MGW Communication Up Ack )

Signaling connection failure

Signaling in service



• 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



• 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


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


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


Thank you for listening!

Questions?

mikko suominen s-38.310 thesis seminar on networking technology helsinki university of technology

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