System Telecommunication Software Maintainability of a · Telecommunication Software System ... • Parameters in RC-file. Ville Häkkinen ... SNA FTAM X.25 HDLC IEE802 UNIX/Digital

Ville Häkkinen03.06.2002

Maintainability of a Telecommunication Software

System

Ville Häkkinen 41679pComptel CorporationValvoja: Professori Raimo Kantola


Contents of the Presentation

• Introduction• Mediation in GPRS• Maintenance and maintainability• Maintainability metrics• Measurements and Results• Conclusions


Introduction

• This thesis will consider the maintainability of the Comptel Corporation mediation system.

• Focus is on mediation systems designed for mediating accounting information from General Packet Radio Service (GPRS) networks.

• Objective is to construct a measurement tool for evaluating the maintainability level of an accounting GPRS Mediation System.


Mediation

MEDIATION DEVICE

Billing System

MSC

Clearinghouse

Fraud ManagementSystem

Interconnect System

Datawarehouse

Customer CareSystem

WAPGateway

PSTN switch

Web-server

IP Router

IN-node

HLR


Mediation

• A mediation device provides an active link between communication networks and administrative applications.

• Example administrative systems– billing systems– network management systems– fraud control systems– data-warehouses– clearing-houses


Comptel Mediation SystemBILLING SYSTEM

MDS/ARD Accounting Record Delivery

Optional Processing With Custom Modules

MDS/ARS Accounting Record Storing

MDS/ARP Accounting Record Pre-rating

MDS/ARM Accounting Record Modification

MDS/ARC Accounting Record Collection

NETWORK ELEMENTS

Network Model

MDS/FTM

SchedulingControllingLogging

CDR Database

Process logs

Schedules,parameters


Mediation in GPRS Network by ETSI

• Collection of GPRS event data records (EDR) from the GPRS nodes.

• Intermediate EDR storage.• Transfer of the EDR data to the billing system.• Optional tasks, consolidation of EDR’s, pre-

processing of EDR fields and filtering of EDR’s.• Charging generally based on transfered data.


Maintenance and Maintainability• Software maintenance is “the continuous process

of keeping the program running, or improving its characteristics”

• Maintainability is “the ease with which a software system can be corrected when errors or deficiencies occur, and can be expanded or contracted to satisfy new requirements”

• Canning “most users of computers recognize that 50% of their programming expenses go for maintaining programs in operation”


Software Maintenance

Target SoftwareItself


User Demandsand User

Involvement

The DevelopmentEnvironment



• Types of software maintenance– Corrective maintenance performed to identify

and correct software faults– Adaptive maintenance performed to adapt

software to changes.– Perfective maintenance performed to enhance

performance, improve processing efficiency, or improve maintainability.


Software Maintainability

Management

SoftwareMaintainability

Target SoftwareSystem

Personnel Process

OperationalEnvironment

Existing Target MaturityAttributes

SourceCode

SupportingDocumentation


Software Maintainability

• A maintainable program has to be:– Testable– Understandable– Modifiable– Portable– Reliable– Efficient– Usable


Maintainability Metrics

• From maintainability classification presented,focus on maintainability of the target software system.

• Software maintainability metrics can be classified in two categories:– Software product metrics are measures of software

products such as source code and design documents. – Software process metrics are measures of software

development process.


Maintainability Metrics

• Target software system maintainability, focus on measuring the source code maintainability, maturity of the source code and characteristics of the supporting documentation.

• Source code metrics are module size, maturity, control flow complexity and amount of possible input-output combinations.


Measurements and Results• Lines of code• Commented lines• McCabe’s cyclomatic complexity (CC)• Input output combinations• Total defects reported per KLOC per year• Age of the source • Existence of documentation• Use of bit-level operations• Parameters in RC-file


Measurements and Results

• Performed measurements to four different customers that have the Comptel mediation system in production use in a GPRS network.

• Results were recorded.• Weight factors were defined for the metrics• Maintainability ratings were counted• Results were presented


Results

0

20

40

60

80

100

120

Customer A Customer B Customer C Customer D Average

Maintainability Rating


Results

40

50

60

70

80

90

100

110

Customer A Customer B Customer C Customer D500

1500

2500

3500

4500

Maintainability LOC


Results Verification

• Verification of the results was based on the amount of support requests received during year 2001 per customer.

• This means that we will investigate how well the constructed tool predicts the amount of future maintenance tasks.


Results Verification

0

20

40

60

80

100

120

Customer A Customer B Customer C Customer D0

2

4

6

8

10

12

Maintainability Maintenance Requests


Result Analysis• Measurement method developed in this thesis does

not produce maintainability ratings that would correlate with the amount of maintenance requests with required accuracy.

• Small sample set used in the measurements affect on the results.

• Reporting process of the maintenance requests unfortunately varies between separate customer cases. Hours used could not be used because of inaccurate reporting.


Conclusions• Maintainability is difficult to measure.• Maintainability measurement tools should be

somewhat application type and programming language –specific.

• There are two major aspects in maintainability, proactive maintainability and active maintainability.

• Constructed tool measures mostyl active maintainability because it focuses on software size and complexity.



Additional - GPRS Network• GPRS, a packet switched bearer service set, is

standardized by ETSI.• GPRS is a new information transfer method to be

used in mobile networks based on GSM networks.• GPRS uses a packet-mode technique to transfer

high-speed and low-speed data and signalling in an efficient manner.

• According to ETSI, charging should be based on the amount of data transferred.

• ETSI view is very simplified


Additional Information - GPRS

Gf

D

GiGnGb

Gc

CE

Gp

Gs

Signalling and Data Transfer InterfaceSignalling Interface

MSC/VLR

TE MT BSS TEPDN

R Um

GrA

HLR

Other PLMN

SGSN

GGSN

Gd

SM-SCSMS-GMSC

SMS-IWMSC

GGSN

EIR

SGSN

Gn

CGF

GaGa

BillingSystem


Additional – MDS in OSI-modelFile Transfer Manager (FTM)

Method Definition

File Transfer Controller (FTC)

ApplicationLayer

FileCollection

from Switch

Conversion(MDS/ARM)

Transfer toAdC

FTAMMTP/SFI

Other

Sort/Process/Delete/Join

TCP/IPDecNet, SNA

FTAM

X.25HDLCIEE802

UNIX/DigitalHP-UX

IBM/AIX

X.25HDLCIEE802

ControlLayer

Program Layer

Protocol/Format Layer

Transport/OS Layer

Documents

System Telecommunication Software Maintainability of a · Telecommunication Software System ... • Parameters in RC-file. Ville Häkkinen ... SNA FTAM X.25 HDLC IEE802 UNIX/Digital