Case Studies for Test Automation
1.1 Automation Approach for GPRS Support Node Testing
GPRS introduces two new network nodes in the GSM PLMN: The
Serving GPRS Support Node (SGSN), which is at the same hierarchical
level as the MSC, keeps track of the individual MSS' location
and performs security functions and access control. The SGSN
is connected to the base station system with Frame Relay.
The Gateway GSN (GGSN) provides interworking with external
packet-switched networks, and is connected with SGSNs via
an IP-based GPRS backbone network
The GSN (GPRS Support Node) Product of Aricent can work as the
GGSN and SGSN. The GSN is having multiple interfaces towards
other network elements like HLR, VLR, BSS e.t.c. Hence each
of these external nodes need to be simulated. This was done
by using in-house developed HLR/VLR and MS/BSS simulators.
For a test case each simulator was having individual scripts
running at various interfaces which were executing the part
of test case, verifying the responses of GSN and then declaring
individual verdicts and in case of failure logged the exact
cause of failure. All these simulators were controlled from
one point. Hence a Test Manager was put in place, which was
serving for synchronization, verdict management, and runtime
control of the interfaces. Test manager triggers different
commands to various end simulators and waits for verdicts
from simulators.
The name for each of the test cases to be run as a complete
test suite in batch mode is specified at the Test manager.
The Test Manager picks the scripts one by one and sends them
to the respective simulators. The simulators execute the scripts
and send back result in form of verdicts. Test manager keeps
result verdicts received from individual simulators. It also
gives final verdict after checking results verdicts from corresponding
Simulators. Hence there was no manual intervention required
for executing any of the tests.
Test automation strategy is totally modular. The Test Manager
does synchronization, verdict control, batch mode script execution
command management, while simulators does scripts execution
and the verdict declaration. Given below is the test automation
configuration.
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GPRS Support Node
Testing
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3.4.4 Test setup
There were three main test setups which were used for testing
and hence automation. Two for functional testing and the third
for load testing. These test setups have been explained below.
Automated scripts have been prepared for the test groups involving
all the three test setups which could be run either one by
one in batch (automated) mode.
Standard Test Setup (Setup no.1)
For testing of GSN system as a combined SGN and GGSN following
setup was used
Gb interface : The GSN product interfaced with the
MSS (Mobile station simulator). This simulator is having combined
functionality of MS +BSS. This simulator is ported on a Linux
platform and is connected to GSN. This is the Gb interface
simulator. At MSS following configuration parameters are defined:
FR bearer
DLCI
NS VCI
NSEI
BVCI
MS IMSI/TLLI
RAI
Similar configuration corresponding to the GSN is created
at the GSN too. This simulator is connected to GSN via FR
link over E1.
MAP interface : For all MAP messages which come from
HLR &EIR, an HLR simulator is used. This HLR simulator
also acts as a VLR simulator to provide message for Gs interface
between GSN & MSC/VLR. The simulators have MAP along with
lower SS7 layers and interfaces with GSN on E1 interface.
At HLR simulators following network data is created
Self point code of HLR
Destination point codes (GSN PC).
SS7 link data
Global title translation table.
Similarly for HLR/VLR interface at GSN, self point code, destination
point code, SS7 link data and is created. For MT-SMS testing
, Short Message is sent through HLR simulator (In this case
this simulator also acts as SMS-GMSC) to GSN.
PDN interface : For PDN interface, at the GSN there
is a GPRS to PDN router at which the IP address of the server
of gateway need to be created.
All testing scenarios are simulated with the help of the
scripts . The scripting language used on these Simulators
was TCL/Tk. Using scripts and the Test Manager the testing
was completely automated.
Test Setup 1
Setup No. 2
As IUT can be used as combined SGSN + GGSN or as SGSN or
GGSN only . This functionality utilizes the GTP and is used
for inter SGSN system handover. There are three GSNs running,
one for GGSN & another two as only SGSN namely SGSN1 &
SGSN2.
Test Setup 2
GGSN SGS
Load Test Setup
Following configuration is used for load tests.
PDN Load Generator ( LG)
A Load generator is used for generating different types of
load as per tests requirement . Load Generator communicates
with GSN using the IP interface. This is required for the
Data Load related cases. LG ( Load Generator )generates certain
statistics like size packets sent , speed of packets.
Load Generator has following capabilities:
- Generating Data Load at a given rate . ( e.g. , 1 kbs,
10 kbs ,1 Mbs etc., )
- It also measures the number of Packets lost, time taken
to transfer packets over IP n/w, rate of transmission during
the data transfer b/w MS & GSN
- Provision of generating Random Load . ( Non-linear )
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Last updated :
March 30, 2006
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