Case study description

The system under test (SUT) is a Nokia mobile terminal. This mobile terminal is running two applications. One of these is the actual one to be tested: this application implements the Session Initiation Protocol (SIP). Conceptually, the SIP laboratory tester consists of two separate parts: a TTCN-3 SIP protocol tester (SIP tester) and a Bearer in a Box (BIB, consisting of an Insite BTS and a BSC Simulator) implementation as depicted in the figure below. The Insite BTS is a small base station for indoor usage.

The SIP protocol tester consists of TTCN-3 SIP test cases whose primary purpose are to simulate SIP entities residing in the network or other terminals, i.e. SIP proxies or user agents. In addition, a separate test component can be used to interact with a SIP application – the SIP test client – in order to automate execution of test cases. The tester supports transport of messages to the SUT via Ethernet and can be used as is in protocol testing. The second part of the SIP laboratory tester is the BIB. Its task is to intercept SIP data packets from the protocol tester and to replace the Ethernet with the desired terminal bearer information and radio interface required by the SUT, and vice versa. Both 2.5G and 3G radio interfaces are considered in the case study.

An important aspect of the test execution is to ensure that the transport of SIP messages via the BIB works, i.e. that no messages are lost in the communication between the protocol tester and the SUT as well as that the BIB fulfils the minimal performance requirements to execute such a test against a real terminal. This case study also investigates to which extend TTCN-3 test cases can be reused between different testing phases by replacing the physical transport bearers.