Normal use versus testing

The design of some T.38 implementations precludes some reasonable tests from succeeding, due to design features which may have been implemented for sane reasons. This means each test failure needs to be investigated in detail, to see if it represents something genuinely bad in an implementation of T.38. For example, the 2M byte torture test page in the Commetrex test suite will not successfully pass through some T.38 implementations, because of a timeout they impose. For example, some ATAs based on Audiocodes silicon have been seen to stop any continuous period of modem transmission after about 90s. This appears to be a backstop timeout, to prevent troublesome implementations jamming the gateway. Legitimate pages just don't take that long, and the timeout is reasonable. However, the 2M byte test page takes up to 20 minutes to transmit, and will always fail on these boxes.