A call-processing traffic study for integrated digital loop carrier applications

The results of a traffic study undertaken to determine if a 64 kb/s common-signalling channel is sufficiently fast to meet the present and future call-processing needs of integrated digital loop-carrier (IDLC) systems are presented. Bell Communications Research (Bellcore) has proposed the use of such a 64 kb/s common signalling channel in a requirement document, technical reference TR-TSY-000303, to satisfy call-processing needs across the IDLC generic interface, whenever out-of-band signalling is used. The IDLC call-processing traffic on this message-oriented common-signalling channel is characterized, and associated design requirements in TR-303 under certain modelling assumptions (Poisson arrivals and exponential service time) are examined. Under worst-case conditions, it is concluded that a critical message requiring a response within 100 ms would practically always meet that delay criterion. Critical messages requiring a response within 40 ms would fail once every 10 busy hours. Since no specific signalling response requirement of 40 ms has been found, the authors conclude that a 64 kb/s common-signalling-channel for IDLC system is sufficiently fast to achieve required signalling response times