Potential Interactions between IP-dial and Voice Traffic on the PSTN

Abstract

This paper considers possible interactions that arise when IP-dial (i.e. Internet access via the PSTN) and voice traffic share the same infrastructure. The concern is caused by the different properties of the two traffic streams, with IP-dial being associated with long call hold times and automatic redialling. In order to gain an understanding, a simple single-link system is extensively studied using simulation. The results show that automatic redialling causes the IP-dial traffic stream to be much more efficient at seizing circuits than the voice traffic when the system is overloaded, and therefore congested. The use of various controls to establish a more equitable distribution of circuit resource between the two traffic streams in the event of congestion is considered and trunk reservation selected as the preferred control. Additional simulations establish appropriate trunk reservation settings and establish its efficacy. The paper concludes that network operators should consider carefully the effect of mixing IP-dial and voice traffic on shared infrastructure, and that trunk reservation is the preferred technique for controlling unwanted interactions.