David J. Malfara, Sr. ETC Group, LLCThe PSTN has always embraced technological advancement on a systemic basis. That is, as technological advancements emerged they were deployed in the network through cooperation by all participants, for the good of the network as a whole. Signaling systems are examples of such cooperation. When outpulsing and automated switches displaced switchboard operators, when DTMF (Dual-Tone Multi-Frequency) and MF (Multi-Frequency) displaced outpulsing and more recently when SS7 displaced DTMF and MF the PSTN moved, in concert, to implement those changes for the benefit of service providers and subscribers alike.


Now, we have the opportunity for another technological advancement – that of transitioning from circuit-switching voice conversations to packet-switching voice conversations. This transition is not unlike the transitions before it. That is, in order to gain maximum benefit the PSTN must move, in concert, to implement the change among all participants. Can it be done in the highly competitive world of real-time communications? Certainly, the economic and operational drivers are there. The cost benefit, for example, of a transition to IP for carrier interconnection can be upwards of 90%. Much of the savings is derived from the efficiencies of packetized facilities, which share capacity, as opposed to TDM facilities which are dedicated to individual calls for the total duration of the call. This “shared transport” also drives the deployment of larger facilities interconnected at fewer points which takes advantage of scale economies. Operational complexity is reduced as well, benefitting from fewer “moving parts” in the network.


We need only look back as far as the SS7 network implementation for a successful example of a packet network deployment and migration – similar to what is required now. For, the SS7 network is a private, managed-packet network that is crucial to the operation of the PSTN and, because of the cooperation between the PSTN participants, functions today with 99.999% reliability. Participants interconnect with each other, according to defined specifications and rules, and because the SS7 packet network provides shared access, further advancements such as Local Number Portability, Toll-Free (800) Portability and other functionality have resulted.


When competitors discuss managed IP network interconnection it is within this same context of reliability, born from cooperation. Just as carrier interconnection to the SS7 managed-packet network is a foregone assumption, critical to the operation and reliability of the PSTN as a whole, so too is managed IP network interconnection to the next generation of the PSTN. The best-effort Internet will simply not suffice.


In order to get there, we simply need to take a page from the circuit-to-packet transition we’ve already implemented – the transition to a SS7 managed-packet network, currently providing the signaling control framework for the PSTN.




ETC Group description


Listen to Mr. Malfara’s participation at the VoIP Workshop for COMPTEL Plus via this link.

VoIP Workshop at COMPTEL


Download a sample of TMI’s VoIP (Digital Phone) Requirements publication.

VoIP (Digital Phone) Requirements