VoIP-7 vs. Current VoIP

The Next Generation Network, a worldwide plan for the future of telecommunications, will feature seamless convergence of the Public Switched Telephone Network (PSTN), the Public Data Network (PDN), open network architecture, and implementation of high-speed network interfaces and protocols. Most experts agree that the movement of voice onto the IP network, at the Class 4/Tandem level, will be the first phase of converging the data and voice networks.

The current VoIP industry has evolved over the past several years from its origins in the data networking industry. The view of the data networking industry originally had been "voice is just data" if voice can be successfully transported in data packets. But voice is not just data; it can be put into data packets but must be treated differently. A truly successful VoIP network model will handle seamless interconnection with PSTN and VoIP networks and support their interconnection business arrangements and billing.

Moving smoothly into this new network depends on choosing the right solution. NACT can meet your business needs today and provide you with that solution with mature, full-featured gateway and billing/OSS technologies.

Current VoIP Signaling Protocols

Many of the current VoIP signaling protocols originated in the data network world. Most were created for a specific purpose and then were adapted or forced to evolve to handle voice calls over an IP network. Because of this heritage, VoIP protocols usually follow a call signaling model patterned after something other than a voice call, and they do not cleanly or efficiently handle voice calls nor do they seamlessly interoperate with the PSTN network.

Another problem with the current VoIP protocols is their inability to perform route look-ahead, pullback, and alternate routing. The PSTN SS7 protocol was designed with these features because it is the nature of telephone networks to encounter blockages for one reason or another and to permit calls to be rerouted to alternate routes at any point within the SS7 network. The VoIP protocols do not perform such functions, and that greatly hinders call completion. Once a call enters a gateway and the gateway routes the call to the VoIP network, almost all current VoIP gateway implementations commit the call; and if a problem is encountered in either the terminating gateway or the network beyond the terminating gateway, there is no provision for pulling the call back out of the VoIP network and trying an alternate route.

NACT Network Model versus VoIP Network Models

The PSTN SS7 network model and the SS7 protocol support many features currently lacking in VoIP protocols and networks. They permit route look-ahead, call setup pullback, and alternate routing so failures in a network are bypassed. They handle redundancy in signaling and signaling points, permit carriers to interconnect at arm's length, and provide the information necessary for billing the end user as well as any interconnected carriers. They allow a network provider to maintain control of its own network and to route traffic around points of congestion.

The NACT network model closely parallels the current PSTN model in that the VoIP gateways are intelligent, self-sufficient, and interconnected end-to-end via SS7. In the NACT model the gateways communicate SS7 messages through the IP network using the M3UA and SCTP protocols. The SS7 messages have been enhanced with the VoIP information needed to set up the VoIP portion of the call through the IP network.

This network model teams the strengths of the PSTN model with the strengths of the IP network. The strengths of the PSTN model are signaling integrity and scalability. The PSTN model can scale upward to truly national and global networks and permits carriers to retain control of their networks because they control their signaling interfaces with other carriers. The strength of the IP network is the transport of voice directly from originating gateway to terminating gateway without the maintenance of many physical circuits and their corresponding expense.

End-to-End SS7 Signaling

A new Internet protocol named SCTP has been created for the purpose of transporting SS7 messages over an IP network. This new protocol, currently available, supports redundant IP networks and transmission paths and can either load share the message transmissions among them, or use one as the primary and the other as the standby. The M3UA protocol has been created to adapt PSTN SS7 ISUP messages at the ISUP/MTP3 interface for transport across SCTP instead of MTP3. These two protocols now allow SS7 ISUP messages to be transported across an IP network, albeit for use by PSTN network switching points.

The NACT VoIP-7 model permits end-to-end SS7 signaling naturally because it is the protocol exclusively used to set up and tear down the VoIP portion of the call as well as the PSTN portions. This model solves the carrier-to-carrier interaction problem because no carrier has to cede control of its gateways to another carrier. A carrier remains in control of its gateways at all times and communicates with neighboring carriers through SS7. Since SS7 generates the events and information that cause the creation of the billing information, the billing problems the current VoIP protocols have are not an issue because each gateway can generate its own, full call record (i.e., no "event" records must be collected from multiple systems and reconciled).