Residential VoIP

Clearing The Way For Widespread Residential VoIP

June 10, 2004

By Micaela Giuhat

VoIP will explode into widespread deployment across North American this year, changing the way telephone calls are made and received more radically than any technology that’s been put into place in the last 100 years. At the same time, VoIP will bring cost efficiencies for carriers and new services and conveniences for consumers.

The new technology will eventually dominate what has been – and promises to continue to be for many years to come. This is thanks to the embedded infrastructure of existing telecommunications carriers – a lucrative $80 billion annual voice services market. Because RBOCs and ILECs have a vested interest in maintaining existing infrastructure for switched telephony services, it’s unlikely that VoIP will transform the way the phone industry runs overnight.

It is, however, likely that VoIP’s attractiveness for both carriers and consumers will drive large-scale residential deployments starting this year. In fact, it’s already happening. Service providers like Vonage, Packet8 and Net2Phone are riding on broadband networks. Regional Bell Operating Companies (RBOCs) like Verizon and its brethren all have announced plans for VoIP migration in the near term. Interexchange Carriers (IXCs) like AT&T, Sprint and MCI are eyeing or entering the space. And, of course, cable operators are standing by to bring in their own versions of voice services running on their broadband networks. Even fixed broadband wireless providers and their cousins in the wireless fidelity (Wi-Fi) space are eyeing voice services over IP networks.

In short, while small in comparison to the existing telecommunications infrastructure, the residential VoIP audience will be a huge change compared to any competing voice technology that has happened in the last century.

Let’s first concede that VoIP technology is, to put it in technical terms, “fully baked.” After some initial start-up kinks, transmitting voice over broadband IP has become commonplace in the transport space, with carriers and service providers packetizing voice into data and carrying it across IP networks internationally to avoid the costs and difficulties of using the Public Switched Telephone Network (PSTN) and to give end users lower charges primarily for long distance calls.

Network Lessons

These early network activities have provided vendors, carriers and service providers with some hard lessons. First and foremost, not every IP network or technology is configured the same. Simply put, each IP provider uses different technology and speaks a different language. When it comes time to hand off between two IP networks, that language becomes a barrier, either breaking down the data transferal or requiring translation devices inserted into the network end points.

Initially many carriers translated the IP packets back to time division multiplex (TDM) voice streams which were understood by the connecting network and then re-packetized those streams for transmission on the new networks. This was not only time-consuming, but expensive, thus session controllers were developed and inserted into key parts of the network to handle the transfer of data from one network –using nativeIP, but taking care of all the issues related to the demarc point.

In addition to Network Address Translation (NAT) transversal – translating the network languages – session controllers could also tear down and rebuild firewalls that were established to prevent unauthorized data transport and protect networks from piracy and virus attacks. Firewalls, because they are constructed to recognize only data, did not recognize voice; session controllers overcame that obstacle and allowed secure transmission of voice and data packets.

As a whole, session controllers were primarily responsible for making VoIP transport across backbones and long-haul networks a reality. Now, these same devices will be expected to overcome the challenges of handling thousands or even tens of thousands of NAT traversals and firewalls as carriers drive VoIP services into the residential space.

In addition, session controllers will be required to overcome additional obstacles that do not occur with carrier-to-carrier traffic: handling oversubscription and seamless consumer provisioning, to name just a few.

Residential Firewall/NAT Traversal

The first problem carriers will encounter when driving VoIP services into the residential space will be residential firewalls and NAT traversal which are similar, but on a much larger scale, than what occurs in carrier-to-carrier handoffs. Session controllers will be called upon to allow service providers to move Session Initiated Protocol (SIP) signaling and media through a firewall and/or NAT so end users can make seamless telephone calls using their new soft phone devices, SIP phones, or even the black phones using terminal adapters.

Without session controller functionality and automation of configuration of their existing devices, a subscriber signing up for a VoIP service would, in the worst case, not receive phone calls and in the best case, need to reconfigure the home broadband set-up to allow these signals to come through, or in an alternative no one wants to see happen, open the network and leave it insecure by completely tearing down the firewalls.

The session controller, sitting in the carrier’s point of presence (POP), auto-configures the consumer premise device and allows seamless integration of VoIP telephony for a residential user. It requires a special type of session controller to help the carrier handle the huge numbers of users that residential VoIP will engender.

With proper session controller technology sitting in a POP, a VoIP subscriber would need only to plug in a VoIP telephone – either through a broadband modem or as a SIP phone running directly on the network – and voice service is initiated.

The session controller’s NAT traversal capabilities deal with a number of messages coming from the customer prem, and filters these periodic messages at the service provider’s network border, making certain that a pinhole remains open through the firewall during the call, while protecting the core proxy/registrar from becoming overloaded.

Residential VoIP – even if only moderately successful – conjures up huge numbers. Carrier-to-carrier peering, of course, has large numbers of calls moving between network points; residential numbers, estimated at 60,000 lines per POP, are much bigger.

Of course, since all telephony is built on numerical equations of contention and usage, there will be some amount of oversubscription built into the services. It would not be unusual for a service provider to purchase a session controller license for 10,000 concurrent sessions while offering service to 50,000 subscribers. The session controller must be able to offer the scale to handle these oversubscription needs as well as grow as more subscribers are attracted to the benefits of VoIP.

Provisioning

VoIP will never happen in a large scale if the consumer is expected to do anything more than plug in a telephone and make and receive calls. Session controllers, sitting in the carrier’s network, can overcome these provisioning nightmares and help operators significantly reduce operating expenses for turning up and supporting new subscribers.

Upon registration by a new user, a session controller will dynamically tweak the necessary message timers that say the network is active and authorized, enabling firewall/NAT traversal at the residence without changing any configuration settings on the consumer’s firewall/NAT device. Thus, data is protected but VoIP is clear – and the subscriber has to do nothing more than plug in the phone.

Portable Customers

A VoIP benefit is the ability to transport the telephone and IP address to other locales. When the phone is connected at another point, although the consumer uses the same phone number, the authentication must be done differently. Session controllers, automated within the carrier’s network, look for identification within the calling device and other criteria that say this phone is authorized, and then work in conjunction with a local proxy server to authenticate and authorize the service.

Again, the consumer who has made his telephone portable and is using a new IP address on a broadband network merely plugs in the phone and gets service because the session controllers – and thus the proxy servers – recognize the device and authorize its functionality.

Emergency services and CALEA

Many carriers offering residential VoIP services will also encounter for the first time regulations concerning emergency services (E-911 calling) and CALEA (Communications Assistance for Law Enforcement Act), the ability of law enforcement authorities to tap and record phone conversations of suspected criminals. Session controllers will be programmed to resolve these issues within the network – setting up points where the lines can be tapped, for instance, and providing locale information for emergency services – so that both outside authorities and consumers are satisfied.

Conclusion

VoIP has many benefits for both carriers and end users; that’s why it will explode onto the scene this year. In the end, the service provider must be able to make the experience of signing up and using VoIP as seamless as current switched telephone services.

Using session controllers, a customer can buy a phone or terminal adapter, plug it in and get service. Behind the scenes, the new device will register with the carrier’s core proxy server by sending a signal that it is online, and service will be available, being enabled by the session controller who makes sure that the firewalls and NAT issues are solved seamlessly.

This behind-the-scenes activity will open the firewall for voice without affecting the customer’s software or consumer premise equipment. By maintaining a message flow between the residence and the session controller and throttling messages at expected rates, it will protect the carrier from being flooded, as well as perform all the security checks required to protect both the carrier network as well as the consumer.

In all, the system is seamless and invisible. The subscriber is auto-configured; the carrier has a new customer for VoIP services; and the session controller is doing its job in between.

Residential VoIP will change the way telephone services are delivered. Session controllers will be part of that change by making it happen transparently and smoothly for all involved parties.