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Will voice-over-X be visible

By Scott Bradner

There has been a lot of buzz of late about voice-overs. Voice over DSL and voice over cable are all the rage in the trade press But much of the buzz misses what may be the real story.

Standards are being defined on how to run voice over these technologies. The model assumes service provider has a DSL circuit or cable connection from a point of presence (POP) to a customer location. At the customer location there is a modem-like piece of customer premises equipment (CPE) attached to the line. The CPE has multiple connectors on it, one or more for each of a number of services that can be offered. For example a cable-modem might have connectors for cable-TV, high-speed Internet service and one or more phone ports. At the POP the other end of the line is attached to some electronics that splits the customer traffic into separate streams, one for each of the connectors on the CPE.

In this model if the customer wants voice service they plug a phone into one of the phone ports on the CPE and the service provider configures the POP equipment to logically connect that phone port to a telephone service provider. The customer appears to have a direct connection to the phone service provider and gets the same type of phone service and bills that any other customer of that phone company would get with potentially some savings resulting from the use of a shared access line. This model is quite attractive to service providers because they can bill for each service.

But this is not the only model. An alternative model is one where the CPE is simpler and is only providing cable TV and Internet service. If the customer wants to make phone calls they do so from an Internet-enabled phone or a PC. In this case the voice data is not separated out, it is just sent along with all the other IP packets on the Internet link. The phone call can be going over the Internet directly to someone with another Internet-enabled phone or to a gateway to the phone network run by a third party.

This is not attractive to the service providers because there is no reliable way for them to figure out which is voice traffic and charge separately for that. It will be attractive to customers for exactly the same reason. The service provider may claim that without being able to separate out the traffic they can not guarantee the right quality of service for the application. I would claim that you should not be buying Internet service from a provider whose basic service is crappy enough that this makes a difference.

In any case this alternative model has been generally ignored in all the buzz but may easily be the dominate model in a few years.

disclaimer: Harvard understands the concept of the dominate model but has expressed no opinion on this topic.