Here’s how they plan to cripple the Vonages and Skype’s, according to friends of mine who have spent 20+ years in engineering positions at telephone companies, cable companies and internet service providers. As the phone and cable companies begin offering their own VoIP services in real volume, they plan to “tag” their own VoIP packets so that at least within their own networks, their VoIP service will have COS (Class of Service) assignments with their routers, switches, etc. They also plan on implementing distinct Virtual Local Area Networks (VLANs) for the tagged packets.

Tagged packets get both less restrictive rules for passage and a private highway lane to drive on.

The net effect is that any packet that isn’t tagged will only get “best effort” service, which means whatever is left.

“Best effort,” as defined by IETF RFC 791, makes almost no guarantees. The packet may arrive damaged, it may be out of order (compared to other packets sent between the same hosts), it may be duplicated, or it may be dropped entirely. And that was in the good old days.

Now imagine “best effort” transport on a backbone that is already clogged with tagged traffic that gets preferential treatment. Where previously all packets got “best effort,” in this new system some packets get better than best effort, which means the remaining packets will effectively get worse than best effort.

The telco and cable guys know enough about their networks that they can throttle their network capacities up and down so that “best effort” service is going to be pretty awful. But have the magic tags on your packets and you’ll have decent service.