A Cable Shopping List For Bandwidth Differentiation

Technology-wise, there are three things cable operators will need if they want to grow their broadband Internet pipe with bandwidth-differentiated services.

What’s a bandwidth-differentiated service? Anything that runs way faster — or with way fewer interruptions — for a temporary slice of time, on broadband.

Two examples always seem to rise to the top. First is an operator-originated or third-party game service, on broadband.

Twitch gamers, playing against each other over the Internet, can suddenly buy six packs of “broadband blasts.” Trigger a blast, get an appreciably fast attempt at your opponent, win. (Buy more bursts, play again.)

The blast is a differentiated broadband service.


The second example is an operator-originated or third-party video download service, to the PC. Maybe the “buy” options include a click to pay more for faster delivery — not unlike springing for FedEx delivery when you’re inspired to receive something quickly.

The theory: When you’re in a big hurry to get to the airport for a long flight, maybe it’s worth a few extra bucks to get the movie into your laptop in 10 minutes. Doing so means the broadband pipe would need to widen itself to something like 7 Megabits per second, sustained for 10 minutes, just to you.

The temporarily super-fast link is a differentiated broadband service.

In both cases, broadband customers receive premium bandwidth, when they needed it. The gamer got a millisecond-level burst speed; the downloader got wider path for a faster delivery. Afterwards, their broadband connections reverted to what they were before the premium “flow.”

Technologists call the differentiation mechanism “quality of service,” or QoS. It’s what made DOCSIS 1.1 different than DOCSIS 1.0 — the ability to set up and tear down different types of guaranteed broadband sessions, as needed.

Meanwhile, any other “non-premium” data riding the same passageway got “best effort” handling, which is the way most cable modems work now: You get what you get. Sometimes it’s more than you need, most times it’s what you need.


Which brings us back to the three things a cable operator will likely need, to offer bandwidth-differentiated services.

Surprise — (not) — the three things are servers. They spawned from the PacketCable Multimedia specification: that’s the one that adds more possibilities than data and voice to the credentials of the industry’s IP paths.

One is a “policy server.” Its purpose is to tell the headend piece of a broadband Internet system, known as the “CMTS” (Cable Modem Termination System), when to nail up and tear down premium sessions for requesting customers. It knows what to do based on the “business rules” it gets (from its owner) for each premium-styled service.

Another is an “applications manager.” It acts as both translator and intermediary between a differentiated service — the game blast or the speedy delivery — and the individual policies of bandwidth providers.

A third, known as a “record-keeping server,” does what its name suggests. It keeps a running log of who’s using what bandwidth, for how long, for accounting (and dispute-resolution) purposes.


To envision the three servers in action, let’s look at a plausible differentiated service “flow.”

Say it’s Customer Bob who wants to (legally) download a movie, quickly, because he’s on the edge of late for his trans-Atlantic flight. He clicks for the speedy-delivery fee, and walks away to finish packing up.

First, the Web site of the movie source consults its applications manager, to find out whose policy server is governing the bandwidth attached to Bob’s cable modem. The applications manager puts a little IP address mapping to the task, locates the policy server, and introduces itself: “Hi, me again. One of your customers just requested a speedy delivery. Shall we proceed?”


The policy server checks that the Bob isn’t in arrears, and is technically capable of receiving an express bit glob. It lists the parameters necessary to get Bob what he needs, and ships that list off to the cable-modem termination system.

Lastly, it pops a note off to the record-keeping server, to track the bandwidth order.

The CMTS receives the list, aims the bit geyser at Bob’s modem, and fires.

Ten minutes later, Bob smooshes his laptop into his bag, and heads for the airport.

As for availability of the three servers, vendors are standing by. Several companies, including CableMatrix, Camiant Inc. and Ellacoya Networks, among others, demonstrated gear at the recent National Show.

Now it’s just a matter of deciding whether to differentiate bandwidth with your own services, or with third-party providers — or both.

Stumped by gibberish? Visit Leslie Ellis online at www.transation-please.com.