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A Reader's Guide to DOCSIS Certification

In case you missed it, eight more cable-modem contestants greenlighted (or re-greenlighted) their way through the CableLabs DOCSIS 3.0 certification process last week.

All in, that's 11 certified cable modems from eight suppliers.

No CMTS (Cable Modem Termination System) gear made the grade last week, which is not to say that anyone failed. No suppliers submitted CMTS gear in the latest and 63rd test wave.

That brings us to this week's translations. When people ask about DOCSIS 3.0 certification, two questions tend to pop up more frequently than others. One is this: What's the deal with the “bronze/silver/full” designations for CMTS units? And then: What's the short version of how the different DOCSIS versions differ from one another?

The answer to the first question gives a pretty clear glimpse into what features you'll see in the marketplace, in what order. Recall that DOCSIS 3.0, as a technical specification, is piled high with features. There's channel bonding, sure, but there's also the migration to IPv6, to widen the number of devices that can be connected via an IP address. And there's stronger security. And more, which we're about to get into.

If you're a DOCSIS 3.0 CMTS vendor trying to get a controller ready for market, in a landscape containing so many potential features, it's good to know which features will be tested, in what order. This is why the “bronze,” “silver” and “full” CMTS qualifications were established up at CableLabs. (Note: This only applies to CMTS gear, not cable modems — which all need to be “full-profile.”)

It goes like this: A bronze designation means a particular DOCSIS 3.0 CMTS can do IPv6 and downstream channel bonding. (Downstream meaning not the upstream signal path, which is also a candidate for channel bonding.) A silver designation adds three more features. One is upstream channel bonding, meaning the ability to bond the channels located between 5 and 42 MHz. This is good for being able to, say, let people stream live HD stuff from their handheld cameras to somebody else. (Could happen.)

Also in the silver category is AES, for “advanced encryption standard.” It's a step up from the as-yet unhacked “triple-DES,” where “DES” is pronounced “dez,” and stands for “data encryption standard.” Think cryptographic chip stuff.

The third component in a “silver” CMTS qualification is IPDR. An IPDR is an IP Detail Record. As you might expect, from its name, IPDRs are big-deal data points for back office systems. What's in an IPDR is up to individual broadband service providers; so far, you see it mostly in places where consumption-based billing is in the works. It's also handy for maintenance testing.

A “full” qualification is all of that, rolled up and ready to go on the day that CMTS rolls in the door to be tested for interoperability.

DOCSIS Version Comparison

As mentioned, there are three DOCSIS versions in the marketplace — soon to be four. Every time a new chapter emerges, it gets harder to remember what was in the earlier versions.

For that reason, here's a quick round-up of how DOCSIS versions 1.0, 1.1, 2.0 and 3.0 grew their feature loads.

DOCSIS 1.0 was the original, obviously, so set the way-back dial to 1999. The first standardized cable modems were built to support best-effort access, with modest security, and shared speeds of up to 38 Mbps downstream.

DOCSIS 1.1 added a prefix to the “quality of service (QoS)” features of the cable modem: D, for “Dynamic.” This was in the 2000 time frame. D-QoS let operators apply specific amounts and types of bandwidth to different services, on the fly, and without having to futz with the modem. (“Futz,” in this case, meant downloading a new configuration file, then rebooting.)

D-QoS is a common component in cable-delivered voice-over-IP services and is a big part of what's “managed” about “managed services.”

Also in DOCSIS 1.1: Better encryption, known as “triple-DES” (see above).

Next up was DOCSIS 2.0, in 2002, with an additional mode of modulation for the upstream path, known as S-CDMA. Old timers in the cable-modem world hear S-CDMA and think “Terayon.” (That was a big part of their special sauce back in the day.)

If that doesn't do it for you, think of S-CDMA as a better way to handle certain upstream impairments (impulse noise, for what it's worth) more efficiently.

That brings us to DOCSIS 3.0. It's already in test in a handful of U.S. cable markets. All operators see it as a very nice, very big gun to roll out in markets with heavy DSL competition — but beyond that, it's featured enough to move the industry into IP-delivered video, and pretty much anything else headed toward the broadband side of the house.

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