So You Want To Split Your Node?
by Leslie Ellis // November 17 2003
In two years, the problem that shivers awake the cable engineer won’t be plug & play devices, or legacy set-tops, or the messy goo of integration.
No, the sleep thief of 2005 is imprinted on the DNA of this industry: Bandwidth. As in, making sure there’s enough.
So said four cable engineers at last week’s (friendly, useful, and MSO-rich) Virginia Cable Television Association (VCTA) show, in Norfolk, when asked to worry ahead. Down the row, the engineers – from Adelphia, Comcast and Cox – said they’re chiefly concerned with making room for all the bits that will need safe passage.
It’s all about high definition TV, they said, and its 6x fatter pictures. And the increasing types of on-demand video, which will need to be stored and streamed. And the headache of peer-to-peer (P2P) traffic on the broadband Internet portion of the network. And whatever else that comes along that needs a ride.
Engineers being engineers, they’re already working out what to do about it, which brings us to this week’s translatable: Node splitting.
Node splitting comes up frequently in discussions about bandwidth, and what to do when consumer demand outstrips capacity. It almost always falls into the “good problem to have” category. The word “just” is often nearby: “We’ll just split the nodes.”
What’s split, when you split a node, isn’t the node. What’s split is the number of homes it serves. Maybe a 500-home mode becomes a 250 home node, or a 2,000-home node becomes a 1,000-home node.
Likewise, splitting a node isn’t like splitting a bagel. (Nor do you need “a really really big splitter,” as one engineer joked last week.)
What’s needed, in most cases, is another node. Node-splitting, in essence, is accomplished by node-doubling. Double the node, halve the number of homes sharing its bandwidth.
Here’s how it works: A person goes to the node site. Let’s call her Jane. What she sees is a gray metal box, which looks like any other amplifier housing you’ve seen in magazines and at trade shows. It opens clamshell-style. Maybe the node is hanging aerially from a telephone pole; maybe it’s in a pedestal.
Two optical fibers are connected to it. One carries downstream signals down (from the headend). The other carries upstream signals up (to the headend.)
Because the primary work of the node is to change optical signals (also called “lightwaves”) back to radio frequencies (RF), and visa versa, there are also coaxial cables connected to the node.
The coaxial runs generally squirt signals directionally: North, south, east, west. Maybe it’s the north and west portions of its serving area that need more capacity. Jane splices in a second node, right there, with its own pair of fibers. Its coaxial legs connect to the northward and westward plant. Suddenly, everyone on both nodes has twice the capacity. Go Jane go.
Aha, you say. But where did she get the extra fiber pair?
In the last big round of upgrades, most cable operators planted at least four, and sometimes six, individual strands of glass to nodes. After all, the big cost of installing fiber optics is the labor, not the glass. It made sense to leave a few “dark fibers” in the conduit, just in case.
There’s also some headend work involved in splitting a node. Specifically, those two new strands of fiber need to be lit up. That requires an extra optical transmitter and optical receiver, in the headend. And, the node needs 60 volts of power from the network, which sometimes (but not always) requires some re-jiggering.
Sometimes, there’s some detail work to be done on the dark fibers. Maybe they were installed, but not spliced in all the way. Some craftsmanship work happens there.
All in, the rule of thumb for node-splitting, is “one person, half a day, about a thousand bucks.” It’s a pay-as-you go expense, directly tied to consumer demand, which operators like.
And, node splitting is just one of several options the cable industry has in its pocket for bandwidth reclamation. Before we get to “all digital,” or at least “way less analog,” there are other useful maneuvers. Bumping the upper bandwidth boundary to 860 MHz, from 750 MHz, is one. Getting more sophisticated with statistical multiplexing is another.
Cable’s quest for more bandwidth isn’t at all new. It propelled this industry, and its hardware suppliers, for several decades. There was the bump from 330 MHz to 550 MHz, when people actually wondered what they’d do with so much bandwidth.
Then there was the more recent hop from 550 MHz to 750 MHz, plus two-way, for digital services: Video, data, and phone.
The good news is, there are bandwidth options. The better news is, the options don’t require ripping up streets (which makes customers spaz), or spending gobs of capital (which makes Wall Street people spaz.)
More potential bandwidth, no spazzing. That’s at least two things to be thankful for, this Thanksgiving season.
This column originally appeared in the Broadband Week section of Multichannel News.
PHILA & DFAST: How Technology Licenses Impact Three Industries
by Leslie Ellis // November 03 2003
We interrupt the ongoing translations of the plug & play agreement, related FCC rules, down-rez, and selectable output controls to delve into the wonkery of security licenses.
From a technology standpoint, the starting point for this discussion is at the corner of “CableCARD” and “host device,” like a TV outfitted with a CableCARD slot. Right there, where the card parks into the slot, and digital bits representing the wares of one industry (movie studios and copyright holders) walk across the pins of a second industry (cable) to a third industry (consumer electronics).
From a strategic standpoint, the intersection matters because it’s an early hot spot for larger, feistier, cross-industry debates – like who gets better content deals based on their ability to “down-rez” copy-protected content, if asked, on high definition analog outputs. Or, who gets damaged/rewarded because their stuff (TVs) was built without down-rez capabilities, before the FCC articulated its position on the matter.
And there’s another multi-billion dollar industry tugging on the licenses for removable security. Calling themselves the “IT Coalition,” where “IT” means “Information Technology,” the personal computer posse includes names like Dell Computer Inc., Intel Corp., Hewlett-Packard Corp., and Microsoft Corp.
Their harrumph: Security deliberations should include their stuff, which falls under the general category of “digital rights management.”
At the heart of this arcane, but relevant, security discussion are two CableLabs licenses, known by the acronyms “PHILA” and the “DFAST Technology License Agreement.” Both involve the techniques that encrypt and protect digital video.
PHILA stands for “POD Host Interface Licensing Agreement.” Most people pronounce it “fie-luh,” or “fee-lah.” It’s especially wonky because of that embedded acronym – “POD” – which stands for “point of deployment” module. POD equals “CableCARD.” So, PHILA is a permission mechanism to build and test things with a CableCARD slot.
DFAST stands for “Dynamic Feedback Arrangement Scrambling Technique.”
No, really. It does.
An anecdotal aside about how these techniques wind up with such densely technical names: I once had an engineering friend who, over dinner one night, expressed his desire to date a woman at his place of work. I asked him how he planned to go about it.
He explained that he had been observing the types of people she seemed to like, and concluded, in an endearingly earnest way: “I can emulate that protocol.”
It is the people who refer to interpersonal skills as “emulating that protocol” who are occasionally asked to name their work. Usually, they name it by describing what it does. DFAST describes how to re-scramble the bits of a TV show, for handoff to a “host” device, such as a TV. In part, it prevents a flourish of “imposter hosts.”
Why are there two licenses, PHILA and DFAST? In short, PHILA was first. It sufficed for licensing the industry’s incumbent suppliers. But in the work of engaging a whole new industry of suppliers – CE manufacturers – things changed.
Mostly, the CE side found PHILA to be too specific, especially about their side of the deal – the “host” devices. A less explicit specification for “host” devices gave them room to be more innovative and competitive. (This spawned cable worries that more interpretive room would mean more corners cut – or, as some quip, “the right to build crap.”)
That’s what begat DFAST, which applies a minimal level of requirements to host devices.
There are similarities between PHILA and DFAST. In essence, DFAST is a subset of PHILA. It defines how to license the “secret sauce” of the security that moves bits across the pins of the CableCARD, to the host device. PHILA references the same security mechanisms as DFAST. It also defines requirements for the host device.
Lastly, PHILA defines a mechanism for testing products, much like cable modems are interoperability-tested, at CableLabs. DFAST, by contrast, allows CE companies to certify products once at CableLabs, then to self-certify after that.
DFAST emerged last December as an appendix to the joint filing made by cable and the CE industry to the FCC, which became known as “the plug and play agreement.” In the filing, DFAST was a draft, submitted for consideration.
After the FCC’s Report & Order on plug & play, CableLabs issued a finalized version of a DFAST license. (They didn’t issue DFAST licenses earlier, they submit, because they didn’t know how the FCC would rule on things like down-resolution, which mattered to the license.)
Boil it all down, and it means this: TVs complying to DFAST will arrive in cable systems. They will be capable of down-resolution on analog outputs. They’ll be built using inevitably different interpretations of the involved technical specifications. Most of them will not be tested at CableLabs, after the first one.
If any of that matters to you, it’s probably best to pay attention to this one.
This column originally appeared in the Broadband Week section of Multichannel News.