DOCSIS Changes Muddle Picture


The cable-modem-vendor and operations communities will
cross a major milestone in the standardization process this week, just as the route toward
selling standards-compliant equipment is getting more complicated.

A demonstration of the interoperability of equipment built
to the specifications of the proposed DOCSIS standard at the National Show marks the
on-schedule completion of a daunting eight-phase process that began a year ago. DOCSIS
stands for Data Over Cable Service/Interoperability Specification.

But for vendors, deciding how to proceed from here has
become a tough assignment, amid ongoing efforts to develop enhancements to standards-based
modems that will meet the demands of operators.

Those enhancements will greatly expand the range of
services that cable operators can provide over their high-speed-data networks, and they
will not in any way affect how the standard itself is written, said Rouzbeh Yassini,
founder and former CEO of LANcity Corp., which is now a unit of Bay Networks Inc.

Yassini is working with Cable Television Laboratories Inc.
as an executive consultant to the DOCSIS group, which is headed by CableLabs vice
president Robert Cruickshank.

The enhancements fall under three categories of technical
extensions to DOCSIS version 1.0.

"It's important that everyone understands that
these are extensions to DOCSIS 1.0, and by no means a modification or new generation of
the specifications," Yassini said. "We keep telling vendors to stay focused on
1.0, because compliance with 1.0 is the undivided requirement set by the MSOs."

But as operators perceive a need for service tiering,
delivery of packet telephony and other advanced capabilities, vendors don't want to
lose business because they haven't included the enhancements that customers want.

The extensions effort is about to add multicasting as an
enhancement category, along with quality-of-service ability and something called
"fragmentation." The effort is aimed at achieving uniformity on approaches to
enhancing standardized modems, "so that people don't go wild and modify DOCSIS
separately," Yassini said.

"What we're creating are the parameters that
people can use to offer different flavors of DOCSIS modems in keeping with the demands of
their customers," CableLabs president Richard Green said. "Customers will
determine what functionalities vendors supply in their purchase orders, but the key thing
is that whatever they choose, we maintain interoperability."

Yassini stressed that the extensions are meant to come
online next year, following initial production of the basic DOCSIS modems that operators
have been clamoring for.

But vendors face difficult decisions with respect to
building platforms that can readily accommodate the addition of the extensions, either as
they are needed over time, or as part of the initial product release.

A senior engineering executive at one of the leading MSOs
in the standards-setting process, who requested anonymity, said he has become
"gravely concerned" that uncertainties surrounding these issues could delay the
introduction of DOCSIS-compliant product to sometime beyond the end of the year.

Terry Wright, chief technical officer of, a
supplier of technical support for operators in the high-speed-data business, agreed that
the higher performance requirements could slow things down. That may create what, for many
cable interests, would be an unwelcome competitive environment, where QOS-equipped modems
conforming to the emerging IEEE 802.14 cable-modem standard are in the pipeline ahead of
similarly equipped DOCSIS modems, he said.

With the IEEE standard draft now out in circulation for
extended comment, the work on the specification "will be done this summer,"
Wright said, noting that he is a participant in the process.

"There's a lot of disagreement and concern over
how to add quality-of-service over DOCSIS," Wright added. "The vendors most
concerned about the extensions are those that have completed their chips and that are
afraid that software enhancements alone won't be enough to make their modems
competitive with the suppliers that can add the extensions in hardware."

While most of the means to be recommended for the DOCSIS
extensions involve the use of software, rather than changes in hardware, there are some
recommendations that might require at least some vendors to modify their hardware if they
want to offer those enhancements, Yassini said.

Moreover, some of the software extensions would have to be
done in "firmware," meaning software that must be added in the production
process, rather than downloaded later on.

Green acknowledged that the "palette of choices"
being created in the extensions process presents vendors with a decision to make, where
"the trade-off is between technical capabilities and time to market." But, given
the growing demand for advanced functionality sooner, rather than later, there is no other
way to proceed, he said.

"I'm particularly grateful that we're really
understanding the problem [of multiple demand profiles from operators], and that we are
coming up with a technical framework that allows our members to make business decisions in
a straightforward manner," Green said. "This will work like any normal
electronic marketplace."

The work on the QOS recommendations is about 80 percent
complete, Yassini said.

As outlined in a document that he supplied to Multichannel
, the QOS plans call for:

• RF MAC (media-access-control) extensions that permit
dynamic reservation of networking services tailored to user applications;

• Improved support for constant-bit-rate and
guaranteed-bit-rate applications, like telephony, that have tighter timing requirements
than Web browsing, e-mail, or other traditional Internet applications;

• Support for dynamic network response to changing
traffic loads consisting of a mix of services, including video, audio, telephony and Web

Fragmentation, also about 80 percent complete, permits the
cable-modem-termination system at the headend to instruct cable modems to fragment packets
into smaller pieces before upstream transmission. This boosts the resolution at which the
CMTS allocates bandwidth, resulting in more efficient and fairer distribution of bandwidth
to user applications.

Fragmentation, working in conjunction with QOS, also
improves support for constant-bit-rate and guaranteed-bit-rate services.

The new multicasting initiative, which kicks off this week,
is meant to ensure that the Internet standard for multicasting is "glued onto"
the DOCSIS gear in a uniform way, Yassini said. This includes defining modem and CMTS
features that improve efficiency of the network's distribution of IP
(Internet-protocol) multicast services; defining mechanisms for exercising dynamic control
over modem access to IP multicast; and ensuring that the infrastructure is in place to
support new services over IP multicast.

Yassini made it clear that the timing of vendor requests
for certification of DOCSIS compliance is strictly up to them.

But, he stressed, the goal remains DOCSIS-compliant product
in the marketplace by year's end.

Leslie Ellis contributed to this story.