Security locked in for next DOCSIS 4.0 interop

Broadband speeds tend to get top billing for DOCSIS 4.0, the new CableLabs data specifications that will enable symmetrical multi-gigabit speeds over widely deployed hybrid fiber/coax (HFC) networks.

But the specs are focused on much more than speed, supporting enhanced security, low latencies and a boost to overall network reliability.

Speeds were front and center at the first DOCSIS 4.0 interop held last month at CableLabs, an interop that featured a group of ten suppliers of cable modems, network gear and test equipment. That interop, which connected new DOCSIS 4.0-based modems to existing DOCSIS 3.1 cable modem termination systems (CMTSs), performed as expected.

Doug Jones, chief architect at CableLabs, confirmed that the interop saw speeds in excess of 8 Gbit/s in the downstream and 1.5 Gbit/s to 1.8 Gbit/s in the upstream. That was enabled using a "high-split" HFC network that utilized an upstream band in the range of 5MHz-204MHz and about 960MHz of spectrum dedicated to the downstream. The interop took advantage of new D4.0 modems equipped with 10-Gig ports paired with 10-Gig traffic generators.

"If you do the math, it's what you'd expect," Jones said, noting that the speeds generated via the interop were achieved without any special optimizations.

Looking ahead, plans are in place to add some of the enhanced security elements of DOCSIS 4.0 to the next interop, currently set to take place August 14-17 at CableLabs' facilities in Louisville, Colorado.

Security enhancements on tap

Alongside speeds, the interop will explore how well the modems and CMTSs work together with the addition of a new, stronger authentication system that exchanges certificates between the network gear and the customer premises equipment (CPE), ensuring there are no "rogue" elements on the system. That security is also strengthened with upgraded encryption algorithms that extend the key length from 128 bit keys to 256 bit keys. That, Jones said, will make it harder to breach the system with a "brute force attack."

Jones said the new and enhanced security components are also important as operators start to migrate to a distributed access architecture (DAA) that places key elements of the CMTS, including hardware and potentially software, toward the edges of the network.

He said CableLabs also has plans to test other pillars of DOCSIS 4.0, including low-latency and higher reliability capabilities that, for example, employ new proactive network maintenance (PNM) tools. Low latency was first introduced as an annex to DOCSIS 3.1, and operators such as Comcast are conducting field trials of the technology.

Jones said the same group of vendors that participated in the first D4.0 interop are on board for the second one.

Fulfilling the need for speed

The initial interops are pairing new DOCSIS 4.0 modems with DOCSIS 3.1 networks. While this does give suppliers a way to come together as new D4.0 CMTSs are in development, it also paves the way for some operators to seed the network with DOCSIS 4.0 modems and provide more speed and capacity before full end-to-end DOCSIS 4.0 systems are ready for prime time.

Running D4.0 modems on D3.1 networks was a business goal for some mid-tier operators, Jones said. It also creates a way for those operators to take advantage of D4.0 modems without migrating to DAA because the modems can run on existing DOCSIS 3.1 chassis that are equipped with updated software.

The big advantage with that setup is that it puts cable operators in position to deploy a greater number of OFDM (orthogonal frequency-division multiplexing) channels, which were first introduced in the DOCSIS 3.1 specs. Those OFDM channels are more data-efficient than the bonded 6MHz-wide channels that were first used with DOCSIS 3.0.

Today's DOCSIS 3.1 modems are limited to two OFDM channels while the new class of DOCSIS 4.0 modems can support more than two OFDM channels. Meanwhile, updated D3.1 CMTSs will also be capable of supporting four or five OFDM channels. The bottom line is that cable operators will be able to push more data into the same amount of bandwidth by operating DOCSIS 4.0 modems on DOCSIS 3.1 networks.

But it also opens up new ground that's being explored during these interops. Until now, DOCSIS 3.1 networks haven't seen a DOCSIS 4.0 modem on the network.

"That's new for everybody," Jones said. "We needed a meeting of the minds to make it all work right. It's not rocket science, but there's a fair amount of detail."

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— Jeff Baumgartner, Senior Editor, Light Reading