Validating Cable Modems for DOCSIS® 3.1 PNM Deployment

Jason Rupe
Principal Architect

Apr 18, 2018

The cable industry is always trying to find ways to improve service. When the cable industry made proactive network maintenance (PNM) a part of the DOCSIS® specifications, we showed great commitment to service. CableLabs supports that commitment through its work in specifications, and particularly through its PNM project.

This blog entry in our PNM series focuses on cable modem validation. Cable modem (CM) validation is the work to assure that the CMs can fully support PNM. When CMs can be assured to report data about impairments in the network, service providers have a tool for finding and fixing network issues before they impact service. CableLabs built the cable modem validation application (CMVA) to help bring that assurance to the industry.

Validating CM PNM functionality for DOCSIS 3.1 network deployments might seem like a small step in a large technology life cycle. But it’s an important step, and one we wish to highlight.

Why is it important to validate PNM data reporting from CMs?

  • Continuous service improvement: Before deploying a technology, it is important to know ahead of time whether CMs will be capable of supporting network maintenance and troubleshooting. We never want to introduce a new technology that costs more to maintain than the previous. Ideally, a new technology will cost less to build, be less expensive to maintain, and provide superior service. PNM capabilities are an important part of this needed improvement. A consistent approach with CMs is the first step toward CMTS testing and having integrated PNM capabilities for the entire architecture.
  • Getting ready for future technology evolutions: New DOCSIS 3.1 modems provide more information about the plant and its ability to support enhanced services and deploy new technologies like FDX. This capability can become an important source of information for all sorts of planning and engineering activities. It is a critical first step toward many possible futures for DOCSIS.
  • Best practices we can share: With a consistent industry approach to PNM data reporting, collection, and certification testing of modems, everyone can validate and verify consistent reporting. Therefore, we can build best practice operation solutions on that strong foundation.

You can’t manage what you can’t measure, so having modems capable of reporting PNM measurements allows cable operators to manage their networks effectively, inexpensively, and reliably! 

Realize: It’s always too late to start thinking about reliability!

You can’t add in reliability as if it’s a separate feature. You need to design it into the system as early as possible for the lowest cost, or work it in later at a much higher cost. DOCSIS is a sophisticated system, especially 3.1 and Full Duplex DOCSIS. This complexity is why having PNM within the DOCSIS specification is an important move for the industry, supporting its ability to evolve. But, this is only a first step. We need to make sure these PNM capabilities work as intended in systems before we deploy and assure we can take full advantage of the capabilities once deployed.

The Common Collection Framework (CCF) and the Cable Modem Validation Application (CMVA)

CableLabs built two solutions that together help address this industry need:

  1. The Combined Common Collection Framework (XCCF): The XCCF provides management of data requests to network elements, and provides the data to a REST API to support applications of all kinds. The CMVA, one of those applications, uses the data provided by the XCCF to validate modem performance in support of PNM. If you want to learn more about the XCCF, you can read the previous entry in our PNM blog series here, or access the public version of the architecture document here. We are building the future of the XCCF right now, so it’s a great time to get involved.
  2. The Cable Modem Validation Application (CMVA): The CMVA allows any of us to test CMs for compliance to DOCSIS 3.1 specifications, specifically the PNM portions. The tests conducted are based on the Acceptance Test Plans (ATPs) supported here at CableLabs, specifically the DOCSIS 3.1 PHY and OSSI ATPs, based on the DOCSIS 3.1 specifications. But not only does CMVA provide concise test results based on these ATPs, but it provides nice graphical output (plots, tables) so you can visually confirm the results too. Sometimes what passes a specification is still not desirable or functional necessarily. Looking at the results is a great way to get introduced to the wealth of data available in DOCSIS 3.1 CMs, allowing the CMVA to be useful toward confirming specific results you may envision for your own PNM deployments. To facilitate that idea further, we are adding to the CMVA a few extra capabilities so that users can test additional PNM workflows, look for test anomalies, or further experiment with PNM capabilities.

We use it…

CableLabs and our subsidiary, Kyrio, are using the CMVA in our own CM certification testing. CableLabs will use it further to explore improved workflows for PNM, in support of the InGeNeOs Forum’s planned work on PNM Best Practices for DOCSIS 3.1 technology. Just like the XCCF is the foundation for a lot of PNM related capabilities, the CMVA is a step beyond and toward greater PNM capabilities that support low cost and high effectiveness in DOCSIS 3.1 network deployments.

…Others use it…

We envision a couple of important use cases for our partners.

  • Vendors can use it to validate their modem for compliance to the PNM portions of the specifications, test chip capabilities, improve firmware, or explore potential PNM developments. We’re aware of a vendor using XCCF to test silicon, so, for example, the CMVA could be added to find issues and share them with their suppliers during design testing.
  • MSOs can verify compliance in their own labs, develop CM builds that help them differentiate, and examine CM sensitivity and capability at PNM tasks and operations workflows. For example, if a particular modem is vulnerable to LTE ingress at the interface, a few lab tests might detect it before deploying the problem, and the CMVA would be one way to detect and display the problem.

…Wouldn't you like to use it too?

CMVA was designed specifically for Kyrio and CableLabs to use in certification testing of CMs, with vendors and members able to use it for their own equivalent needs. But, CMVA is well suited for exploring a lot of other needs. Thus, we look forward to working with you to get the full benefit from the XCCF, CMVA and all the CableLabs PNM developments completed and yet to be built.

If you first just want to learn more, please look for our demonstration video to be announced soon. When you are interested in gaining access or discussing it with me further, please feel free to contact me directly by clicking below.

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