With unprecedented demand facing local broadband networks, operators are under pressure to prepare for congestion and capacity issues before they happen. In this blog I’ll share some tips that will help alleviate and mitigate congestion, while addressing capacity concerns on cable operator DOCSIS plants.

A Nielsen.com study on streaming video minutes on networks compared usage this year versus the same time last year. The study showed that usage increased 90%, from 69.8 million minutes per week to 161.4 million minutes per week. Now that’s a lot of binge-watching!

So, what are we all watching? The big increase is fitness programming and videos – up 147%. Life and home programming were also up with a traffic increase of 64%, and premium channel content was up 54%, while music was down 10% from this time last year.

How does your broadband connection handle all this new traffic?

To help cable operators keep up with the traffic demands, our operations and engineering teams are working ’round the clock taking fast actions. What can cable operators do now to tweak their cable modem termination systems (CMTSs) for the current traffic surge?

Seven Tips for Managing Capacity and Congestion

  1. Decrease subscribers per service group (SG)
    a. The easiest way could be to segment the upstream
  2. Verify no uncorrectable forward error correction (FEC) codewords and “clean” plantAll rights reserved to Sandra Cifo
  3. Increase capacity without physical node splits or SG changes
    a. Allocate more spectrum for high-speed data carriers
    b. Take advantage of PowerBoost™ by eliminating
    the typical 10% over-provisioning
  4. Eliminate Overhead
    a. Split MAC domains to have fewer upstreams per domain
    – More upstreams (USs) in a MAC domain creates more downstream (DS) MAP overhead at ~0.4 Mbps per US
    b. Don’t make all the DSs primary-capable
    c. Remove “stale” service flows
  5. Control abusers and denial of service (DoS) attacks
  6. Optimize CMTS efficiency
    a. Load balancing
    b. DOCSIS 3.1 graceful profile management and US/DS resiliency/partial mode
  7. Implement cache servers
    a. Netflix, YouTube, and others may reduce video quality to save bandwidth

CMTS “Tweaks” Include

  • Cable modem (CM) insertion interval – CM ranging opportunities
    o Experiment with (config-if) #cab insertion-interval auto 120 1000
  • US range and data backoff
    o Cable upstream x range-backoff 3 6
    o This can be experimented with in case CM transmissions collide at init(r1)and have to back-off
  • Throttle CM ranging
    o Experiment with [no] cable throttle-modem init-rate <1-1000> holdoff-time <5-100> flush-rate <100-1000>
    o Suggested values: 32 CM/s; 45 sec; 300 CM/s
  • Prioritize pre-registration traffic
    o During high congestion, CMs that are trying to register could be “stalled” at init(d) since the default priority of this traffic is 0
    o (config) #cable qos pre-registration us-priority [0-7]
  • Voice over IP (VoIP) call signaling insurance
    o Utilize non real-time polling service (nRTPS) for call signaling as it provides non-contention request opportunities that will guarantee call signaling during high US congestion.

For more information visit our Cable Access website. Also, be sure to register for the upcoming Cisco Knowledge Network webinar on May 7, How Is Your Broadband Holding Up,” to hear from Cisco expert John Chapman, Cisco Fellow and CTO, Cable Access Business Unit, and me, where we’ll share valuable information you can use today to quickly adapt your cable network.



John Downey

Sr. CMTS Technical Leader

Cable Access Business Unit