How cable internet providers limit their bandwith?

Are they using SFTP service? If yes, how does all that work?

  • Did any of the answers help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively you can answer your own question and accept the answer.
    – Ron Maupin
    Aug 6 '17 at 3:03

The DOCSIS Service Profile within the configuration downloaded when it registers on the network tells the modem (and headend) how much bandwidth an individual modem is allowed. Exactly how the modem (or headend) polices this is implementation specific.


Simplistically: Cable networking, a true broadband, uses multiple channels that get aggregated to provide your overall bandwidth. The more channels, the higher the bandwidth.

  • Just to clarify, this answer is saying that cable providers aren't providing a link with a fairly high bandwidth and then throttling the allowed traffic down to the bandwidth purchased by the subscriber, instead they are actually tailoring the bandwidth of each subscriber's connection. Did I get that right? Jul 24 '15 at 16:57
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    @Todd Wilcox, the gross method for bandwidth provisioning on cable systems is by limiting the number of channels on the cable modem (see DOCSIS). Beyond that, throttling traffic can be used, and I suspect that many, if not most, cable ISPs employ some sort of throttling. My answer was predicated on what is specific to cable ISPs since that seemed to be the question. I have seen someone break into a cable modem and increase the number of channels, increasing his bandwidth. This is why the cable ISP maintains control of the modem, and I suspect the cable ISP has something to check on this.
    – Ron Maupin
    Jul 24 '15 at 17:09

A subscriber delivery engine (SDE) is commonly used to control traffic to individual subscribers.

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