How Cable Modems Work

[@Juliozz3]

Great explanation, thank you for making this video!

[@TelecomTraining]

You 're welcome.

[@babydevi9587]

Good work, Trevor. Appreciate the diagrams and your very detailed explanations. Thx for sharing your knowledge. You're such a good teacher.

[@TelecomTraining]

Thank you. I do appreciate that.

[@VinuVinu10001]

Very clearly explained. Also covered all the important points. Thanks a lot...

[@thomaspgeorge4339]

This was a really detailed and well explained video. Thank you so much!

[@TelecomTraining]

You are welcome.

[@gir489returns2]

Finally, a guy who knows what he's talking about and isn't just reading a Wikipedia article with an Indian accent.

[@level80888]

very good video. Thank you. 👏🔥

[@TelecomTraining]

You are welcome.

[@geroldholloway1270]

Nice work

[@TelecomTraining]

Thank you! Cheers!

[@ntag411]

I'm wondering how the physical cable works using only a single center conductor. I get the impression it works like a walkie talkie or Ham radio, the transceiver can only transmit or receive at a given time, not both at the same time. Cable is just whole lot faster making it appear almost seamless.

[@TelecomTraining]

You are correct. It works in a half duplex mode just like a Ham Radio or Walkie talkie. The transmission time is devided between downstream and upstream sharing the same single center conductor.

[@Ulaser0]

So did I understand correctly? While the cable infrastructure is saturated during peak hours, will DSL be less saturated under the same conditions?

[@TelecomTraining]

Cable is a shared service. During peak hours they are more subscribers using the service. Resulting in slower speed. Dsl service is not shared, so speed is generally constant. Hope my answer was helpful.

[@Ulaser0]

@@TelecomTraining Understood thanks. However, does the performance of DSL not decrease due to the congestion experienced in the MPLS backbone, or is this related to the capacities of the ISPs?

[@Ulaser0]

@@TelecomTraining In the country I live in (TR), the ISP named Türk Telekom is the company that undertakes almost all other DSL infrastructure and provides services with VAE. So isn't it shared like cable?

[@oleksandrone]

How does CM will receive configuration file from TFTP if according to your scheme, DHCP process will be the second step after TFTP? That is not right. DHCP process is first, after that CM receives configuration file through the TFTP (IP of which he receives from DHCP server)

[@TelecomTraining]

Thank you for the question. The first step with cable modems is to negotiate a secure communication path with the Head End. Only after this path has been established with the CMTS would an ip address be send from the DHCP server to the modem. You cannot have the dhcp assignment first with out first establishing the physical communication path between the subscriber's modem and the Headend. Hope my answer was helpful to you. Thanks again for the question.

[@shorthand1121]

A cable modem will have two IP addresses ... one private one for administration (including the TFTP configuration file download) and one for actual public traffic. ... Its buried in the spec.

[@mikewolf5367]

Actually the link light has nothing to do with the communication between the modem and the CMTS. The link light you’re referring to is simply what indicates communication between the modem and whatever is connected to it such as a computer or router. It’ll flash or blink when there’s communication between the two or the outside internet.

[@TelecomTraining]

Thanks for the heads up. Unfortunately manufacturers don't standardize the naming convention.

[@Ebolachicken]

might as well get cell service or fios

[@ThaddeusSteven]

Just a minor comment you interchange CMTS and CTMS throughout the video.

[@TelecomTraining]

I do apologize. Thank you for bringing that to my attention. It is CMTS. Cable Modem Termination System. Thanks again.

[@danc3677]

Nokia’s BTS work?

[@elalemanpaisa]

You are mixing up up and downstream

[@TelecomTraining]

In what way?

[@elalemanpaisa]

@@TelecomTraining after one month I have seen too many other videos I don't recall anymore I would have to rewatch again

[@bigvitojr]

If you are on dsl with fiber . No problem

[@TelecomTraining]

That is correct. End to end Dsl on fiber is great. However most Dsl lines only use fiber from the Central Office to local areas. The Fiber is generally connected to a twisted pair of copper wires in order to carry the service to each customer premises. The length of the twisted pair is generally between 100 meters and 1000 meters and the greater the length of the copper wire the slower the service will be. However DSL is also a great service and is a perfect High Speed Internet Solution to thousands of subscribers. It can also be be a very cost effective solution to many.