Talk:DOCSIS

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DOCSIS 3.1 specifications have come out now supporting 10Gbps Down and 1Gbps up.^[1] Whiskytaxidriver (talk) 19:59, 30 October 2013 (UTC)[reply]

That link is lost in time. 404.

Regardless. I don't see that 10Gbps download limit established anywhere in the present DOCSIS 3.1 spec. 2601:40D:8101:1900:0:0:0:3 (talk) 09:58, 14 September 2022 (UTC)[reply]

References

^ http://www.cablelabs.com/cablemodem/specifications/specifications31.html

Distances and degradation

It would be desirable to have a sentence or two (maybe even a table) on for what distances on the last mile the DOCSIS would provide what bandwidth. --eugrus (talk) 14:28, 25 September 2018 (UTC)[reply]

Are maximum number of DOCSIS channels dictated by spec, which this article seems to reference?

https://en.wikipedia.org/wiki/DOCSIS#Comparison

In this "comparison" chart, DOCSIS 3.0 maximum download throughput is stated to be 1Gbps. Where does this 1Gbps figure come from?

At 42.88 Mbps per 6MHz channel for 256-QAM, that means the maximum number of bonded channels is 24. 24 x 42.88 == 1029.12 Mbps. DOCSIS 3.0 is limited to 24 bonded channels? Who says so?

If this is a de facto standard imposed by modem chipset manufacturers, ISPs, et al, this article should say so.

Separately but related. That 42.88 Mbps rate per channel for 256-QAM is obtained by multiplying 8 bits per symbol times the symbol rate 5.360537 Msym/s stated in DOCSIS 3.0 PHY spec. (pg 100). 8 x 5.360537 == 42.884296 Mbps

Likewise, the data rate per channel for 64-QAM can be obtained by multiplying 6 bits per symbol times the symbol rate 5.056941 Msym/s. 6 x 5.056941 == 30.341646 Mbps

The 10Gbps download limit stated here for DOCSIS 3.1 does not seem to be established by its corresponding spec, either.

I'm going to have to take down several of my online posts which recited this Wikipedia DOCSIS article.

What an embarrassment. — Preceding unsigned comment added by 2601:40D:8101:1900:0:0:0:3 (talk) 09:51, 14 September 2022 (UTC)[reply]

Not overselling

The article says:

Also note that, since in many cases, DOCSIS capacity is shared among multiple users, most cable companies do not sell the maximum technical capacity available as a commercial product, to reduce congestion in case of heavy usage.

Cable companies are more or less notorious for over-selling shared capacity. This has been a huge bulk of the complaints about them online and otherwise. Their advertising contains fine print saying the maximum speeds may not be achievable during periods of congestion without clarifying when "congestion" is so they could sell sell whatever the maximum speed of their equipment is and not run into any issues, legally. As regional monopolies on cable internet (with no alternatives such as fiber for modern internet in many areas), user complaints don't really matter. You need to be in a pretty remote area to get gigabit speeds 24/7 on Comcast, for example, and prior to DOCSIS 3.1 they were selling 24/8 stream configs of DOCSIS 3.0 as gigabit despite it being beyond the technological capacity after overheads, which they could get away with by using the pre-overhead data speed somewhere in the fine print. I'd often see people who'd called about this and were told that gigabit ethernet couldn't support faster than ~900Mb/s, which was nice and safe since there was no equipment available to convert the cable signal to any higher speed. I'd say if anything they don't sell it because people don't yet commonly have hardware that supports higher than gigabit speeds and it would just lead to many plan downgrades within the first week of service which doesn't really do much for them. They need at least synthetic speed tests to roughly agree with what they're selling to keep people buying. A Shortfall Of Gravitas (talk) 03:54, 20 October 2022 (UTC)[reply]

Totally agree. I've removed that dubious uncited sentence. — voidxor 13:17, 20 October 2022 (UTC)[reply]

[1] ttp://www.cablelabs.com/cablemodem/specifications/specifications31.html

[1]