Thread: 10meg & NTL Modem
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Old 20-04-2006, 11:10   #11
James Henry
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Re: 10meg & NTL Modem
Quote:
Originally Posted by agatward
Incorrect. The physical cable media rate is defined by DOCSIS, but the bridge layer in the CM doesn't necessarily have to forward at full (max) 36Mbit/s rate to be DOCSIS compliant. The compliance only deals with what is and isn't forwarded, how the CM deals with customer equipment, and the signalling used between the CM and CMTS (aka UBR). There's also recommendations on things like LEDs but most vendors appear to ignore these!
Yep. To comply with SCTE / Cablelabs, and indeed to actually work, all modems must on the DOCSIS / EurodDOCSIS downstream be able to tune and decode all 30.3Mbps / 42.88Mbps / 41.72Mbps / 55.62Mbps of DOCSIS or EuroDOCSIS related info on the wire (am including MPEG framing, FEC and R-S encoding there, the whole shebang), however the CPU and buffer memory in the modem doesn't need to be capable of forwarding all of this.

Only how the bridging must work is defined, not how much data it is capable of shifting.

Same as with the Pace STBs, they had no issue with the cable modem itself the issue was CPU limitation in the box as it shared the same CPU between the TV tuner and cable modem tuner.
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