The MAC address you identified, 01E02F000001 is called out in Annex A of the DOCSIS specification. This is defined using the Ethernet/ISO8802-3 [ISO8802-3] convention. Specifically, it states:

The following multicast address MUST be used to address the set of all CM MAC sublayers; for example, when transmitting Allocation Map PDUs:
01-E0-2F-00-00-01

So, to answer your question, yes, it will be sent with all UCDs.

Regards,
-Brady

Yet another informative post. Simply these posts are real stepping stones to understand the base of working of Cable modem.

Enormous amount of info is present in UCD.
This PDU DA 01E02F000001, you mentioned this a Multicast address.

Whether this address is unique for each UCD, that will be sent for CM’s ?

Thanks,
Sathish.

Anyway, thanks for your speedy reply and this great blog!

Oh, and you might want to wait till I note that 160Ksym/sec would be correct and 1.6Msym/sec would be wrong before you recruit me!

I really should recruit you to help me on these blogs – you are reading them very thoroughly! You are correct on the symbol rate, it is 160 ksym/sec, the lowest rate DOCSIS supports. 1.6 Msym/sec is not even a supported rate, so I completely dropped the ball there. Supported DOCSIS rates are 160, 320, 640, 1280, 2560 and 5120 ksym/sec. Yes, I also made a typo – I’ll fix these in a minute and no one will know aside from these comments.

Regarding the preamble offset, I have double checked this and believe that it is correct. 624/8 bits = 78 bytes. Counting in from the beginning of the preamble 78 bytes (two hex characters) leaves you with 14 “F3″ bytes left in the preamble before the first “33″ byte. This matches exactly with the Request preamble shown. Maybe I’m not seeing what you are seeing.

-Brady

I’m wondering if there is a typo or two in this post.

First, I think the symbol rate should be 1600000 symbols/sec, if it is 1.6M as you state in the text.

Second, I think the Preamble Offset for the Request IUC should be 640 instead of 624, or am I misunderstanding how that’s derived? If I did understand it as an index into the Preamble Pattern sent by the CMTS, then I’m assuming that only the the length and offset are really sent by the modem as that would be enough to derive the preamble itself.

Sorry if the second question is very elementary, but I’m brand new to docsis.

Thanks! Carol

PS: I think the second paragraph of the explanation should read “is the PDU DA” instead of “in the PDU DA”.