Re: Request for link-layer header type (XRA)

[Bruno Verstuyft <bruno.verstuyft () gmail com>]

2017-12-01 18:25 GMT+01:00 Guy Harris <guy () alum mit edu>:

> On Dec 1, 2017, at 3:34 AM, Bruno Verstuyft <bruno.verstuyft () gmail com>
> wrote:
>
> > > Type 75 is still labeled as "ODMA REQ" rather than "OFDMA REQ".  Also,
> it
> > > says "ODMA REQ (75): as described by section 7.4.8 "REQ Messages" of the
> > > DOCSIS 3.1 Physical Layer Specification. This is the "REQ message in
> MAC"
> > > in figure 7-11 (56 bits).", but I don't see a figure numbered 7-11 in
> the
> > > DOCSIS 3.1 Physical Layer Specification (CM-SP-PHYv3.1-I12-171026) - is
> > > this from another version of that document?
> >
> > Apparently, the figure had number 7-11 in version I11 of the PHY spec,
> and
> > is figure number 14 in version I12 of the spec. I updated the number to
> 14,
> > to reflect the number in the more recent spec. I also added references to
> > the DOCSIS MULPI and PHY specification version numbers, to avoid
> confusion
> > in the future.
>
> Figure 14 shows how it's generated, but the surrounding text doesn't say
> what the content is; it just says "REQ messages are short messages used by
> the CM to request transmission opportunities from the CMTS. These messages
> have a different structure than the data messages: they are always 56 bits
> long, they always use QPSK modulation, do not apply any FEC and are block
> interleaved."
>
> What do the 56 bits in question contain?  Are they one of the -REQ
> messages described in the DOCSIS 3.1 MAC and Upper Layer Protocols
> Interface Specification, or are they something else?
>
> These are the Queue-depth Based Request Frames described in the MULPI
spec. Changed the reference from the section in the PHY spec to the section
in the MULPI spec.
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