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

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

2017-12-04 22:21 GMT+01:00 Guy Harris <guy () alum mit edu>:

> On Nov 16, 2017, at 1:21 AM, Bruno Verstuyft <bruno.verstuyft () gmail com>
> wrote:
>
> > we put the specification of the XRA header online.
>
> The MAC document speaks of "logical" upstream and downstream channels; are
> those what the "Downstream Channel ID" and "Upstream Channel ID" TLVs refer
> to?
Yes, from the MULPI spec:
Logical (Upstream) Channel: A MAC entity identified by a unique channel ID
and for which bandwidth is allocated by an
associated MAP message. A physical upstream channel may support multiple
logical upstream
channels. The associated UCD and MAP messages completely describe the
logical channel.

5.2.1.1.3.1  Downstream Data Forwarding in a MAC Domain:
A MAC Domain provides downstream DOCSIS data forwarding service using the
set of downstream channels
associated with the MAC Domain. Each downstream channel in a MAC Domain is
assigned an 8-bit Downstream
Channel ID (DCID).



> To what do the start and stop minislots in the "Minislot ID" TLV refer?

These are the minislots, relative in an OFDMA frame. The minislot with the
lowest subcarriers has id 0.


> What do the "Symbol ID", "Burst ID", and "Subplot ID" TLVs contain?

Symbol ID is a number assigned to each symbol by our hardware. This is
mainly used for timing calculations. It can also be used to visualize the
correlation between NCP (Next Codeword Pointers) and the corresponding
downstream data packets.

Burst ID is used to map mac frames to the corresponding databurst. A
databurst can e.g. contain a segment:(see MULPI 7.2.4
 Continuous Concatenation and Fragmentation). This means a segment can
contain multiple Mac frames, or a Mac frame can be spread over multiple
segments. In our sniffer, we extract these Mac frames from the segments. To
save the information of which Mac frame belongs to which segment (or
multiple segments), we use the Burst ID: each data burst gets a unique
Burst ID. In the Mac Frame the "Burst Info"/"Burst ID reference" is used to
reference these Burst IDs.

Subslot ID: A minislot can be divided into multiple subslots to provide
multiple transmission opportunities for Bandwidth requests
(see PHY 8.2.4.1  Subslot Structure). This is the ID of this subslot. The
leftmost subslot has id 0.




> Does the SID TLV contain the Service Identifier for the service flow in
> which the packet was sent?

Yes

> Does the IUC TLV contain the Interval Usage Code for the burst if the
> packet is a burst?


Yes
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