Re: Linktype allocation for ATSC link layer protocol

[Guy Harris <gharris () sonic net>]

On Oct 14, 2019, at 12:10 PM, Nick Kelsey <nickk () silicondust com> wrote:

> > > ATSC 3.0 includes a new link layer protocol known as ALP (ATSC Link-layer protocol). 
>
> > So the first two octets of the packet data contain the Base Header?
> > That appears to be a 16-bit header; in a capture, in what order are the bytes of the Base Header, and in what order 
> > are the bit fields?  The same applies to other fields.
>
> There are a few different packet formats...

But they all have the Base Header, and that header has:

        3 bits of packet type;

        1 bit of payload configuration;

        1 bit of:

                header mode, if the payload configuration bit is 0;

                segmentation/concatenation, if the payload configuration bit is 1;

        11 bits of length;

for a total of 16 bits, right?

If so, in a capture file:

        1) the Base Header has 2 octets - in what order in the file are the two octets?

        2) in what order are the bit fields?

For example, does the first octet of a packet contain:

        3 bits of packet type in its upper 3 bits;

        1 bit of payload configuration in the next lower bit;

        1 bit of header mode or of segmentation/concatenation in the next lower bit;

        the uppermost 3 bits of length in the lowest 3 bits;

and does the second octet contain the lowermost 8 bits of length?
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