AD Review Comments on draft-ietf-ipdvb-ule-05.txt

[Margaret Wasserman <margaret@thingmagic.com>]

Hi All,

I have reviewed draft-ietf-ipdvb-ule-05.txt.  I do have a few 
comments/questions on this document (see below), but they are not 
very fundamental issues.  So, I will send this document to IETF Last 
Call, and we can resolve my issues along with any other IETF LC 
comments.

Gorry and Bernhard, thanks for your excellent work on this document.

Margaret

---

4. SNDU Format

   PDUs are encapsulated using ULE to form an SNDU. (Each SNDU is an
   MPEG-2 Payload Unit.) The encapsulation format to be used for PDUs
   is illustrated below:

   < ----------------------------- SNDU ----------------------------- >
   +-+-------------------------------------------------------+--------+
   |D| Length | Type |                 PDU                   | CRC-32 |
   +-+-------------------------------------------------------+--------+

   Figure 1: SNDU Encapsulation

   All multi-byte values in ULE (including Length, Type, and
   Destination fields) are transmitted in network byte order (most
   significant byte first). The most significant bit of each byte is
   placed in the left-most position of the 8-bit field. Appendix A
   provides informative examples of usage.

> >  A destination field is mentioned in the text, but not shown in
> >  the diagram?  It might make sense to how/where the destination
> >  may be included before mentioning it.

   5.1 Test SNDU

   A Test SNDU (figure 10) is of a Mandatory Extension Header of Type
   1. This header must be the final (or only) extension header
   specified in the header chain of a SNDU.

[...]

   5.2 Bridge Frame SNDU Encapsulation

   A bridged SNDU is a Mandatory Extension Header of Type 1. It must be
   the final (or only) extension header specified in the header chain
   of a SNDU.

> >  Is it intentional that the Test SNDU and the Bridge Frame SNDU
> >  headers cannot be used in the same SNDU?

3. Description of the Method

[...]

   The ULE encapsulation is limited to TS private streams only. The
   header of each TS Packet carries a one bit Payload Unit Start
   Indicator (PUSI) field. A PUSI field with a value of 1 indicates the
   presence of at least one Payload Unit (SNDU) within the TS Packet
   payload.

> >  s/the presence of at least one/the start of at last one/  ??
> >
> >  If I understand this correctly, the PUSI field will be 0 if
> >  the TS does not include the start of an SNDU.