Subject: AD review of draft-ietf-ipdvb-ule-05.txt

From: Margaret Wasserman <[email-masked]>
Date: Fri, 29 Apr 2005 00:49:36 -0400

Hi All,

I have finished my AD review of draft-ietf-ipdvb-ule-05.txt.  This 
document appears to be in very good shape.  I just have a couple of 
comments/questions on the document (see below) that I would like to 
resolve before sending the document to the IESG for final review.

Since any changes related to these comments are likely to be very 
small, I will send the document to IETF LC in parallel with resolving 
these issues.  Gorry, if you like, you can wait until the IETF LC 
completes and make any changes resulting from these comments at the 
same time as you make any changes to address the IETF LC comments.

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