[Sls-slp] Extending USLP SCID - more generic approach - reusing TM Transfer Frame Secondary Header but signaling it with 'all ones' SCID

[KAZZ, GREG J. (MSFC-HP27)[MOSSI2]]

Dear SLP WG and others,

Yesterday, Oct 21 in the SLS joint meeting, we reached consensus on extending the USLP (Version-4) SCID to 64 bits.
We need to make the existing USLP (732.1-B-3) backward compatible with the future B-4 book that will contain this option.

I propose we reuse the Transfer Frame Secondary Header concept from TM (132.0-B-3). The format of the USLP TF secondary header will then appear in Section 4 of the USLP BB. This will provide us with more than one way to extend the USLP protocol for the future.

The TM Secondary header provides up to 4 versions of the TF Secondary Header. Similarly, using the same format, we can define TF 2nd Hdr Version 1 ('00') for the "Extended SCID". That leaves us with up to 3 additional undefined versions for the future. Like in TM, this 2nd header would be optional, to make it backward compatible with existing USLP implementations.

The Transfer Frame Secondary Header is optional; its presence or absence shall be signaled by the value of the SCID field set to 'All ones' in the Transfer Frame Primary Header (see TBD). (So unlike TM, there will be no 2nd header flag in the USLP Primary TF header).
NOTE - This field applies to both Truncated and Non-truncated USLP Primary Headers.

In a new TBD USLP Annex, the format of the Version 1 USLP Transfer Frame Secondary Header is specified:

#1) It will consist of two 64-bit fields:

  1.  Source SCID - 64 bits;
  2.  Destination SCID - 64 bits.
#2) In addition, the Source/Destination Flag in the Transfer Frame Primary Header shall be ignored.

Please see the format of the USLP Transfer Frame Secondary Header in the attached word file.

Your comments are most welcome.

Regards,
Greg




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