Subject: [rohc] Tsc field interpretation for RFC 3095

From: Alan Kennington <[email-masked]>
Date: Sun, 20 Jul 2003 09:43:43 +0930

I've just come across another small apparent ambiguity in RFC 3095.

For the extension type 3, the RFC has this on page 85:

================================================
      0     1     2     3     4     5     6     7
   +-----+-----+-----+-----+-----+-----+-----+-----+
   |  1     1  |  S  |R-TS | Tsc |  I  | ip  | rtp |            (FLAGS)
   +-----+-----+-----+-----+-----+-----+-----+-----+

[....]

      S, R-TS, I, ip, rtp, ip2: Indicate presence of fields as shown to
      the right of each field above.

      Tsc: Tsc = 0 indicates that TS is not scaled;
           Tsc = 1 indicates that TS is scaled according to section
           4.5.3, using value(TS_STRIDE).
           Context(Tsc) is always 1.  If scaling is not desired, the
           compressor will establish TS_STRIDE = 1.

      SN: See the beginning of section 5.7.

      TS: Variable number of bits of TS, encoded according to
          section 4.5.6.  See the beginning of section 5.7.
================================================

Suppose I have R-TS = 0.
This means there is no TS field in the extension 3.

Question: Does this mean that Tsc is ignored?
In other words, does Tsc only apply to the TS field in the extension 3?
If I send a UOR-2 with extension 3 with R-TS = 0 and Tsc = 0, does this mean
that the 6 bits of TS in the base header are unscaled?
Both interpretations seem reasonable.

Could someone please tell me what the current consensus on this is?
I think this should be in the ROHC implementer's guide.

Cheers,
Alan Kennington.

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