Hi Carsten,
On Sep 20, 2009, at 7:55 AM, Carsten Bormann wrote:
one change I don't understand:
OLD (-04):
TF: Traffic Class, Flow Label:
00: Traffic Class + 4-bit Pad + Flow Label (4 bytes)
NEW (-05):
TF: Traffic Class, Flow Label:
00: 4-bit Pad + Traffic Class + Flow Label (4 bytes)
This is not in the change notes.
It destroys the byte-alignment of the Traffic Class field.
It also hurts the (code-saving) similarities -04 had between the TF
values 00, 01, and 10.
Clearly, this is a regression.
(Unfortunately, it is almost identical to the old version so I
didn't notice the change in July.)
If you want to be precise in the text you call out, neither version
sufficiently specifies how the fields are encoded - that specification
is delayed until Section 2.2.1 in both drafts. Would you prefer to
list ECN and DSCP separately and in the order that they appear in a
LOWPAN_IPHC encoded header? For example:
00: ECN + DSCP + 4-bit Pad + Flow Label (4 bytes)
01: ECN + 2-bit Pad + Flow Label (3 bytes)
10: ECN + DSCP (1 byte)
11: Version, Traffic Class, and Flow Label are compressed.
Or would you prefer a note that points towards Section 2.2.1? Or
something else?
As an editorial comment, it would help to just say that the meaning
of DAC/DAM simply is the same as that for SAC/SAM for M=0.
There is a proposal to make SAC=1, SAM=00 to indicate the Unspecified
Address. Would you prefer text that says they are the same with
exception? Or keep the text as is?
As another technical note: Are we sure that these changes really
don't impact ISA100, which appear to be stuck on -04? I haven't
managed to verify that yet.
I defer to Pascal who has more knowledge of ISA100 than me.
--
Jonathan Hui
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