editorial changes in compression/decompression logic (R-mode)

[zhigang.liu@nokia.com]

Hi Carsten and others,

Happy new year! After a long vacation I have to propose some
editorial changes in section 5.5.1.2 and 5.5.2.2. It's based on
discussion with Khiem. Hopefully, it can catch the -07.

Only two paragraphs need to be changed. Below is the proposed new 
text, followed by the reasons for those changes.

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5.5.1.2.  Compression logic and packets used (R-mode)

...

The compressor will transit to the SO state after it has determined
the presence of a string (see section 2), while also being confident
that the decompressor has the string parameters. The confidence can 
be based on ACKs. For example, in a typical case where the string 
pattern has the form of non-SN-field = SN * slope + offset, one ACK 
is enough if the slope has been previously established by the 
decompressor (i.e. only the new offset needs to be synchronized). 
Otherwise, two ACKs are required since the decompressor needs two 
headers to learn both the new slope and the new offset. In the SO 
state, R-0* packets will be sent.

...

5.5.2.2.  Feedback logic (R-mode)

...

2) For a sequence of UOR-2, IR, or IR-DYN packets, the first X
of them MUST be ACKEd, where X is the number of ACKs needed to give
the compressor confidence that the decompressor has acquired the
new string parameters (see second paragraph of 5.5.1.2). In case
the decompressor cannot determine the value of X, the default value
2 SHOULD be used. If the subsequently received packets continue 
the same change pattern of header fields, sparse ACK can be applied.
Otherwise, each new pattern MUST be treated as a new sequence, i.e.
the first X packets that exhibit a new pattern MUST be ACKed.

...
---------------------------------------------------------------

Here are the reasons:

5.5.1.2. To be consistent with other parts of the draft, the (linear) 
string parameters should include the offset. 

5.5.2.2. The original text in -06 "the first two MUST be ACKed" is
too restrictive and not consistent with 5.5.1.2. I picked two to keep
the protocol simple. However, the new text should still achieve the same 
goal while providing more flexibility. 

Comments?

Br,
Zhigang