Subject: [lp-wan] Profile Questions

From: Ana Minaburo <[email-masked]>
Date: Tue, 28 Jan 2020 16:53:41 +0100

Dear LPWANers,

The last version of SCHC document gives quite an extensive list of things
that need to be defined in something called 'Profiles.' This concept is
broadened, and I presume it is only a list of parameters to be set and
functionalities that need to be restricted in used or avoided to be used.
But while defining parameters for NB-IoT draft the following question
raised:

The draft is not clear about where these profiles get into the
communication or not, do they?

How are they distinguishable from other profiles? Is an identifier needed?

Who can define a new one?

Does a profile contain Rules or Rules are separate things?

Do we need to be formal in the number of "profiles" we need?

Is profile a configuration that is used locally and then only requires to
define all the SCHC parameters and so these configurations are merely
informative and not mandatory?

Here I put a non-exhaustive list of what the draft talks about profiles:
The draft SCHC specifies in page 7 the definition of Profiles as
"Profile: SCHC offers variations in the way it is operated, with a
 number of parameters listed in Appendix D.  A Profile indicates a
      particular setting of all these parameters.  Both ends of a SCHC
      communication must be provisioned with the same Profile
      information and with the same set of Rules before the
      communication starts, so that there is no ambiguity in how they
      expect to communicate."

But all are not in Appendix D because you can find through the document a
number of things that need to be addressed as:
-The use or not of Fragmentation (page 9, 21)
-The size of the Rule_ID (page 11)
-The way the Rule ID is sent (page 16)
-The IID value (page 20)
- The Fragmentation Modes used (page 21)
- The restriction or not of interleaving fragments for different fragmented
SCHC packets" (page 21)
- Window_Size (page 23)
- Specify how integrity check is performed (page 24)
- The size  and presence of DTag
- The size and presence of W- The FCN size for each Rule_ID
- The size and algorithm for RCS field for each Rule_ID
- The All-1 SCHC Fragment is distinguishable from Send-Abort msg
- Which Rule_ID values correspond to SCHC F/R msg
- The expiration time of the Inactivity Timer
- The meaning of values sent in the FCN field
- Which Rule ID corresponds to each SCHC F/R
- The penultimate tile is regular size or regular minus L2 Word
- Last tile must be sent either as regular fragment or multi-tiles or alone
in an All-1 SCHC fragment
- Other times the sender must listen for SCHC ACK msg
- the size of L2 Word
- The value of padding bits
- Whether and when the UDP CHECKSUM is elided
- MAX_PACKET_SIZE
- A delay to be added after each SCHC message transmission
- The MAX_ACK_REQUESTS
- Settings and choices specific to a technology or a product
and many others that I've not listed

Thanks,
 Ana