Minutes interim-2017-lpwan-12: Tue 17:00
minutes-interim-2017-lpwan-12-201712051700-04

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*    Date: December 5th 2017
*    Time: 8-9AM DST, 17:00 CEST:
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Agenda
------

*    [17:05] Administrivia                                           [10min]
    o    Note-Well, Scribes, Agenda Bashing
    o    Status of drafts (WGLC / forthcoming WGLC)

*    [17:15] SCHC Fragmentation update from IETF 100                 [30min]
*    [17:45] Fragmentation comments (Carles)                         [20min]
*    [18:00] AOB                                                     [ 0min]

Minute takers
-------------

*    Ana Minaburo
*    Arunprabhu Kandasamy
*    Alexander Pelov

Attendees
---------
Pascal Thubert
Alex Pelov
Laurent Toutain
Carles Gomez
Ana Minaburo
Edgar Ramos
Juan Carlos Zuniga
Arunprabu Kandasamy

Past Attendees
---------

*    Alex Pelov
*    Ana minaburo
*    Dominique Barthel
*    Laurent Toutain
*    Carles Gomez
*    Ivaylo Petrov
*    Juan-Carlos Zuniga
*    Julien Catalano
*    Orne Brocaar
*    Pascal Thubert
*    Vijay Gharge
*    Orne Brocaar
*    Paventhan Arumugam
*    Paul Duffy

Action Items from last time
----------------------------

* Update SCHC draft

Minutes
-------

Alex: Note Well, IETF Meeting
Alex: agenda Updates for fragmentation, and the side meeting updates
Alex: Need to update and finished the SCHC draft, is a main point and the new
working aspect for later. Alex:

[17:15] SCHC Fragmentation update from IETF 100                 [30min]

Ana: About the side meeting in Singapore.

Pascal: We found three corner cases, and the goal was to fix them.

Ana: 2 timers in the fragmentation.  inactivity timer newly added for abort
functionality.

Ana: Making a new section in the draft called functionalities; added timers
explanation, more on all ones, all zeroes, padding etc...

Ana: Changed the max_ack_req as a counter not a timer. It is a number of wait
till an error is triggered. So we have 2 timers and one counter.

Ana shows the changes in the FSM.

Ana: red squares show the abort states - when do we exit the state, when there
is an error ?

Ana: inactivity timer is initialized in the beginning and after the reception
of a frame.

Ana: The timer duration is still undefined. This could be defined in the
SCHC-over-Foo; Do we do it like this?

Ana: MIC check bit is added for an undetected CRC error in all ones answer.
When the MIC is not correct, a bitmap is resent.

Ana: a questoon that is still undefined is - which algorithm to use for the MIC.

Laurent: When we answer to all-1, we set the bit 1 informing that MIC is right?

Ana: we need to define the algorithm for MIC to finish the draft. We need to
leave it open for SCHC-over-foo doc?

Need atleast one to have it for default behaviour. Alex, agrees.

Laurent; useful for interoperability, regular crc32 is sufficient.

Pascal: need to look at the security mechanism for particular tech that shall
override the default.

Pascal. CRC commonly available, with other lib.

Laurent: Problem is when all 0's (**why?) checksum is not a feasible solution.

Alex: Technology specific or hardware specific algorithms shall be defined in
schc-over-foo.

Laurent: What is the mechanism that can be stronger having it in lower layer
than having udp checksums. for legal reasons..+ technical as well(pascal)

Pascal: It is also technical. Agree with Alex - have something that is simple
to implement in software; Add a text that SCHC-over-FOO should redefine with
something stronger (if necessary).

Pascal: CRC seems to be efficient on hardware but questionable on the software
implmentation.
https://en.wikipedia.org/wiki/Hash-based_message_authentication_code

Pascal: Have a TODO for next time - to define the Default-SCHC-MIC.

Laurent: Implmenting SHA-1 is not trivial.

Pascal: It can also be said that there is something on the message level... or
not. If a frame is compressed, BUT not fragmented, then maybe in some cases, we
can have stronger protection than UDP checksum.

Ana: Bitmap optimization. The example is local bitmap with errors.

Ana: Abort will now have only on byte of bitmap. padding in ack is after the
bitmap, and depends on it

Pascal: When will this be in the document, and when do we start the WGLC ?

Ana: What is missing is to join the baseline definition with the state machine
definition. Other thing still missing is the optimization description.

Ana: Then, the next version will be out. When? End of next week?

Pascal: Christmass season is coming. We need to decide before or after. Even if
we start it, we can start in 2 weeks, but we need to end it mid-january.

Ana: It would be a good thing to do a review.

Pascal: Number of people have reviewed it.. it's good to have implementations.
If the implementation is at the same level as the document, no problems.

Ana: Better, to get last call after Christmass?

Pascal: We need at least 2 weeks, probably more for this document. If we start
before Christmass, then that would be perfect. If we wait after Christmass, it
would not be a bit problem.

Juan Carlos: Coming back after Christmass, it would give more motivation to
people.

Laurent: target is to finish doc in 1 week

Pascal: if we do so, we will publish, start WGLC, and say that it will take 5
weeks.

[17:45] Fragmentation comments (Carles)                         [20min]

Carles: Minor updates and remaining issues. Added text in github on downlink
fragments as discussed in previous meetings.

Carles: on multiple window sizes. If transmitting large packets, use a large
window size. Also, not chnage the window size in the middle of a fragmented
packet.

Carles: Addition of ACK on ACK-on-error at the end of the packet, in the last
window,

Carles: Q: adding a final ack in ack on error? this is to let the sender know
that no false positive. Laurent and Juan Carlos agree ist is a good idea.

Ana: In the State Machine is not difficult and will help to unblock an error
situation in this window mode. The modification is not difficult.

Laurent: for the change of fragment size, if only LoRaWAN has this behavior so
put it on schc-over-lorawan. If we indentify several technologies, then go for
a separate document.

Carles: 2nd level bitmaps problem.

Alex: This is probably work for the future but not for this version of the
document

Maybe in the future we will have more sophisticated ways of representing
bitmaps. We also have the problem when many fragments that cause long bitmaps

Edgar: There could be a problem for the compressor/fragmentor to know the size
of the fragment (which is on the radio level)

Ana: If this specific to one technology so we do not need to added in this
document, but in the technology document as LORAWAN

Alex: Time goes, thanks everybody, sorry but we need to end the meeting. See
you in two weeks.

[18:00] AOB                                                     [ 0min]