Minutes interim-2017-lpwan-12: Tue 17:00

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Meeting Minutes IPv6 over Low Power Wide-Area Networks (lpwan) WG Snapshot
Title Minutes interim-2017-lpwan-12: Tue 17:00
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Last updated 2017-12-05

Meeting Minutes

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*    Date: December 5th 2017
*    Time: 8-9AM DST, 17:00 CEST:
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*    Meeting number: 204 648 433

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*    [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

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


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]