Subject: [lp-wan] Ticket #6: Full used window All-0 and All-1 (closed)

From: Ana Minaburo <[email-masked]>
Date: Tue, 3 Apr 2018 14:37:00 +0200

Window normally starts at 2N-2, and all the FCN numbers are used, if not
there could be a confusion between detecting an error and detecting a
non-used FCN number.

In ACK-on-error this possibility will force the use of ACK and the
attractivity of this mode is compromised. In ACK-always it could be
possible to have this behavior.
comment:1 <https://trac.ietf.org/trac/lpwan/ticket/6#comment:1>Changed 2
months ago
<https://trac.ietf.org/trac/lpwan/timeline?from=2018-01-26T02%3A52%3A42-08%3A00&precision=second>
 by laurent.toutain@…

If the bitmap is too big to fill a frame, then the sender cannot use all
the FCN.
comment:2 <https://trac.ietf.org/trac/lpwan/ticket/6#comment:2>Changed 5
weeks ago
<https://trac.ietf.org/trac/lpwan/timeline?from=2018-02-26T10%3A18%3A44-08%3A00&precision=second>
 by ana@…

   - *Resolution* set to *fixed*
   - *Status* changed from *new* to *closed*

This behavior will only be possible for ACK-Always, where ACK is used after
each window. In ACK-on-Error the window must be filled completely.
comment:3 <https://trac.ietf.org/trac/lpwan/ticket/6#comment:3>Changed 1
second ago
<https://trac.ietf.org/trac/lpwan/timeline?from=2018-04-03T05%3A34%3A08-07%3A00&precision=second>
 by ana@…

To close this ticket, we have added two things in the last version of the
document v-10:
In section 7.2 Fragmentation Tools

The rest of the FCN values are assigned in a sequentially

decreasing order, which has the purpose to avoid possible
ambiguity for the receiver that might arise under certain
conditions.

In section 7.5.2 ACK-Always

When an All-0 fragment is received, it indicates that all the SCHC

fragments have been sent in the current window. Since the sender is
not obliged to always send a full window, some SCHC fragment number
not set in the receiver memory SHOULD not correspond to losses. The
receiver sends the corresponding ACK, the Inactivity Timer is set and
the transmission of the next window by the sender can start.