Subject: [6tisch] Webex OTF authors, March 19, 2014

From: "Prof. Diego Dujovne" <[email-masked]>
Date: Mon, 24 Mar 2014 17:25:44 -0300

Webex OTF authors, March 19, 2014 Attendance

   - Maria Rita Palattella
   - Diego Dujovne
   - Nicola Accettura
   - Thomas Watteyne

Goal

This meeting was scheduled in order to discuss specific items for the
development of the OTF draft and the interaction with 6top and other
components of the 6TiSCH stack. Both the Note Well and the Reminder
sections are included in the call at the beginning.
Agenda

   - 6top & OTF *(Maria Rita Palattella)*
   - OTF Interface *(Diego Dujovne)*
   - OTF Open Issues *(Nicola Accettura)*
   - OTF triggering events *(Alfredo Grieco)*
   - AOB

Action items

   - *Maria Rita Palattella* to discuss the need for cell selection
   algorithm in 6op-sublayer draft after the negotiation phase.
   - *Maria Rita Palattella* to send general comments about 6top-sublayer
   to Qin/Xavi on 6TiSCH ML
   - *Nicola Accettura* to discuss the use of chunks with soft cells on the
   ML
   - *Maria Rita Palattella* discussing the relationship between tracks and
   soft cells reserved through OTF
   - *Thomas Watteyne* to discuss extensions of the YANG model for optional
   modules e.g. OTF. (proposal: coap://[aaaa::1]/6t/ext/otf/alg)
   -

   *Nicola Accettura* to discuss simplification of pre/post allocation on ML
   -

   6top & OTF *(Maria Rita Palattella)*
   - *Maria Rita* presents a set of slides defining the relationship
      between OTF and 6top.
      - The first discussion item is whether OTF can allocate soft cells
      exclusively.
         - Even though bundles are mentioned in the 6top draft, for OTF
         purposes, the only meaning is to generate a group of more than one
         allocated cells.
      - The second item under discussion is the absence of a process to
      select soft cells after the negotiation phase between 6top to 6top of two
      neighbours.
         - *Thomas* recommends to discuss this item with Qin and Xavi.
      - The third discussion item is Cell collision: The 6top layer cannot
      differentiate collisions from other sources of packet loss. The use of
      Chunks may solve them, but Cells within Chunks are reserved as
hard cells,
      thus OTF should not use them.
         - *Nicola* proposes that Chunks could be used either for DeTAS and
         for OTF.
         - *Thomas* comments that Chunks are still unclear but they should
         work in centralized mode (PCE). This matter is still under discussion.
         - *Diego* asks if there is call to reserve Bandwidth instead of
         soft cells on 6top. It also provides an example about the use of cell
         statistics: If a BW of 150Kbps is required and each soft
cells supports
         100Kbps, 6top can use 100Kbps of Cell1 and 50Kbps of Cell2,
both with 100%
         PDR, or, if both Cell1 and Cell2 have a 75% PDR, then 6top
must reserve
         Cell1 and Cell2 with 75Kbps, totalling 150Kbps. Does 6top take this
         decision, or should it be OTF? Response:?
      - *Maria Rita* believes that this should be part of the soft cell
      selection procedure that right now it is missing in 6top.
      - *Maria Rita* presents the lack of procedure in 6top to select the
      cells to be added or deleted from the schedule. Where should it
be defined?
      - *Maria Rita* shows the use of 6top monitoring commands and 6top
      statistic commands, to provide input to OTF to estimate more or less BW
      requirement. She also describes that the policy to generate Create/Delete
      soft cell commands is out of 6top scope but OTF provides one.
      - *Diego* comments about the requirement of cells to belong to a track
      - *Thomas* proposes that, since tracks were created to be compatible
      with a centralized approach (using a PCE), a single track ID can be used
      for all the cells with OTF, as a starting point.
   - OTF Interface *(Diego Dujovne)*
      - *Diego* presents OTF interface requirements and issues. He proposes
      to use the YANG data model for algorithm selection and parameter passing,
      while leaving a direct connection with no intermediate layer to 6top.
      - *Diego* also describes the data structure and the functions needed
      to identify the algorithm and pass the parameters.
      - After a question from *Thomas*, asking if this supposes a
      centralized algorithm selection and parameter passing process,
*Diego*comments that, a centralized distribution approach could be
available as a
      start, OTF<->OTF communication will be needed when scheduling is
completely
      distributed.
      - As a consequence, *Thomas* proposes to use IEs to transmit the
      algorithm selection and parameters between nodes when a new node
arrives: a
      GET command can be issued to receive an (extended) IE with the required
      information through 6top.
      - *Nicola* comments that another way to distribute the algorithm is
      to do something similar than RPL with Objective Functions.
      - *Thomas* proposes also to standardize algorithm identifiers by IANA.
      - Finally, following a short discussion with Alfredo at the IETF
      meeting, *Diego* proposes to add a recommendation on the OTF draft to
      implement lightweight and stateless scheduling algorithms due to
      constrained resources available. Furthermore, he proposes to use
only data
      provided by 6top instead of storing data from the current run to the next
      one.
   - OTF Open Issues *(Nicola Accettura)*
      - *Nicola* describes several OTF open issues. The first item is
      similar to the one of the points previously discussed by Maria Rita: OTF
      only allocates soft cells, since bundles are automatically created after
      more than one cell is allocated between two neighbours.
      - He proposes to use a single allocation policy comprising the hybrid
      one; *Maria Rita* comments that the existence of three policies is
      required providing options to attach to any of them.
      - *Diego* asks if the pre-allocation policy should be strict:
      preallocate only at the beginning and any other allocation (even
      over-provisioning) after this turn this policy into hybrid.
      - *Maria Rita* recaps the meaning of pre-allocation policy, showing
      to Nicola that it does not imply a static behavior.
      - *Nicola* proposes to obtain input parameters from the 6top layer,
      for example, using trickle. This is an alternative to the previous
      discussion (from Thomas) of using IEs and a centralized distribution as a
      start (from Diego).
      - Finally, *Nicola* discusses the use of Chunks in OTF: allowing them
      in distributed scheduling and enabling the use of soft cells;
this could be
      discussed in the ML.
   - OTF triggering events *(Alfredo Grieco)*

   Alfredo Grieco could not attend this call. This discussion is pushed to
   a future call.

   - The call finishes by a concluding remark from Thomas, asking about the
   possibility to implement OTF either by simulation / hardware implementation
   / Ptolemy model.

-- 
DIEGO DUJOVNE
Académico Escuela de Ingeniería en Informática y Telecomunicaciones
Facultad de Ingeniería UDP
www.ingenieria.udp.cl
(56 2) 676 8125