[6tsch] minutes webex 7 June 2013

[Thomas Watteyne <[e-mail]>]

All,

You will find the minutes of the last webex below, and the presented slides
at https://bitbucket.org/6tsch/meetings/.

Thanks to Xavi for taking notes!

As usual, fix anything we might have missed directly in the e-mail and
reply.

Also, please remember that, exceptionally, there will be no call this
Friday.

Thomas

---

# Minutes Webex 07 June 2013, 6TSCH group #

Note: timestamps in PDT.

Taking notes (using Etherpad)
-------------------------------

1. Xavi Vilajosana
1. Thomas Watteyne

Present (alphabetically)
--------------------------

* Alfredo Grieco
* Elvis Vogli
* Pascal Thubert
* Pouria Zand
* Raghuram Sudhaakar
* Robert Assmiti
* Penny Chen
* Thomas Watteyne
* Tina Tsou
* Xavi Vilajosana

Recording
---------

* Webex recording (audio+slides,streaming)
*
https://cisco.webex.com/ciscosales/lsr.php?AT=pb&SP=MC&rID=68915952&rKey=a6aa751cea420bdf[58min]

Slides
------

*
https://bitbucket.org/6tsch/meetings/src/5b67d87897b4d6f90657483b9458b832bf969d4d/130607_webex/slides_130607_webex.ppt?at=master

Agenda
------

* Logo Challenge [5min]
* Opportunistic Track reuse [15min]
* 6LoWPAN Fragment Forwarding [10min]
* Simplest TSCH [30min]

Minutes
-------

* [08.05] Meeting starts
* Pascal reviews agenda for the call.
* Logo Challenge [5min]
    * winner in Xavi's design
    > Official logo now available at
https://bitbucket.org/6tsch/meetings/src/
* [08.07] Opportunistic track reuse
    * Pascal presents slides.
    * we decided to avoid tracks being merged/split. Instead, use L3
capabilities.
    * reservation is a waste of resources if they are not used
    * idea: opportunistically reuse a one-hop time slot, but we need
intermediate node to distinguish between a packet being switched on track,
or opportunistically routed on that cell.
    * proposal:
        * packets being switched have L2 MAC destination set to 0xffff
(broadcast). This bypasses L2 MAC address check, but indicates to 6TUS that
this packet has to be switched.
        * packets being routed, and using this cell opportunistically set
the L2 MAC destination address to the next hop.
    * Destination MAC restored at ultimate or penultimate hop?
        * Discussion indicates ultimate hop makes the most sense.
* PCE installing routes on top of schedule
    * allow PCE to install (RPL) routes on top of tracks.
    * Use different RPL instance IDs.
    * Ends up adding information in the nodes' routing table.
    > '''TODO''': start thread on ML about allows PCE to install routes.
    * [Thomas]
        * This only applies when we want to do p2p inside the network.
        * If you don't install anything the routes will go to root
        * Without this feature, P2P works, but suffers from the "RPL
stretch" whereby a P2P packet has to go "upstream" before going "downstream"
* [08.21] Fragment Forwarding
    * Pascal presents slides illustrating the following draft:
    >
http://tools.ietf.org/html/draft-thubert-6lowpan-simple-fragment-recovery-07
    * This forwarding mode comes in addition to L2 switching and L3 routing.
    * Uses datagram tag as (explicit) switchable label.
    * Enable one not to reconstruct the packet at each hop, better latency
and memory use
    * Problem: there is no IP header in anything but the 1st fragment.
    * 1st fragment sets up the state in each node along the way, to allow
the switching to happen.
    * end-to-end bitmap to retry fragments.
    * Discussion
        * [Thomas] all for this method. But what is the price for
end-to-end ACKs?
        * [Pascal] Needed when bundle breaks.
        * [Thomas] We should not modulate the number of times you
retransmit a packet depending on whether it is a fragment or data
    * Proposal: change classical fragment with recoverable fragments (new
6LoWPAN dispatch patterns)
    * Discussion
        * [Thomas] where does this draft go? Do we want to address this
withing 6TSCH?
        * [Pascal] No. If 6lo becomes WG, that's a good location to do this.
* [08.32] Simplest TSCH [Xavi]
    * Intro Thomas
        * Started by e-mail from Kris: what the absolutely simplest way of
using a TSCH network
        * Problem statement: if we meet in Berlin and we want to
interoperate without any scheduler, what is the simplest way.
        * Input from Alfredo, Elvis, Maria Rita, Pouria, Xavi.
    * Xavi presents slides.
    * How to implement the minimum configuration/code to build a TSCH
network?
    * Idea:
        * single slotframe, 101 slots, 16 channel offset
        * hard-coded schedule. All slots are shared.
        * First slot is used for ADV. Next 5 for "slotted Aloha" behavior.
        * Each slot marked as TX, RX and shared.
        * All other slots are off.
        * 3 TX attempts
    * Motes start running, receive EB to join the network.
    * EB are generated periodically. Put in the TX queue for tranmsmission.
No ACK.
    * Slotted Aloha behavior comes for "free" in TSCH if the slot is marked
TX, RX and shared.
    * Neighbor table maintained, with statistics. RPL can use that
information.
    * Time parentL: best connected parent (based on neighbor table stats).
Option: stability counter.
    * Xavi presents the format of the packets:
        * IEEE802.15.4e general format
        * IE (either header or payload)
        * EB contains the following IEs:
            * sync IE
            * Frame and Link IE
                * Xavi proposes to have all links appear in the IE.
                * Thomas Lets see whether it fits
                * Pouria Whether it all fits in a EB depends on the EB
            * timeslot template IE
            * channel hopping IE
    * Pouria presents the ACK frame format
        * sequence number repeats the DSN of the data
        * IE is used to provide time synchronization between node (ACK/NACK
time correction IE)
    * Thomas how do you pick time source neighbors when you don't have any
routing state yet
    * Xavi RSSI?
     * Thomas Let's take this on the ML.
    * Thomas where do DIO/DAOs go?
    * Xavi On the data cells?
    * Thomas How does TSCH know ADV needs to go on slotoffset 0 and not the
others?
    * Pouria we can use the broadcast cell.
* AOB
    * Xavi Next steps for logo?
    * Thomas this logo is pretty much done. Can you send a high resolution
version?
    * Xavi Will do.
* [09.05] Meeting ends.