1. 6TSCH Webex
06/21/2013

2. Agenda draft-thubert-6tsch-architecture-02 [5min]
draft-vilajosana-6tsch-basic-00 [10min]
Architecture with remote BBR [10min]
Soft cell assignment: random or not? [20min]
Track IDs [10min]
AOB [5min]

3. draft-thubert-6tsch-architecture-02
Not published yet

4. Centralized vs. Distributed Routing
6TSCH supports a mix model of centralized routes that are computed by a Path Computation Entity and distributed routes that are computed by RPL over a common physical LLN. Both RPL and the PCE may inject routes in the Routing Tables of the 6TSCH routers. In either case, each route is associated with a topology that is indexed by an instanceID, as defined in RPL [RFC6550]. RPL and PCE rely on shared sources to define Global and Local InstanceIDs. It is possible for RPL and PCE to share a same topology, in which case the PCE routes have precedence over RPL routes in case of a conflict. Inside the 6TSCH domain, the flow label is used to indicate the topology that must be used for routing and the associated Routing Tables as discussed in [I-D.thubert-roll-flow-label].

5. Tunnel Mode
In tunnel mode, the frames originate from an arbitrary protocol over a compatible MAC that may or may not be perfectly synchronized with the 6TSCH network. An example of this would be a router with a dual radio that is capable to receive and send Wireless HART or ISA100.11a frames with the second radio, by presenting itself as an Access Point or a Backbone Router, respectively. In that mode, the PCE may coordinate with a WiHART Network Manager or an ISA100.11a System Manager in order to specify the flows that are to be transported transparently over the Track.

6. Tunnel Mode
| IPv6 | | 6LoWPAN HC | set restore | 6TUS | +dmac+ +dmac | | | | | TSCH MAC | | | | | | LLN PHY | | ingress egress | | | | | | LLN PHY | | | | TSCH MAC | | | |ISA100/WiHART | | v

7. Tunnel Mode
In that case, the flow information that identifies the Track is uniquely derived from the information at the receiving end, for instance the incoming Timeslots, or an ISA100.11a ContractId. At the ingress 6TSCH router, the packet destination is recognized as self but the flow information indicates that the frame must be tunneled over a particular 6TUS Track so the packet is not punted to upper layer. Instead, it is passed to the 6TUS sublayer for switching. The 6TUS sublayer in the ingress router overrides the destination MAC to broadcast and forwards. At the egress 6TUS router, the reverse operation occurs. Based on metadata associated to the Track, the frame is passed to the appropriate link layer with the destination MAC restored.

8. Transport Mode
| ^ | | | IPv6 | | | | 6LoWPAN HC | | | ingress egress | 6TUS | sets restores dmac to | | | | dmac to | TSCH MAC | brdcst | | | | self | | | | | | | LLN PHY |

9. draft-vilajosana-6tsch-basic-00

10. Status Follow-up on webex discussion on 06/07/2013
Published on 06/19/2013
Same ideas as discussed over the phone
Comments welcome!

11. Architecture with remote BBR

12. Current Architecture ? Remote BBR ---+------------------------
| External Network |
| | Router | | PCE
| | | |
| |
| Subnet Backbone |
| | |
| | Backbone | | Backbone | | Backbone
o | | router | | router | | router
o o o o o
o o o o o o o o o o o
o o o LLN o o o o
o o o o o o o o o o o o ?
Remote BBR

13. Tunneling/VLAN ---+------------------------ | External Network |
| | Router | | PCE
| | | |
| |
| Subnet Backbone | ==========
TUNNEL
| | ========== |
(remote)
| | Backbone | | Backbone | | Backbone
o | | router | | router | | router
o o o o o
o o o o o o o o o o o
o o o LLN o o o o
o o o o o o o o o o o

14. PCE as forwarding engine
| External Network |
| | PCE/Router
| |
^ ^ ^
| | | |
| | |
v v v
| | Backbone | | Backbone | | Backbone
o | | router | | router | | router
o o o o o
o o o o o o o o o o o
o o o LLN o o o o
o o o o o o o o o o o o
Protocol?

15. Hybrid ---+----------------------- | External Network |
| | Router | | PCE
| | | | |
| | ^ ^ ^
| | | | |
| | |
| | | |
| | |
v v v
| | Backbone | | Backbone | | Backbone
o | | router | | router | | router
o o o o o
o o o o o o o o o o o
o o o LLN o o o o
o o o o o o o o o o o o

16. Question PCE, ND must be maintained as separate elements
6TSCH does not need to define anything to create the connectivity between the BBRs
Discovery?

17. soft cell assignment: random or not?

18. Problem Applies to distributed scheduling only
Two neighbor nodes negotiate the allocation of a cell in the schedule
If this cell already used by other nodes in the neighborhood  collision
Options:
random allocation. Collisions unlikely. Detect and fix collisions
Informed allocation. Neighbors maintain state. Collisions less likely. Still detect and fix (less frequent) collisions.

20. Collision probability
10 node neighborhood
Each node sends 3 pk/s
101 cells
16 channels
Random cell allocation
Collision detection
Collision occurrence? Collapse?
Overhead of re-negotiation?
Overhead maintaining state?

21. Informed allocation
exchanging the changes in a node’s cell usages bitmap instead of reporting all cell usage bitmap periodically
Approaches:
Active
Passive
Hybrid

22. Using Trickle RFC6206, used in RPL To use Trickle, we need to define
What constitutes a "consistent" transmission.
What constitutes an "inconsistent" transmission.
What "events", if any -- besides inconsistent transmissions -- reset the Trickle timer.
What information a node transmits in Trickle messages.
What actions outside the algorithm the protocol takes, if any, when it detects an inconsistency.

23. Using track IDs

24. Proposal Use a TrackID to associate incoming cells and outgoing cells
TrackID is internal only, i.e. is does not appear in the packets
Add TrackID to cell commands
Track (switching) table using trackID
Schedule is union of all track tables

25. Any Other Business?