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meetings / 140422_webex_6top

Minutes Webex 22 April, 6top call 6TiSCH WG


Note: timestamps in PDT.

Taking notes (using Etherpad)

  1. Xavi Vilajosana
  2. Pascal Thubert

Attendance (alphabetically)

  1. Bryan Mclaughlin
  2. Raghuram Sudhaakar
  3. Pascal Thubert
  4. Hannes Tschofening
  5. Xavi Vilajosana
  6. Qin Wang
  7. Pouria Zand

Action items

  • QW to request an slot to present 6top to 6top negotiation at the next WG meeting
  • XV to send the OpenWSN CoAP link to RS
  • RS to look at the block option from CoAP to determine overhead
  • XV to present in next wg meeting the proposed mechanism.


  • [8:05] meeting starts
    Wrapping CoAP for 6top to 6top communication
    how to port to the draft

    2 interfaces, management and negotiation
    - discuss requirements

Qin: From a management interface is basic: SET AND GET
Qin: Negotiation requires a more complex interaction where several IEs are exchanged
Qin: Use a CoAP to transport that information. The information will be encoded in CBOR and embedded in an IE
Qin: Wrapper IE formed to transport that information (i.e encapsulate CoAP meta packets)

Qin: RPC already defined

Qin: 6top to 6top negotiation by means of rpc. this is materialized in a CoAP request to an URI like
6t/6top/sn (softcell-negotiation)

Qin: How to fragment? Do we use Block option from CoAP?

Raghu: 15.4e payload size limited, need fragments to transport the coap packet in IE payload.
Raghu: What happens is fragment is lost? goal is a very minimal parser
Xavi: should look at block option, for sure solution for that

Xavi: Packet reassembly from blocks. We assume that CoAP parser will be able to reassemble blocks. Is there any concern on that assembly? should we go deep on that study?
Qin: If block option adds too much complexity to the parsing, then we can limit the size of the Wrapper IE.

Raghu: Critical point is to know the overhead in the header introduced by the block option.

Xavi: In the interaction, how to handle errors?
Xavi: slide 11 what happens if fails, how is response sent from node A to node B

  • Use CoAP error codes as payload of the response. Use Wrapper IE to encapsulate them
  • This needs to be defined in the draft

Qin: needs more work
Raghu: payload of IE is used by COAP, full coap protocol including returned codes

Qin: Open discussion. Is Observe extension also needed? What about the use of URI-POrt.
The topic needs further investigation.

Qin: What draft should include what topic.

Suggestion to be confirmed in the ML after presentation:

6top Sublayer draft -- should include the wrapper IE
CoAP support will go to the CoAP draft. This will require a differentiated section as this is to address 6top to 6top which is mainly for decentralized scheduling.

[8:40] Meeting ends