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Minutes Webex 22 April, 6top call 6TiSCH WG
Recording: https://cisco.webex.com/ciscosales/lsr.php?RCID=c9a14146f9b8420788c4bb1a1071847a
Note: timestamps in PDT.
Taking notes (using Etherpad)
- Xavi Vilajosana
- Pascal Thubert
Attendance (alphabetically)
- Bryan Mclaughlin
- Raghuram Sudhaakar
- Pascal Thubert
- Hannes Tschofening
- Xavi Vilajosana
- Qin Wang
- 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.
Discussion
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[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
Updated