Re: [6tisch] Comment to draft-wang-6tisch-6top-coapie-01.txt

[Alexander Pelov <[e-mail]>]

Dear all,

For me the ideal solution would be if one of the 16 payload types could 
be allocated to CoAP. This way, we could use it for 6TiSCH and 
long-range, low-rate WANs. However, this would provide for a generic, 
extensible mechanism of operating these networks. Adding too much 
overhead (not sure how many bytes 802.15.9 takes) would make it 
impractical for LR-WANs.

On the packet fragmentation, I like the approach taken by the 802.15.4k 
LECIM group, which introduces a new type of frame - 110 Fragment Frame - 
and sends the full 802.15.4 MAC header only in the first frame (context 
establishment - some other info is added also). Afterwards, the set of 
fragments is identified only through a 7 bit identifier assigned by the 
sender. In each consecutive fragment, only a 2 byte MAC header is 
included (3 bits frame type (= 110), 7 bits frame ID, 6 bits frame 
counter). Extremely efficient in terms of overhead (e.g. MAC addresses 
are sent only during the context establishment), and particularly well 
adapted to infrastructure networks. Not sure if it would fit all 6TiSCH 
scenarios though.

Best,
Alexander


Le 25/09/2015 12:31, Thomas Watteyne a écrit :
> We need to discuss this point urgently, and do the work to ask the 
> IEEE for carve out some IE space for IETF/6TISCH if applicable.
>
> On Thu, Jul 23, 2015 at 4:28 PM, Qin Wang <[e-mail] 
> <mailto:[e-mail]>> wrote:
>
>     Hi Pat,
>
>     Since there are two approaches mentioned in the discussion, i.e.
>     (1) containing 6top-to-6top message in a specific payload IE
>     (coapie), (2) using the mechanism provided by IEEE802.15.9 to
>     convey the 6top-to-6top message, I would like to do more
>     evaluation. I couldn't find the IEEE802.15.9 spec on IEEE802
>     website. Can you tell me how to get it?
>
>     Thanks
>     Qin
>
>
>
>     On Tuesday, July 21, 2015 8:59 PM, Tero Kivinen <[e-mail]
>     <mailto:[e-mail]>> wrote:
>
>
>     This draft plans to put the coap messages directly on the payload IEs
>     in the 802.15.4. The problem is that we only have 16 payload IE types
>     in total for 802.15.4, so reserving one number for coap might be hard.
>
>     On the other hand IEEE 802.15.9 needed to have solution to this same
>     problem, i.e how to multiplex upper layer data packet over 802.15.4
>     frames and how to fragment them so they can fit on the 802.15.4
>     frames.
>
>     The 802.15.9 is split in two layers, first one is the multiplexed data
>     service, which takes 16-bit MultiplexId and the data packet to be sent
>     to the other end, and it will fragment and deliver it to the other
>     end. The MultiplexId is used to separate different protocols using
>     this mechanism. One of those protocols is the key management protocols
>     providing KMP for 802.15.4, which is the second part of the 802.15.9.
>
>     Instead putting the coap messages in the payload IEs, it would
>     possible to allocate one MultiplexId for coap messages, and then coap
>     messages could be transmitted using multiplexing layer of 802.15.9.
>     This would also take care of fragmentting the messages (with PHY using
>     127 octet PSDU, the maximum size of the data packet is around 24kB).
>
>     The 802.15.9 recommended practice is already past the working group
>     letter ballots, and is starting its sponsor ballot soon. It is
>     expected to come out around the end of year. The draft will be
>     available on the ieee document store after the sponsor ballot starts,
>     i.e. very soon.
>     -- 
>     [e-mail] <mailto:[e-mail]>
>
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