[lp-wan] Window mode as default fragmentation in SCHC + Minutes from Interim on 24/05

[Alexander Pelov <[e-mail]>]

Dear all,

The minutes from the last interim meeting have been uploaded and can be found at the following address: https://www.ietf.org/proceedings/interim-2017-lpwan-03/minutes/minutes-interim-2017-lpwan-03-201705241600-00

One of the main topics that were discussed was the advancement of the fragmentation part of the IP/UDP SCHC document ( https://tools.ietf.org/html/draft-ietf-lpwan-ipv6-static-context-hc-03 ). 

During the call we have reached a rough consensus that the Window mode covers all use-cases, is simple (from implementation and protocol point of view), is well understood, and can be included as a default mode for fragmentation in the RFC. 

We have also indicated that there are other ways of doing the fragmentation (most notably the Packet mode), but some corner cases still need to be covered (e.g. bitmap sizes bigger than available payload limiting the MTU to less than 1280), and some advanced ways of actually solving this (Bloom filters were mentioned I think). These are all interesting ideas and they merit a longer discussion to find the right balance. These are to be kept in a separate document, which can continue its life independently, and if the WG decides can be included as a future WG item. If a future devices implement these other fragmentation mechanisms, they will be perfectly compatible with the default Window mode (the Rule ID can indicate which fragmentation mode is used).

We would like to confirm that you approve the Window mode as the default mode for fragmentation to be included in the SCHC IP/UDP document. 

Best,
The chairs