All, In preparation of the 6TiSCH interim meeting later today, below is my review of draft-ietf-6tisch-6top-sf0-01. I'm reading the XML file directly at https://bitbucket.org/6tisch/draft-ietf-6tisch-6top-sf0/src/master/draft-ietf-6tisch-6top-sf0-02.xml, to be most up-to-date.
*@authors*, could you confirm you will attend the 6TiSCH interim meeting later today? Thomas *issue tracking* This is now a WG doc. Per the 6TiSCH best practice, this means issues should be tracked by https://trac.tools.ietf.org/wg/6tisch/trac/report/1 *@editor*, please: - report the open issue on the bitbucket issue tracker into the IETF 6TiSCH issue tracker - disable the bitbucket issue tracker *organization* The idea is that the definition of an SF follows the recommendations from https://tools.ietf.org/html/draft-ietf-6tisch-6top-protocol-02#section-5, in particular answers all the requirements and follows the structure. *@editor*, please add an appendix at the draft to indicate whether you answer all requirements (checklist) and formatting. You can mark this appendix a temporary by putting the "[temporay]" keyword. One example is https://tools.ietf.org/html/draft-ietf-6tisch-6top-protocol-02#appendix-A. *implementation/.performance evaluation* The WG needs to know (1) who implemented this and (2) how good the proposed solution performes. *@editor*, follow the implementation section by a "Performance Evaluation" section in which you list the key results. The WG needs to know the limits of the SF: how does it scale with number of motes, network dynamics, etc. *figure* *@editor*, as discussed in IETF96 Berlin, Figure "The SF0 Allocation Policy" is not clear. Please comment on the changes you agreed to do. *general confusion about cells/bandwidth* I fail to understand the relationship between cells and bandwidth. You express bandwidth in kbps, but a cell carries one packet, and that packet can contain ~0-100 bytes of payload. Many small packets is very different from a few large packets from a scheduling point of view. I therefore STRONGLY suggest to think about number of packets, no kbps. *general questions about PDR* I'm not at all convinced about using PDR to calculate the number of cells, based on a number of kbps. It's unbelievably complex for no reason. Rather, I suggest to think only about number of cells used: if I'm using 90% (resp. add) of the outgoing cells to a particular neighbor over some period of time, I should probably add (resp. delete) some. *about timeout* The draft now says "The general timeout equals the equivalent time of the number of slots until the next scheduled cell." Next scheduled cell to whom? In RX or TX? What are retries? Similarly, "Node Behavior at Boot" states that the "timeout" is calculated as: timeout = (2^(macMaxBE+1)-2^macMinBE) * SM - what timeout is this exactly? - minimal Slotframe, SM: is that a duration, a number of slots? - what is the unit of timeout? *metadata* I don't understand the use of the metadata in Section "Meaning of Metadata Information". *PDR threshold* "Relocating Cells" now states: SF0 uses Packet Delivery Rate (PDR) statistics to monitor the currently allocated cells for cell re-allocation (by changing their slotOffset and/or channelOffset) when it finds out that the PDR of one or more softcells below 20% of the average PDR. The average PDR of what? Why 20%? *editorial suggestions* - the many acronyms (BEA, COBU, NIBR,NOB, AP, etc) add confusion more than clarity. THere appears to be a new term/acronym every 2 sentences! Can we not simply talk about "incoming", "outgoing" and "generated"? Not every word needs an acronym. - I don't understand what Whitelist and Blacklist mean in the "Rules for CellList" section. - "delete one or more cells" and "add one or more cells" is not precise enough. How many should be added/deleted? - the term bandwidth is confusing. Is it a number of packets per second? per frame? a number of cells? *@editor*, please add a definitions section, and consider changing the terminology. - isn't "NOB=NIBR-COBU", not "NOB=COBU+NIBR" - the draft starts very abruptly by referencing triggering events, BEA and allocation policy in the "Rules for Adding/Deleting Cells" Section. At that point of the draft, the reader has no idea what that is. *@editor*, please add an "Overview" section which contains a couple of paragraphs. *nits and typos* [use Ctrl+F] - "and determine" -> "and determines" - re-allocation-> relocation - dissappears -> disappears - 6P ALL Request -> 6P ADD Request? -- _______________________________________ Thomas Watteyne, PhD Research Scientist & Innovator, Inria Sr Networking Design Eng, Linear Tech Founder & co-lead, UC Berkeley OpenWSN Co-chair, IETF 6TiSCH www.thomaswatteyne.com _______________________________________
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