Hi all, I have a few questions on the RPL settings described in RFC 8180. Could anyone help me find answers...?
https://tools.ietf.org/html/rfc8180#section-5 --- (1) Rank Computation RFC 8180 says: rfc8180> 5.1.1. Rank Computation rfc8180> (...) rfc8180> Sp SHOULD be calculated as (3*ETX)-2. The minimum value of rfc8180> Sp (MINIMUM_STEP_OF_RANK) indicates a good quality link. The rfc8180> maximum value of Sp (MAXIMUM_STEP_OF_RANK) indicates a poor rfc8180> quality link. The default value of Sp (DEFAULT_STEP_OF_RANK) rfc8180> indicates an average quality link. Candidate parents with rfc8180> ETX greater than 3 SHOULD NOT be selected. https://tools.ietf.org/html/rfc8180#section-5.1.1 MAXIMUM_STEP_OF_RANK is defined to 9. Why? Sp is calculated as (3 * ETX) - 2 and the worst acceptable ETX is 3. It looks like 7 is the possible largest value of Sp... (2) Trickle Timer RFC 8180 says: rfc8180> 5.3. Trickle Timer rfc8180> (...) rfc8180> For this specification, the Trickle timer MUST be used with the rfc8180> RPL-defined default values (see Section 8.3.1 of [RFC6550]). https://tools.ietf.org/html/rfc8180#section-5.3 So, Imin for DIO Trickle timer starts with 8 ms, which looks too short for the minimal TSCH schedule where one shared cell in a slotframe of 1.01s. This setting could cause congestion by DIO traffic... Why is this default value (DEFAULT_DIO_INTERVAL_MIN) reasonable for the 6TiSCH minimal configuration...? rfc6550> 17. RPL Constants and Variables rfc6550> (...) rfc6550> DEFAULT_DIO_INTERVAL_MIN: This is the default value used to rfc6550> configure Imin for the DIO Trickle timer. rfc6550> DEFAULT_DIO_INTERVAL_MIN has a value of 3. This rfc6550> configuration results in Imin of 8 ms. https://tools.ietf.org/html/rfc6550#section-17 --- There are some email threads on RPL configuration found in 6TiSCH ML archive. But, I could not find any discussion about above mentioned points... - [6tisch] On 2*ETX in Minimal https://mailarchive.ietf.org/arch/msg/6tisch/oWmlpcq2evOlf4gH90moG2gyxzg - [6tisch] 6TiSCH Minimal: step_of_rank https://mailarchive.ietf.org/arch/msg/6tisch/BXbfFtysPHJTekkeQXScv1GVxCM - [6tsch] Zero Objective Function discussion https://mailarchive.ietf.org/arch/msg/6tisch/McGiW7IPnhITB74Vz2y2SKXot80 Thank you! Yatch _______________________________________________ 6tisch mailing list 6tisch@ietf.org https://www.ietf.org/mailman/listinfo/6tisch
