Setting of DTIM Interval for MCCA April 2011 doc.: IEEE 802.11-11/0554r0 April 2011 Setting of DTIM Interval for MCCA Date: 2011-04-19 Authors: Michael Bahr, Siemens AG Michael Bahr, Siemens AG

April 2011 doc.: IEEE 802.11-11/0554r0 April 2011 Abstract The setting of the DTIM interval in MCCA to a limited set of 19 values is not flexible enough for many applications that would benefit greatly from MCCA, for instance, industrial WLAN networks. This presentation lists several options that would allow a flexible and application specific setting of the DTIM interval in MCCA in order to support many applications such as industrial WLAN networks. Normative text for these flexible settings of the DTIM interval is provided. Michael Bahr, Siemens AG Michael Bahr, Siemens AG

History of DTIM interval for MCCA in IEEE 802.11s April 2011 History of DTIM interval for MCCA in IEEE 802.11s D0.01-D3.03: Mesh DTIM element D3.04-D5.0: “Mesh STAs that use MCCA share a DTIM interval of common length.” D5.01-D10.0 (current): “Mesh STAs that use MCCA shall use a DTIM interval with a duration of 2^n * 100 TU with n a non-negative integer less than or equal to 5 (18 since D7.04).” Michael Bahr, Siemens AG

Comment 3192 on DTIM interval for MCCA April 2011 Comment 3192 on DTIM interval for MCCA Sponsor Ballot on D10.0 – CID 3192 Michael Bahr, Siemens AG

Problems to Be Solved ensure interoperability with the use of MCCA April 2011 Problems to Be Solved ensure interoperability with the use of MCCA enable a wide range of applications to use MCCA by providing a flexible configuration of MCCA reservations allow any distance (in multiples of 32µs) between subsequent MCCAOPs of the same reservation enable an easy check of overlapping MCCA reservations Michael Bahr, Siemens AG

Options for setting of DTIM interval April 2011 Options for setting of DTIM interval remove any restriction since there is no problem with different DTIM intervals state the requirement but leave it open to the external configuration to ensure it – we don‘t have to prevent people from doing dumb things ensure the requirement during mesh discovery with flexible inital value provide a limited set of possible absolute values for DTIM interval distribute a common wrapper DTIM interval in the MBSS as common time basis / virtual DTIM interval Michael Bahr, Siemens AG

Option A Different DTIM intervals are no problem April 2011 Option A Different DTIM intervals are no problem interoperability is ensured by the MCCA setup procedure even with different DTIM intervals overlap of MCCAOP reservations can be verified with any DTIM interval only capacity for reservations and performance of check of overlapping MCCA reservations might decrease different DTIM intervals can be made DTIM intervals of same length for the sake of an easy check of overlapping MCCA reservations: Assume 2 DTIM intervals dtimA and dtimB Assume MCCA reservation in dtimA with offsetA, durationA, and periodicityA, the same for an MCCA reservation in dtimB dtimA1 = dtimB1 = LCM(dtimA, dtimB) [least common multiple] offsets and durations unchanged periodicityA1 = periodicityA * dtimA1 / dtimA periodicityB1 = periodicityB * dtimB1 / dtimB Michael Bahr, Siemens AG

Option A – Necessary text changes (D10.2) April 2011 Option A – Necessary text changes (D10.2) remove „Mesh STAs that use MCCA shall use a DTIM interval with a duration of 2n x 100 TU with n being a non-negative integer less than or equal to 18.“ from clause 9.9a.3.1 General (page 115, lines 29-32) remove „NOTE—The DTIM interval of the form 2n x 100 TU has been chosen to ensure that the starting times of the reservations do not change relative to each other between consecutive DTIM intervals. The restriction that n be less than or equal to 18 has been chosen to be compatible with the maximum DTIM interval and so that the range of the MCCAOP Offset in the reservation, see 7.3.2.106.2 (MCCAOP Reservation field), is compatible with the maximal DTIM interval length.“ from clause 9.9a.3.1 General (page 115, lines 34-38) remove „When dot11MCCAActivated is true, the mesh STA shall choose a DTIM interval with a duration of 2n x 100 TU with n a non-negative integer less than or equal to 18.“ from clause 11C.12.4.3 TBTT selection (page 281, lines 21-23) Michael Bahr, Siemens AG

Option B State requirement realize it by external management entity April 2011 Option B State requirement realize it by external management entity State requirement: same DTIM interval or multiples where the factors are powers of the same n requirement is realized by external management component outside the MLME MCCA networks assumed to be used mainly in controlled (administrated) environments (e.g., industrial networks, machine-to-machine, VoIP, …) provides high flexibility in using costumized and usage specific DTIM and MCCA settings in controlled environments if misconfiguration happens, only MCCA capacity and MCCAOP overlap comparison performance might degrade, but wireless mesh will still be working correctly we don‘t have to prevent people from doing dumb things allows any DTIM value in order to be flexible for many usages may provide a default value Michael Bahr, Siemens AG

Option B – Necessary text changes (D10.2) April 2011 Option B – Necessary text changes (D10.2) Change „Mesh STAs that use MCCA shall use a DTIM interval with a duration of 2n x 100 TU with n being a non-negative integer less than or equal to 18.“ in clause 9.9a.3.1 General (page 115, lines 29-32) to „Mesh STAs that use MCCA shall use a common DTIM interval or DTIM intervals that are multiples where the factors are a power of the same natural number, e.g. 2^n.“ Change „NOTE—The DTIM interval of the form 2n x 100 TU has been chosen to ensure that the starting times of the reservations do not change relative to each other between consecutive DTIM intervals. The restriction that n be less than or equal to 18 has been chosen to be compatible with the maximum DTIM interval and so that the range of the MCCAOP Offset in the reservation, see 7.3.2.106.2 (MCCAOP Reservation field), is compatible with the maximal DTIM interval length.“ in clause 9.9a.3.1 General (page 115, lines 34-38) to „ NOTE—The DTIM interval of this form has been chosen to ensure that the starting times of the reservations do not change relative to each other between consecutive DTIM intervals.“ Change „When dot11MCCAActivated is true, the mesh STA shall choose a DTIM interval with a duration of 2n x 100 TU with n a non-negative integer less than or equal to 18.“ in clause 11C.12.4.3 TBTT selection (page 281, lines 21-23) to „When dot11MCCAActivated is true, the mesh STA shall choose a common DTIM interval or a DTIM interval that is a multiple where the factor is a power of the same natural number, e.g. 2^n.“ if „shall“ is a problem, replace with „should“ in order to give a strong indication for the prefered setting Michael Bahr, Siemens AG

Option C Requirement ensured during mesh discovery April 2011 Option C Requirement ensured during mesh discovery State requirement: same DTIM interval or multiples where the factors are powers of the same n mesh station that establishes new mesh BSS sets DTIM value with no restrictions flexible initial value allowing the use of costumized and usage specific DTIM and MCCA settings „same n“ is specified in standard, possibly n=2 mesh stations that become a member of the mesh BSS set their DTIM value according to the requirement based on the DTIM interval of the candidate peer mesh STA provides same flexibility as option B in controlled environments provides larger flexiblity and same ensurance as restricted set of fixed values (option D) Michael Bahr, Siemens AG

Option C – Necessary text changes (D10.1) April 2011 Option C – Necessary text changes (D10.1) Change „Mesh STAs that use MCCA shall use a DTIM interval with a duration of 2n x 100 TU with n being a non-negative integer less than or equal to 18.“ in clause 9.9a.3.1 General (page 115, lines 29-32) to „Mesh STAs that use MCCA shall use a common DTIM interval or DTIM intervals that are multiples where the factors are a power of 2.“ Change „NOTE—The DTIM interval of the form 2n x 100 TU has been chosen to ensure that the starting times of the reservations do not change relative to each other between consecutive DTIM intervals. The restriction that n be less than or equal to 18 has been chosen to be compatible with the maximum DTIM interval and so that the range of the MCCAOP Offset in the reservation, see 7.3.2.106.2 (MCCAOP Reservation field), is compatible with the maximal DTIM interval length.“ in clause 9.9a.3.1 General (page 115, lines 34-38) to „ NOTE—The DTIM interval of this form has been chosen to ensure that the starting times of the reservations do not change relative to each other between consecutive DTIM intervals.“ remove „When dot11MCCAActivated is true, the mesh STA shall choose a DTIM interval with a duration of 2n x 100 TU with n a non-negative integer less than or equal to 18.“ in clause 11C.12.4.3 TBTT selection (page 281, lines 21-23) insert text from next slide in clause 11C.2.8 11C.2.8 Establishing or becoming a member of a mesh BSS (based on 11-11/521r4), complete instructions are provided in 11-11/0560r0. Michael Bahr, Siemens AG

Option C – Necessary text changes in Mesh Discovery (11-11/521r4) April 2011 Option C – Necessary text changes in Mesh Discovery (11-11/521r4) Michael Bahr, Siemens AG

Option D Limited set of allowed absolute values April 2011 Option D Limited set of allowed absolute values limited flexibity in the choice of DTIM interval and interval between reserved MCCA timeslots not flexible enough for certain appliation areas, especially in industrial communication or machine to machine communication, that require a high flexibility in setting the interval between subsequent transmissions. This might be a very exact value that cannot be approximated close enough by the allowed values. approximation between required and possible intervals necessary leading to some difference relative difference can be above 5% The same concept of exponentially increasing superframe lengths has been one of the reasons why the IEEE 802.15.4 beacon-enabled mode has not been adopted widely. An exponentially increasing beacon interval is simply to inflexible for many applications and usage scenarios. An “unlucky” configuration of MCCA reservations (e.g. prime periodicities) is possible even with this scheme Michael Bahr, Siemens AG

Option E Common wrapper DTIM interval April 2011 Option E Common wrapper DTIM interval distribute a common wrapper DTIM interval in the MBSS as common time basis / virtual common DTIM interval virtual common DTIM interval is computed according to Option A new Information Element in DTIM beacons distributing the information throughout the mesh BSS Michael Bahr, Siemens AG

April 2011 Conclusion Options B and C provide the required flexibility in setting the DTIM interval for MCCA by simple means option B puts more responsibility to an external management entity, but this would be acceptable since MCCA will be often used in controlled / managed environments the world will not end and the wireless mesh will still work correctly if different DTIM intervals are used option C allows flexibility for the initial setting of the DTIM interval for MCCA in an MBSS and deriving further DTIM interval settings for MCCA in the MBSS from this Option D is too inflexible for important classes of applications and usage scenarios Suggested resolution to CID 3192: Option C provides the flexibility required by applications and ensures the preferred characteristics on the DTIM interval in MCCA (same or multiple with factor 2) Michael Bahr, Siemens AG

April 2011 Motion Move to adopt Option C of presentation 11-11/0554r0 and the text changes provided in 11-11/0560r0 as resolution to CID 3192 with resolution status „Principle“ and resolution detail „see option C in submission 11-11/0554r0. Text provided in submission 11-11/0560r0“ Michael Bahr, Siemens AG

April 2011 Backup Michael Bahr, Siemens AG

Strawpolls (I) is acceptable to me is not acceptable to me don‘t know April 2011 Strawpolls (I) is acceptable to me is not acceptable to me don‘t know Option B Option C Option D Michael Bahr, Siemens AG

Comments on DTIM interval for MCCA (I) April 2011 Comments on DTIM interval for MCCA (I) LB 161 on D5.0 – CIDs 3043, 3224 Both commenters suggested to remove the restriction „Mesh STAs that use MCCA share a DTIM interval of common length.” 3043 3224 Michael Bahr, Siemens AG

Comments on DTIM interval for MCCA (II) April 2011 Comments on DTIM interval for MCCA (II) Sponsor Ballot on D7.0 – CIDs 143, 248 Michael Bahr, Siemens AG

Comments on DTIM interval for MCCA (III) April 2011 Comments on DTIM interval for MCCA (III) Sponsor Ballot on D9.0 – CID 2168 counter notes on Resolution Detail: MCCAOP reservations can be selected even if the DTIM intervals drift with respect to each other Such a shared DTIM interval can be arrived at by configuration. Most deployments of MCCA will be in an „administrated“ network environment so that there is some entity that ensures the correct configuration Michael Bahr, Siemens AG

Comments on DTIM interval for MCCA (IV) April 2011 Comments on DTIM interval for MCCA (IV) Sponsor Ballot on D10.0 – CID 3192 Michael Bahr, Siemens AG

April 2011 References IEEE 802.11s Draft Standard, different versions up to D10.02 11-10/0478r9 Comments of LB 161 on IEEE 802.11s D5.0 and their resolutions 11-10/1283r14 Comments of 1st Sponsor Ballot on IEEE 802.11s D7.0 11-11/0287r8 Comments of 2nd Recirculation Sponsor Ballot on IEEE 802.11s D9.0 11-11/0519r4 Comments of 3rd Recirculation Sponsor Ballot on IEEE 802.11s D10.0 Michael Bahr, Siemens AG