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Doc.: IEEE 802.11-09/533r1 Submission May 2009 David Bagby, ARC Chair Submitted on behalf of ARC SC. Slide 1 ARC Recommendation: MIB Attribute Types &

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Presentation on theme: "Doc.: IEEE 802.11-09/533r1 Submission May 2009 David Bagby, ARC Chair Submitted on behalf of ARC SC. Slide 1 ARC Recommendation: MIB Attribute Types &"— Presentation transcript:

1 doc.: IEEE /533r1 Submission May 2009 David Bagby, ARC Chair Submitted on behalf of ARC SC. Slide 1 ARC Recommendation: MIB Attribute Types & Usage Date: Authors:

2 doc.: IEEE /533r1 Submission May 2009 David Bagby, ARC Chair Submitted on behalf of ARC SC. Slide 2 MIB Exercise Motivation MIB attributes are used for multiple purposes in the 2007 document, not all of which are consistent with the purpose of the MIB. MIB syntax is used to define “local” variables –…and these are in the same section as true MIB variables (even though they are not exposed MIB variables). –This causes confusion re functionality ARC SC was asked to –Survey current usage of MIB variables, –Recommend a practice for categorization and use of MIB variables.

3 doc.: IEEE /533r1 Submission May 2009 David Bagby, ARC Chair Submitted on behalf of ARC SC. Slide MIB usage…

4 doc.: IEEE /533r1 Submission May 2009 David Bagby, ARC Chair Submitted on behalf of ARC SC. Slide 4 MIB background MIB is Management Information Base Purpose is to manage STAs and entities within STAs to allow proper and useful interoperation in a wireless network Such management is provided by interaction between entities to provide status and exert control –This is management interaction, not functional interaction provided by primitives. –MIB attributes (a.k.a. “objects” or “variables”) provide an implicit interface between entities through read (“GET”) and write (“SET”) operations.

5 doc.: IEEE /533r1 Submission May 2009 David Bagby, ARC Chair Submitted on behalf of ARC SC. Slide 5 Entities defines many entities – Some high level entities include: –MAC – Media Access Control entity –MLME – MAC layer management entity –SME- Station Management entity –PHY – Physical Layer entity –PLME – PHY layer management entity

6 doc.: IEEE /533r1 Submission May 2009 David Bagby, ARC Chair Submitted on behalf of ARC SC. Slide 6 High Level Entities

7 doc.: IEEE /533r1 Submission May 2009 David Bagby, ARC Chair Submitted on behalf of ARC SC. Slide 7 Existing MIB usage The Current MIB has a variety of usage models. –Some Variables have multiple usage models –Some Variables are interpreted differently by different readers (does “enabled mean implemented. Currently turned on/off or both?)

8 doc.: IEEE /533r1 Submission May 2009 David Bagby, ARC Chair Submitted on behalf of ARC SC. Slide 8 So ARC SC cogitated and developed some Recommendations for improvements…

9 doc.: IEEE /533r1 Submission May 2009 David Bagby, ARC Chair Submitted on behalf of ARC SC. Slide 9 MIB Usage Recommendation Adoption Actions…

10 doc.: IEEE /533r1 Submission May 2009 David Bagby, ARC Chair Submitted on behalf of ARC SC. Slide 10 ARC Recommended actions Executive Actions –Add recommendations to Editor guidelines as part of OP manual. Action for TGs working on amendments to 2007: –TG chairs to check drafts for conformance as part of TG Chair’s “is it technically ready for LB” review prior to WG and/or SG LB. Action for improving 2007 contents –TGMb review current std MIB contents and update appropriate portions Portions with the effort to update are TBD by TGMb; Some sections might be marked “not up to date with 2009 MIB usage standards” General Membership Actions: –Consider MIB usage vs recommendations when reviewing drafts.

11 doc.: IEEE /533r1 Submission May 2009 David Bagby, ARC Chair Submitted on behalf of ARC SC. Slide 11 ARC SC MIB Usage Recommendations…

12 doc.: IEEE /533r1 Submission May 2009 David Bagby, ARC Chair Submitted on behalf of ARC SC. Slide 12 Recommended types of MIB attributes Three types: –Capability: Static, initialized by entity as part of instantiation, read by other entities. –Status: Dynamic, written by the entity to expose current conditions to reading entities. –Control: Dynamic, written by another entity to control the applicable entity’s manageable behaviors. The definition and described usage of each attribute should be clear about its type, and which entities use the interaction for read and write. Dynamic attributes should have discussion about how and when changes are allowed/caused, and what the effect(s) of the change are.

13 doc.: IEEE /533r1 Submission May 2009 David Bagby, ARC Chair Submitted on behalf of ARC SC. Slide 13 Derivation of attribute types Read by other entity(ies) Written by other entity(ies) Read by applicable entity CapabilityControl Written by applicable entity StatusNot used

14 doc.: IEEE /533r1 Submission May 2009 David Bagby, ARC Chair Submitted on behalf of ARC SC. Slide 14 MIB attribute usage guidelines Reading and Writing –One or more entities may read an attribute –One entity shall write an attribute (multiple writers creates interlock uncertainty) –The single entity writing to an attribute may or may not be the entity to which it applies. Static and Dynamic Values –Dynamic attributes can be written while STA in in operation, affecting management changes –Static attributes are not written during operation MIB attributes are not local variables –Attributes accessed solely within the entity do not provide any management function. They are implementation dependant to ensure the entity’s state-based behaviors conform to the Standard. –Such variables may be useful to describe behavior in the Standard, but are inappropriate in the MIB.

15 doc.: IEEE /533r1 Submission May 2009 David Bagby, ARC Chair Submitted on behalf of ARC SC. Slide 15 MIB attribute modification No more than one entity shall write (“SET”) a MIB attribute, to avoid mutex problems and other timing assumptions violations Every MIB attribute should be examined for how and when a write/update is allowed or caused, and the effects of the update should be explcit. –For each attribute the following should be given: “May be written by when. Changes take effect by.” A MIB attribute whose change requires other actions, should be represented with a specific Management SAP primitive, instead of a MIB attribute. This allows the specification of actions that must be taken upon a change. –For example, if an Association must be re-established, or a BSS re- initialized

16 doc.: IEEE /533r1 Submission May 2009 David Bagby, ARC Chair Submitted on behalf of ARC SC. Slide 16 Examples of types Capability – –dot11CFPollable, dot11ManufacturerID, dot11XxxImplemented, dot11RadioMeasurementCapable, dot11ChannelAgilityPresent, dot11RRMMeasurementPilotCapability, dot11FTResourceRequestSupported, dot11ExtendedChannelSwitchEnabled Status – –dot11XxxCount, dot11RadioMeasurementEnabled Control – –dot11RTSThreshold, dot11ShortRetryLimit, dot11LongRetryLimit, dot11FragmentationThreshold, dot11PrivacyInvoked, dot11WEPDefaultKeyID, dot11CurrentFrequency, dot11RSNAConfigPairwiseCipherEnabled

17 doc.: IEEE /533r1 Submission May 2009 David Bagby, ARC Chair Submitted on behalf of ARC SC. Slide 17 Naming conventions To avoid confusion about type and purpose, name MIB attributes based on type: –Capability: dot11XxxImplemented –Status: dot11XxxCount, dot11XxxValue (statistics, etc.) –Status: dot11XxxActivated (capability that is enabled) –Control: dot11XxxThreshold, dot11XxxLimit, dot11XxxID Avoid names that –leave writer entity ambiguous dot11XxxEnabled –Reference the amendment TGxxx or VHT –Use relative wording terms HT, VHT, faster, better, even mo’ better

18 doc.: IEEE /533r1 Submission May 2009 David Bagby, ARC Chair Submitted on behalf of ARC SC. Slide 18 Separate & Move Local variables Local variables are those that are not exposed outside an entity, for read or write Some example local variables – NAV, used_time, admitted_time, aXxxXxx (e.g. aSlotTime), CW, SSRC, SLRC Local variables should not be part of the MIB Recommend creating a separate Annex listing local variables. –If MIB syntax is used, for local variable definitions, It should be made clear that these are not accessible externally to the applicable entity. The definition syntax should exclude the "::=" part of the syntax (so the varables can not be accesseed externally). –Separate Annex especially useful if usage is not localized to a small section of the text. Some local variables could be used solely within the Standard’s text, if useful to clarify conforming behaviors, and don’t need formal definition

19 doc.: IEEE /533r1 Submission May 2009 David Bagby, ARC Chair Submitted on behalf of ARC SC. Slide 19 Local variable naming conventions (Still under discussion).11local[entityname]variablename –There is still discussion of the name format – this may change…


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