1. MAC State Generic Convergence Function
October 2007
doc.: IEEE /2629r1
October 2007
MAC State Generic Convergence Function
Date:
Authors:
Matthew Gast, Trapeze Networks
Matthew Gast, Trapeze Networks

2. October 2007
doc.: IEEE /2629r1
October 2007
Abstract
This presentation describes proposed changes to the u draft to support the MAC State Generic Convergence Function originally described in 11-07/ The text of the full proposal is found in 11-07/2604r1.
Matthew Gast, Trapeze Networks
Matthew Gast, Trapeze Networks

3. Architectural Overview of Convergence Function
October 2007
doc.: IEEE /2629r1
October 2007
Architectural Overview of Convergence Function
Matthew Gast, Trapeze Networks
Matthew Gast, Trapeze Networks

4. Architecture Overview: Replacing Figure 5-10
October 2007
doc.: IEEE /2629r1
September 2007
Architecture Overview: Replacing Figure 5-10
MIH
Other higher layers using
MAC state information
MAC_STATE_GENERIC_CONVERGENCE_SAP
MAC State Generic
Convergence Function
802.1X
MAC_SAP
MSCF-SME_SAP
MAC
MLME
SME
Mobility
Management
MLME_SAP
PHY_SAP
MLME_PLME_SAP
Interworking
Service
Management
PLCP sublayer
PLME
PMD_SAP
PLME_SAP
PMD sublayer
RSNA Key
Management
Note: The base standard version of this diagram is Figure 5-10 on page 42 of
Matthew Gast, Trapeze Networks
Matthew Gast, Trapeze Networks

5. The Need for a State Machine
October 2007
doc.: IEEE /2629r1
October 2007
The Need for a State Machine
MIH events apply to the whole ESS, not individual APs
Events are network-based, so they occur when things happen relative to multiple APs
Is the ESS up or down?
State machine operates on “ESS Links,” which are a new construct defined to support MIH
Matthew Gast, Trapeze Networks
Matthew Gast, Trapeze Networks

6. Convergence Function State Machine
October 2007
doc.: IEEE /2629r1
October 2007
Convergence Function State Machine
ESS_CONNECTED
ESS_DISENGAGING
ESS_DISCONNECTED
STANDBY
Matthew Gast, Trapeze Networks
Matthew Gast, Trapeze Networks

7. Classification of 802.21 Primitives
October 2007
doc.: IEEE /2629r1
October 2007
Classification of Primitives
Link Operations
Link_Up
Link_Down
Link_Going_Down
Link_Event_Rollback
Link_Detected
Link_PDU_Transmit_Status
Mobility Operations
Link_Handover_Imminent
Link_Handover_Complete
MAC “API”
Link_Event_Subscribe
Link_Event_Unsubscribe
Link_Capability_Discover
Link_Action
Link Parameter operations
Link_Configure_Thresholds
Link_Get_Parameters
Link_Parameters_Report
Matthew Gast, Trapeze Networks
Matthew Gast, Trapeze Networks

8. Events for Network Operation (corresponding to MIH Link Operations)
October 2007
doc.: IEEE /2629r1
October 2007
Events for Network Operation (corresponding to MIH Link Operations)
Supporting the following primitives:
Link_Up, Link_Down, Link_Going_Down, Link_Event_Rollback, and Link_Detected
Matthew Gast, Trapeze Networks
Matthew Gast, Trapeze Networks

9. MSGCF-ESS-Link-Up October 2007 Corresponding 802.21 primitive: Link_Up
doc.: IEEE /2629r1
October 2007
MSGCF-ESS-Link-Up
Corresponding primitive: Link_Up
English meaning for : A network (i.e., a set of APs offering identical data-link services) is now up at layer 2
802.11u proposal
Adds timestamp to the MLME-Associate.confirm primitive for time-based filtering
SME mobility manager may also report initial associations, so that indication was added to the SME SAP with the convergence function
Interactions of with this event
LINK_TUPLE_ID (Table B4, page 171 of D7.1) must be put together by MIH. It contains a link identifier and a link address. Both of these parameters are defined in this CF event
Link_Up has an optional IP_RENEWAL_FLAG that can be set (see D7.1 clause 7.3.4). This is supplied by the L2 network, and therefore, will not be present in Link_Up messages regarding networks
Note: The Link_Up indication in has MAC Access Router options which are not supplied on interfaces
Matthew Gast, Trapeze Networks
Matthew Gast, Trapeze Networks

10. MSGCF-ESS-Link-Down Corresponding 802.21 primitive: Link_Down
October 2007
doc.: IEEE /2629r1
October 2007
MSGCF-ESS-Link-Down
Corresponding primitive: Link_Down
English meaning: The network has gone down and can no longer send packets
802.11u draft changes
Added MIB entries to Annex D to describe threshold parameters to be used to declare links down
Method of declaring link down is specific to SME, and may include explicit disconnection, key expiration or power saving
interactions
The MIB can only store one set of parameters; therefore, the MIH function is required to mediate between any applications with conflicting performance thresholds
Matthew Gast, Trapeze Networks
Matthew Gast, Trapeze Networks

11. MSGCF-ESS-Link-Going-Down
October 2007
doc.: IEEE /2629r1
October 2007
MSGCF-ESS-Link-Going-Down
Corresponding primitive: Link_Going_Down
English meaning: The network is going down and may no longer be able to send packets soon
Notes
This specifies the time in time units (TU), which is the native “time quantum.” One TU = 1,024 μs = msec.
said that threshold was configurable, so the desired time threshold is added to the MIB
802.11u proposal
This event indicates a prediction of link failure
Link quality degradation is no longer a reason for predicted failure, but this event may be simultaneous with a ESS-Link-Threshold-Report event indicating decreasing quality
interactions
The MIHF will need to translate TUs into other time units
can provide parameters for the confidence interval calculation, but not the confidence level itself. This is an open question.
Multiple users may wish for different prediction thresholds, and the MIH function needs to mediate between them
future implications
Need ANA management of the values of the reason code in the table
Matthew Gast, Trapeze Networks
Matthew Gast, Trapeze Networks

12. MSGCF-ESS-Link-Event-Rollback
October 2007
doc.: IEEE /2629r1
October 2007
MSGCF-ESS-Link-Event-Rollback
Corresponding primitive: Link_Event_Rollback
English meaning: The network has gone down and can no longer send packets
802.11u draft text simply uses the Event ID to indicate that the previous event is no longer valid
Matthew Gast, Trapeze Networks
Matthew Gast, Trapeze Networks

13. MSGCF-ESS-Link-Detected
October 2007
doc.: IEEE /2629r1
October 2007
MSGCF-ESS-Link-Detected
Corresponding primitive: Link_Detected
How it works
MLME-SCAN.request primitives are sent to learn about the area networks. These requests may be scheduled by the SME to avoid interrupting service
Networks are stored in the dot11MacStateNetworkDetectedTable. Each entry in this table has a timestamp of when the network was detected, its constituent BSSes, and the MIH capabilities (as defined in Table B4 on page 183 of D7.1)
The CF can assemble the Network Identifier from the MLME-SCAN.confirm primitive because it has both the SSID and the Interworking information, and the latter contains the HESSID (as per 11-07/2494)
Notes on u text
MIH support is inferred from the presence of the GAS Advertising Protocol IDs used in the Interworking information u has values for MIH IS (GAS APID #1) and MIH ES/CS (GAS APID #2)
Note for
GAS in u does not provide separate capability information for MIH CS & ES
Matthew Gast, Trapeze Networks
Matthew Gast, Trapeze Networks

14. Supporting the following 802.21 primitives:
October 2007
doc.: IEEE /2629r1
October 2007
Events for Threshold Configuration (corresponding to MIH parameter operations)
Supporting the following primitives:
Link_Configure_Thresholds, Link_Get_Parameters, and Link_Parameters_Report
Matthew Gast, Trapeze Networks
Matthew Gast, Trapeze Networks

15. MSGCF-Set-ESS-Link-Thresholds
October 2007
doc.: IEEE /2629r1
October 2007
MSGCF-Set-ESS-Link-Thresholds
Corresponding primitive: Link_Configure_Thresholds
How it works
This provides a “window” to set parameters in the MIB that may be of interest
Provides access to RSSI on both Beacon and Data frames, SNR, frame error rates on both Beacon and Data frames, the BER of the radio channel, the peak operational rate observed, and the throughput of Data frames
interaction notes
Any future parameters need to be added to both this primitive and the MIB
Matthew Gast, Trapeze Networks
Matthew Gast, Trapeze Networks

16. MSGCF-Get-ESS-Link-Parameters
October 2007
doc.: IEEE /2629r1
October 2007
MSGCF-Get-ESS-Link-Parameters
Matching primitive: Link_Get_Parameters
Proposal for u: Simple primitive operation to retrieve relevant information from the MIB
Matthew Gast, Trapeze Networks
Matthew Gast, Trapeze Networks

17. MSGCF-ESS-Link-Threshold-Report
October 2007
doc.: IEEE /2629r1
October 2007
MSGCF-ESS-Link-Threshold-Report
Matching primitive: Link_Parameters_Report
D7.1 states that this primitive returns a list of LINK_PARAM_REPORT objects, as defined in table B4 on page 182
Each LINK_PARAM_REPORT is composed of the link parameter plus the threshold crossing direction (upward or downward)
Proposal for u
This report contains the set of parameters whose thresholds have been crossed, plus a set of directions (one for each parameter) to indicate whether the threshold was passed as the value was going up or down
Matthew Gast, Trapeze Networks
Matthew Gast, Trapeze Networks

18. MAC Control Operations (corresponding to MIH “API” primitives)
October 2007
doc.: IEEE /2629r1
October 2007
MAC Control Operations (corresponding to MIH “API” primitives)
Supporting the following primitives:
Link_Capability_Discover and Link_Action
Matthew Gast, Trapeze Networks
Matthew Gast, Trapeze Networks

19. MSGCF-ESS-Link-Capability
October 2007
doc.: IEEE /2629r1
October 2007
MSGCF-ESS-Link-Capability
Matching primitive: Link_Capability_Discover
implementation
All events which are supported by the convergence function are available for use
Notes
The convergence function can report on its own capabilities, but those must be translated by the MIHF as in Table L2 in D7.1. For example, Link_Up in is equivalent to Network-Up in
MIH events that are always unsupported are the link handover events (Link_Handover_Imminent and Link_Handover_Complete), the link event subscription events (Link_Event_Subscribe and Link_Event_Unsubscribe)
The MIH event Link_Transmit_PDU_Status is always available on because it maps directly to a MAC data service primitive that is always supported
Obviously, Get-ESS-Link-Parameters and Set-ESS-Link-Parameters must be supported if the corresponding threshold events are
Matthew Gast, Trapeze Networks
Matthew Gast, Trapeze Networks

20. MSGCF-ESS-Link-Command
October 2007
doc.: IEEE /2629r1
October 2007
MSGCF-ESS-Link-Command
Matching primitive: Link_Action
Notes for u proposal
Maps DISCONNECT action to MLME-Deauthenticate & MLME-Disassociate
Maps LOW_POWER action to MLME-POWERMGT
Maps SCAN to MLME-SCAN
There is no mapping for power up and power down, since those are not defined primitives by
DATA_FORWARDING_REQUEST is standard behavior, and is not part of this proposal
LINK_RESOURCE_RETAIN is a resource reservation attribute used for future reconnections, which is not a concept implemented by ; therefore, it is not part of this proposal
Matthew Gast, Trapeze Networks
Matthew Gast, Trapeze Networks

21. Convergence Function MIB
October 2007
doc.: IEEE /2629r1
October 2007
Convergence Function MIB
Matthew Gast, Trapeze Networks
Matthew Gast, Trapeze Networks

22. What needs to be in the MIB?
October 2007
doc.: IEEE /2629r1
October 2007
What needs to be in the MIB?
Configuration table
Indicates frequency of scanning for network detection
Parameters on a per-network basis
Minimum signal strength, error rates, and so on
Error rates may be expressed in scientific/exponential notation, so multiple MIB variables are needed to store such numbers (compare to geospatial entries in existing u draft)
Network list table
Most SMEs maintain a list of area networks, so this MIB table is a gateway to data already maintained by implementations
Matthew Gast, Trapeze Networks
Matthew Gast, Trapeze Networks

23. 802.21 Primitives not Implemented by 802.11u CF proposal
October 2007
doc.: IEEE /2629r1
October 2007
Primitives not Implemented by u CF proposal
Discussion of the following primitives:
Link_Handover_Imminent, Link_Handover_Complete Link_Event_Subscribe, Link_Event_Unsubscribe
Matthew Gast, Trapeze Networks
Matthew Gast, Trapeze Networks

24. October 2007
doc.: IEEE /2629r1
October 2007
Link Handover Events
primitives: Link_Handover_Imminent and Link_Handover_Complete
These would need to apply to networks of APs
Reporting on intra-ESS transitions is out of scope for , and would be extremely frequent
No clear use case identified for networks
Best example: a network can refrain from sending packets when an inter-ESS transition that disrupts L3 networking is about to occur so that it does not lose packets in transition
It seems more likely that mobility-aware applications will need to be designed to tolerate occasional packet loss and recover accordingly
Matthew Gast, Trapeze Networks
Matthew Gast, Trapeze Networks

25. Link Event Subscriptions
October 2007
doc.: IEEE /2629r1
October 2007
Link Event Subscriptions
primitives: Link_Event_Subscribe and Link_Event_Unsubscribe
Designed for link layer technologies where there are clear types of native events that map to primitives
So a device can say that it supports Link_Up, but not Link_Going_Down
The convergence function maps all primitives that make sense for , so all events that can be supported are supported
Matthew Gast, Trapeze Networks
Matthew Gast, Trapeze Networks

26. References 802.11-2007 – the baseline standard
October 2007
doc.: IEEE /2629r1
October 2007
References
– the baseline standard
P802.11u-D1.0 – the TGu amendment
D7.1 – MIH specification and initial motivation for this idea
11-07/2488 – the initial high-level proposal for the state convergence function
11-07/2604 –proposed text for the specification, described in this presentation
Matthew Gast, Trapeze Networks
Matthew Gast, Trapeze Networks