Transcript MAC State Generic Convergence Function Text

October 2007
doc.: IEEE 802.11-07/2629r0
MAC State Generic Convergence Function
Date: 2007-10-22
Authors:
Name
Matthew Gast
Submission
Affiliations
Address
Phone
email
Trapeze Networks
5753 W. Las Positas Blvd,
Pleasanton, CA 94588 USA
925-474-2273
[email protected]
Slide 1
Matthew Gast, Trapeze Networks
October 2007
doc.: IEEE 802.11-07/2629r0
Abstract
This presentation describes proposed changes to the
802.11u draft to support the MAC State Generic
Convergence Function originally described in 1107/2488. The text of the full proposal is found in 1107/2604.
Submission
Slide 2
Matthew Gast, Trapeze Networks
October 2007
doc.: IEEE 802.11-07/2629r0
Classification of 802.21 Primitives
• Link Operations
–
–
–
–
–
–
Link_Up
Link_Down
Link_Going_Down
Link_Event_Rollback
Link_Detected
Link_PDU_Transmit_Status
• MAC “API”
–
–
–
–
• Link Parameter operations
– Link_Configure_Thresholds
– Link_Get_Parameters
– Link_Parameters_Report
• Mobility Operations
– Link_Handover_Imminent
– Link_Handover_Complete
Submission
Link_Event_Subscribe
Link_Event_Unsubscribe
Link_Capability_Discover
Link_Action
Slide 3
Matthew Gast, Trapeze Networks
October 2007
doc.: IEEE 802.11-07/2629r0
Events for Network Operation
(corresponding to MIH Link Operations)
Supporting the following 802.21 primitives:
Link_Up, Link_Down, Link_Going_Down,
Link_Event_Rollback, and Link_Detected
Submission
Slide 4
Matthew Gast, Trapeze Networks
October 2007
doc.: IEEE 802.11-07/2629r0
MSGCF-Network-Up
•
•
•
Corresponding 802.21 primitive: Link_Up
English meaning for 802.11: 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 802.21 with this event
– LINK_TUPLE_ID (Table B4, page 171 of 802.21-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 requires that the IP_RENEWAL_FLAG be set (see 802.21-D7.1 clause
7.3.4). 802.11 has information only about layer 2, and therefore, this event cannot
supply the IP_RENEWAL_FLAG.
– Table B-12, page 193 in 802.21-D7.1 defines mobility management protocols.
Should an “802.11 native” mobility management protocol be defined?
•
Because this event applies to a network of 802.11 APs, the MIHF should
not define access router MAC addresses in terms of BSSIDs
Submission
Slide 5
Matthew Gast, Trapeze Networks
October 2007
doc.: IEEE 802.11-07/2629r0
MSGCF-Network-Down
• Corresponding 802.21 primitive: Link_Down
• English meaning: The 802.11 link 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
• 802.21 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
Submission
Slide 6
Matthew Gast, Trapeze Networks
October 2007
doc.: IEEE 802.11-07/2629r0
MSGCF-Network-Going-Down
•
•
•
Corresponding 802.21 primitive: Link_Going_Down
English meaning: The 802.11 link has gone down and can no longer send packets
Notes
–
–
•
802.11u proposal
–
–
–
•
The predictive algorithm for link quality degradation resides in the SME, so an SME indication
is passed to indicate one type of network going down event
Explicit network down predictions may also occur because of MLME events
The convergence function takes any of these inputs as reason to issue this event
802.21 interactions
–
–
–
•
This specifies the time in time units (TU), which is the native 802.11 “time quantum.” One TU
= 1,204 μs = 1.204 msec.
802.21 said that threshold was configurable, so the desired time threshold is added to the MIB
The MIHF will need to translate 802.11 TUs into other time units
802.11 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
802.11 future implications
–
Submission
Need ANA management of the values of the reason code in the table
Slide 7
Matthew Gast, Trapeze Networks
October 2007
doc.: IEEE 802.11-07/2629r0
MSGCF-Network-Event-Rollback
• Corresponding 802.21 primitive: Link_Event_Rollback
• English meaning: The 802.11 link 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
Submission
Slide 8
Matthew Gast, Trapeze Networks
October 2007
doc.: IEEE 802.11-07/2629r0
MSGCF-Network-Detected
•
•
Corresponding 802.21 primitive: Link_Detected
How it works
–
–
–
•
Notes on 802.11u text
–
–
•
CF issues MLME-SCAN.request primitives to learn about the area networks
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 802.21-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)
Timestamps included in the MIB are integers with no valid range, following the TSF timer
values in MLME-SCAN.confirm in 10.3.2.2.2 of 802.11-2007
MIH support is inferred from the presence of the GAS Advertising Protocol IDs used in the
Interworking information. 802.11u has values for MIH IS (GAS APID #1) and MIH ES/CS
(GAS APID #2)
Note for 802.21
–
Submission
GAS in 802.11u does not provide separate capability information for MIH CS & ES
Slide 9
Matthew Gast, Trapeze Networks
October 2007
doc.: IEEE 802.11-07/2629r0
Events for Threshold Configuration
(corresponding to MIH parameter operations)
Supporting the following 802.21 primitives:
Link_Configure_Thresholds, Link_Get_Parameters, and
Link_Parameters_Report
Submission
Slide 10
Matthew Gast, Trapeze Networks
October 2007
doc.: IEEE 802.11-07/2629r0
MSGCF-Set-Network-Thresholds
• Corresponding 802.21 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
• 802.21 interaction notes
– Any future parameters need to be added to both this primitive and
the MIB
Submission
Slide 11
Matthew Gast, Trapeze Networks
October 2007
doc.: IEEE 802.11-07/2629r0
MSGCF-Get-Network-Parameters
• Matching 802.21 primitive: Link_Get_Parameters
• Proposal for 802.11u: Simple primitive operation to
retrieve relevant information from the MIB
Submission
Slide 12
Matthew Gast, Trapeze Networks
October 2007
doc.: IEEE 802.11-07/2629r0
MSGCF-Network-Threshold-Report
• Matching 802.21 primitive: Link_Parameters_Report
– 802.21-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 802.11u
– 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
Submission
Slide 13
Matthew Gast, Trapeze Networks
October 2007
doc.: IEEE 802.11-07/2629r0
MAC Control Operations
(corresponding to MIH “API” primitives)
Supporting the following 802.21 primitives:
Link_Capability_Discover and Link_Action
Submission
Slide 14
Matthew Gast, Trapeze Networks
October 2007
doc.: IEEE 802.11-07/2629r0
MSGCF-Network-Capability
•
•
Matching 802.21 primitive: Link_Capability_Discover
802.11 implementation
– All events which are supported by the convergence function are available for use
•
802.21 Notes
– The convergence function can report on its own capabilities, but those must be
translated by the MIHF as in Table L2 in 802.21-D7.1. For example, Link_Up in
802.21 is equivalent to Network-Up in 802.11.
– 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 802.11 because
it maps directly to a MAC data service primitive that is always supported
– Obviously, Get-Network-Parameters and Set-Network-Parameters must be
supported if the corresponding threshold events are
Submission
Slide 15
Matthew Gast, Trapeze Networks
October 2007
doc.: IEEE 802.11-07/2629r0
MSGCF-Network-Command
• Matching 802.21 primitive: Link_Action
• Notes for 802.11u proposal
– Maps DISCONNECT action to MLME-Deauthenticate & MLMEDisassociate
– 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 802.11
– DATA_FORWARDING_REQUEST is standard 802.11 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 802.11;
therefore, it is not part of this proposal
Submission
Slide 16
Matthew Gast, Trapeze Networks
October 2007
doc.: IEEE 802.11-07/2629r0
Convergence Function MIB
Submission
Slide 17
Matthew Gast, Trapeze Networks
October 2007
doc.: IEEE 802.11-07/2629r0
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 802.11u 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
Submission
Slide 18
Matthew Gast, Trapeze Networks
October 2007
doc.: IEEE 802.11-07/2629r0
802.21 Primitives not Implemented by
802.11u CF proposal
Discussion of the following 802.21 primitives:
Link_Handover_Imminent, Link_Handover_Complete
Link_Event_Subscribe, Link_Event_Unsubscribe
Submission
Slide 19
Matthew Gast, Trapeze Networks
October 2007
doc.: IEEE 802.11-07/2629r0
Link Handover Events
• 802.21 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 802.21, and
would be extremely frequent
• No clear use case identified for 802.11 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
Submission
Slide 20
Matthew Gast, Trapeze Networks
October 2007
doc.: IEEE 802.11-07/2629r0
Link Event Subscriptions
• 802.21 primitives: Link_Event_Subscribe and
Link_Event_Unsubscribe
• Designed for link layer technologies where there are
clear types of native events that map to 802.21
primitives
– So a device can say that it supports Link_Up, but not
Link_Going_Down
– The convergence function maps all 802.21 primitives that make
sense for 802.11, so all events that can be supported are supported
Submission
Slide 21
Matthew Gast, Trapeze Networks
October 2007
doc.: IEEE 802.11-07/2629r0
References
• 802.11-2007 – the baseline standard
• P802.11u-D1.0 – the TGu amendment
• 802.21-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 802.11 specification,
described in this presentation
Submission
Slide 22
Matthew Gast, Trapeze Networks