doc.: ieee 802.11-04/579r0 submission may 2004 michael montemurro, chantry networksslide 1 roaming...
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May 2004
Michael Montemurro, Chantry Networks
Slide 1
doc.: IEEE 802.11-04/579r0
Submission
Roaming Applications and Use Cases
Michael Montemurro, Chantry Networks
Chris Durand, Spectralink
Jim Wendt, HP
Stephano Faccin, Nokia
Keith Amann, Spectralink
May 2004
Michael Montemurro, Chantry Networks
Slide 2
doc.: IEEE 802.11-04/579r0
Submission
Purpose
• Define Applications that drive BSS-transition requirements
• Define Conditions for BSS-Transition (use cases)
May 2004
Michael Montemurro, Chantry Networks
Slide 3
doc.: IEEE 802.11-04/579r0
Submission
Roaming Applications Summary Class Applications Traffic Latency
Delay
Packet Loss Sensitivity
Guar. BW
Conversational VoIP
Video Phone
?Internet Game
Bidirectional
Small Pkts (VoIP, Gaming)
Large Pkts (Video Phone)
Strict&Low
<50ms
High Yes
RT Streaming ? Unidirectional
Large Pkts / Multicast
Bounded
<1s
High Yes
Non-RT
Streaming
VOD
Cable TV
Unidirectional
Large Pkts / Multicast
Bounded
<5s
Low Yes
Fast Interactive Video Gaming Bidirectional / Asymetric
Variable Pkts
Tolerable
<100ms
High Yes
Interactive Web
Telnet
Bidirectional / Asymetric
Variable Pkts
Tolerable
<1s
Low No
Background FTP
Bidirectional / Asymetric
Variable Pkts
Unbounded
<5-10s
Low No
May 2004
Michael Montemurro, Chantry Networks
Slide 4
doc.: IEEE 802.11-04/579r0
Submission
Basic Roaming Use CaseConditions
• AP’s on different channels, single ESS
• AP’s connected via a switch
• Traffic (characterized by application)
• Both AP’s remain powered up during roam
May 2004
Michael Montemurro, Chantry Networks
Slide 5
doc.: IEEE 802.11-04/579r0
Submission
Overlay Conditions ToRoaming Use Cases
• Enhanced Security• Enhanced QoS – no admission control• Enhanced QoS – admission control • Roaming Coverage Zone
– Cell overlap distance vs STA velocity (walking, slow vehicle, automotive)
– Are these use case conditions or network engineering constraints?
May 2004
Michael Montemurro, Chantry Networks
Slide 6
doc.: IEEE 802.11-04/579r0
Submission
Roaming Topology
Switch
AP
NetworkNetwork Switch
AP
MU
AP and MUShare Link State MAC,DS,Security, QoS
MU Roaming DeterminationLink Quality, Scan Results, Service Availability, Velocity
ESS
AuthenticationServer
May 2004
Michael Montemurro, Chantry Networks
Slide 7
doc.: IEEE 802.11-04/579r0
Submission
STA Considerations for Roaming• TGe and TGk provid metrics for a roaming
decision
• Depends on roaming time versus velocity of the client – When is roaming calculated versus when does it
roam?
• Depends on service availability on new AP?– Is there bandwidth available?– Will the connection be secure?
May 2004
Michael Montemurro, Chantry Networks
Slide 8
doc.: IEEE 802.11-04/579r0
Submission
State Transition Considerations
• Needs to be secure
• Do AP’s need to communicate?– Over the air? Over the wired network?– Could we leverage IAPP? CAPWAP?
• AP-AP communications needs to be secure
• Should the AP’s share state information?
May 2004
Michael Montemurro, Chantry Networks
Slide 9
doc.: IEEE 802.11-04/579r0
Submission
What about?(Scope / Use Case / Reqmt / Constraint / Punt / Other?)
• L3 Roaming Tunnel DS– Two APs with same SSID / but on diff subnets– Client IP address is unchanged on L2 roam– How does L2 handoff (security/QoS/etc) relate to L3 cross-subnet
roaming/tunneling?
• Roaming Load– Frequency and distribution of roam events
• Roaming control packet delivery guarantees– DS Capacity/QoS for roaming control packets– Is this a network engineering constraints?
• VLANs
May 2004
Michael Montemurro, Chantry Networks
Slide 10
doc.: IEEE 802.11-04/579r0
Submission
Next Steps
• Expand the use case descriptions
• Identify the scenarios in more details
• Define the process flow
• Address Mesh Network BSS Transition
May 2004
Michael Montemurro, Chantry Networks
Slide 11
doc.: IEEE 802.11-04/579r0
Submission
Backup
May 2004
Michael Montemurro, Chantry Networks
Slide 12
doc.: IEEE 802.11-04/579r0
Submission
Snarfed Table Class Applications Traffic Latency
Delay
Jitter Guar. BW
BER
Conversational VoIP
Internet Game
Strict&Low Yes 10(-3)
Streaming VOD
Cable TV
Bounded Yes 10(-5)
Interactive Web
Telnet
Tolerable No 10(-8)
Background FTP
Unbounded No 10(-9)
May 2004
Michael Montemurro, Chantry Networks
Slide 13
doc.: IEEE 802.11-04/579r0
Submission
Terminology (needs work)• System Attributes
– Distinct characteristics of FRFH environments• E.g. PHYs, Channels, Security mechanisms, QoS
• Scope– Environments in which FRFH is applicable – as defined by the fixed system
attributes• E.g. 802.11 MACs only
– Assumptions regarding surrounding components in the FRFH environment • E.g. Upstream L2 bridge table
• Requirements– Range of system attribute values that must be supported by FRFH
• Use Case– Specific example scenarios that are supported by FRFH - as defined by collections of
specific values for system attributes• Constraint (on network design)
– A design constraint placed on a network design• E.g. AP cell overlap for maximum intended STA velocity must allow for 100ms of co-
coverage
May 2004
Michael Montemurro, Chantry Networks
Slide 14
doc.: IEEE 802.11-04/579r0
Submission
FRFH ScopeIS
• Client IP address doesn’t change• Roam is between 802.11 cells/APs• APs have same:
– ESS (SSID)– Others TBD
• APs may have:– Different 802.11 PHYs (a/b/g/n)– Different channels– Others TBD
• DS may be:– L2 infrastructure (bridging table)– AP Mesh– ? L3 infrastructure with non-changing client IP
addresses
• Should/Must support or address:– TGi– TGe / BW reservation issues– ? Extensible state transferal
IS NOT
• Client IP address changes on roam
• Roam is between 802.11 and other PHYs / mediums
– 802.16 / 802.3 / Cellular
• AP Failure
May 2004
Michael Montemurro, Chantry Networks
Slide 15
doc.: IEEE 802.11-04/579r0
Submission
Basic Roaming Use Case
• AP’s on different channels
• AP’s connected via a L2 switch
• Both AP’s remain powered up during roam
• Downlink traffic only
• Assumes (based on FRFH scope)– Single ESS / same SSID
May 2004
Michael Montemurro, Chantry Networks
Slide 16
doc.: IEEE 802.11-04/579r0
Submission
Additional Use Case Conditions
• Enhanced Security (TGi)• Enhanced QoS (TGe)
– no admission control– admission control
• Roaming Coverage Zone– Cell overlap distance vs STA velocity (walking, slow
vehicle, automotive)– Are these use case conditions or network engineering
constraints?• Mesh Network
May 2004
Michael Montemurro, Chantry Networks
Slide 17
doc.: IEEE 802.11-04/579r0
Submission
Roaming Transition Process
• Roaming Determination– Could include pre-authentication– Could include network interaction
• Connection Process – Authentication/Re-association– Key Derivation/Exchange– Flow negotiation
• Re-establish Data Communications• NOTE: PROCESS STEPS DON’T NEED TO BE
SERIALIZED
May 2004
Michael Montemurro, Chantry Networks
Slide 18
doc.: IEEE 802.11-04/579r0
Submission
The Elements of Roaming
• How to determine when/where to roam?
• How to minimize the time it takes to move state from one AP to another or establish state at the new?
May 2004
Michael Montemurro, Chantry Networks
Slide 19
doc.: IEEE 802.11-04/579r0
Submission
When/Where to Roam?
• IEEE 802.11 standards – States that the STA/MU can be only connected
to one BSS/AP at any point in time– MU has to decide when and where to roam
• Cellular standards – Roaming is network driven– MU moves within the network– The Network hands off the connection from
cell to cell
May 2004
Michael Montemurro, Chantry Networks
Slide 20
doc.: IEEE 802.11-04/579r0
Submission
Minimizing Roaming Time
• What can a STA or AP do to minimize re-connection time?
• Need to moving connection state for the STA from the current AP to the new AP
• Need to update the DS with the new link state
May 2004
Michael Montemurro, Chantry Networks
Slide 21
doc.: IEEE 802.11-04/579r0
Submission
State Transitions for Roaming
Two options:1. Transition connection state from one AP to
another ( requires AP to AP communications)
2. Derive a new connection state between one MU and the AP (MU to AP communications only)
• State transition could occur before or during the roaming event
May 2004
Michael Montemurro, Chantry Networks
Slide 22
doc.: IEEE 802.11-04/579r0
Submission
MU/AP Connection State
• MAC/PHY – link state, radio parameters, rate, etc.
• Security – PMK, PTK, etc.
• QoS – TSPEC’s
• DS – physical port map (MAC – Port Number)
May 2004
Michael Montemurro, Chantry Networks
Slide 23
doc.: IEEE 802.11-04/579r0
Submission
Other considerations
• Does the process start before the MU roams? (i.e. like Pre-authentication)
• Should the MU reserve resources before it moves?
• Should the DS reserve resources before the MU moves?
May 2004
Michael Montemurro, Chantry Networks
Slide 24
doc.: IEEE 802.11-04/579r0
Submission
Recap Reported Roaming Measurements
• Based on 11-04/377 without IAPP or IP interactions (DHCP, etc.):
• PMK cached/Active Scanning:– Using Passive Scanning: 14 ms – 1034 ms– Using Active Scanning: 34 ms – 380 ms
• PMK not cached (w/ 802.1x Fast Resume– Using Passive Scanning: 154 ms – 1304 ms– Using Active Scanning: 170 ms – 620 ms
May 2004
Michael Montemurro, Chantry Networks
Slide 25
doc.: IEEE 802.11-04/579r0
Submission
Conclusions
• The two elements to fast roaming are:– Determination of when/where to roam
• Need to consider service availability
– Minimize the time it takes to establish a new connection state at the new • Needs to be secure
• Minimize roaming time