1. The Need for Fast Roaming
January 2004
The Need for Fast Roaming
Keith Amann
SpectraLink Corporation
Keith Amann, SpectraLink

2. January 2002
doc.: IEEE /xxxr0
January 2004
Is there a problem?
Question of great debate since March 2003, or possibly earlier
Empirical data, does it exist or not?
Some, but not well organized or distributed
Can a client perform a “fast roam” today (or in the near future)?
(Opinion) Not without some help
Keith Amann, SpectraLink
John Doe, His Company

3. Issues (Opinion) 802.11 being incorporated into more and more devices
January 2004
Issues (Opinion)
being incorporated into more and more devices
Many have limited resources (memory, processor)
Increasing on air requirement for context transfer
More time sensitive applications
becoming more and more complex!
Keith Amann, SpectraLink

4. The “Debate” Mostly centered around 802.11i/Security Issues
January 2002
doc.: IEEE /xxxr0
January 2004
The “Debate”
Mostly centered around i/Security Issues
One side claims the facilities exist within i to allow this to work
Other side claims these facilities are inadequate, or don’t satisfy the needs of the applications
Not enough data to substantiate claims one way or the other
Little or no discussion regarding QoS, Radio Resources, etc.
Largely an “emotional” debate
Keith Amann, SpectraLink
John Doe, His Company

5. What about existing 802 “enhancements”?
January 2004
What about existing 802 “enhancements”?
802.11e
Ability to send a Traffic Specification (either eDCA or HCCA) via (re)association
Nothing else related to context transfer of “stream”
802.11f
Not well deployed
Lacks the necessary specifics
802.11k
looking at providing assistance
Not attempting to solve the problem
802.11i
Several “mechanisms” defined
Finding many interpretations of how to best use these mechanisms
802.1 Handoff Study Group
Really oriented toward handoff between differing network technologies
NOTHING TO TIE ALL OF THIS TOGETHER!!
Keith Amann, SpectraLink

6. 802.11e Enhancements Ability to send TSPEC in (re)association
January 2004
802.11e Enhancements
Ability to send TSPEC in (re)association
Fails to address successful association with failed TSPEC request
Requires a full context negotiation following the roam
Keith Amann, SpectraLink

7. 802.1 Handoff, 802.11f, 802.11k 802.1 Handoff Study Group
January 2004
802.1 Handoff, f, k
802.1 Handoff Study Group
Looking at addressing inter-technology handoff, not inner-technology handoff
802.11f
Lacks sufficient deployment base
Does not provide specifics about how to improve roaming efficiency, or how to use it for this situation
802.11k
Only trying to help with identification of roaming candidates
Not addressing roaming efficiency improvements
Keith Amann, SpectraLink

8. 802.11i Enhancements “Key Caching”
January 2004
802.11i Enhancements
“Key Caching”
Allows the STA and AP to “cache” credentials for authentication
Requires memory at both the AP and STA
Requires some “loose” interpretation of i
Doesn’t solve the “initial” roam problem
“Pre-Authentication”
Allows the STA to authenticate through an existing association
Requires memory at the AP and STA
Creates a “window of opportunity” for potential threats, and synchronization issues between AP and STA
“Pre-Shared Key Mode”
Reduces the overhead of authentication
Designed to be used in the SOHO market
Efficiency issues with current implementations
Keith Amann, SpectraLink

9. Examples of the Problem
January 2004
Examples of the Problem
Discussions with Infrastructure Vendors
Different thoughts on how to utilize i mechanisms
Different signaling requirements/mechanisms
Pre-Shared Key Testing
3 Different Manufacturers
2 traditional APs
1 “switch style” AP
Embedded Client
VoIP Phone
Non-optimized encryption (no hardware assist)
Keith Amann, SpectraLink

10. PSK Testing (times in milliseconds)
January 2004
PSK Testing (times in milliseconds)
Message
AP1
AP2
AP3
Assoc Resp
4-Way Message 1
.876
992.02
4-Way Message 2
19.903
20.279
20.328
4-Way Message 3
1.409
2.621
2.032
4-Way Message 4
5.617
5.66
5.862
4-Way GTK 1
6.397
1.744
2.442
4-Way GTK 2
7.774
7.33
7.463
Total Time
41.976
Keith Amann, SpectraLink

11. What does it all mean? Ongoing 802.11 efforts Proprietary Solutions
January 2004
What does it all mean?
Ongoing efforts
Problem is only going to become worse, not better
Proprietary Solutions
Difficult for client specific developers to implement because of diversity of solutions
Requires client side changes in all cases
No standard “expectation”, barrier to broad market acceptance
Nothing tying all the pieces together
802.11f, e, i, k, Handoff
Keith Amann, SpectraLink

12. Summary The industry needs this effort, help support it! January 2004
Keith Amann, SpectraLink