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

Email

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

Email

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