802.11 WLAN Architectural Considerations for IETF CAPWAP

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802.11 WLAN Architectural Considerations for
IETF CAPWAP
L. Lily Yang Editor of IETF CAPWAP Architecture
Design Team lily.l.yang_at_intel.com
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Overview

• Introduction IETF CAPWAP and IEEE
• Current 802.11 standard on architecture
• Autonomous AP architecture
• Deployment problems
• Hierarchical APAC architecture
• CAPWAP architectural considerations
• Functional split continuum
• Topology
• Security
• Open questions and suggestions
• Summary

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Introduction

• IETF CAPWAP (Control and Provisioning of Wireless
  APs)
• Newly chartered WG in Jan 2004
• Problem interoperability
• Co-chairs Mani, Mahalingam Dorothy Gellert
• Need close collaboration with IEEE
• Liaison Dorothy Stanley
• Technical Advisor Bob OHara
• First WG meeting in March 2004 at Seoul
• Architecture Design Team (12 members, L. Yang
  Editor)
• Task 802.11 architecture taxonomy
• Will be reviewed by experts from IEEE IETF

http//www.ietf.org/html.charters/capwap-charter.h
tml
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WLAN Architecture Defined by 802.11 today

• MAC Services defined by .11
• Station Services (4)
• Distribution System Services (5)
• Other AP functions
• AP Load balancing
• Dynamic RF mgmt control
• Station Mobility support
• Better network security

Distribution System (DS)
Portal
External Network
Implementation of DS is not specified in 802.11
standard, for good reason flexibility.
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Autonomous AP Architecture
STA 5
STA 1
STA2
STA 3
STA 4
AP
AP
AP
External Network

• Autonomous (standalone) AP fat and
  self-contained AP
• No explicit infrastructure support for wireless
• Each AP provides most of the WLAN functions
  including distribution, integration and other
  L3 services within itself.

Traditional WLAN Architecture
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Problems in Large WLAN Deployment

• Network administration burden
• Management
• Monitoring
• Control
• Effective RF Dynamic Provisioning needs
  coordination among APs
• Maintaining Consistent Configuration
• Security
• Access to the network (e.g., physical security of
  APs)
• Rogue AP detection

One Solution Hierarchical Architecture
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Hierarchical ArchitectureAP AC (Access
Controller)
STA 5
STA 1
STA2
STA 3
STA 4
AP
AP
AP
Access Controller (AC)
External Network

• AP AC together implements AP functions
• Advantages of AC
• centralized controller(s) gt manageability for
  large networks
• network wide visibility gt better coordination
  across the network
• Challenges
• no standard way of splitting AP functions onto AP
  and AC

No interoperability
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Split Architecture Examples
AP Functional Stack
Split AP
Split MAC
Antenna AP
Split Continuum
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Split Implications on 802.11 MAC PHY
Split MAC
Antenna AP

• Performance implications ?
• Timing constraints gt separation constraints?

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Network TopologyHow AP and AC are connected?
Via L3 cloud
Via L2 cloud
Directly Connected
AC
AC
AC
L3
L2
L2
router
Switch/bridge
AP
AP
AP
AP
AP
AP
AP
AP
AP
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Inter-dependency between split architecture and
topology
topology
x
L3
?
?
x
?
x
L2
x
x
x
Direct
Split AP
Split MAC
Antenna AP
Split architecture Continuum
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Security in CAPWAP

• CAPWAP security issues
• Mutual authentication of AP and AC
• Secure the CAPWAP segment of AP-AC
• Dependent on split architecture

AP
STA
AC
OTA security
Authentication Server
CAPWAP segment
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Next Steps for CAPWAP
WG
Architecture Survey
Architecture Taxonomy
DT
Expert Review
IEEE IETF
AP functional Definition
IEEE
IEEE IETF
03/24
v01 April

• Functional split of AP and AC
• Design considerations
• Network topological considerations
• Security threats
• Pros and cons

• Data analysis
• Categorization
• Tradeoff of Interoperability vs. flexibility
• Recommendations

Interoperability solution
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Open Questions Suggestions

• Issues for IEEE to ponder
• Split implications on 802.11 PHY and MAC
• Clearer AP functional definitions
• Expert review
• Future update in WNG from CAPWAP

WLAN architecture issues border on L2 L3 Need
IEEE/IETF collaboration
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Summary

• Autonomous AP
• Hierarchical APAC
• Functional split continuum
• Topology Constraints
• Security Issues
• Update on CAPWAP WG Plan
• Issues that need attention feedback from IEEE
• Closer collaboration between IETF and IEEE