1. 802.11 WLAN Architectural Considerations for IETF CAPWAP
Feb-19
WLAN Architectural Considerations for IETF CAPWAP
L. Lily Yang
Editor of
IETF CAPWAP
Architecture Design Team
Lily Yang, IETF CAPWAP Design Team Editor

2. Overview Introduction: IETF CAPWAP and IEEE
Month 2002
doc.: IEEE
Feb-19
Overview
Introduction: IETF CAPWAP and IEEE
Current standard on architecture
Autonomous AP architecture
Deployment problems
Hierarchical “AP+AC” architecture
CAPWAP architectural considerations
Functional split continuum
Topology
Security
Open questions and suggestions
Summary
Lily Yang, IETF CAPWAP Design Team Editor
John Doe, His Company

3. Introduction IETF CAPWAP (Control and Provisioning of Wireless APs):
Feb-19
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 O’Hara
First WG meeting in March 2004 at Seoul
Architecture Design Team (12 members, L. Yang Editor)
Task: architecture taxonomy
Will be reviewed by experts from IEEE & IETF
Lily Yang, IETF CAPWAP Design Team Editor

4. WLAN Architecture Defined by 802.11 today
Feb-19
WLAN Architecture Defined by 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
STA1
STA2 AP
STA3
STA4 AP
Distribution System (DS)
STA5
STA6 AP
Portal
External Network
Implementation of DS is not specified in standard, for good reason: flexibility.
Lily Yang, IETF CAPWAP Design Team Editor

5. Autonomous AP Architecture
Month 2002
doc.: IEEE
Feb-19
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
Lily Yang, IETF CAPWAP Design Team Editor
John Doe, His Company

6. Problems in Large WLAN Deployment
Feb-19
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
Lily Yang, IETF CAPWAP Design Team Editor

7. Hierarchical Architecture: “AP + AC” (Access Controller)
Month 2002
doc.: IEEE
Feb-19
Hierarchical Architecture: “AP + 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) => manageability for large networks
network wide visibility => better coordination across the network
Challenges:
no standard way of splitting AP functions onto AP and AC
No interoperability
Lily Yang, IETF CAPWAP Design Team Editor
John Doe, His Company

8. “Split” Architecture Examples
Feb-19
“Split” Architecture Examples
AP Functional Stack
Fat AP AP
MAC
PHY
L3 & above
Split AP AC AP
MAC
PHY
L3 & above
Split MAC AP AC
Real Time MAC
PHY
Non RT MAC
L3 & above
Antenna AP
MAC
PHY
L3 & above AP AC
“Split” Continuum
Lily Yang, IETF CAPWAP Design Team Editor

9. Split Implications on 802.11 MAC & PHY
Month 2002
doc.: IEEE
Feb-19
Split Implications on MAC & PHY
Split MAC AP AC
Real Time MAC
PHY
Non RT MAC
L3 & above
Antenna AP
MAC
PHY
L3 & above AP AC
Performance implications ?
Timing constraints => separation constraints?
Lily Yang, IETF CAPWAP Design Team Editor
John Doe, His Company

10. Network Topology: How AP and AC are connected?
Feb-19
Network Topology: How AP and AC are connected?
Via L3 cloud
Directly Connected
Via L2 cloud AC AC AC L2 L2 L3
Switch/bridge
router AP AP AP AP AP AP AP AP AP
Lily Yang, IETF CAPWAP Design Team Editor

11. Inter-dependency between split architecture and topology
Feb-19
Inter-dependency between split architecture and topology
topology L3 x ? ? L2 x x ? x x x
Direct
Split AP
Split MAC
Antenna AP
Split architecture Continuum
Lily Yang, IETF CAPWAP Design Team Editor

12. Security in CAPWAP AP STA Authentication Server STA AP AC
Feb-19
Security in CAPWAP AP
STA
Authentication Server
OTA security
Current Security Standard
CAPWAP security issues
Mutual authentication of AP and AC
Secure the CAPWAP segment of AP-AC
Dependent on split architecture
STA AP AC
OTA security
CAPWAP segment
Authentication Server
Lily Yang, IETF CAPWAP Design Team Editor

13. Next Steps for CAPWAP WG Architecture Survey DT Architecture Taxonomy
Feb-19
Next Steps for CAPWAP WG
Architecture
Survey DT
Architecture
Taxonomy
IEEE
&
IETF
Expert
Review
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
Lily Yang, IETF CAPWAP Design Team Editor

14. Open Questions & Suggestions
Feb-19
Open Questions & Suggestions
Issues for IEEE to ponder:
“Split” implications on 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
Lily Yang, IETF CAPWAP Design Team Editor

15. Summary Autonomous AP Hierarchical “AP+AC” Update on CAPWAP WG Plan
Feb-19
Summary
Autonomous AP
Hierarchical “AP+AC”
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
Lily Yang, IETF CAPWAP Design Team Editor