802.11 WLAN Architectural Considerations for IETF CAPWAP

1. 802.11 WLAN Architectural Considerations for IETF CAPWAP L. Lily Yang Editor of IETF CAPWAP Architecture Design Team lily.l.yang@intel.com Lily Yang, IETF CAPWAP Design Team Editor

2. Overview • Introduction: IETF CAPWAP and IEEE • Current 802.11 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

3. 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: 802.11 architecture taxonomy • Will be reviewed by experts from IEEE & IETF http://www.ietf.org/html.charters/capwap-charter.html Lily Yang, IETF CAPWAP Design Team Editor

4. STA3 STA1 STA4 STA2 AP AP AP STA5 STA6 WLAN Architecture Defined by 802.11 today • MAC Services defined by .11: • Station Services (4) • Distribution System Services (5) • Other AP functions: • AP Loadbalancing • 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. Lily Yang, IETF CAPWAP Design Team Editor

5. Autonomous AP Architecture • 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. STA 5 STA 1 STA2 STA 3 STA 4 AP AP AP External Network Traditional WLAN Architecture Lily Yang, IETF CAPWAP Design Team Editor

6. 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) • “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 STA 5 STA 1 STA2 STA 3 STA 4 AP AP AP Access Controller (AC) External Network No interoperability Lily Yang, IETF CAPWAP Design Team Editor

8. Autonomous(fat AP) PHY MAC Control & config WTP PHY MAC Control & config WTP AC PHY Real Time MAC Non RT MAC Control & config WTP AC PHY MAC Control & config WTP AC AP Architecture Examples AP Functions Local MAC(split AP) Split MAC Remote MAC(antenna AP) “Split” Continuum Lily Yang, IETF CAPWAP Design Team Editor

9. PHY Real Time MAC Non RT MAC L3 & above AP AC PHY MAC L3 & above AP AC Split Implications on 802.11 MAC & PHY • Performance implications ? • Timing constraints => separation constraints? Split MAC Antenna AP Lily Yang, IETF CAPWAP Design Team Editor

10. Network Topology:How 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 Lily Yang, IETF CAPWAP Design Team Editor

11. 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 Lily Yang, IETF CAPWAP Design Team Editor

12. Current 802.11 Security Standard STA AP Authentication Server OTA security Security in CAPWAP • 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 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 • 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 Lily Yang, IETF CAPWAP Design Team Editor

15. 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