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AP/AR Discovery

AP/AR Discovery. CAPWAP BOF IETF-57, Vienna Inderpreet Singh isingh@chantrynetworks.com. Discovery Requirements. Scalability 100’s of AP’s per AR Multiple AR’s Minimal administration Speed msecs per discovery? Minimize code size of protocol/mechanism Work in general topologies

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AP/AR Discovery

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  1. AP/AR Discovery CAPWAP BOF IETF-57, Vienna Inderpreet Singh isingh@chantrynetworks.com

  2. Discovery Requirements • Scalability • 100’s of AP’s per AR • Multiple AR’s • Minimal administration • Speed • msecs per discovery? • Minimize code size of protocol/mechanism • Work in general topologies • on-subnet (switches) • off-subnet (multiple router hops) • Service Availability (robustness)

  3. Discovery Steps • Discovery • AR IP address • Capabilities (protocols supported, link speed, etc) • Bootup discovery • Dynamic discovery • Service Availability • Fault tolerance

  4. Potential Solutions • SLP based discovery • Service Location Protocol • RFC 2608 • RFC 2609 • RFC 2610 • DHCP based discovery • New vendor specific option • Static Config • No brainer • Scalability issues

  5. SLP Based discovery (Unicast) DHCP server DA AR network AP • AR/SA registers service with DA • Looks up location of DA with DHCP Option 78/79 • Statically configured DA location • AP/UA looks up location of service with DHCP Option 78/79 • Needs to get IP address anyway from DHCP • AP/UA contacts DA with service-type = [WLAN] • AP attempts to connect to AR for WLAN services (continues with discovery/join process)

  6. SLP Based Discovery (Multicast/B’cast w/ no DA) AP multicast multicast unicast AR L2 switch AP unicast multicast • AP (or UA) issues multicast svr. request • AR (or SA) issues unicast svr. response • AP continues with discovery/join process

  7. SLP based discovery • Advantages • Works with “on” or “off” subnet topologies • AR addition to network is also automatic (registers with DA) • Disadvantages • SLP deployment in existing networks • AP assignment to AR’s is not automatic – may require admin intervention

  8. DHCP options for AP/AR Discovery DHCP server AR network AP • AP sends DHCP-inform for WLAN AR option • DHCP server responds with IP address of AR • AP proceeds with discovery/join process

  9. DHCP based discovery • Advantages • AP already has DHCP code (maybe?), needs to just be changed with DHCP options • Works in L2 and L3 (need DHCP relay) • Disadvantage • Admin overhead for adding AR’s to system • Admin overhead to assign specific AP’s to specific AR’s

  10. Next steps • Other requirements • I-D for Discovery • If SLP based – then best practices draft? • If DHCP based – then option draft • If other – then other draft

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