CAPWAP BOF IETF-57, Vienna Inderpreet Singh isingh@chantrynetworks.com 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 on-subnet (switches) off-subnet (multiple router hops) Service Availability (robustness)

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

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

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) Advantage:Note that the AR automatically gets added to the DA. As new AR’s come on line, the service is automatically available to the existing AP’s. Disadvantage: most probably there is administrative overhead to allocate AP’s to “specific” AR or ARs. In L2 multicast/broadcast this is not an issue….one AR per group of APs.

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

SLP based discovery Advantages Disadvantages 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

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 In this case every time a new AR comes online the administrator must add that to the list of AR’s available in the DHCP server.

DHCP based discovery Advantages Disadvantage 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

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