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Discovery Modes and Discovery Proxy of Web Services Discovery

Discovery Modes and Discovery Proxy of Web Services Discovery. Date: 2013-07-16. Authors:. Abstract. This presentation introduces Discovery Modes and Discovery Proxy of Web Services Dynamic Discovery to discuss the 11aq design. Managed Mode of WS-Discovery. AP Discovery Proxy. Non-AP

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Discovery Modes and Discovery Proxy of Web Services Discovery

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  1. Discovery Modes and Discovery Proxy of Web Services Discovery Date: 2013-07-16 Authors: RYU Cheol, ETRI

  2. Abstract This presentation introduces Discovery Modes and Discovery Proxy of Web Services Dynamic Discovery to discuss the 11aq design. RYU Cheol, ETRI

  3. Managed Mode of WS-Discovery AP Discovery Proxy Non-AP STAs Service Discovery Capable Device Hello (unicast) Probe (unicast in GAS) Probe Match (GAS) Bye (unicast) RYU Cheol, ETRI

  4. Ad Hoc Mode of WS-Discovery AP Discovery Proxy Non-AP STAs Service Discovery Capable Device Hello (PAM) Hello (multicast) Probe (multicast in GAS) Probe (multicast) Probe Match (GAS) Probe Match (unicast) Bye (PAM) Bye (multicast) RYU Cheol, ETRI

  5. Discovery Proxy for two modes AP Discovery Proxy Non-AP STAs Service Discovery Capable Device Hello for Service A (PAM) Hello for Service A (multicast) STA X Probe for Service B (multicast in GAS) Probe for Service B (multicast) STA Y in ad hoc mode Probe Match for Service B (GAS) Probe Match for Service B (unicast) Probe for Discovery Proxy Service (multicast in GAS) STA Z in ad hoc mode Probe Match for Discovery Proxy Service (GAS) Probe for Service A or B (unicast in GAS) STA Z in managed mode Probe Match for Service A or B (GAS) Bye (PAM) Bye (multicast) RYU Cheol, ETRI

  6. Services AP Connection W/O Association STA Non-AP STA Associated Discovery Proxy UDP multicast/ unicast GAS UDP multicast/ unicast PAM Service Advertisement Local Server on LAN M I B Wired Beacon Probe Probe response PAM: Pre-Association Message RYU Cheol, ETRI

  7. Consideration for high-density environment • The combination of PAM and GAS • By adopting a request/response protocol similar to ANQP which is based on GAS, 11aq could increase the traffic to discover available services. But it is assured to find available services and does not rely on the probability to be reached by PAM. • PAM is the one-way frame(e.g. broadcasting or multicasting public action frame) supports passive way of service discovery which could relieve the traffic. It can minimize the need for polling. • Still PAM generates some amount of traffic even when there is no body listening. • But PAM traffic can be controlled by limiting the frequency, and service availability information is not time sensitive. The PAM frequency need to be designed considering reachability and traffic. RYU Cheol, ETRI

  8. Maintaining the storage of Discovery Proxy • WS-Discovery is well designed to maintain discovery cache by defining version number of metadata for target services. And other discovery protocols which support one-way-service announcement have similar mechanisms, i.e. cache-flush bit in the unsolicited announcement for mDNS of Bonjur and max-age for SSDP of UPnP . • The upper limit of the storage size is the implementation issue which can be determined by AP considering its resource. But we can assume it will be benefited from the cache locality. RYU Cheol, ETRI

  9. Summary • Discovery Proxy in AP can tunnel WS-Discovery protocol without inventing a new service registration interface. • AP should have Service Advertisement module to transmit one-way PAM(Pre-Association Message)s which are required for ad hoc mode operation of WS-Discovery. • Discovery Proxy, which has cache functionality, might stop messing around with the network. • We also need to investigate further the behaviors of Bonjour and UPnP to find that they go well with Discovery Proxy. RYU Cheol, ETRI

  10. References • Web Services Dynamic Discovery (WS-Discovery) Version 1.1, OASIS standard at http://docs.oasis-open.org/ws-dd/discovery/1.1/wsdd-discovery-1.1-spec.html • SOAP-over-UDP Version 1.1, OASIS Standard at http://docs.oasis-open.org/ws-dd/soapoverudp/1.1/os/wsdd-soapoverudp-1.1-spec-os.html RYU Cheol, ETRI

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