Support of Multimedia SIP Applications over Proactive MANETs – Extension of OLSR for Service Discovery Li Li and Louise Lamont CRC Canada Communications Research Centre (CRC) Defence R&D Canada - Ottawa
Outline • Overview of MANET Service Discovery Schemes • OLSR Extension to Support Service Discovery • SIP MANET Networking Architecture • Performance Results • Conclusions Communications Research Centre (CRC) Defence R&D Canada - Ottawa
Service Discovery • To find the IP-address of a service provider by specifying the desired service properties, which can then be contacted by the client for the service session. • The key service properties: service type, service URL/AOR, attributes, preference of attributes, etc. • Service discovery schemes developed for the fixed networks often employ the centralized servers which may not exist in the MANET, e.g., DNS, DHCP, ENUM etc. Communications Research Centre (CRC) Defence R&D Canada - Ottawa
Overview of MANET Service Discovery Schemes • Host-name-to-address mapping – Adapt DNS protocol to MANET (draft-jeong-manet-dns-service- 00.txt) – Piggyback onto reactive routing protocol (draft-engelstad-manet- name-resolution-01.txt) • SLP adapted to MANET – Piggyback onto reactive routing protocol (draft-koodli-manet- service-discovery-00.txt) – Building distributed service directory layer in MANET (U Kozat and L Tassiulas ) • Service advertising and discovery on Multicast Protocols – Often reactive multicast routing protocols are assumed (e.g., Liang Cheng) Communications Research Centre (CRC) Defence R&D Canada - Ottawa
Service Discovery in Proactive MANET • Proactive MANET is more suitable for certain application scenarios, e.g., for support of real-time multimedia SIP applications with minimum end-to- end latency • Apply cross-layer design between networking and application layers to reduce the infrastructure and protocol overhead – Service advertisement may fit well in OLSR’s forwarding mechanism – Can service query-and-response messages be supported by OLSR forwarding mechanism? Communications Research Centre (CRC) Defence R&D Canada - Ottawa
Extension on OLSR to Support Service Discovery A new message type to handle the • functionality of service discovery: Service MPR Location Extension (SLE) OLSR MPR forwarding to disseminate the • MANET Server MPR SLE message MPR MPR forwarding to advertise the service capability – MPR Service query-and-response using MPR – MPR forwarding MPR Response SLE is the same as the advertising SLE – • SLE refresh timer, SLE minimum refresh timer and limited maximum number of queries to control message load • Backward compatibility with OLSR nodes that do not support the SLE extension Communications Research Centre (CRC) Defence R&D Canada - Ottawa
SLE Message • Major fields include: Service Sequence Number, Service Type, Service Attributes, AOR URL, Location, Weight, Query Flag, etc. • Service Attributes are service type dependent, including attribute values and preferences • The AOR URL can be omitted when the Query Flag is enabled • Location field stipulates IP address Communications Research Centre (CRC) Defence R&D Canada - Ottawa
SIP MANET Networking Architecture • Two types of servers, proxy server and UAS are involved MN_UA MN_UA2 MN_UA MN_UA2 MN_UA 3 3 1 1 MANET 1 MN_Proxy1 MANET MN_UA MN_UA MN_Proxy2 2 MN_UA MN_UA 2 MN_UA MN_UA1 MN_UA MN_UA1 MN_UA3 MN_UA 1: register 1: send INVITE request directly to the called 2: send INVITE request 3. route the INVITE request to the called (b) Proxy-less SIP MANET (a) Proxy-based SIP MANET • Proxy-based vs. Proxy-less SIP MANET Architecture – Proxy server offers SIP directory service – Need to discovery either the proxy server(s) or all destination UAS Communications Research Centre (CRC) Defence R&D Canada - Ottawa
Support SIP MANET Over OLSR • Use OLSR SLE to automatically discover the SIP MANET architecture and locate the server(s) • Listen for server advertisement • Query message first solicits the proxy server to respond. A UAS only responds when there is no proxy server heard in the SIP MANET • To further reduce the message overhead, uni-cast response may be used Communications Research Centre (CRC) Defence R&D Canada - Ottawa
Performance Evaluations - Comparison of OLSR SD scheme with SD scheme piggybacked on the reactive routing protocol MPR 1 1 MANET Server MPR Server MANET MPR MPR MN_UA MPR MPR MN_UA MN_UA Assume two broadcast queries generating more message load than a MPR • forwarded query-and-response pair • OLSR SLE scheme can outperform the reactive SD scheme in many cases Communications Research Centre (CRC) Defence R&D Canada - Ottawa
Simulation Results Call Setup Time: proxyless network SLE Message Overhead in total OLSR traffic Percentage of SLE 0.12 0.80% setup time (sec) 0.1 0.60% big net 0.08 Case1 0.40% 0.06 small net 0.20% Case2 0.04 0.00% 0.02 proxy-less one proxy 0 server 0 sec 1600.68 2237.76 2746.94 3018.47 3219.06 3511.54 3699.97 Scenarios simulation time (sec) • SLE overhead is insignificant in proportion to the overall OLSR overhead • Satisfactory performance results of SIP applications are achieved with the proposed service discovery scheme Communications Research Centre (CRC) Defence R&D Canada - Ottawa
Conclusions • Cross-layer support of service discovery utilizing the OLSR protocol achieves implementation, architecture and protocol efficiency • The extra message overhead generated by SLE is very limited • OLSR SLE scheme may outperform reactive SD schemes in many cases • The proposed OLSR SD scheme delivers satisfactory performance metrics for support of multimedia real-time applications Communications Research Centre (CRC) Defence R&D Canada - Ottawa
Thank You! Communications Research Centre (CRC) Defence R&D Canada - Ottawa
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