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-service00.txt) – Piggyback onto reactive routing protocol (draft-engelstad-manetname-resolution-01.txt)
• SLP adapted to MANET – Piggyback onto reactive routing protocol (draft-koodli-manetservice-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-toend 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 • MPR
MANET
Server
•
MPR MPR
A new message type to handle the functionality of service discovery: Service Location Extension (SLE) OLSR MPR forwarding to disseminate the SLE message – MPR forwarding to advertise the service capability – Service query-and-response using MPR forwarding – Response SLE is the same as the advertising SLE
MPR MPR MPR
•
•
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
3
MANET
1
MN_Proxy1
2
MN_UA
MN_UA1
1
3
MN_UA
MN_UA
MANET MN_Proxy2
MN_UA
2
MN_UA 1: register 2: send INVITE request 3. route the INVITE request to the called
(a) Proxy-based SIP MANET
MN_UA3
MN_UA1
MN_UA2 1 MN_UA
MN_UA
MN_UA
MN_UA
1: send INVITE request directly to the called
(b) Proxy-less 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
MANET
1
Server
MPR
MANET
MPR MN_UA
Server
MPR 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 netw ork
3699.97
3511.54
3219.06
Scenarios
3018.47
one proxy server
Case2
2746.94
proxy-less
Case1
2237.76
small net
1600.68
big net
0.12 0.1 0.08 0.06 0.04 0.02 0 0 sec
0.80% 0.60% 0.40% 0.20% 0.00%
setup time (sec)
Percentage of SLE in total OLSR traffic
SLE Message Overhead
simulation tim e (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
