Support of Multimedia SIP Applications over Proactive MANETs

1
Support of Multimedia SIP Applications over
Proactive MANETs Extension of OLSR for Service
Discovery

• Li Li and Louise Lamont
• CRC Canada

2
Outline

• Overview of MANET Service Discovery Schemes
• OLSR Extension to Support Service Discovery
• SIP MANET Networking Architecture
• Performance Results
• Conclusions

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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.

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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)

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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 OLSRs
  forwarding mechanism
• Can service query-and-response messages be
  supported by OLSR forwarding mechanism?

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Extension on OLSR to Support Service Discovery

• 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
• 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

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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

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SIP MANET Networking Architecture

• Two types of servers, proxy server and UAS are
  involved

• 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

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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

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Performance Evaluations
- Comparison of OLSR SD scheme with SD scheme
piggybacked on the reactive routing protocol

• 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

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Simulation Results

• 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

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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

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Thank You!