Wei Dong and Jan Newmarch June 2005

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Wei Dong and Jan NewmarchJune 2005

• Session Management for Web Services by using SIP

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Web Services

• Latest version of Client-Server computing
• Supported by major vendors
• Enormous amount of work being done
• Allows machine-to-machine interaction
• Replaces human-to-machine interaction

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Technologies

• SOAP to carry messages
• WSDL to describe services
• UDDI to find services
• Many, many layers above this
• WS-resources
• WS-security
• WS-reliable messaging
• ...

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Session state

• SOAP is stateless
• There is no standard way of adding state
• There is no standard way to create
• a shopping cart
• user login and personalised interaction
• a database transaction
• Just like the Web was in 1995

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Adding session state

• Web documents use techniques such as
• Cookies
• URL rewriting
• Hidden form fields
• These don't work for web services
• No way of accessing HTTP cookies
• No way of accessing URL information
• No forms to hide fields in

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Some ways to add state

• Add cookies to session headers (MicroSoft)
• Not standard
• Cookies have no semantic content
• WS-Resources (grid)
• Not standard
• Workaround by adding another heavy-weight layer

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SIP

• Session Initiation Protocol
• IETF standard since 1999
• Lightweight, simple, well-understood
• Used (and designed) for a variety of session
  management situations
• Not a one-off solution to a self-imposed
  problem

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Using SIP within Web Services

• First, client opens a SIP session with a SIP
  session server, and gets a SIP session ID
• Client sends SIP session ID to Web Service on
  each call
• First time, Web Service joins session
• SIP server manages session
• e.g. when client says bye bye to SIP server,
  server sends bye bye to web service

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Implementation

• Added session management to Apache Axis server
• Demonstration built for Online Video Shopping Web
  Service

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Transaction management

• Transactions involve techniques like 2-phase
  commit, supporting properties such as ACID
• Web Services have not standardised this
• WS-Coordination
• WS-Transaction
• Complex and still being developed

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SIP Transaction Management

• We have built an ACID Transaction Manager as a
  Web Service
• A transaction is set up as a SIP session between
  the transaction manager and the transaction
  parties
• Demonstration of a bank transfer done

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Conclusion

• Web Services have re-invented the wheel for many
  well-known concepts
• Current Web Service proposals are complex and
  still under development
• SIP is a well-known, standard and simple
  mechanism for session management
• We have shown that re-use of a known concept is
  better than re-invention of the concept
• We have shown that this can be easily used for
  transaction management as well