1. Master Thesis Presentation Implementation and Performance Analysis of a UDP Binding for SOAP Fahad Aijaz [email_address] Supervised by: Prof. Dr. -Ing. B. Walke Dipl.-Ing. Guido Gehlen Chair of Communication Networks RWTH Aachen, Germany Wednesday, February 8, 2006

6. 4: Web Services Based Middleware Architecture Middleware Glue (IT World) Computing (Telco World) Communication WS-Discovery, WS-Addressing, WS-Security etc. Middleware to support developers Can be bound to either session or transport layer protocols (Transport Neutral)

7. 5: Mapping to OSI Reference Model Transport Support for Mobile and Desktop Clients Algorithm Recommendation by SOAP-over-UDP Specification Based on the unique MessageId in SOAP Messages and WS-Addressing Selective Repeat (Explicit Request) ARQ is realized by introducing additional header in UDP datagram. 3 (N) 4 (T) 5 (S) 6 (P) 7 (A) HTTP TCP IP UDP SOAP HTTP-Binding Unreliable UDP-Binding Reliable UDP-Binding SOAP Session Management SOAP Session Management ARQ

8. 6: SOAP Message Exchange Patterns (MEP) and Service Access Points (SAP) UDP SOAP UDP-SAP Reliable Binding Unreliable Binding WS-Sec. WS-Addr. SOAP Parser Rel. One-Way SAP Rel. Req-Resp SAP Unrel. One-Way SAP Unrel. Req-Resp SAP One-Way Req-Res SOAP MEPs  Core SOAP Parser providing 4 SAPs to upper layers, by using WS-Addressing properties

12. 7: Selective Repeat ARQ (Explicit Request)  Selective Repeat attempts to retransmit only those packets that are actually lost. Required due to packet size constraint.  Explicit NACK is sent for only lost packets.  Packet assembly is done at the receiver when all packets are received and buffered in correct sequence.  Segmentation is done by the sender in adjustable sized chunks of bytes. Seq. No. Flag S, C, E UUID UDP Headers SOAP Data Current Time [msec], IP-Addr. In HEX , Object hash code , Random Number

13. 8: Mobile Web Service Server Architecture Server UI decoupled from the business logic. Common for both listeners.

14. 9: Performance Analysis (Measurements) 9.1: RTT: Reliable UDP Vs HTTP Including HTTP/TCP Processing Overhead Major Selective Repeat latencies are discarded, since not comparable to low-level TCP ARQ Java performance, memory and bytecode loading time overhead exists Mean RTT of the Reliable UDP ≈ 20-25% of RTT of the HTTP (On laptop)

15. 9.2: RTT: Unreliable UDP Vs Reliable UDP Extra time for NACK processing, additional headers ... No re-transmission in this case

17. 10: Analytical Model of Selective Repeat ARQ over UDP P lost : Probability for loss of datagram n D : Number of datagrams to be send T D : Transmission time of a datagram T timeout : Timeout T NACK : Transmission time for NACK n lost : Number of lost datagrams n x : Number of datagrams except last one excluding the last one CASE: No datagram loss CASE: Last datagram lost CASE: n lost datagrams lost Mean Transmission Latency of sending SOAP over reliable UDP using selective-repeat ARQ

18. 10.1: Comparison With HTTP Model Used Model Used Without Loss Probability With Loss Probability Model Used Model Used HTTP UDP Analytically the UDP performance ≈ 25% of the TCP Analytically the UDP performance ≈ 17% of the TCP

19. 11: Theses  Web Service invocation over reliable UDP can be used as a substitute to the default SOAP/HTTP binding in mobile communication environment for better performance.  The reliable UDP with selective-repeat ARQ (explicit request) as a reliability mechanism is approximately 20-25% faster than the HTTP on average.  Unreliable UDP binding enables the sending of multicast probe messages in ad-hoc environments to consume and announce Mobile Web Services hosted by and to its peers respectively.  The analytical model can be used to calculate the mean transmission latency of the SOAP messages over UDP in mobile communication environment.  The analytical model has been validated against the measurements.

22. Selective Repeat ARQ State Machine