1. MOTIVATIONAs demand for wireless portable access to multimed...We propose to achieve low latency and high reliabi...1.1 Characteristics of windows-based multimedia.Windows-based graphics includes operations like t...Figure 1. A trace of X server pixel traffic measur...Application use of corrupted information is almost...Graphics and video differ from audio, however, in ...Figure 2. Corrupted Windows-based Graphics at 4x10...1.2 Estimate of single-packet latencyIf we insist that only reliable data will be displ...The total one-way latency consists of transmission...Block or convolutional FEC can be added, trading r...1.3 Estimate of multiple-packet latencyWhile the single-packet latency gives a hint of de...Table 1: Latency due to limited bandwidth for 200x...Channel rate (kbit/s)101001000No compression32 sec3.2 sec.32 secCompression by 10:13.2 sec.32 sec32 msCompression by 100:1.32 sec32 ms3.2 msIn summary, FEC is needed to keep the number of re...2. MULTIPLE-DELIVERY TRANSPORT SERVICETechniques for improving on the raw BER of an inhe...The multiple-delivery transport service is illustr...Figure 3. General Multiple-Delivery Transport Serv...Multiple delivery is a transport service, as disti...Multiple-delivery transport service can subsume bo...Table 2: Multiple-delivery transport service eleme...Source to transportTransport to destinationFieldSubfieldsFieldSubfieldsApplication data unit (ADU)ADU headerApplication data unit (ADU)ADU headerADU payloadADU payloadADU correlation labelADU sequence numberADU flow headerTo support multiple delivery, configuration inform...We now describe some particulars of the proposed t...2.1 Application-level framingFigure 4. Application-level framing is needed to s...Because of the delivery of corrupt packets, messag...Each ADU is partitioned into two elements: the ADU...2.2 ADU sequence numbersInternally, the transport service will associate a...2.3 Implicit annihilation of stale ADU’s.An optional primitive of the transport service is...Figure 5. Implicit annihilation uses correlation l...As an example of the correlation label, it could b...The destination application must be able to identi...2.4 Traffic shaping of retransmissionsAs will be mentioned in Section 3, the desirable s...Figure 6. Traffic shaping of retransmissions: (a) ...2.5 Flow headerAs described in [22], it is important for a source...3. EXAMPLE: X WINDOWS SERVERWhile a multiple delivery transport service has no...We have modified an X11 Windows Release 6 server t...There are many benefits to spreading retransmissio...To emulate asymptotically reliable delivery, we im...4. PROTOCOL IMPLEMENTATION ISSUES: LEAKY ARQThe implementation of a multiple-delivery transpor...One configuration option for the multiple delivery...The other option in multiple delivery service is a...Classical ARQ retransmission schemes include Selec...4.1 Detecting ADU loss and corruptionAn ADU that is never delivered is said to be lost,...Figure 7. Error detection is performed separately ...Packet loss and corruption due to bit errors can b...If the ADU payload is corrupted, the ADU may be de...4.2 Successive refinement via packet combiningA key property of the multi-version service model ...Packet combining has been incorporated within sing...Leaky ARQ modifies “ARQ with packet combining” to ...Packet combining at the receiver can take several ...Packet combining can be performed either at the gr...Caching requirements for the receiver’s packet com...4.3 Segmentation of ADU’sBecause of application-level framing, leaky ARQ is...Figure 8. Retransmission granularity. (a) Segment ...Internal to the protocol we define an ADU segment....The payload CRC is also embedded within the segmen...Another field in the header indicates the overall ...Both the payload CRC and message length fields sha...The second property shared by these two fields is ...4.4 Non-sliding windowsThe sliding windows characteristic of most ARQ pro...4.5 ARQ AcknowledgmentsThe granularity of acknowledgments directly depend...The relationship between the granularity of acknow...In order to support abbreviated retransmission hea...4.6 Other issuesWe have left many unresolved issues for future wor...5. CONCLUSIONSWe have presented a multiple-delivery transport se...6. REFERENCES[1] C. Kantarjiev, A. Demers, R. Frederick, R. Kri...[2] E. Brewer, T. Burd, F. Burghardt, A. Burstein,...[3] D. Weissman, A. Levesque, R. Dean, “Interopera...[4] A. Baier, U. Fiebig, W. Granzow, W. Koch, P. T...[5] D. 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Messers...[24] Y. Chang, C. Leung, “On Weldon’s ARQ Strategy...[25] D. Towsley, “The Stutter Go Back-N ARQ Protoc...[26] M. A. Jolfaei, “Stutter XOR Strategies: A New...[27] V. Rhee, J. Gibson, “Rate-constrained two-lay...[28] D. Raychaudhuri, H. Sun, R. Girons, “ATM tran...[29] P. Sindhu, “Retransmission Error Control with...[30] J. Metzner, D. Chang, “Efficient Selective Re...[31] D. Chase, P. Muellers, J. Wolf, “Application ...[32] J. Hagenauer, “Rate-Compatible Punctured Conv...[33] S. Kallel, D. Haccoun, “Generalized Type II H...[34] S. Wicker, “Adaptive Rate Error Control Throu...[35] B. Harvey, S. Wicker, “Packet Combining Syste...[36] R. Cam, C. Leung, C. Lam, “A Performance Comp...[37] S. Kallel, C. Leung, “Efficient ARQ Schemes w...Asymptotically Reliable Transport of Multimedia/Gr...Richard Y. Han and David. G. MesserschmittDepartment of Electrical Engineering and Computer ...University of California at