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UCCS CS 622 - An Efficient and Cache- Friendly Transfer Protocol for the Web

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DHTTP: An Efficient and Cache-Friendly Transfer Protocol for the WebOverviewIntroductionIntroduction Interception CacheIntroduction Performance ImplicationsIntroduction Main Ideas of DHTTPIntroduction UDP vs TCPIntroduction DHTTP Server-established TCP connectionsDHTTP ProtocolDHTTP Protocol Message ExchangeDHTTP Protocol Message Format DescriptionDHTTP Protocol Message FormatSlide 13DHTTP Protocol Channel Selection/AlgorithmDHTTP ImplicationsDHTTP Implications Server Design DescriptionSlide 17DHTTP Implications Server DesignPerformance AnalysisPerformance Analysis SimulationSlide 21Slide 22Slide 23Slide 24Performance Analysis Prototyped Testing ResultsSlide 26Slide 27Slide 28Performance Analysis Performance ComparisonSlide 30Slide 31Future WorkSummary12 Nov 0712 Nov 07CS 622CS 62211DHTTP: An Efficient and Cache-DHTTP: An Efficient and Cache-Friendly TransferFriendly TransferProtocol for the WebProtocol for the WebBy Michael Rabinovich and Hua WangBy Michael Rabinovich and Hua WangPresented by Jerry UseryPresented by Jerry Usery12 Nov 0712 Nov 07CS 622CS 62222OverviewOverview• IntroductionIntroduction• DHTTP protocolDHTTP protocol• Implications of DHTTPImplications of DHTTP• Server designServer design• Performance analysisPerformance analysis• Future workFuture work• SummarySummary12 Nov 0712 Nov 07CS 622CS 62233IntroductionIntroduction• Two issues addressedTwo issues addressed 1) Violation of end-to-end principle by interception 1) Violation of end-to-end principle by interception caches (Web proxies)caches (Web proxies)• Impersonation of origin serversImpersonation of origin servers• Web interactions may be disruptedWeb interactions may be disrupted 2) Performance implications of client-initiated 2) Performance implications of client-initiated TCP (Transmission Control Protocol) as transport TCP (Transmission Control Protocol) as transport protocolprotocol• HTTP generally conceived as file transfer protocolHTTP generally conceived as file transfer protocol• TCP connection overhead, persistence & pipeliningTCP connection overhead, persistence & pipelining12 Nov 0712 Nov 07CS 622CS 62244IntroductionIntroductionInterception CacheInterception Cache12 Nov 0712 Nov 07CS 622CS 62255IntroductionIntroductionPerformance ImplicationsPerformance Implications• TCP connection overhead, persistence & TCP connection overhead, persistence & pipelining penaltiespipelining penalties• Persistent connectionsPersistent connections• Degradation of throughput and increasing connectionsDegradation of throughput and increasing connections• Pipelined transmissionsPipelined transmissions• Server must maintain connections, send responses in Server must maintain connections, send responses in orderorder• Head-of-line delays can occur with slow responsesHead-of-line delays can occur with slow responses12 Nov 0712 Nov 07CS 622CS 62266IntroductionIntroductionMain Ideas of DHTTPMain Ideas of DHTTP• Two main ideas of DHTTP (Dual-Transport Two main ideas of DHTTP (Dual-Transport HTTP protocol)HTTP protocol) 1) Split Web traffic between UDP (User Datagram 1) Split Web traffic between UDP (User Datagram Protocol) and TCPProtocol) and TCP• Client typically sends requests via UDPClient typically sends requests via UDP• Server sends response via UDP or TCPServer sends response via UDP or TCP• Response sizeResponse size• Network conditionsNetwork conditions 2) Server establishes TCP connection to client2) Server establishes TCP connection to client12 Nov 0712 Nov 07CS 622CS 62277IntroductionIntroductionUDP vs TCPUDP vs TCP• UDP use for short responsesUDP use for short responses• Reduced number of open server connectionsReduced number of open server connections• Reduced number of TCP connection setupsReduced number of TCP connection setups• DHTTP benefitsDHTTP benefits• Improves client latencyImproves client latency• Fewer Web interactions wait for connectionsFewer Web interactions wait for connections• Increases server capacityIncreases server capacity• Servers manage fewer open connectionsServers manage fewer open connections• Remaining TCP connections reserved for larger objectsRemaining TCP connections reserved for larger objects• Improved utilization of TCP connectionsImproved utilization of TCP connections• Ordering constraints of pipelining doesn’t existOrdering constraints of pipelining doesn’t exist12 Nov 0712 Nov 07CS 622CS 62288IntroductionIntroductionDHTTP Server-established TCP connectionsDHTTP Server-established TCP connections• TCP connection client/server roles reversedTCP connection client/server roles reversed• Some firewall implications (existing Some firewall implications (existing countermeasures suffice)countermeasures suffice)• BenefitsBenefits• Retains end-to-end Internet principleRetains end-to-end Internet principle• True interception cache IP address useTrue interception cache IP address use• Allows arbitrary deployment of interception cachesAllows arbitrary deployment of interception caches• Server-initiated TCP reduces message round trips Server-initiated TCP reduces message round trips (even with initial UDP request)(even with initial UDP request)• Message round trips decreases with UDPMessage round trips decreases with UDP• Bottleneck process removed (server-accepted TCP Bottleneck process removed (server-accepted TCP connections)connections)12 Nov 0712 Nov 07CS 622CS 62299DHTTP ProtocolDHTTP Protocol• Web clients and servers listen on two portsWeb clients and servers listen on two ports• One UDP, one TCPOne UDP, one TCP• Servers use well-known ports (or URL-specified)Servers use well-known ports (or URL-specified)• Clients use ephemeral ports (short-lived, per Clients use ephemeral ports (short-lived, per download)download)• Two channels exist between client and serverTwo channels exist between client and server• UDP used for requests below 1460 bytesUDP used for requests below 1460 bytes• Most HTTP requests metMost HTTP requests met• Server opens TCP connection or reuses open Server opens TCP connection or reuses open one for larger messagesone for larger messages• If TCP request sent by client, server may use itIf TCP request sent by client, server may use it12 Nov 0712 Nov 07CS 622CS 6221010DHTTP ProtocolDHTTP ProtocolMessage ExchangeMessage Exchange(a) HTTP (b) DHTTP over UDP (c) DHTTP over TCP(a) HTTP (b) DHTTP over


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UCCS CS 622 - An Efficient and Cache- Friendly Transfer Protocol for the Web

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