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Dos presentation by ahlam shakeel Dos presentation by ahlam shakeel Presentation Transcript

  • Distributed Operating System Presented By Ahlam Ansari Ahlam Ansari 1
  • ABSTRACT•In today’s world streaming media plays a vital role, with the advancedtechnologies recently developed in the areas of high-speed networks andmultimedia, video-on- demand service (VOD) is considered as the emergingtrend in home entertainment, as well as in education, banking, homeshopping, and interactive games. Better quality video, as well as efficient wayto send and receive them is necessary. Streaming media is multimedia that isconstantly received by and presented to an end-user while being delivered bya streaming provider. With streaming, the client browser or plug-in can startdisplaying the data before the entire file has been transmitted. Quality ofvideo, streaming time of video and the streaming protocols that we use formake a lot of difference. Hence we present two different types of streamingmedia protocols, HTTP Live Streaming (HLS) and Real Time Streaming Protocol(RTSP) and their comparison, a DoS resilient self healing video architecture toprovide a better quality video and a survey on different VoD Batchingtechniques.. Ahlam Ansari 2
  • INTRODUCTION•HTTP Live Streaming (HLS) is an HTTP-based media streaming communicationsprotocol implemented by Apple Inc.It works by breaking the overall stream into a sequence of small HTTP-based filedownloads, each download loading one short chunk of an overall potentiallyunbounded transport stream. Ahlam Ansari 3
  • The Real Time Streaming Protocol (RTSP) is a network control protocol designedfor use in entertainment and communications systems to control streaming mediaservers.RTSP was developed by the Multiparty Multimedia Session Control WorkingGroup (MMUSIC WG) of the Internet Engineering Task Force (IETF) Ahlam Ansari 4
  • Video request is delayed for a period of time so that more requests for the samevideo are collected. The batch of requests is then served by a multicast videostream.The major drawback of this scheme is that the customers have to wait for abatching interval until the video is started to play. Hence, it may increase thecustomer dissatisfaction if the waiting interval is too long. Ahlam Ansari 5
  • STREAMING PROTOCOLS Ahlam Ansari 6
  • HLS ARCHITECTURE Ahlam Ansari 7
  • 1. Media Encoder:The Encoder encodes the video/audio. Videos are compressed into H.264/MPEG-4format and the audio is encoded using advance audio coding. The video or audioformat is encapsulated in MPEG 2.Transport Stream is specified in MPEG-2 Part 1, Systems (formally known asISO/IEC standard 13818-1 or ITU-T Rec. H.222.0) [3][4][5]. Transport streamspecifies a container format encapsulating packetized elementary streams, witherror correction and stream synchronization features for maintaining transmissionintegrity when the signal is degraded.Program stream is a container format for storage applications specified in MPEG-1Systems and MPEG-2 Part 1. A program stream contains only one content channeland is suited to authoring and storage not broadcasting. Contrast with transportstream, which is designed to address the delivery of the content. Ahlam Ansari 8
  • 2. Stream SegmenterThe Segmenter segments the video/audio in small duration segmentation. All thesegments are placed in separate files. For protection purpose, the Segmentermight encrypt the segments and create a key file. Ahlam Ansari 9
  • 3. Distribution SystemDistributed System is a regular HTTP Server. It could be Apache or any embeddedserver. Segments are stored with .ts extension and the index files are storedwith .m3u8 extension. The file format of index is as follows: Ahlam Ansari 10
  • 4. Client:The client gets all the videos or audios through a HTTP connection. HTTP creates a sessionbetween the client and the file at the DS. The session can be either a Live Stream Broadcastsession or a Video on Demand Session. A) Live Stream Broadcast Session LSD contains an index file that is dynamic in type and is continuously updated and refreshed. It includes a moving window of segments. B) Video on Demand Session VoD contains an index file that is static in type and it contains all the segments of the file. [2] Ahlam Ansari 11
  • Deploying HTTP Live StreamingStep 1: Creating a HTML PageStep 2: Configuring a Web ServerStep 3: Validating the StreamsStep 4: downloade video / audio at client side Ahlam Ansari 12
  • Step 1: Creating a HTML PageThe easiest way to distribute HTTP Live Streaming media is to create a webpage thatincludes the HTML5 <video> tag, using an .M3U8 playlist file as the video source. Anexample is shown below:<html><head> <title>HTTP Live Streaming Example</title></head><body> <video src="http://devimages.apple.com/iphone/samples/bipbop/bipbopall.m3u8" height="300" width="400" > </video></body></html> Ahlam Ansari 13
  • Step 2: Configuring a Web Server•HTTP Live Streaming can be served from an ordinary web server; no specialconfiguration is necessary, apart from associating the MIME types of the filesbeing served with their file extensions.Configure the following MIME types for HTTP Live Streaming: File Extension MIME Type .M3U8 application/x-mpegURL or vnd.apple.mpegURL .ts video/MP2T Ahlam Ansari 14
  • Step 3: Validating the Streams•The media stream validator tool is a command-line utility for validating HTTP LiveStreaming streams and servers . The media stream validator simulates an HTTPLive Streaming session and verifies that the index file and media segmentsconform to the HTTP Live Streaming specification. It performs several checks toensure reliable streaming. If any errors or problems are found, a detaileddiagnostic report is displayed. You should always run the validator prior to serving a new stream or alternatestream set. The media stream validator shows a listing of the streams you provide,followed by the timing results for each of those streams. (It may take a fewminutes to calculate the actual timing.) An example of validator output follows. Ahlam Ansari 15
  • •Validatinghttp://devimages.apple.com/iphone/samples/bipbop/gear3/prog_index.m3u8against iPhone OS 3.1.0Average segment duration: 8.77 secondsAverage segment bitrate: 510.05 kbit/sAverage segment structural overhead: 96.37 kbit/s (18.89 %)Video codec: avc1Video resolution: 480x360 pixelsVideo frame rate: 29.97 fpsAverage video bitrate: 407.76 kbit/sH.264 profile: BaselineH.264 level: 2.1Audio codec: aacAudio sample rate: 22050 HzAverage audio bitrate: 5.93 kbit/s Ahlam Ansari 16
  • Step 4: Download video/audio at client sideHow actually the video / audio is downloaded at client side [8]1. Download the wowza URL (playlist)2. Display the contents of the file3. Download the first/second playlist url4. Display the contents5. wget the key URL6. wget the ts file sequenceIf the file is encrypted7. Hexdump the key8. Using calc get the HEXADECIMAL Value of "MEDIA-SEQUENCE", to get IV -> 95 = 5F using openssl decrypt the file9. Now play the file "decr_tmp.ts" using "VLC media player" Ahlam Ansari 17
  • RTSP vs. HTTPInteroperabilityRTSP is an interoperability disaster. None of the three big commercialimplementations seem to abide by the standard (Microsoft Windows Media,Apple/Darwin and RealMedia), and writing a client stack that can handle all ofthem, plus the open-source servers properly, is tough to say the least.HLS is widely interoperable. It has countless implementations both on the serverand client sides. It has Apache as a de facto reference implementation that everyclient can interoperate with. Ahlam Ansari 18
  • •Transport Layer ProtocolRTSP uses UDPHTTP uses TCP•SeekingRTSP, the server takes care of itWith HLS, client will probably be the one Ahlam Ansari 19
  • • Play and PauseRTSP does have built-in PLAY and PAUSE commands, which namely respectivelyplay and pause the media.There are several ways you can pause a stream with HTTP: . Stop de-queuing data from the TCP session, and let the TCP stacks handle pause with TCP congestion control, until you want to resume, . Shutdown/reset the TCP session to pause, and start a new one to resume Ahlam Ansari 20
  • •CongestionIn case of network congestion or packet loss, RTSP will cause part of the stream to be lost.In case of network congestion or packet loss, HLS will never cause part of the stream to belost.•You TubeRTSP is used in YouTube Mobile.HLS is used on You Tube main site. Ahlam Ansari 21
  • •ReliabilityRTSP only carries the signaling reliably.HTTP conveys both signaling and payload reliably. •NAT Traversal RTSP just does not work, without ugly TCP encapsulation that makes it look like HTTP. HLS just works through Network address translation Ahlam Ansari 22
  • •Firewall traversalNot so many firewalls handle or allow RTSP. RTSP has theoretical firewall traversalcapability.HLS goes through almost any firewall. Even from tightly restricted Intranets, youcan always find an outgoing HTTP proxy to use. Ahlam Ansari 23
  • VoD BATCHING Ahlam Ansari 24
  • Basic Video-on-Demand (VoD) System Ahlam Ansari 25
  • •I n the basic architecture of a VoD system consists of: Video Encoder Video Server Directory Server Client NetworkThe Network connects all the other VoD system components together as they aredistributed geographically. The encoder accepts the video input and then uploads it on thevideo server after compressing/encoding the video stream received. The video server is aserver with huge amount of disk space to accommodate day by day increasing videos insegments, not as a single file. The directory server keeps the index file which points to allthe segments of those videos in video server, and these videos are published to the client sothat they can access it. The figure below shows the architecture of basic VoD system. Ahlam Ansari 26
  • Types of Streaming1. RealtimeThe data have a pre-determined sequence and time of presentation.For example, video and audio.2. Non-RealtimeThe data does not have presentation time requirement.For example, progressive JPEG. Ahlam Ansari 27
  • Types of Video Services1. Broadcast / Multicast Video2. Near-Video-on-Demand3. True Video-on-Demand Ahlam Ansari 28
  • Broadcast / Multicast Video Ahlam Ansari 29
  • •The multicast facility of modern communication networks [12] offers an efficientmeans of one-to-many data transmission. The basic idea is to avoid retransmittingthe same packet more than once on each link of the network by having branchrouters duplicate and then send the packet over multiple downstream branches.Multicast can significantly improve the VoD performance.Passive receive with no control except selecting the channels. One channel isneeded per movie / programme. Ahlam Ansari 30
  • Near-Video-on-Demand Ahlam Ansari 31
  • •Near video on demand is a video delivery service that allows a customer to selectfrom a limited number of broadcast video channels when they are broadcast.NVOD channels have pre-designated schedule times and are used for pay-per-viewservices. Passive receive with limited controls. System response time inverselyproportional to number of required channels [12]. Ahlam Ansari 32
  • True Video-on-Demand Ahlam Ansari 33
  • •True Video-on-Demand system uses one dedicated channel for each servicerequest, offering the client the best TVoD service. However, such a system incursvery high costs, especially in terms of storage-I/O and network bandwidths. Fullinteractive controls, like pause/resume, seeking, fast forward, etc . Ahlam Ansari 34
  • Comparisons Broadcast Video True Video-on- Near-Video-on-Demand Demand (Pay-Per-View) Yes, but limited to a Yes, but limited to a fewSelect video? Yes few channels programmesSelect time to No Yes (limited to fixed time slots) Anytime watch? Interactive? No None or very little VCR-like controlNo. of Viewers Unlimited Unlimited LimitedCost / Viewer Low Medium High Ahlam Ansari 35
  • LITERATURE SURVERYSome authors have worked on reducing the start-up delay inmulticast delivery systems as the major problem with the batchingapproach is that it introduces a significant start-up delay to thecustomer, which in fact contradicts the idea of on-demand service. Ahlam Ansari 36
  • Batching policy for video-on-demand in multicast environmentW.-F. Poon, K.-T. Lo and J. Feng Says:•Piggybacking approachIt merges different requests together by adjusting the play-out rate of the videosso as to reduce the start-up delay of the system. The greedy policy attempts tomerge the requests as many times as possible during the entire video session inorder to save more bandwidth.If the play-out rate is adjusted in real time, a specialized hardware is required tokeep up with the demand. If a replica of the video is generated in advance, since itis possible that requests can be merged during the entire video session, very largedisk storage is required at the server side. Ahlam Ansari 37
  • •Double-rate (DR) batching policy  Considering the waiting time (conventional batching approach) of the customersand the complexity (piggybacking approach) of the VoD system, we develop adouble-rate (DR) batching scheme that attempts to merge the customer requestsin an improvised manner by means of buffering. Instead of changing the play-outrate of the video, we double the transmission rate so that the trailing customersare able to catch up with the leading customer. Once the transmitting frames ofthe customers are the same, they are grouped together and served by a multicaststream.A new batching scheme has been proposed to reduce the start-up delay of VoDservices in a multicast delivery system. When a new customer arrives, a unicaststream is immediately opened for the new request so that the customer does nothave to wait. The transmission rate is then doubled so that the customer can catchup with the previous multicast stream. Ahlam Ansari 38
  • Advantage:A new batching scheme has been proposed to reduce the start-up delay of VoDservices in a multicast delivery system. When a new customer arrives, a unicaststream is immediatelyopened for the new request so that the customer does not have to wait. Thetransmission rate is then doubled so that the customer can catch up with theprevious multicast stream.Drawback:It is shown that the DR batching scheme outperforms the greedy policy of thepiggybacking approach only in terms of the bandwidth requirement. As it has fixedbatching time, popularity of the movies affects the performance of the VoDsystem. Ahlam Ansari 39
  • Adaptive Batching Scheme for Multicast Video-On-Demand SystemsW.-F. Poon, K.-T. Lo, Member, IEEE, and J. Feng, Member, IEEE says:•An adaptive algorithm is developed for providing true video on demand (VoD)services in multicast environment. If the batching time is wrongly estimated, theperformance of the system will be greatly degraded. This algorithm tries todynamically find the optimal batching time by the newly updated arrival rate so asto minimize the bandwidth requirement.Adaptive algorithm enhances the double-rate batching policy so that thepopularity of the movies will not affect the performance of the VoD system as thebatching time can be adjusted. Ahlam Ansari 40
  • •Advantage:Adaptive algorithm enhances the double-rate batching policy so that thepopularity of the movies will not affect the performance of the VoD system as thebatching time can be adjusted.Drawback:If the batching time is wrongly estimated, the performance of the system will begreatly degraded. Ahlam Ansari 41
  • Virtual Batching: A New Scheduling Technique for Video-On-Demand ServersSimon Sheu and Kien A. Hua and Ta-Hsiung Hu says:•In a video-on-demand (VOD) environment, batching of requests is often appliedto reduce the I/O demand and increase the availability of VOD services. However,batching unfairly forces first comers to wait for subscribers arriving late at thebatch. Some of these victims may become impatient and decide to renege. Toaddress this issue, we introduce a chaining technique which allows a client stationbeing served to forward its video data to other client stations, which requestedthe same video, at a slightly later time.Thus, chaining enjoys the benefit of batching without its side effect of causing longaccess latencies. By combining batching and chaining, we also design a schemecalled Virtual Batching.This property reduces the service latencies and therefore improves the renegingprobability. This characteristic addresses the network-I/O bottleneck problemfacing today’s media servers. Ahlam Ansari 42
  • •Advantage:First comers no longer have to wait for requests arriving late at the batch. Thisproperty reduces the service latencies and therefore improves the renegingprobability. This characteristic addresses the network-I/O bottleneck problemfacing today’s media servers.Drawback:This policy makes use of Batching as well as Chaining hence it is more complex.The clients should also have chaining and forwarding mechanism in order toimplement Virtual Batching policy. Ahlam Ansari 43
  • DoS RESILIENCE SELFHEALING ARCHITECTURE Ahlam Ansari 44
  • Ahlam Ansari 45
  • •The self-healing architecture comprises of four main components: performance analyzer, repair planner, sensors and effectors. The performance analyzer takes:(1) server performance parameters collected by sensors to detect performancedegradation; and (2) service parameters collected from synthetic sessionsestablished with the server. It detects performance degradation and pinpoints theresources responsible for these anomalous states. The repair planner takesnotifications issued by the performance analyzer, decides the best repair action tobe executed (e.g., session migration and protocol-level redirection of sessions) andplans the repair to be executed by effectors. Ahlam Ansari 46
  • •Sensors are responsible for collecting performance parameters. Two types ofsensors are devised server-side: (1) pace sensors; and (2) resource sensors. Pace sensors capture delays on accomplishment of scheduling of video content. Theunit of scheduled work depends on server implementations and streamingprotocols. In RTSP streaming the packet is the unit of work to be scheduled andtransmitted. Other video standards require coarse-grain performance metrics atserver: HTTP Streaming and HTTP Adaptive streaming. They fragment videoobjects into slices that are selectively requested by clients and downloadedsimilarly to other web objects. Ahlam Ansari 47
  • Conclusion•YouTube uses HTTP/TCP to buffer video into the flash player on its main site. Thevideo is stored on Google Videos content distribution network. Its not streamedas much as just sent as fast as possible to your computer. However, for 3g mobilehandsets, m.youtube.com uses RTSP to stream video. So, YouTube uses bothtransfer methods [10]. Another thing to consider is that YouTube is popularbecause "it just works". RTSP isnt always supported well through routers, whichwould prevent that for use on the desktop. Also, m.youtube.com doesnt streamthe same video file as youtube.com. Most YouTube videos are not streamed, butprogressively download over HTTP. A small number of partner videos are securelystreamed, using RTMPE. Ahlam Ansari 48
  • •DR batching scheme reduce the start-up delay of VoD services in a multicast deliverysystem. When a new customer arrives, a unicast stream is immediately opened for the newrequest so that the customer does not have to wait. The transmission rate is then doubledso that the customer can catch up with the previous multicast stream.Adaptive batching scheme enhances the double-rate batching policy so that the popularityof the movies will not affect the performance of the VoD system as the batching time canbe adjusted.Virtual Batching scheme generalize the conventional batching methods to allow requestsarriving at a virtual batch to receive immediate services. First comers no longer have to waitfor requests arriving late at the batch. This property reduces the service latencies andtherefore improves the reneging probability. This characteristic addresses the network-I/Obottleneck problem facing today’s media servers. Ahlam Ansari 49
  • Reference[1] Http://develpr.apple.com/library/ios/#documentation/NetworkingInternet/Conceptual/StreamingMediaGuide/Introduction/Introduction.html[2] http://www.slideshare.net/DSPIP/apples-live-http-streaming[3] ITU-T (2006-05). "H.222.0 Summary". Retrieved 2010-06-03.[4] ITU-T. "H.222.0 : Information technology - Generic coding of moving pictures andassociated audio information: Systems". Retrieved 2010-06-03.[5] ISO/IEC 13818-1:2000 - Information technology -- Generic coding of moving pictures and audio information: Systems, neuron2.net, 2000-12-01, retrieved2010-06-03[6] http://www.remlab.net/op/vod.shtml Ahlam Ansari 50
  • [7]http://developer.apple.com/library/ios/#documentation/NetworkingInternet/Conceptual/StreamingMediaGuide/DeployingHTTPLiveStreaming/DeployingHTTPLiveStreaming.html%23//apple_ref/doc/uid/TP40008332-CH2-DontLinkElementID_29[8] http://www.wowza.com/forums/showthread.php?13363-Is-it-possible-to-deploy-Apple-HTTP-Live-streaming-(HLS)-encryption-on-wowza-server/page2[9] Carlos A S Cunha, “Application of a Self-Healing Video-Streaming Architecture to RTSPServers”, 2011 IEEE International Symposium on Network Computing and Applications.[10] http://answers.yahoo.com/question/index?qid=20071126005233AA4h3Ox[11] W.-F. Poon, K.-T. Lo and J. Feng, “Batching policy for video-on-demand in multicastenvironment”, ELECTRONICS LETTERS 20th July 2000 Vol. 36 No. 15[12] Huadong Ma and Kang G. Shin, ”Multicast Video-on-Demand Services”, ACMSIGCOMM Ahlam Ansari 51
  • THANK YOUFor your Attendance and Attention Ahlam Ansari 52