Distributed Multimedia Systems Tarek Elshaarani Vahid Rafiei Informationsteknologi
Distributed Multimedia Systems Tarek Elshaarani Vahid Rafiei
Informationsteknologi Examples of DMMS And more! Institutionen för informationsteknologi | www. it. uu. se
Informationsteknologi Introduction Definition: "A distributed multimedia system (DMS) is an integrated communication, computing, and information system that enables the processing, management, delivery, and presentation of synchronized multimedia information with quality-ofservice guarantees. " http: //encyclopedia. jrank. org/articles/pages/6729/Distributed-Multimedia-Systems. html Institutionen för informationsteknologi | www. it. uu. se
Informationsteknologi Characteristics Delivering the streams of multimedia data Audio samples, Video frames To meet the timing requirements Qo. S (Quality of Service) Flexibility (adapting to user needs) Availability Scalability Institutionen för informationsteknologi | www. it. uu. se
Informationsteknologi Factors that affect a system Server bandwidth Cache space Number of copies The number of clients Institutionen för informationsteknologi | www. it. uu. se
Informationsteknologi Basic Schema Institutionen för informationsteknologi | www. it. uu. se
Informationsteknologi Typical infrastructure components for multimedia applications Institutionen för informationsteknologi | www. it. uu. se
Informationsteknologi Institutionen för informationsteknologi | www. it. uu. se
Informationsteknologi Different Designs and Architectures Database Proxy/information servers Clients Wired or wireless networks Institutionen för informationsteknologi | www. it. uu. se
Informationsteknologi Approaches Proxy-based approach Parallel or clustered servers approach Varies based on clip duration, number of clients, bandwidth available, etc Caching Institutionen för informationsteknologi | www. it. uu. se
Informationsteknologi Quality of Service (Qo. S) DMMS are real-time systems as data must be delivered on time Not critical – Some flexibility exists Loss is acceptable when resync is possible. “Acceptable” service is measured by: Bandwidth (Throughput) Latency (Access time) Data Loss Rate (Acceptable loss ratio) Institutionen för informationsteknologi | www. it. uu. se
Informationsteknologi Qo. S Management “Qo. S Management” Process of managing resources to meet the Acceptable service criteria. Resources include: CPU / processing power Network bandwidth Buffer memory(on both ends) Disk bandwidth Other factors affecting communication Institutionen för informationsteknologi | www. it. uu. se
Informationsteknologi Why do we need Qo. S? As multimedia becomes more widespread, strain on network increases! Networks provide insufficient Qo. S for distribution of multimedia. Ethernet (wired or wireless) is best effort Collisions, data loss, congestion, etc. For some multimedia applications, synchronization is vital. Institutionen för informationsteknologi | www. it. uu. se
Informationsteknologi Qo. S Managers Software that runs on network nodes which have two main functions: Qo. S negotiation: get requirements from apps and checks feasibility versus available resources. Admission control: If negotiation succeeds, provides a "resource contract" that guarantees reservation of resources for a certain time. Institutionen för informationsteknologi | www. it. uu. se
Informationsteknologi Ways to achieve Qo. S Buffering (on both ends) Compression More load on the nodes, but that is okay Bandwidth Reservation Resource Scheduling Traffic Shaping Flow Specifications Stream Adaptation Institutionen för informationsteknologi | www. it. uu. se
Informationsteknologi Traffic Shaping Output buffering at the source to keep data flowing smoothly. Two main algorithms: Leaky bucket: guarantees that data flows at a constant rate without bursts - completely eliminate bursty traffic. Token bucket: variation of leaky bucket where tokens are generated to allow for some bursty traffic when bandwidth is unused for a certain period of time. Institutionen för informationsteknologi | www. it. uu. se
Informationsteknologi Traffic Shaping Institutionen för informationsteknologi | www. it. uu. se
Informationsteknologi Flow specifications RFC 1363 defines Qo. S parameters: Bandwidth Latency and jitter constraints Data loss limits Token bucket size Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 3 © Pearson Education 2001 Institutionen för informationsteknologi | www. it. uu. se
Informationsteknologi Stream Adaptation Adjust the data flow based on resource availability. Scaling Scale down content at the source to reduce bandwidth required: Audio: reduce the rate of audio sampling or dropping channels Video: reduce resolution, number of pixels, change compression algorithm, color depths, color spaces, and combinations. Filtering One target asks the source to reduce quality for all the clients, even if some can handle higher quality. Suitable for more than one simultaneous target and guarantees the same Qo. S for all the targets Institutionen för informationsteknologi | www. it. uu. se
Informationsteknologi Applications of DMMS Digital Libraries Distance learning Teleconferencing Video on Demand (Vo. D) & Video on Reservation (Vo. R) Pay Per View Audio Streaming Video Streaming E-commerce P 2 PTV Institutionen för informationsteknologi | www. it. uu. se
Informationsteknologi Voddler Video on Demand Pay Per View Long movies Requires high bandwidth Hybrid P 2 P distribution network Institutionen för informationsteknologi | www. it. uu. se
Informationsteknologi Voddler http: //en. wikipedia. org/wiki/File: P 2 ptv. PNG Institutionen för informationsteknologi | www. it. uu. se
Informationsteknologi You. Tube, Platform Apache Python Linux My. SQL Psyco lighttpd for video instead of Apache, because of overheads Institutionen för informationsteknologi | www. it. uu. se
Informationsteknologi You. Tube, Serving Video Each video hosted by a mini-cluster. Each video is served by more than one machine. Most popular content is moved to a CDN (content delivery network) Less popular content (1 -20 views per day) uses You. Tube servers in various proper sites Institutionen för informationsteknologi | www. it. uu. se
Informationsteknologi You. Tube, Data Center Strategy Used manage hosting providers at first. Living off credit cards so it was the only way. Managed hosting can't scale with you. You can't control hardware or make favorable networking agreements. So they went to a colocation arrangement. Now they can customize everything and negotiate their own contracts. Videos come out of any data center. Not closest match or anything. If a video is popular enough it will move into the CDN. Institutionen för informationsteknologi | www. it. uu. se
Informationsteknologi Questions? Institutionen för informationsteknologi | www. it. uu. se
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