An Overlay Network Providing Application-Aware Multimedia Services Maarten Wijnants Bart Cornelissen Wim Lamotte Bart De Vleeschauwer

10/10/2006AAA-IDEA20062 Problem Statement Increased use of real-time streaming of multimedia content in networked apps –Efficient user communication –In the future: also more “enhanced” uses Consequence: growing demand for services that can be applied on multimedia streams –Continuously diversifying market of end-user computation devices –Sometimes also requested by applications

10/10/2006AAA-IDEA20063 Problem Statement What is the optimal location to provide/ implement these multimedia services? –At sender-side? –At receiver-side? –Inside the transportation network, in the delivery path between sender and receiver Benefits of in-network service provision –Senders need to transmit only 1 version/ quality of a multimedia stream –Destinations receive (near-)optimal stream

10/10/2006AAA-IDEA20064 Our Overlay Network Our overlay network consists of interconnected proxy servers Goals –Concurrently provide powerful services for a wide variety of networked applications –Extensibility This is achieved by combining –A generic base layer –A plug-in mechanism which allows deployment of application-aware services

10/10/2006AAA-IDEA20065 Outline Introduction –Problem Statement –Our Overlay Network Software Architecture Example Overlay Services –Sound Mixer Service –Face Detection Service –Performance Evaluation Conclusions Future Work

10/10/2006AAA-IDEA20066 Software Architecture Proxy servers run on the GNU/Linux OS –Implemented as a userspace process –Uses iptables/netfilter to transfer packets from kernel- to userspace and vice versa Proxy process consists of 2 subsystems –Generic base layer Application independent –Plug-in manager through which additional functionality can be added to the proxy Plug-ins are application-aware Each multimedia service is implemented as plug-in

10/10/2006AAA-IDEA20067 Software Architecture Generic base layer –Basic user management functionality –Moves packets between kernel- and userspace Plug-in manager –Enables/manages the installation of plug-ins –Plug-ins can register interest for certain network streams –Intercepted network packets are handed over to the plug-ins which have registered interest In the order in which they have registered interest –Checks the packet verdict returned by plug-ins

10/10/2006AAA-IDEA20068 Software Architecture

10/10/2006AAA-IDEA20069 Sound Mixer Service EDM NVE framework –Supports real-time audio (and video) communication between users –Originally developed for the PC platform Sufficient processing power PC users receive all audio streams sent out by clients currently located in their Area of Interest (AoI) –Recently also ported to mobile devices Processing requirements associated with receiving and decoding multiple audio streams simultaneously and mixing them together locally is too high Decision to limit number of audio streams a mobile client can receive to one

10/10/2006AAA-IDEA Sound Mixer Service Substantial difference between audio experience available to desktop and mobile NVE users Sound mixer service bridges this gap –Maintains separate mixing unit for every client –Ensures proxy receives necessary input audio streams –Incoming audio packets are decoded and subsequently transferred to the correct mixing units –Also considers positional information to generate a 3D spatialized output signal

10/10/2006AAA-IDEA Sound Mixer Service + + = Advantages –Improves the audio experience provided to mobile NVE users –No additional bandwidth or processing requirements are introduced at client- side Drawback –Sound mixer service introduces a small amount of additional delay

10/10/2006AAA-IDEA Face Detection Service iConnect meeting system –Goal = enable both collocated and geographically dispersed participants to meet in an efficient manner –Computer-augmented meeting room containing a touch-sensitive digital whiteboard Acts as shared workspace (display documents, …) Each participant is represented as an avatar –Remotely connecting to iConnect also possible Shared workspace is displayed on the remote screen Same collaboration possibilities –Audio and video conferencing support

10/10/2006AAA-IDEA Face Detection Service Video conferencing streams of remote participants need to be displayed on whiteboard –Can consume a lot of screen space! Face detection service –Intercepts video conferencing streams –Decodes these streams and applies face detection –Result is encoded at much lower resolution and framerate and transmitted to the shared whiteboard as “video” avatar

10/10/2006AAA-IDEA Face Detection Service Need for displaying video stream of remote users is eliminated in many cases –Feedback provided by video avatars suffices to guarantee meeting effectiveness Saves screen space on the shared whiteboard –Scarce resource! –Freed up screen space can be used to display other content

10/10/2006AAA-IDEA Performance Evaluation Average CPU UtilizationMaximum CPU Utilization Sound Mixer Service1,5 %4 % Face Detection Service7,5 %20 % Both services simultaneously 9,5 %22 % Performance of the 2 overlay services was tested on a single proxy server –Intel Pentium D 3 Ghz –Linux kernel Simultaneous use of services introduces nearly no overhead!

10/10/2006AAA-IDEA Conclusions I have presented our overlay network consisting of interconnected proxy servers –Generic base layer –Plug-in mechanism enables installation of application- aware services  Overlay network can provide powerful and efficient services for a wide variety of networked applications  Need for deploying and managing a separate overlay network for each distinct networked application is eliminated –Is confirmed by the experimental results produced by the two presented overlay services

10/10/2006AAA-IDEA Future Work Improve the efficiency of the face detection service Implementation of an overlay routing plug-in –Would enable proxy servers to route packets around failing or congested network links –Proxy-to-proxy communication would become more resilient to network errors Beneficial for end-user Continue integration in iConnect system

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