Maarten Wijnants Wim Lamotte Outline

The NIProxy: a Flexible Proxy Server Supporting Client Bandwidth Management and Multimedia Service Provision

• Maarten Wijnants

• Wim Lamotte

Outline

• Introduction

• System Overview

• Software Architecture

• Bandwidth Distribution Algorithm

• An Example Service: Video Transcoding

• Evaluation

• Test Application
• Experimental Results

• Conclusions & Future Work

Introduction

• Popularization of multimedia content and real-time multimedia streaming

• E.g. multiplayer games: verbal communication through voice streaming
• E.g. academic applications: also video communication

• Multimedia streaming requires considerable amount of bandwidth

• Client downstream bw does not always suffice
• Mechanisms are needed to maximize clients’ Quality of Experience (QoE)

NIProxy: System Overview

• The NIProxy

• Network intermediary (a “proxy”)
• Abbreviation for Network Intelligence Proxy
• Goal = introduce more intelligence in the network so that it can deliver MM content to clients more intelligently and efficiently
• Outcome = improved QoE for users

NIProxy: System Overview

• NIProxy introduces 2 kinds of intelligence in the transportation network

• Network awareness
• NIProxy has knowledge of the client’s network link
• Is acquired through periodic network probing
• Current end-to-end throughput, latency, packet loss rate, …
• Also encompasses knowledge of the bandwidth requirements of network streams
• Application awareness
• NIProxy is aware of the application it is serving
• Is acquired through support library called the NILayer
• E.g. relative importance of streams

NIProxy: System Overview

• The NIProxy provides 2 QoE-increasing mechanisms

• Automatic client bandwidth management
• Multimedia service provision
• NIProxy == MM service provision platform

• Both mechanisms can exploit the NIProxy’s dual awareness/intelligence

• The mechanisms are

• Complementary
• NOT isolated entities (i.e. they can collaborate)

Software Architecture

Software Architecture

• Bandwidth Manager

• Responsible for managing the proxy client's available downstream bandwidth
• Has access to the NIProxy's bandwidth distribution algorithm
• Computes verdicts for the network packets it receives
• Accept
• Drop
• Block
• Only packets for which an accept verdict is computed are transmitted to the proxy client

Software Architecture

• Service Manager

• Applies services on MM streams on behalf of proxy clients
• Hands intercepted network packets to the currently loaded (and interested) services
• Service traversing order == load order
• Services are allowed to alter the contents of the packets they receive
• Multiple services can collaborate on a single stream
• Each client has its own Service Manager instance

• Services are implemented as NIProxy plug-ins

Bandwidth Distribution Algorithm

• Manages/distributes proxy client downstream bandwidth by arranging MM streams in a stream hierarchy

• Leaf nodes: actual network streams
• Internal nodes: implement a certain bandwidth distribution technique
• Mutex (e.g. group multiple qualities of same stream)
• Priority (e.g. distinguish between different types of network streams)
• Weight (e.g. distinguish between individual network streams of the same type)

• Stream hierarchy is maintained by client

An Example Service: Video Transcoding

• NIProxy video transcoding service

• Enables NIProxy to reduce bandwidth requirements of video streams
• Is implemented using the cascaded pixel-domain approach to transcoding
• For each received video stream, a new node is added to the proxy client’s stream hierarchy
• Is linked to the transcoded video stream
• Is added as sibling of original video stream

An Example Service: Video Transcoding

• Mode of operation

• Registers interest for video streams with Service Manager
• Consults proxy client’s stream hierarchy
• Transcode only if Bandwidth Manager computes an accept verdict for transcoded version of video stream
• If transcoding took place, original video frame is replaced by its transcoded counterpart
• Subsequent services will receive transcoded frame

• Notice collaboration between services and bandwidth distribution algorithm!

Evaluation: Test Application

• Test application

• Simple in-house developed NVE
• Provides users with a top-down 2D view of the shared virtual world
• Supports voice and video communication

• Required modifications

• Provide NIProxy with application awareness
• Voice: stream importance inversely proportional to virtual distance
• Video: virtual orientation is also considered
• Maybe more meaningful for 3D NVEs
• “Easy” thanks to availability NILayer library

Evaluation: Experimental Results

• Experiment

• 1 proxy client, 3 “regular” clients (C1, C2, C3)
• Goal = register MM experience provided to the sole proxy client
• Only 1 type of MM was considered  video
• Places largest load on network
• Allows demonstration of video transcoding plug-in
• Consisted of 3 intervals
• Within each interval, all conditions remained constant
• Transition between intervals was triggered by changing conditions

Evaluation: Experimental Results

Evaluation: Experimental Results

Evaluation: Experimental Results

• Findings

• NIProxy respects client downstream bandwidth
• Packet loss and packet latency are kept to a minimum
• Improved playback of MM streams at client-side
• Client receives MM streams that are most important to it in the highest quality possible
• Has a positive impact on the user QoE
• Video transcoding service enables NIProxy to forward lower-quality video to a proxy client
• Alternative = drop video all together
• NIProxy's service provision mechanism is also capable of improving the user QoE

Conclusions

• Increasing use of MM content & streaming

• If done improperly, can result in deterioration of user QoE instead of an improvement

• NIProxy

• Introduces more intelligence in the network
• Both application- and network awareness
• Complementarily leverages this awareness to
• Intelligently manage client downstream bandwidth
• Apply services on MM streams on behalf of clients
• Important feature: collaboration possible
• Outcome = improved MM experience for users
• Confirmed by the presented experimental results

Future Work

• NIProxy still lacks knowledge of the client terminal and the end-user's preferences

• Third kind of awareness

• Process of (un)loading services is at the moment directed entirely by proxy client

• Migrate (some) of this control to NIProxy

• Bandwidth distribution algorithm is optimized for continuous streams

• Provide support for bursty, short-lived streams

• Make video transcoding service dynamic

• Transcode to range of output qualities

Thank you for your attention! Any questions?