Managing Client Bandwidth in the Presence of Both Real-Time and non Real-Time Network Traffic

Maarten WijnantsWim Lamotte

08/01/2008 COMSWARE2008 2

Outline

• Introduction– Need for Bandwidth Management– Real-time vs non real-time network traffic

• NIProxy– System Overview– Objectives & Mode of Operation

• Client Bandwidth Management• Evaluation

– Experimental Setup & Results

• Conclusions & Future Work

08/01/2008 COMSWARE2008 3

Introduction

• Increasing incorporation of multimedia content into networked applications– E.g. evolution textual chat to more immersive

forms of user communication– Will normally provide user with better

experience– However: considerable bandwidth is required

to exchange multimedia data over a network

• Bandwidth consumption of networked applications has risen substantially– Clients do not always dispose of sufficient

downstream bandwidth

08/01/2008 COMSWARE2008 4

Introduction

• Need for client bandwidth management– Should occur both intelligently and effectively– Goal = maximize user experience/satisfaction

• Possible approaches– Implement unique solution for each application– Develop reusable solution

• Economically more favorable• “Communication middleware”

• NIProxy: network intermediary supporting client bandwidth management– Example of communication middleware

08/01/2008 COMSWARE2008 5

Introduction

• Real-time network traffic– Content/media with real-time characteristics– Very sensitive to delay– Needs to be delivered to destination “in time”– Typically continuous, long-lived streams that

are transmitted using e.g. UDP

• Non real-time network traffic– E.g. file or P2P data– Less stringent constraints on its delivery time– Requires reliable and error-free delivery (TCP)– Often bursty and relatively short-lived

NIProxy

• The NIProxy– Network intermediary (a “proxy server”)– Objective = enhance the experience and

satisfaction of users of networked applications• Quality of Experience (QoE)

– Approach = introduce additional awareness or context in the transportation network

– Abbreviation for Network Intelligence Proxy

08/01/2008 COMSWARE2008 6

NIProxy

• NIProxy is network- and application aware– Network awareness: knowledge of the current

state of the transportation network• Acquired through active network probing• Network-related measurements (e.g. current

throughput, latency, packet loss rate, …)

– Application awareness: knowledge of the networked application(s) the client is running

• Provided by client software– Facilitated by reusable auxiliary library called NILayer

• Depends on application’s requirements and its type– Example: relative stream importance

08/01/2008 COMSWARE2008 7

NIProxy

• NIProxy performs QoE-optimization through– Automatic and dynamic client downstream

bandwidth management– Multimedia service provisioning– Both can exploit NIProxy’s dual awareness

• Supported QoE-improving mechanisms are complementary & interoperable

08/01/2008 COMSWARE2008 8

Client Bandwidth Management

• NIProxy manages client bandwidth by organizing network flows in a stream hierarchy– Tree-like structure– Leaf nodes always correspond

to an actual network flow– Internal nodes implement a

certain bandwidth distribution strategy, e.g.• Mutex• Weight• Percentage

08/01/2008 COMSWARE2008 9

Client Bandwidth Management

• Real-time network traffic– Stringent reception delay constraints– Only limited operations are possible

• E.g. no mid-stream buffering or reduced-rate transmission

• Management by NIProxy through discrete stream hierarchy leaf nodes– Sets the flow's bandwidth consumption to a

discrete number of values– Simplest approach: turn network stream on/off– More complex: e.g. scalable network streams

08/01/2008 COMSWARE2008 10

Client Bandwidth Management

• Non real-time network traffic– Less stringent reception delay constraints– Bit more management latitude

• Management by NIProxy through continuous stream hierarchy leaf nodes– Capable of setting a flow's transmission rate to

a continuous range of values– Operation resembles that of leaky bucket:

• Local buffering of content transported by flow• Rate-controlled transmission of buffered data to

client

08/01/2008 COMSWARE2008 11

Client Bandwidth Management

• Responsibility for constructing and maintaining stream hierarchy lies with client– Determine suitable stream hierarchy structure

• Provides NIProxy with application awareness

– Adequately incorporate individual network flows

• Is facilitated by availability of– NILayer support library– NIProxy new/dead stream notification system

08/01/2008 COMSWARE2008 12

Client Bandwidth Management

• Once stream hierarchy has been constructed, managing client downstream bandwidth = assigning correct amount of bandwidth to hierarchy root node– Internal nodes apportion bandwidth according

to their bandwidth distribution technique– Discrete leaf nodes switch to the highest

possible discrete bandwidth consumption level– Continuous leaf nodes adjust their tx rate

• Process is repeated periodically

08/01/2008 COMSWARE2008 13

Implementation

• At which granularity should the NIProxy manage non real-time network traffic?– Fine-grained: incorporate each individual non

real-time content object in stream hierarchy+Allows high & subtle level of control- Frequent updates of stream hierarchy necessary- Calculating client's bandwidth distribution consumes

more time due to the increased stream hierarchy size

– Coarse: provide support at the level of non real-time network flows

• Treat all non real-time data transferred over same flow identically

08/01/2008 COMSWARE2008 14

Evaluation: Experimental Setup

• Networked application allowing user to set up real-time and non real-time network streams with remote hosts– Real-time traffic: video streaming

• Most demanding in terms of bandwidth• Transmitted using RTP

– Non real-time traffic: P2P file sharing• Transmitted using TCP

• File sources transmit files sequentially in order of file request reception

08/01/2008 COMSWARE2008 15

Evaluation: Experimental Results

• Validate if NIProxy is capable of managing client bandwidth in presence of both real-time and non real-time network traffic

• Approach– Real-time video connection between local

client and two remote hosts H1 and H2– Non real-time communication channel between

local client and H1 as well as another remote host representing a dedicated file server (FS)

• geom.3ds: 484652 bytes; requested from FS• img.png: 23419 bytes; requested from host H1

08/01/2008 COMSWARE2008 16

Evaluation: Experimental Results

• Additional constraints and requirements– Significance video stream H1 > H2– Priority non real-time connection FS > H1– Non real-time communication should receive

“fair” amount of the total downstream bandwidth available to the client (i.e. at least 30 percent)

• Allows comprehensive demonstration of the capabilities of NIProxy's bandwidth distribution mechanism

08/01/2008 COMSWARE2008 17

Evaluation: Experimental Results

• Experiment was repeated three times– Without including NIProxy– With NIProxy (no video transcoding service)– With NIProxy (with video transcoding service)

• Video transcoding service allows NIProxy to reduce bandwidth requirements of video flows

• Experiment objectives– Investigate MM experience provided to client– Introduction of NIProxy improves user’s QoE?

08/01/2008 COMSWARE2008 18

Evaluation: Experimental Results

Without including NIProxy

• Simultaneous reception of real-time & non real-time traffic yielded issues

– Wrongful penalization of non real-time traffic

• In disaccord with our “fair share” requirement

– Video suffered from contention from non real-time traffic

• Deteriorated playback

08/01/2008 COMSWARE2008 19

Evaluation: Experimental Results

With NIProxy (no transcoding)

• Stream hierarchy constructed according to specified constraints

• Issues did not occur– Use percentage node

guarantees non real-time traffic receives its bw share

• Faster file reception

– Unaffected video reception• Non real-time rate-control

08/01/2008 COMSWARE2008 20

Evaluation: Experimental Results

With NIProxy (and transcoding)

• Additional advantage: allows video traffic to more fully consume its bandwidth percentage

– H2 TV when file traffic is initiated

• Has lower bandwidth requirements than H2 OV

• Forwarding it does not deny file transfer its fair bw share

08/01/2008 COMSWARE2008 21

Evaluation: Experimental Results

• Principal findings– Client bandwidth was distributed correctly over

real-time and non real-time network traffic– Allowed fulfillment of postulated requirements

with minimal effort• No substantial modifications to client software

Incorporation of NIProxy in experiment had positive influence on user's QoE

• Experiment also illustrates added value of allowing interoperation between NIProxy’s two QoE-increasing mechanisms

08/01/2008 COMSWARE2008 22

Conclusions

• Networked applications are increasingly exploiting multimedia content– Client bw management gains in importance

• NIProxy: network intermediary aiming to improve user QoE– Through incorporating awareness in network– Client bw management & MM service provision

• NIProxy is capable of managing client downstream bw in presence of real-time as well as non real-time network traffic

08/01/2008 COMSWARE2008 23

Future Work

• Extend NIProxy’s awareness with knowledge of client terminal and the end-user's preferences

• Investigate impact of employing NIProxy to manage client downstream bandwidth in a more realistic networked application– In-house developed NVE application

• Supports real-time voice and video chat• Uses non real-time network communication to

exchange different types of geometry information (IBR data, 3D models, textures, …)

08/01/2008 COMSWARE2008 24

Thank you for your attention!Any questions?