Networked games: a QoS-sensitive application for QoS-insensitive - - PowerPoint PPT Presentation

Networked games: a QoS-sensitive application for QoS-insensitive users?

Tristan Henderson and Saleem Bhatti

{T.Henderson,S.Bhatti}@cs.ucl.ac.uk

Department of Computer Science, University College London

SIGCOMM RIPQoS workshop — 27/08/03 – p.1/14

Introduction

Why do we care about QoS? Apparently QoS is a requirement for next-gen networks There are lots of applications that require QoS What are these applications? Multimedia conferencing?

Not that popular. . . (but Apple, AOL?)

VOIP?

Reasonably popular. . .

Networked games?

Very popular But where’s the QoS?

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Outline

Games —QoS requirements Our experiments —methodology Results What next? Discussion

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Games

Ever popular —Spacewar (1969) was networked Some market research (don’t forget the salt):

$1.5bn revenue / year (total games market =$11bn) 114 million players by 2006 55 million “casual” players

Three main genres:

FPS — Half-Life, Quake, Doom MMORPG — Everquest, Star Wars: Galaxies RTS — Civilization, Age of Empires

Typically client-server, UDP Delay is most important QoS parameter

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Requirements for games

Delay is most important QoS parameter: Human factors

200ms requirement for interaction

DIS

100-300ms for simulations

VR studies

interaction difficult ≥225ms

Game studies

100ms for racing games around 150-250ms for FPS 150ms for MiMaze

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Experiments

Do players care about QoS? Can they notice? We can find out. . .

Set up some public game servers Alter the QoS (delay) See what happens

How does delay affect:

Joining a server —are players dissuaded? Leaving a server —are players annoyed enough to leave?

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Methodology

GAME DELAY SERVERS GENERATOR

Two popular public Half-Life game servers One Linux gateway for adding delay

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Joining a server

5 10 15 20 25 16/06 17/06 18/06 19/06 20/06 21/06 Players Time Session membership server1 server2

With no additional delay, both servers are similar. . .

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Joining a server (2)

5 10 15 20 25 01/05 02/05 03/05 04/05 05/05 06/05 07/05 08/05 Players Time Session membership server1 server2

Add some delay and people go away. . .

50ms seems to be enough to deter

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Leaving a server

Add random amount of delay to all players on server

Add up to 250ms, i.e. 2× “tolerable” amount

Players who leave tend to have higher delay Delay affects performance of players (kills/min) Amount of extra delay (as a %) has no significant effect Regular players no less likely to leave Duration has an effect —players who have played longer less likely to leave

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Leaving a server (2)

Does “relative delay” (player’s delay relative to others) have an effect?

Add delay to a subset of players on the server

Seems to have little effect

Even though relative differences in delay have an effect on performance Time again has an effect —players who didn’t leave in event

• f additional delay had been playing longer

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"Conclusions"

How important is QoS for game players?

Controlled experiments indicate players can notice 150ms and don’t like 250ms It appears they tolerate much more in the “real world”

Might QoS requirements change over time?

Utility of application is not static over time Can ISPs exploit this?

Pricing/charging for QoS

Surveys indicate players unwilling to pay for QoS If can’t notice QoS, they will be even less willing to pay. . .

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Future work

Further experiments

Other QoS parameters Other strategies for annoying players

Different games

driving, MMORPG etc.

Different environments

Mobile

Modelling time-variant QoS

Cooperative users versus non-cooperative ISPs

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Discussion

What applications require end-user QoS?

Is choosing a QoS level an appropriate end-user decision?

Will we ever see end-user QoS pricing?

What will it look like?

Are users too accustomed to a free best-effort service?

Napster → no-one is paying for music Console users, MMORPGs

Should ISPs fool customers? Is dynamic QoS desirable/feasible?

Will users pay for it?

SIGCOMM RIPQoS workshop — 27/08/03 – p.14/14