QoS research in a complicated world Christian Huitema Architect Windows Networking & Communications Microsoft Corporation

Infocom 2002QoS research in a complex world2 The state of research ? We need QoS for VoIP, video on demand, etc. To implement QoS, we need queuing models, signaling protocols, QoS contracts, etc. And I get to do tons of maths and publish papers.

Infocom 2002QoS research in a complex world3 The contrarian's view Look at the real network! We don’t really need QoS for VoIP, we need bandwidth for video on demand, etc. QoS signaling is dead. Maths are nice, use them for adaptivity.

Infocom 2002QoS research in a complex world4 Myth : QoS provides better service Myth: In a QoS enabled network, you get more bandwidth, less delays Reality: QoS = access control. You can only provide better service to some if you exclude others. Deployment issue: Only develop an application, if there is enough bandwidth “in most places”

Infocom 2002QoS research in a complex world5 Myth: Applications will require QoS Myth: Applications will use a QoS API, because that will give better service. Reality As long as QoS is not ubiquitous, applications must be adaptive. Deployment issue Since applications don’t require it, little incentive to upgrade the network. Little incentive to maintain the API

Infocom 2002QoS research in a complex world6 Myth: congestion occurs in the network Myth: There are bottlenecks in the network, each hop adds delays Reality: Look at Global Crossing, Qwest, Worldcom Price of Mbps divided by 6 in 2 years Congestion occurs mostly at the edges. Deployment issue: Operators of large networks don’t perceive any benefit to QoS, just costs.

Infocom 2002QoS research in a complex world7 Myth: QoS mechanism provide quality Myth: We can use QoS mechanisms to protect users from network issues Reality: How exactly do we use QoS to protect a web server against a denial of service attack? Deployment issue: Making the network more robust requires “last mile” solutions.

Infocom 2002QoS research in a complex world8 Myth: eventually, QoS everywhere Myth: Eventually, all routers will provide QoS Reality: “Wireless guarantee” is an oxymoron Deployment issue: A broken QoS promise will break the application. If you cannot have QoS everywhere, the application must be adaptive

Infocom 2002QoS research in a complex world9 A short summary The difference between theory and practice is even larger in practice than in theory

Infocom 2002QoS research in a complex world10 Three QoS research suggestions Apply local solutions to local problems Get more data If you don’t have guarantee, adapt!

Infocom 2002QoS research in a complex world11 Suggestion: research edge solutions Backbone = large, edge = small The law of big numbers does not apply to small numbers Edge = degrees of liberty for innovation MAC layer for wireless (802.1p ?) Cooperation between local players Receive side enforcement First router solutions… Liberty => research playground

Infocom 2002QoS research in a complex world12 Suggestion: get as much data as we can! Understand delays and losses In the network, at the edges What is the distribution? What are the causes? Fix the obvious bugs! E.g. router hiccups, bad hardware Repeat the measurements Don’t settle for yesteryear data. History matters! Praise the XVI century astronomers!

Infocom 2002QoS research in a complex world13 Suggestion: research adaptation models Today’s model are very crude The 1988 Internet 6 nodes NS simulations… TCP slow-start is probably wrong If we learn about the network, we can design better adaptation models APP Need the right black box model

Infocom 2002QoS research in a complex world14 A short summary Success is, finding something your professors don’t know Even better, prove them wrong Learn how the Internet really behaves, Find where the old hypotheses are wrong, Build on it!