TKK | Tietoverkkolaboratorio | Opetus
Definition
Quality of Service (QoS) is defined to express end-to-end delay, delay variation or packet loss ratio depending of the context. These all measure the time in which the most of the information is received by the other end. QoS is a hot topic in current network dimensioning for the near-future service billing.
2.6.2 Billing of different services
QoS is heavily based on marking packets with identifiers that express the needed or wanted priority of a stream. These identifiers express the traffic class of a service. The service differentiation can be done by a special server, called DiffServ. This service labels packets depending of the address they are coming from or protocol in use. Routers are combined to this by priorising packet forwarding according to traffic classes.
Nowadays there are several traffic classes for real-time services like audio and conferencing, lower classes for Web and file transmission. Some streams, like mail, can be left without labelling and will be delivered when the network is far of being congested.
If a customer is willing to pay more of his connection, his streams can be labelled with higher traffic classes to ensure good quality real-time Internet connection. Of course, this can lead to differentiation of customers to rich and poor.
Rescue services like 911 should always be priorized with highest traffic class.
2.6.3 Problems
Internet wasn't designed for real-time applications. No guaranteed QoS can be ensured because of the connectionless packet switching, only "best effort" method can be used. Instantaneous traffic is hard to be forecasted and network congestion can occur and it could be possible that only customers or clients paying for the best traffic class will be served.
Because future Internet use is probably based on paying for the service type it might be possible to use payload cheating. It is possible to tunnel real-time traffic in other protocols. One could use HTTP to tunnel audio and speak much more cheaper than using the real telephony protocol.
0.1 Introduction
1.0 Internet
2.0 Services
3.0 Advantages and Disadvantages
Antti Hätinen (AH)
Li Yaohui (LY)
Martti Mela (MM)