Abstract
IP networks are built around the idea of best effort networking, which makes no guarantees regarding the delivery, speed, and accuracy of the transmitted data. While this model is suitable for a large number of applications, and works well for almost all applications when the network load is low (and therefore there is no congestion), there are two main factors that lead to the need for an additional capability of quality of service guarantees. One is the fact that an increasing number of Internet applications are related to real-time and other multimedia data, which have greater service requirements in order to be satisfying to the user. The other is that Internet usage is steadily increasing, and although the network infrastructure is also updated often, it is not always certain that network resource offerings will be ahead of usage demand. In order to deal with this situation, IETF has developed two architectures in order to enable QoS-based handling of data flows in IP networks. This article describes and compares these two architectures.
Key Terms in this Chapter
Differentiated Services (DiffServ): An architecture that has been defined by IETF in order to provide quality of service in IP networks, which works based on aggregates of flows, by classifying traffic into different types of service, allowing the core routers of the network to deal with only a limited number of aggregated flows.
Quality of Service (QoS): The ability to provide specific guarantees to traffic flows regarding the network characteristics such as packet loss, delay, and jitter experienced by the flows.
Internet Engineering Task Force (IETF): The organization comprised of a large open international community of network designers, operators, vendors, and researchers concerned with the evolution of the Internet architecture and the smooth operation of the Internet.
RSVP: Resource Reservation Protocol.
Per-Hop Behaviour (PHB): The aggregated way packets are forwarded at a differentiated servicescompliant node.
First-In, First-Out (FIFO): Queue organization method, where each element exits the queue in the order it originally arrived.
Integrated Services (IntServ): An architecture that has been defined by IETF in order to provide Quality of Service in IP networks, which is based on flow-based allocation of resources using RSVP.