Probe-based admission control in IP networks

Sammanfattning: The current Internet design is based on a best–effortservice, which combines high utilization of network resourceswith simplicity. As a consequence of this design, the Internetis unable to provide guaranteed or predictable quality ofservice (QoS), required to offer real–time services thathave constraints on end–to–end delay, delay jitterand packet loss.To add QoS capabilities to the present Internet, newfunctions need to be simple to implement, while allowing highnetwork utilization. In recent years, different methods havebeen investigated to provide the required QoS. Most of thesemethods include some form of admission control so that newflows are only admitted to the network if the admission doesnot decrease the quality of connections that are already inprogress below some defined level. To achieve the requiredsimplicity a new family of admission control methods, calledend–to–end measurement–based admission control(EMBAC) moves the admission decision to the edges of thenetwork.This thesis presents the probe–based admission control(PBAC), which belongs to the family of EMBAC schemes. PBACprovides a reliable upper bound to the packet loss probabilitya flow will suffer in the network. The delay in the network isbounded by using small, packet–scale buffering in therouters. The admission control is done by measuring the lossratio of a stream of probe packets. Probe packets and datapackets of accepted flows are transmitted with low and highpriority respectively, to protect accepted flows from the loadof the probe streams. The probing is done at the peak rate ofthe connection and the flow is accepted if the probe packetloss rate is below a predefined threshold. This procedureensures that the packet loss of accepted flows is always belowthe threshold value.The thesis offers a description of the probing procedure,with an extensive performance analysis by simulation, as wellas a mathematical model for the admission decision. The authoralso addresses the application of the admission control formulticast communications, and gives a general method to providesecurity features to measurement–based admission controlschemes.