Implementing Real Time Packet Forwarding Policies

This paper describes an implementation of the class based queueing (CBQ) mechanisms proposed by Sally Floyd and Van Jacobson 1] 2] to provide real time policies for packet forwarding. CBQ allows the traac ows sharing a data link to be guaranteed a share of the bandwidth when the link is congested, yet allows exible sharing of the unused bandwidth when the link is unloaded. In addition, CBQ provides mechanisms which give ows requiring low delay priority over other ows. In this way, links can be shared by multiple ows yet still meet the policy and Quality of Service (QoS) requirements of the ows. We present a brief description of the implementation and some preliminary performance measurements. The problems of packet classiication are addressed in a exible and extensible, yet eecient manner, and whilst the Streams implementation cannot cope with very high speed interfaces, it can cope with the serial link speeds that are likely to be loaded.