Implementing Real Time Packet Forwarding Policies Using Streams

This paper describes an implementation of the class based queueing (CBQ) mechanisms proposed by Sally Floyd and Van Jacobson to provide real time policies for packet forwarding. CBQ allows the traffic flows sharing a data link to be guaranteed a share of the bandwidth when the link is congested, yet allows flexible sharing of the unused bandwidth when the link is unloaded. In addition, CBQ provides mechanisms which give flows requiring low delay priority over other flows. In this way, links can be shared by multiple flows yet still meet the policy and Quality of Service (QoS) requirements of the flows.

We present a brief description of the implementation and some preliminary preformance measurements. The problems of packet classification are addressed in a flexible and extensible, yet efficient 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.