Implementing Real Time Packet Forwarding Policies
using Streams

Ian Wakeman, Atanu Ghosh, Jon Crowcroft
Computer Science Dept.
University College London
Gower Street, London WC1E 6BT

Van Jacobson and Sally Floyd
Lawrence Berkeley Laboratory
One Cyclotron Road
Berkeley,  CA  94720


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

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.

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