A New Scheme of Combining Advanced Packet Discard and Dynamic Bandwidth Allocation for Low Delay/Low Jitter Realtime Communication Using CBQ/ALTQ

Shunsuke NAKAMURA  Nei KATO  Kohei OHTA  Yoshiaki NEMOTO  

IEICE TRANSACTIONS on Communications   Vol.E84-B   No.12   pp.3124-3132
Publication Date: 2001/12/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Network Software)
Category: Internet Technologies
CBQ,  CoS,  bandwidth allocation,  RED,  

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Recently, demand on class-of-service (CoS) has known a great increase thanks to a set of real-time applications such as Internet Telephony service. Class-Based Queuing (CBQ) is considered as an efficient queuing mechanism to guarantee CoS. ALTQ is a widely used platform for realizing CBQ. In this paper, we verify through experiments that bandwidth control of CBQ/ALTQ contains overhead for fluctuating traffic. To avoid such an overhead, we introduce dynamic bandwidth allocation scheme for real-time traffic fluctuating within fixed ranges. In the light of the limited network resources, it quickly becomes obvious that when the traffic rate exceeds the maximum available bandwidth, arriving packets will be accumulated in the router queue. As a result, the traffic delay increases and the quality of real-time applications is degraded. To cope with such a problem, we revise the RED algorithm for a large amount of traffic and propose a new packet discard algorithm that uses bandwidth as a trigger. Experiment results show that our proposal outperforms the already existing packet discard algorithms (RED, DropTail) in providing lower delay/jitter services. We show the efficiency of our proposal using a real system.