Performance analysis of queue scheduling mechanisms for EF PHB and AF PHB in DiffServ networks

Expedited Forwarding Per-Hop Behavior (EF PHB) and Assured Forwarding Per-Hop Behavior (AF PHB) are the forwarding schemes operating in DiffServ networks. EF PHB is appropriate for flows with low delay, low latency and low jitter, and AF PHB provides guaranteed services with minimum bandwidth and buffer. The two PHB can be implemented by several queue scheduling mechanisms such as weighted round-robin (WRR), priority round-robin (PRR) and priority-weight round-robin (PWRR) which is the queue scheduling mechanism conjoining the WRR and PRR. The EF queue in PWRR is served based on PRR, and WRR mechanism is used in scheduling non-EF queues. In this paper, we evaluate the WRR, PRR and PWRR under the conditions that both EF PHB and AF PHB operate in a DiffServ router. We show PWRR is the best queue scheduling mechanism simultaneously gratifying the delay and jitter criteria of the EF class as well as the target throughput of AF classes.