Queuing and Scheduling

This chapter analyzes the internals of the queuing and scheduling mechanism. It also analyzes the parameters associated with any queuing and scheduling mechanism and their common ground. Routers can handle packet queuing in two different ways, either queuing the entire packet or splitting it into fixed-size cells, a process commonly called cellification. The chapter presents some major well-known disciplines regarding scheduling are first in-first out (FIFO) queuing, fair queuing (FQ), priority queuing (PQ), weighted fair queuing (WFQ), weighted round robin (WRR), deficit weighted round robin (DWRR) and priority-based deficit weighted round robin (PB-DWRR). The most powerful of these and perhaps the most interesting is PB-DWRR. PB-DWRR incorporates the lessons learned from most other queuing algorithms. It incorporates most of the features introduced by these algorithms, such as byte deficit scheduling and priority levels.