A low-jitter guaranteed-rate scheduling algorithm for packet-switched ip routers

Abstract

A guaranteed-rate scheduling algorithm for packet-switched IP routers with rate, delay and jitter guarantees is proposed. The algorithm can be used to schedule traffic with 100% throughput in Input-Queued IP routers with unity speedup. The traffic is scheduled according to transmission frames of duration F time-slots. An N x N doubly stochastic traffic rate matrix specifies a traffic rate between each pair of IO ports. The matrix is quantized and recursively decomposed into a sequence of F permutations. Each permutation is used to configure the crossbar switch for one time-slot without requiring additional scheduling. The recursive fair stochastic matrix decomposition is based upon the routing of a permutation through a binary rearrangeable network. In the resulting transmission schedule, the expected Inter-Departure Time (IDT) of a cell equals the Ideal IDT (IIDT), and the maximum IDT and service lag of a cell are bounded by an integer number of IIDTs. The delay and delay jitter experienced along an end-to-end path in a packet-switched IP/MPLS network are therefore small and bounded by an integer number of IIDTs, and the buffer sizes within the IP routers are small and bounded. The proposed algorithm can be used to schedule Guaranteed-Rate traffic in packet-switched IP/MPLS networks, to provide near-optimal queueing delays and essentially-zero delay jitter along end-toend paths when playback buffers are employed.