Parallel packet switching by packet distribution


Problem

Line speeds continue to increase faster than do memory and logic speeds. With future 40 or 100-Gbps Ethernet, the line speed will begin to exceed memory bandwidth even for an input buffered switch architecture. One solution is a parallel packet switch (PPS) with internal switch planes running at a rate less than line speed. The key problem in a PPS is how packets should be distributed between planes so that packet ordering is maintained.

Objective

Parallel Packet Switches (PPS) use internal, parallel switch planes that operate at less than line speed. A PPS can scale-up to faster line speeds than a single-plane switch can. Load balancing between planes and providing QoS to flows are open problems. Our objective is to investigate and evaluate methods of implementing fast and scalable per-packet distribution in a PPS.

Work completed

We have proposed and evaluated the performance of a new "VIQ PPS" that distributes cells (segmented packets) to multiple planes and uses multiplexors with novel virtual input queues (VIQ). A VIQ at an output multiplexor consists of one FIFO queue for each input. It was found that at high offered loads the mean delay of a VIQ PPS switch is lower than that of a single-plane iSLIP switch and of all other existing feasible-to-implement PPS designs.

Work in progress

We are currently implementing in FPGA technology the mutliplexor and demultiplexor of the VIQ PPS. We are also exploring phased-memory designs to enable low-speed DRAM to be used with high-speed links (i.e., where the link speed exceeds the memory read and write speed). We are applying for a small grant from Cisco's University Research Program to continue this work beyond the scope of this CAREER project.

Results

This material is based upon work supported by the National Science Foundation under grant No. 9875177. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflects the views of the National Science Foundation (NSF).
Last updated by Ken Christensen on DECEMBER 20, 2003