Scaling Internet Routers Using Optics

Shang-Tse Chuang, Kyoungsik Yu, David Miller, Mark Horowitz Olav Solgaard and Nick McKeown. Proceedings of SIGCOMM, 2003. Balanced Birkhoff-von Neumann Switches

Proceedings of SIGCOMM 2003.

The goal of the paper is to design a 100 Tb/s router using optical components while minimizing power consumption. The paper begins with the idea of using the 'Load-balancing Switch Architecture' proposed by C. S Chang. This architecture obviates the need for a centralized scheduler and can guarantee 100% throughput for a broad class of traffic (stochastic & weakly mixing).

The paper presents ideas to use a fixed mesh of optical channels for the switching fabric, using a Full Frames First (FFF) algorithm to avoid mis-sequencing of packets and ideas to partition the switch for flexible placement of line cards. Two probable candidates for implementing the architecture - a hybrid electro-optical switch and a complete optical switch are also presented.

Critique:

1. The main idea of the paper is based on C. S Chang's Load Balancing Switch architecture and the FFF algorithm was published in a previous paper.
2. The problem of flexible line card placement is solved by partitioning the switch. However, for uniform load-balancing to occur, all the 'M' middle stages of the partitioned switch have to be functional irrespective of the number of line cards in use. While, this doesn't consume much power, it is probably an expensive option for a provider who would use, say only 100 of the 640 ports.
3. Most of the components (line cards, number of lasers per card etc) of the two candidate switches are expected to be feasible for implementation in 3 years. While, such forecasts make for an agreeable case, work needs to be done to make a more compelling argument

Critique by Prashanth Pappu