Packet reordering in the Lightpath Bundling & Anycast Switching (LB+AS) paradigm

In optical networks, Lightpath Bundling & Anycast Switching paradigm (LB+AS) consists of (i) bundling together the lightpaths which follow a common route (LB), and (ii) perform a fine-grained per-packet granularity balance of the traffic among the lightpaths in the bundle (AS). Recent works suggest that, with seamless changes in the electronic equipment, and no changes in the optical infrastructure, LB+AS can bring promising advantages to existing optical networks. In particular, AS operation spreads the traffic among the lightpaths in the bundle, to enhance the statistical multiplexing gain. However, this type of operation could bring up packet reordering problems if different packets of the same flow traverse different lightpaths. Packet reordering issues especially affect protocols such as TCP, reducing the goodput and increasing the flow completion time. This paper addresses this problem and investigates viable implementations of anycast switching techniques that: (i) allow a practical implementation in commercial high-speed switches, and (ii) eliminate the packet reordering problem in practice. Among several solutions presented and tested, the e-JSQ scheme has emerged as a solution fulfilling both requirements.