Optimal Burst Scheduling in Optical Burst Switched Networks

Abstract

Abstract-Optical burst switching (OBS) is an emerging technology that allows variable size data bursts to be transported directly over dense wavelength division multiplexing links. In order to make OBS a viable solution, the burst-scheduling algorithms need to be able to utilize the available wavelengths efficiently, while being able to operate fast enough to keep up with the burst incoming rate. For example, for a 16-port OBS router with 64 wavelengths per link, each operating at 10 Gb/s, we need to process one burst request every 78 ns in order to support an average burst length of 100 kB. When implemented in hardware, the well-known horizon scheduler has O(1) runtime for a practical number of wavelengths. Unfortunately, horizon scheduling cannot utilize the voids created by previously scheduled bursts, resulting in low bandwidth utilization. To date, minimum starting void is the fastest scheduling algorithm that can schedule wavelengths efficiently. However, while its complexity is O(log m), it requires 10 log m memory accesses to schedule a single burst. This means that it can take up to several microseconds for each burst request, which is still too slow to make it a practical solution for OBS deployment. In this paper, we propose an optimal burst scheduler using constant time burst resequencing (CTBR), which has O(1) runtime. The proposed CTBR scheduler is able to produce optimal burst schedules while having processing speed comparable to the horizon scheduler. The algorithm is well suited to highperformance hardware implementation.Index Terms-Algorithm, optical burst switching (OBS), optical packet switching, scheduling, wavelength division multiplexing (WDM), wavelength routing.

Deduction of TWCs and Internal Wavelengths Needed for a Design of Asynchronous OPS System with Shared or Output FDL Buffer

“…scheduling algorithms without void filling [15][16][17]20] and scheduling algorithms with void filling [16][17][18][19][20] .…”

“…For this reason, efforts are required to increase buffer capacity in an optical packet switch with a limited number of FDLs [7][8][9][10][11][12][13][14] . For asynchronous and variable-length packets, scheduling algorithms without void filling as well as those with void filling can be used to allocate incoming packets in each output channel using an FDL buffer [15][16][17][18][19][20] .…”

“…Most studies on contention resolution of asynchronous and variable-length packets have fully assumed the use of switch resources such as TWCs and internal wavelengths, while a number of OPS architectures to share FDLs and wavelength converters have been addressed for synchronous and fixed length packets [16][17][18][19][20] . However, the number of TWCs in an asynchronous optical packet or burst switch is a factor in the system cost, and the number of internal wavelengths is related to the conversion range of the TWC and is also a factor in the system cost [8,[21][22][23] .…”

RED-f routing protocol for complex networks

“…RED-f protocol is designed for the OBS network architecture [20]. In OBS networks, multiple packets are grouped into one data burst and a burst control header (BCH) packet is created.…”

Contour-Based Priority Scheduling in Optical Burst Switched Networks

“…Such a resequencer is denoted as RSQ(∆). An O(1) runtime resequencer design can be found in [14]. As mentioned previously, the resequencer is an electronic buffer implemented in the control path.…”