Fragmentation metrics and fragmentation-aware algorithm for spectrally/spatially flexible optical networks

Abstract

Spectrally/spatially-flexible optical networks (SS-FONs) are a promising solution to cope with future traffic requirements in optical backbone networks. SS-FONs exploit the spatial dimension to increase network capacity while preserving resource management flexibility, as they still operate within a flex-grid composed of small frequency slots (slices). Flex-grid allows realizing transmission using super-channels (SChs) that comprise a set of contiguous slots. In this paper, we focus on spectral SChs, i.e., a SCh realized only on one spatial mode on each fiber. In SS-FONs, setting up and tearing down multiple lightpath requests within flex-grid may result in spectrum fragmentation, and, in turn, blocking of requests. In this work, we investigate several fragmentation metrics in SS-FON. The problem of identifying appropriate metrics to measure fragmentation has been investigated in single-core elastic optical networks (EONs), but, to the best of our knowledge, there is lack of such investigation for SS-FONs. Therefore, we propose several fragmentation metrics for SS-FON. We introduce the concept of bordering super-channels (B-SChs), i.e., SChs whose spectrum is allocated at the "border" of already allocated spectrum slots that are promising SChs to be chosen to minimize fragmentation. The investigation of all candidate B-SCh for a request allows us to find the one which minimizes network fragmentation, and, in turn spectrum waste. Hence, we propose a fragmentation-aware algorithm with bordering super-channels (FA-BSC) that assigns optical resources to dynamic requests utilizing information from the proposed fragmentation metrics and the set of candidate B-SChs. Experiments on a representative network topology show that the investigation of multiple B-SChs in the fragmentation-aware algorithm reduces the blocking probability when compared to the reference fragmentation-aware algorithms. Finally, we analyze the impact of a spatial continuity constraint on the network fragmentation.

LBFA: A Load-Balanced and Fragmentation-Aware Resource Allocation Algorithm in Space-Division Multiplexing Elastic Optical Networks

“…This method reduces spectral fragmentation by allocating a uniform bandwidth connection for each core. In [21], several fragmentation metrics were evaluated in SDM-EONs to achieve lower RBP. All these studies focused on the connection [20,21,[30][31][32] assuming that only one mode or core could be utilized by each connection request.…”

“…In SDM-EONs, an on-demand spectrum and core allocation method was designed in [20] to reduce spectral fragmentation at the cost of the flexibility in spectral allocation. In [21], fragmentation could be reduced by allocating SChs just at the border of already occupied FSs. However, both methods were designed for allocating spectral SChs that are realized with only one core on each fiber.…”

TDTS: Three-Dimensional Traffic Scheduling in Optical Fronthaul Networks with Conv-LSTM

“…The authors of [29] showed a multi-features weighted scheme including path lengths, link-spectrum utilization, and other features. The authors of [30][31][32][33] focused on fragmentation in the spectrum to optimize RMSA, where perceptible fragmentation and defragmentation can usefully reduce spectrum fragmentation. However, the above works were unable to achieve real-time RMSA allocation because they only apply fixed RMSA strategies without considering comprehensive perceptions of the EON state.…”

Dynamic adaptive spectrum allocation in flexible grid optical network with multi‐path routing

“…In [8], authors proposed various fragmentation metrics for spectrally/spatially flexible optical networks (SS-FONs), as extended evaluation techniques of fragmentation in EONs. Moreover, the new concept of bordering super-channels (B-SChs) was introduced.…”