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Random contentions occur in optical burst-switched (OBS) networks because of one-way signaling and lack of optical buffers. These contentions can occur at low loads and are not necessarily an indication of congestion. The loss caused by them, however, causes TCP at the transport layer to reduce its send rate drastically, which is unnecessary and reduces overall performance. In this paper, we propose coordinated burst cloning and forward segment redundancy, a proactive technique to prevent data loss during random contentions in the optical core. With forward segment redundancy (FSR), redundant segments are appended to each burst at the edge and redundant burst segmentation (RBS) is implemented in the core so that when a contention occurs, primarily redundant data is dropped. With burst cloning, an entire redundant burst is created at the edge and sent at the same time as the original burst. Coordinated burst cloning and FSR creates clones of bursts (with FSR) and transmits them independently, creating a second-level of redundancy. We evaluate the performance of our proposed loss recovery technique through extensive simulations. We observe that the proposed hybrid technique significantly improves TCP performance at both low and high network loads.
Date of Conference: 6-10 Dec. 2010