Abstract-This paper addresses the issue of reliable transport of emerging data services in Ethernet over SONET (EoS) networks that require protection guarantees beyond standard best effort delivery. We argue that the current consensus of using Ethernet spanning tree and a SONET 1+1 protection, while providing reliability, is an inefficient use of resources. Instead, we claim that EoS opens novel opportunities for protection heretofore unavailable in other environments. In particular, the deployment of Virtual Concatenation and LCAS protocols enables "route splitting", creating a fundamentally new routing paradigm for circuit-switched environments. We propose a scheme called PESO, appropriate for EoS, with innovative routing, failure notification and switching components. More importantly, it is competitive with SONET protection without its 100% bandwidth overhead. We also suggest a enhancement in LCAS that can further improve PESO's switching time. PESO leverages the underlying protocols, making it extremely attractive to implement and use in practice.
Abstract-We study the problem of bandwidth fragmentation in links that comprise rings and meshes in SONET networks. Fragmentation is a serious challenge for network operators since it creates "holes" in the transport pipe causing new demands to be rejected, in spite of sufficient bandwidth being available. Unlike the well-studied, general fragmentation problem, link defragmentation is "hard" and novel due to some unique constraints imposed by the SONET standard. Since a defragmentation operation typically occurs on a network carrying live traffic, in addition to the "quality" of the output, any link defragmentation algorithm has to avoid traffic hit and also optimize the "cost" of reorganizing circuits. We propose an algorithm called MöbiPack that is optimal in its defragmentation quality. Moreover, we demonstrate via extensive simulations, that it also achieves its goal in a hitless manner with only marginal additional cost over the optimal, making it extremely attractive to use in practice.
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