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Ethernet is a success story in Local Area Networks (LAN). Efforts for extending its boundaries beyond LAN to the carriers' backbone networks are in progress. We study the problem of designing reliable and cost-efficient high-rate (100 Gbit/s) carrier-grade Ethernet in a multi-line-rate telecom network under signal transmission-range constraints. Reliability is achieved using shared-path protection at two levels: (1) Protection-at-Connection (PAC) level, or (2) Protection-at-Lightpath (PAL) level. We study the two cases for their impact on network cost and other performance parameters. We construct a graph, called Mixed Topology (MT), using which it is possible to: (1) identify traffic grooming possibilities, (2) select a path which requires the minimum amount of 3R regeneration, and (3) effectively choose the data rate of a lightpath to be established. Our algorithms, tested on the 17-node German network, lead to the following findings: (1) for both PAL and PAC, our MT-based algorithm resulted in lower network cost and higher lightpath utilization compared with other schemes; and (2) in general, PAL incurs slightly higher cost than PAC.

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We study cost-efficient routing in a MLR WDM network for carrier-grade Ethernet. We also study the benefits of a MLR network compared with a Single-Line Rate (SLR) network. IntroductionEthernet is a strong candidate as a transport technology in a carrier's backbone network. In a carrier's network, Ethernet is a connection-oriented service with carrier-grade characteristics. According to one school of thought, carrier-grade Ethernet can be transported over SONET/SDH (Ethernet-over-SONET/SDH) with maximum rate constrained by that of SONET/SDH (40 Gbit/s today). But efforts are also under way to carry native Ethernet frames directly over a WDM network (Ethernet-over-WDM) with possibly high rates (100 Gbit/s) [1] where streams of Ethernet frames (Ethertunnels) are carried by lightpaths. These lightpaths are established using Ethernet interfaces and are used to carry Ethernet traffic (the term Etherpath is used to denote a lightpath carrying only Ethernet traffic).Even though Ethernet-over-WDM is a more flexible and cost-efficient solution (and newer) than Ethernet-over-SONET/SDH, it is expected that Ethernet-over-WDM may coexist with Ethernet-over-SONET/SDH because of legacy customers needs. In addition, the heterogeneity in application-specific bandwidth requirements, and the possible asymmetry in traffic exchanged between any two nodes in a network as well as the asymmetry in the network topology may lead to differential link capacities. A network with heterogeneous line rates is an ideal way to meet this composite heterogeneity. In our previous study [2], we investigated the problem where each link operated at a single rate but different links may have different rates.In this study, a link may have mixed-rate wavelength channels (e.g., 10/40/100 Gbit/s) (Mixed-Line Rate). With MLR, the network operator can: (1) avoid provisioning low-bandwidth connections over high-capacity pipes (lightpaths), (2) support multi-rate transport protocols and, hence, avoid complex multiplexing schemes, and (3) use the optimal combination (number/rate) of wavelengths on each link which addresses both traffic and network asymmetry. Along with this flexibility, an efficient routing algorithm is required so that the benefits of a MLR network are exploited which is discussed in the subsequent sections.