Multi-MetaRing fairness control in a WDM folded-bus architecture

The paper deals with fairness issues in a slotted, single-hop, WDM (Wavelength Division Multiplexing) optical architecture, based on a folded bus topology, previously proposed as a broadband access system or as a metro network. The peculiar fairness problem arising in this folded bus based architecture is addressed and an extension of the MetaRing protocol to the WDM scenario, named Multi-MetaRing, is proposed. Feasible Multi-MetaRing strategies are defined and analyzed. Both fair access and high aggregate network throughput can be achieved with a low complexity distributed access protocol by properly handling node access through all WDM channel

Robustness of bus overlays in optical networks

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.Includes bibliographical references (p. 53-56).This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Local area networks (LANs) nowadays use optical fiber as the medium of communication. This fiber is used to connect a collection of electro-optic nodes which form network clouds. A network cloud is a distribution network that connects several external nodes to the backbone, and often takes the form of a star or tree. Optical stars and trees have expensive and inefficient recovery schemes, and as a result, are not attractive options when designing networks. In order to solve this problem, we introduce a virtual topology that makes use of the robustness that is inherently present in a metropolitan area network (MAN) or wide area network (WAN) (long haul network). The virtual topology uses a folded bus scheme and includes some of the elements of the real topology (architecture). By optically bypassing some of the router/switch nodes in the physical architecture, the virtual topology yields better recovery performance and more efficient systems (with respect to cost related to bandwidth and recoverability). We present a bus overlay which uses simple access nodes and is robust to single failures. Our architecture allows the use of existing optical backbone infrastructure. We consider a linear folded bus architecture and introduce a T-shaped folded bus. Although buses are generally not able to recover from failures, we propose a loopback approach. Our approach allows optical bypass of some routers during normal operation, thus reducing the load on routers, but makes use of routers in case of failures. We analyze the behavior of our linear and T-shaped systems under average use and failure conditions. We show that certain simple characteristics of the traffic matrix give meaningful performance characterization. We show that our architecture provides solutions which limit loads on the router.by Ari Levon Libarikian.S.M

Load-balanced optical switch for high-speed router design

A hybrid electro-optic router is attractive, where packet buffering and table lookup are carried out in electrical domain and switching is done optically. In this paper, we propose a loadbalanced optical switch (LBOS) fabric for a hybrid router. LBOS comprises N linecards connected by an N-wavelength WDM fiber ring. Each linecard i is configured to receive on channel λ i. To send a packet, it can select and transmit on an idle channel based on where the packet goes. The packet remains in the optical domain all the way from an input linecard/port to an output linecard/port. Meanwhile, the loading in the ring network is perfectly balanced by spreading the packets for different destinations to use different wavelengths, and packets for the same destination to use different time slots. With the pipelined operation of the LBOS, we show that LBOS is an optical counterpart of an efficient load-balanced electronic switch, and close-to-100% throughput can be obtained. To address the ringfairness problem under the inadmissible traffic patterns, an efficient throughput-fair scheduler for LBOS is also devised. ©2010 IEEE.published_or_final_versio