Modern high-performance communication networks pose a number of challenging problems concerning the efficient allocation of resources to connection requests. In all-optical networks with wavelength-division multiplexing, connection requests must be assigned paths and colors (wavelengths) such that intersecting paths receive different colors, and the goal is to minimize the number of colors used. This path coloring problem is proved NP-hard for undirected and bidirected ring networks. Path coloring in undirected tree networks is shown to be equivalent to edge coloring of multigraphs, which implies a polynomial-time optimal algorithm for trees of constant degree as well as NP-hardness and an approximation algorithm with absolute approximation ratio 4:3 and asymptotic approximation ratio 1:1 for trees of arbitrary degree. For bidirected trees, path coloring is shown to be NP-hard even in the binary case. A polynomial-time optimal algorithm is given for path coloring in undirected or bidir...

Call admission control is the problem of deciding for a given set of connection requests which of them to accept and which to reject, with the goal of maximizing the profit obtained from the accepted requests. The problem is considered in a scenario with advance reservations where users can specify several alternatives for when and how they want their connections to be established. Two variants are studied: In BCA (batch call admission), all calls request to be established at the same time. In GCA (general call admission), every request specifies a starting time and duration. Both variants generalize the well-studied unsplittable flow problem. For star networks, approximation algorithms with constant ratio for BCA with arbitrary edge capacities and for GCA with unit edge capacities are presented. For GCA with arbitrary edge capacities, ratio O(logR) is achieved, where R is the ratio of the maximum to the minimum edge capacity. For trees and trees of rings with unit edge

. To exploit the full capacity of distributed systems for image analysis tasks they must be processed in parallel. However, developing parallel programs is complicated and often results in architecture-dependent code that is difficult to port to different machines. Thus there is the need of more flexible, architecture independent methods for an automatic parallelization of tasks. This paper introduces such a method and describes a multi-agent system for the automatic parallelization of image analysis tasks. The user provides a specification of the task that is used by the agents to plan and control its parallel processing within a distributed system. At this, they make use of different methods of parallel processing and consider the specific qualification and the actual load of processors when deciding about the scheduling and mapping of tasks and data. 1. Introduction On the hardware sector there is still a strong trend to parallel hardware to speed up image analysis task...

Abstract: Scheduling resources on Grids is a well-known problem. The extension of Grids to LambdaGrids requires the sched-uling of lambdas, i.e., end-to-end high-speed circuits. In this paper, we propose a scheduling heuristic for such lambdas in sup-port of large-scale scientific applications that require high-throughput transfers of large files. We refer to this heuristic as “Varying-Bandwidth List Scheduling ” (VBLS) because the scheduler returns a Time-Range-Capacity (TRC) allocation vector with varying bandwidth levels assigned for different time ranges within the duration of a transfer. The advantage of VBLS over a fixed-bandwidth allocation scheme is that it allows the scheduler to backfill any holes left in resource allocations. Enabling VBLS requires end host applications to specify the file size in their transfer requests. To characterize VBLS, we ran simulation experiments that show that VBLS performance approaches packet-switching performance. This result means that file transfers can take advantage of bandwidth that becomes available subsequent to the start of transfers, a current and critical drawback of typical fixed-bandwidth allocation schemes in circuit-switched networks. Next, we identify the key features needed in a transport protocol that works in conjunction with VBLS and develop the “Varying Bandwidth Transport Protocol” (VBTP). VBTP is a rate based flow control scheme that is coupled with Selective-ARQ based error control. Finally, the paper concludes with a discussion on the impact of transport problems on VBLS scheduling.

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Multiplexing (TDM/FDM) schemes are typically used in a fixedbandwidth allocation mode, which means a call is assigned a fixed amount of bandwidth for its whole duration. For file transfers, such schemes compare unfavorably against statistical multiplexing schemes such as packet switching. This is because in fixedbandwidth TDM/FDM schemes, once a file transfer is allocated a certain bandwidth, it cannot take advantage of bandwidth that becomes available as a result of other transfers completing. In this paper, we propose a Varying-Bandwidth List Scheduling (VBLS) heuristic for TDM/FDM networks in which a sender specifies the file size, maximum bandwidth limit and a desired start time, and the network returns a time-range-capacity allocation vector assigning varying bandwidth levels in different time ranges for the transfer. Simulation results show that VBLS performance is indistinguishable from packet-switching performance, and hence superior to the fixed-bandwidth allocation mode.

We discuss several problems in the area of scheduling in WDM networks. We start with a short overview of WDM technologies. Then, we shortly describe scheduling on a single optical fiber, in a WDM LAN, and in a WDM WAN. In the end we give a sample of scheduling problems in WDM networking. We mainly overview the computational complexity, the off-line approximability, and the online approximability of the problems. We summarize what is known about these problems, we discuss related results, and provide many pointers to the literature.