Prioritized Contention Resolution Scheme for Grid Services over OBS Networks Burak Kantarci, Sema Oktug, and D.Turgay Altilar Istanbul Technical University, Department of Computer Engineering, Istanbul, Turkey (bkantarci, oktug, altilar@itu.edu.tr) Abstract In this paper a novel contention resolution scheme, namely Expanded Priority Vector (EPV) approach is proposed to support differentiated Grid service over OBS networks. EPV is an enhancement to a previously proposed application-aware contention resolution scheme for the OBS-based-Grid services in the literature. By using the EPV, we keep all the advantages of the application-aware contention resolution. Moreover, we introduce fairness among the contending jobs of the same class by taking care of the two least significant digits of the vector. Those two digits pay attention to the remaining distance to the resource and the job size. By simulations, we show that EPV based policy reduces the blocking probability for all classes of submitted jobs. 1. Introduction As a result of the high computational and storage demand in scientific applications in the technical community, local resources became suffering from less efficient computational power. This phenomenon has caused the philosophy of Grid Computing to develop [1]. The most favorable example of an high computational demand application is the particle physics experiments. Those experiments require a computational resource of several petabytes/year and expected to rise up to several exabytes/year. Therefore the users are expected to access and use remote resources that are distributed in different locations forming a grid. Basically, the grid consist of heterogeneous computing and storage units that are connected to each other via LANs, WANs or metro networks, and that are distributed into multiple administrative domains. Besides these, the grid is also supposed to have no central administration unit. Several types of data and processing intensive grid applications can be considered in order to make the proposed architecture be based on. The first one is high performance computing and visualization applications. Multimedia video editing is a good example for this kind of computationally intensive jobs and that require TBytes of storage and TFlops of computational resources. An online visualization application is another type of job in which the computational capacity requirement is as much as a few thousands of GFlops, and a few tens of milliseconds of transmission and processing latency even though the storage requirement is not as much as the previous application example. Today, in order to build the communication backbone for the grid, optical networking technologies are employed [2]. Most of the optical networking technologies are based on optical circuit switching (OCS). In OCS, wavelength division multiplexing is used on the fibers. In order to transmit a job from a source to destination, the source has to set up a connection with the destination over a pre-determined routing path and a wavelength. Unless the connection is terminated, the transmission resources are dedicated to the source. For a high performance computing and visualization application, the required transmission times of jobs are as short as a few hundred microseconds or tens of milliseconds. However, in an OCS architecture, the main overhead of the job submission into the grid comes from the connection setup and release times that are in hundreds of milliseconds. Besides these, since the resources are devoted to a connection until the connection is released, OCS leads to a waste of the grid resources. The data intensive user applications need high access bandwidth. As we state above, dedicating the network resources to a job submission in a connection oriented structure increases the cost of constructing a grid dramatically. Although the dedicated grid architecture provides a job to be submitted at full wavelength capacity, as a result of the grid service requests' non- deterministic arrival, this may not be the optimal case. In many of the grid applications, the job sizes are significantly short, which leads to the holding time of Communication Networks and Services Research Conference 978-0-7695-3135-9/08 $25.00 © 2008 IEEE DOI 10.1109/CNSR.2008.55 232 Communication Networks and Services Research Conference 978-0-7695-3135-9/08 $25.00 © 2008 IEEE DOI 10.1109/CNSR.2008.55 232 Communication Networks and Services Research Conference 978-0-7695-3135-9/08 $25.00 © 2008 IEEE DOI 10.1109/CNSR.2008.55 234 Communication Networks and Services Research Conference 978-0-7695-3135-9/08 $25.00 © 2008 IEEE DOI 10.1109/CNSR.2008.55 234 Communication Networks and Services Research Conference 978-0-7695-3135-9/08 $25.00 © 2008 IEEE DOI 10.1109/CNSR.2008.55 234