20946285
Auction Based Resource Allocation in Grids
Auctions have been used as the market mechanism for allocating resources to users in a grid. However, most of the existing work either consider only homogeneous resources, or pick a resource randomly for bidding to increase the number of jobs finishing within their deadlines. Random selection does not consider resource capabilities and hence, do not optimize other important metrics like the average turnaround time and the average budget spent per job etc. In this paper, we consider the resource allocation problem in a grid with heterogeneous resources. We present allocation policies using sealed-bid auction that reduce the average turnaround time and the average budget spent per job, while still maintaining a high number of jobs finishing within their deadlines. Simulation results are presented to evaluate the performance of the policies.
19017935
Fault-containing network protocols
Self-stabilization is a simple and elegant approach towards designing fault-tolerant network protocols. While self-stabilization provides automatic recovery from arbitrary transient faults, self-stabilizing systems do not incorporate any optimization for more efficient recovery from limited transient faults, even though such limited faults are more likely to occur in practice than arbitrary faults. Fault-containing self-stabilizing protocols are proposed to efficiently contain the effects of more frequent, limited transient faults while retaining the desirable property of self-stabilization. In this paper, we propose a methodology for designing fault-containing selfstabilizing network protocols. The methodology views the properties of self-stabilization and fault-containment in separation. Since self-stabilizing protocols already exist for many important network problems, the design starts with an existing self-stabilizing protocol, and adds to it the fault-containment property. The feasibilitv of this technique is illustrated bv the design of a fault-containing self-stabilizing protocol for the breadthfirst-search (BFS) spanning tree problem. The applicability of the technique used in deriving the BFS protocol to other problems is also discussed.
3086074
An Exercise in Fault-Containment: Self-Stabilizing Leader Election
Self-stabilizing algorithms are designed to guarantee convergence to some desired stable state from arbitrary initial states arising out of an arbitrarily large number of faults. However, in a well-designed system, the simultaneous occurrence of a large number of faults is rare. It is therefore desirable to design algorithms that are not only self-stabilizing, but also have the ability to recover very fast from a bounded number of faults. As an illustration, we present a simple self-stabilizing leader election protocol that recovers in O(1) time from a state with a single transient fault on oriented rings. Only the faulty node and its two neighbors change their state during convergence to a stable state. Thus, the effect of a single fault is tightly contained around the fault. The technique for transforming a self-stabilizing algorithm into its fault-contained version is simple and general, and can be applied to other problems as well that satisfy certain properties.
32945610
A Framework for Automatic Identification of the Best Checkpoint and Recovery Protocol
Fault tolerance is important for a distributed system to increase its reliability and throughput. Checkpoint and recovery protocols have been proposed as fault tolerance for non-critical applications. The performance of checkpoint and recovery protocols plays an important role in the overall performance of a distributed system. The performance of these protocols depends on system characteristics as well as an application characteristics. In this paper, we propose a novel technique to automatically identify the checkpoint and recovery protocol which is likely to perform the best for a given system and an application the system is currently running. We present experimental results to show that the scheme can efficiently determine a suitable checkpoint and recovery protocol for many applications.
65058359
Group Based Routing in Disconnected Ad Hoc Networks
In this paper, we propose a routing protocol for disconnected ad hoc networks where most nodes tend to move about in groups. To the best of our knowledge, no routing protocol for disconnected ad hoc networks has been designed earlier keeping in mind possible group patterns formed by the movement of nodes. Our protocol works by identifying groups using an efficient distributed group membership protocol, and then routing at the group level, rather than at the node level. The protocol is designed so that existing concepts of routing in disconnected ad hoc networks can be extended to work at the group level. Initial simulations across a broad spectrum of parameters suggest that our protocol performs better in terms of delivery ratio and latency over traditional approaches like AODV [1], and also over disconnected routing approaches like the 2-Hop routing protocol [2].
9811083
Performance enhancement of a contract net protocol based system through instance-based learning
The contract net protocol (CNP) is a widely used coordination mechanism in multiagent systems. It has a lot of communication overhead due to the broadcast of the task announcements. The performance of the CNP degrades drastically when the number of communicating agents and the number of tasks announced increases. Hence, it has problems of scalability. In order to overcome this limitation, an instance-based learning (IBL) mechanism is designed that uses previously stored instances in order to select a target agent. This avoids the expensive bidding process. The scheme is implemented in a simulated distributed hospital system where the CNP is used for resource sharing across hospitals. Experimental results demonstrate that with the incorporation of the IBL, the system performance improves significantly. The system is better scalable with respect to the number of tasks.
14465668
The economics of network management
Why are pricing issues the key to infrastructure investment and future growth of the Internet? The Economics of network management I t is not surprising that researchers in network technology are utilizing ideas from the field of economics since it provides the conceptual understanding of underlying constructs such as usage and resource allocation. Proper resource allocation plays a key role in improving network performance. There are two primary approaches to economic resource allocation: quantity limits, and pricing. The former has the advantage of low accounting costs. However, it requires central administration and, for network users wishing to purchase more quantity than allocated, a pricing schedule has to be developed. The pricing approach does not enforce any quantity limits. Instead, users self-select the quantity they are willing to purchase at prevailing prices. The pricing approach decentralizes the resource allocation problem but has higher accounting costs since usage needs to be monitored and billed. The role of pricing as a resource allocation mechanism will be examined here, since central administration of quotas would be difficult in a global network. Furthermore, a pricing mechanism may still be needed to meet user demands in e-commerce. While the short-term role of economic pricing is to manage the network resources more efficiently, in the long run it could play an important role in the design of new network protocols. For example, new technological developments with priority classes in the IPv6 Internet protocol [3] will present the challenge of defining an economic basis for priority allocation. The Internet traffic-pricing problem for e-commerce subsumes traditional telecommuni-cation pricing policies and is much more complex. Traditional telecommunication systems offer a single quality level for their services on a given type of network, for example, the ability to carry voice data at a desired rate on a telephone network. However, in e-commerce there is a rich collection of services that require different levels of service quality over the same data communication network. For example, during a telnet session a user requires a high-speed and low-volume data transfer for real-time interaction with a server. On the other hand, a video conference needs clarity and coordination in picture and sound, necessitating a much more complex set of service quality attributes, such as synchronization of information sent via different interoperable applications (video, audio, and text). In addition, audio and video applications require high-volume and high-speed transfers with low variability in data transfer rates. These …
11033759
Oblivious network design
Consider the following network design problem: given a network <i>G = (V, E)</i>, source-sink pairs {<i>s</i><inf><i>i</i></inf>, <i>t</i><inf><i>i</i></inf>} arrive and desire to send a unit of flow between themselves. The cost of the routing is this: if edge <i>e</i> carries a total of <i>f</i><inf><i>e</i></inf> flow (from all the terminal pairs), the cost is given by Σ <inf><i>e</i></inf><i>l</i>(<i>f</i><inf><i>e</i></inf>), where <i>l</i> is some concave cost function; the goal is to minimize the total cost incurred. However, we want the routing to be <i>oblivious</i>: when terminal pair {<i>s</i><inf><i>i</i></inf>, <i>t</i><inf><i>i</i></inf>} makes its routing decisions, it does not know the current flow on the edges of the network, nor the identity of the other pairs in the system. Moreover, it does not even know the identity of the function <i>l</i>, merely knowing that <i>l</i> is a concave function of the total flow on the edge. How should it (obliviously) route its one unit of flow? Can we get competitive algorithms for this problem?In this paper, we develop a framework to model <i>oblivious network design</i> problems (of which the above problem is a special case), and give algorithms with poly-logarithmic competitive ratio for problems in this framework (and hence for this problem). Abstractly, given a problem like the one above, the solution is a multicommodity flow producing a "load" on each edge of <i>L</i><inf><i>e</i></inf> = <i>l</i>(<i>f</i><inf>1</inf>(<i>e</i>),<i>f</i><inf>2</inf>(<i>e</i>), ..., <i>f</i><inf><i>k</i></inf>(<i>e</i>)), and the total cost is given by an "aggregation function" agg (<i>L</i><inf><i>e</i>1</inf>,...,<i>L</i><inf><i>em</i></inf>) of the loads of all edges. Our goal is to develop oblivious algorithms that approximately minimize the total cost of the routing, knowing the aggregation function agg, but merely knowing that <i>l</i> lies in some class C, and having no other information about the current state of the network. Hence we want algorithms that are simultaneously "function-oblivious" as well as "traffic-oblivious".The aggregation functions we consider are the max and σ objective functions, which correspond to the well-known measures of <i>congestion</i> and <i>total cost</i> of a network; in this paper, we prove the following:• If the aggregation function is Σ, we give an oblivious algorithm with <i>O</i>(log<sup>2</sup> <i>n</i>) competitive ratio whenever the load function <i>l</i> is in the class of <i>monotone sub-additive functions</i>. (Recall that our algorithm is also "function-oblivious"; it works whenever each edge has a load function <i>l</i> in the class.)• For the case when the aggregation function is max, we give an oblivious algorithm with <i>O</i>(log<sup>2</sup> <i>n</i> log log <i>n</i>) competitive ratio, when the load function <i>l</i> is a <i>norm;</i> we also show that such a competitive ratio is not possible for general sub-additive functions.These are the first such general results about oblivious algorithms for network design problems, and we hope the ideas and techniques will lead to more and improved results in this area.
2367227
Parallel Algorithms For Vehicle Routing Problems
Vehicle routing problems involve the navigation of one or more vehicles through a network of locations. Locations have associated handling times as well as time windows during which they are active. The arcs connecting locations have time costs associated with them. In this paper, we consider two different problems in single vehicle routing. The first is to find least time cost routes between all pairs of nodes in a network for navigating vehicles; we call this the all pairs routing problem. We show that there is an O(log3 n) time parallel algorithm using a polynomial number of processors for this problem on a CREW PRAM. We next consider the problem in which a vehicle services all locations in a network. Here, locations can be passed through at any time but only serviced during their time window. The general problem is -complete under even fairly stringent restrictions but polynomial algorithms have been developed for some special cases. In particular, when the network is a line, there is no time cost in servicing a location, and all time windows are unbounded at either their lower or upper end, O(n2) algorithms have been developed. We show that under the same conditions, we can reduce this problem to the all pairs routing problem and therefore obtain an O(log3 n) time parallel algorithm on a CREW PRAM.
2668248
A Data Model for Querying Wavelet Features in Image Databases
Multimedia databases deal with storage and retrieval of complex descriptors of image contents, called features. Traditional techniques consider features as “black boxes,” often represented as vectors for which the only operation defined is distance computation. This “modus describendi” resulted in the widespread utilization of similarity queries, which rest solely on the computation of distances between feature vectors. The capacity to express queries more complex than simple similarity, however, rests on the possibility of describing and manipulating the structure of the features. In order to achieve this, features should be described as complex data types inside the database, and opportune operators for manipulating these data types should be defined. In this paper we try to demonstrate the efficacy and feasibility of such a program by modeling a widely used image feature: the wavelet transform. We represent features using a complex data type derived from arrays, and propose a basic algebra from which operators can be derived to manipulate and query wavelet features.
9282309
Approximation via cost-sharing: a simple approximation algorithm for the multicommodity rent-or-buy problem
We study the multicommodity rent-or-buy problem, a type of network design problem with economies of scale. In this problem, capacity on an edge can be rented, with cost incurred on a per-unit of capacity basis, or bought, which allows unlimited use after payment of a large fixed cost. Given a graph and a set of source-sink pairs, we seek a minimum-cost way of installing sufficient capacity on edges so that a prescribed amount of flow can be sent simultaneously from each source to the corresponding sink. The first constant-factor approximation algorithm for this problem was recently given by Kumar et al.; however, this algorithm and its analysis are both quite complicated, and its performance guarantee is extremely large. In this paper, we give a conceptually simple 12-approximation algorithm for this problem. Our analysis of this algorithm makes crucial use of cost sharing, the task of allocating the cost of an object to many users of the object in a "fair" manner. While techniques from approximation algorithms have recently yielded new progress on cost sharing problems, our work is the first to show the converse - those ideas from cost sharing can be fruitfully applied in the design and analysis of approximation algorithms.