UWSpace

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Recent Submissions

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    DEWS: A decentralized engine for web search
    (University of Waterloo, 2012-09-04) Ahmed, Reaz; Haque, Rakibul; Bari, Md. Faizul; Boutaba, Raouf; Mathieu, Bertrand
    The way we explore the web is largely governed by centrally controlled, clustered search engines, which is not healthy for our freedom in the Internet. A better solution is to enable the web to index itself in a decentralized manner. In this work we propose a decentralized web search mechanism, named DEWS, which will enable the existing webservers to collaborate with each other to form a distributed index of the web. DEWS can rank the search results based on query keyword relevance and relative importance of websites. DEWS also supports approximate matching of query keywords and incremental retrieval of search results in a decentralized manner. We use the standard LETOR 3.0 dataset to validate the DEWS protocol. Simulation results show that the ranking accuracy of DEWS is very close to the centralized case, while network overhead for collaborative search and indexing is logarithmic on network size. Simulation results also show that DEWS is resilient to changes in the available pool of indexing webservers and works efficiently even in presence of heavy query load.
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    αRoute: A name based routing scheme for information centric networks
    (University of Waterloo, 2012-09-04) Ahmed, Reaz; Bari, Md. Faizul; Chowdhury, Shihabur Rahman; Rabbani, Md. Golam; Boutaba, Raouf; Mathieu, Bertrand
    One of the crucial building blocks for Information Centric Networking (ICN) is a name based routing scheme that can route directly on content names instead of IP addresses. However, moving the address space from IP addresses to content names brings scalability issues to a whole new level, due to two reasons. First, name aggregation is not as trivial a task as the IP address aggregation in BGP routing. Second, the number of addressable contents in the Internet is several orders of magnitude higher than the number of IP addresses. With the current size of the Internet, name based, anycast routing is very challenging specifically when routing efficiency is of prime importance. We propose a novel name-based routing scheme (αRoute) for ICN that offers efficient bandwidth usage, guaranteed content lookup and scalable routing table size. αRoute consists of two components: an alphanumeric Distributed Hash Table (DHT) and an overlay to underlay (Internet topology) mapping algorithm. Simulation results show that αRoute performs significantly better than Content Centric Network (CCN) [1] in terms of network bandwidth usage, lookup latency and load balancing.
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    Minimizing cache usage in paging
    (University of Waterloo, 2012-09-30) L'Opez-Ortiz, Alejandro; Salinger, Alejandro
    Traditional paging models seek algorithms that maximize their performance while using the maximum amount of cache resources available. However, in many applications this resource is shared or its usage involves a cost. In this work we introduce the Minimum Cache Usage problem, which is an extension to the classic paging problem that accounts for the efficient use of cache resources by paging algorithms. In this problem, the cost of a paging algorithm is a combination of both its number of faults and the amount of cache it uses, where the relative cost of faults and cache usage can vary with the application. We present a simple family of online paging algorithms that adapt to the ratio between cache and fault costs, achieving competitive ratios that vary with, and that are between 2 and the cache size k. Furthermore, for sequences with high locality of reference, we show that the competitive ratio is at most 2, and provide evidence of the competitiveness of our algorithms on real world traces. Finally, we show that the offline problem admits a polynomial time algorithm. In doing so, we define a reduction of paging with cache usage to weighted interval scheduling on identical machines.
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    On minimum- and maximum-weight minimum spanning trees with neighbourhoods
    (University of Waterloo, 2012-08-27) Dorrigiv, Reza; Fraser, Robert; He, Meng; Kamali, Shahin; Kawamura, Akitoshi; Lopez-Ortiz, Alejandro; Seco, Diego
    We study optimization problems for the Euclidean minimum spanning tree (MST) on imprecise data. To model imprecision, we accept a set of disjoint disks in the plane as input. From each member of the set, one point must be selected, and the MST is computed over the set of selected points. We consider both minimizing and maximizing the weight of the MST over the input. The minimum weight version of the problem is known as the minimum spanning tree with neighborhoods (MSTN) problem, and the maximum weight version (max-MSTN) has not been studied previously to our knowledge. We provide deterministic and parameterized approximation algorithms for the max-MSTN problem, and a parameterized algorithm for the MSTN problem. Additionally, we present hardness of approximation proofs for both settings.
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    Delay differentiation without rate tinkering
    (University of Waterloo, 2012-08-23) Karsten, Martin; Schmitt, Jens; Beck, Michael
    Link buffering is a key element in packet-switched networks to absorb temporary traffic bursts without excessive dropping. The resulting queuing delay is a critical performance factor. Research on buffer management typically studies differentiated buffer allocation to control forwarding rates or buffer size management to control the overall queuing delay. On the other hand, delay differentiation is typically accomplished by packet scheduling and thus implies rate differentiation. In this paper a radically simpler approach to delay differentiation through buffer management is studied. Instead of actively managing throughput, Delay Differentiated FIFO (DDF) uses a simple drop-based mechanism to offer multiple delay classes, but closely tracks the per-class throughput of the corresponding single-class FIFO queuing system. End systems choose which delay class best balances their loss and delay requirements. Architecturally, DDF does not interfere with management and policy decisions at end and edge systems and does not add another control loop to the existing mix of traffic management techniques. The forwarding characteristics of DDF are analyzed using stochastic models. Refinements to the basic algorithm are presented and it is shown how DDF can be implemented with very little execution overhead compared to FIFO. Packet-level simulation results are presented to complement the analytical findings.