L. Guo and I. Matta. Search Space Reduction in QoS Routing. Computer Networks: The Int. Journal of Comp. and Tel. Networking, 41(1):73--88, 2003.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....optimization problems, e.g. delay constrained ]east cost routing. Depending on the specifics of a constrained optimization problem, SAMCRA can be used with different length functions, provided they obey the criteria for length in vector algebra. Example length functions are given in [17] In [11] and [13] TAnCP based algorithms with specific length functions are proposed and evaluated. By using length function (1) all QoS measures are considered as equally important. An important corollary of a non linear path length as (1) is that the subsections of shortest paths in multiple dimensions ....

Guo, L. and I. Matra, Search space reduction in QoS routing, Proc. of the 19th III Int. Conference on Distributed Computing Systems, III, May 1999, pp. 142-149.

....problem, its running time grows exponentially in the worst case. Another approach to the RSP problem is to find the k shortest paths w.r.t. a cost function defined based on the combination of link weights and the given constraint, hoping that one of these paths is feasible and near optimal [24] [25], 26] 27] The value of k determines the performance and overhead of this approach; if k is large, the algorithm has good performance but its computational cost is expensive. A similar approach to the k shortest paths is to implicitly enumerate all feasible paths [28] but this approach is ....

L. Guo and I. Matta, "Search space reduction in QoS routing," in Proceedings of the 19th IEEE International Conference on Distributed Computing Systems. IEEE, May 1999, pp. 142 -- 149.

....impact on the number of tickets issued. Probes can only travel along the paths that satisfy the delay requirement. Hence any probe arriving at the destination detects a feasible path. This can also be applied to bandwidth constrained least cost routing. Delay Cost Constrained Routing (DCCR) [27] rapidly generate a near optimal delayconstrained path, then, it employs the k shortest path algorithm proposed by Chong et al. with a new non linear weight function of path delay and cost to efficiently search for a path subject to both the requested delay constraint and the (introduced) cost ....

Liang Guo, lbrahim Matta, "Search Space Reduction in QoS Routing", College of Computer Science, Northeastern University, USA, October 1998, Technical Report NU-CCS-98-09.

....has been identified with the optimal condition relaxed, i.e. Multi constrained path problem(MCP) aiming to find feasible paths (not necessarily optimal) subject to multiple constraints (for example, on delay, cost, etc. A number of heuristic algorithms have been proposed [22] 23] 24] 25] [26]. An extensive survey can be found in [23] Proposal for incorporating QoS routing support into OSPF routing protocol has also been made by Guerin etc. 27] VII. CONCLUSIONS This paper studies the security problem of preventing traffic analysis in wireless ad hoc networks. Our approach inserts ....

Liang Guo and Ibrahim Matta, "Search space reduction in qos routing," in International Conference on Distributed Computing Systems, May 1999.

....researchers have resorted to several heuristics and approximation algorithms. 2 One common approach to the RSP problem is to find the k shortest paths w.r.t. a cost function defined based on the link weights and the given constraint, hoping that one of these paths is feasible and near optimal [20, 32, 15, 19]. The value of k determines the performance and overhead of this approach; if k is large, the algorithm has good performance but its computational cost is prohibitive. A similar approach to the k shortest paths is to implicitly enumerate all feasible paths [3] but this approach is also ....

L. Guo and I. Matta. Search space reduction in QoS routing. In Proceedings of the 19th IEEE International Conference on Distributed Computing Systems, pages 142 -- 149. IEEE, May 1999.

....s and a destination d, and a positive delay constraint # d , find a path P whose cost is minimum among the paths whose delay is less than the delay constraint, # d . Among the proposed heuristics, we will look at the DelayCost Constrained Routing with Search Space Reduction (SSR DCCR) algorithm [6] and Delay Constrained Unicast Routing (DCUR) algorithm [14] Guo and Matta [6] suggest converting the problem into a delay cost constraint problem and using a nonlinear path length definition (as explained in Section 3.3.1) which gives priority to low cost paths. By doing this, a path constrained ....

....cost is minimum among the paths whose delay is less than the delay constraint, # d . Among the proposed heuristics, we will look at the DelayCost Constrained Routing with Search Space Reduction (SSR DCCR) algorithm [6] and Delay Constrained Unicast Routing (DCUR) algorithm [14] Guo and Matta [6] suggest converting the problem into a delay cost constraint problem and using a nonlinear path length definition (as explained in Section 3.3.1) which gives priority to low cost paths. By doing this, a path constrained path optimization problem is converted into a multiple constraints routing ....

L. Guo and I. Matta. "Search Space Reduction in QoS Routing". In Proceedings of the 19th International Conference on Distributed Computing Systems,, Austin, Texas, June 1999.

....an ecient QoS routing algorithm that is able to nd low cost paths that can satisfy varying QoS. The QoS routing problem can be formulated as a constrained shortest (least cost) path routing problem and is known to be NP hard. For one to one (unicast) communication, we proposed a fast algorithm [8], namely SSR DCCR to nd a near optimal solution. This algorithm rst uses Lagrangian relaxation method to de ne a tighter bound on path cost. It then exploits the salient ability of a non linear function of link 3 metrics to accurately search for the optimal feasible solution. Such hybrid ....

L. Guo and I. Matta. \Search Space Reduction in QoS Routing". Proc. Fourth IEEE Symposium on Computers and Communications (ICDCS'99).

....complexity of CAO is O(t(A) Theta jRj) where A is the algorithm used to find unicast paths. The original version of CAO uses a constrained breadth first search algorithm, thus its time complexity can be exponential in some cases. However, even with an efficient unicast routing heuristic (e.g. [8]) it may still need a much longer time than QDMR to form a tree. Table 1 compares various heuristics, including QDMR, in terms of execution time complexity for generating a multicast tree. In Section V, we also compare the various heuristics in terms of actual execution time via extensive ....

....may fall back on using least delay paths (or segments of them) so as to find a feasible tree. A more sophisticated search may yield lower cost paths that are also feasible. To that end, we will investigate the use of our recently proposed heuristic to find low cost QoSconstrained (unicast) paths [8]. An interesting question here is whether the gain in tree cost will justify the additional computational cost. It is worth mentioning that our QDMR algorithm, as well as all the other algorithms presented in this paper, assumes that information regarding the state of each link (i.e. link cost ....

L. Guo and I. Matta, "Search space reduction in QoS routing," in Proc. 19th International Conf. Distributed Computing Systems (ICDCS'99), Austin, Texas, June 1999.

....defines the DCLC problem. Section 3 describes our SSR DCCR algorithm after motivating the design of our path weight function. We compare our SSR DCCR algorithm with some other heuristics via simulations in Section 4. We conclude the paper in Section 5. Due to lack of space, we refer the reader to [6] for more details on the analysis and implementation of the algorithms. 2 Problem Description The Delay Constrained Least Cost (DCLC) problem has been formulated in [12] For completeness, we briefly restate it here. We represent the network by a directed graph G = V; E) where V is the set of ....

....of BG and DCCR, runs in almost the same speed as the original DCCR algorithm. The speed of all of the above 3 algorithms, TAMCRA, DCCR and SSR DCCR, is about 4 times that of the LDP algorithm. The SSR DCCR algorithm was found to be orders of magnitude faster than the optimal CBF algorithm [6]. To see the role k plays in the performance of the heuristics that use the k shortest path method, we conduct another experiment whose results are shown in Figure 4. Increasing k s value results in more candidate paths being examined, thus both heuristics, namely DCCR and TAMCRA, return a cheaper ....

L. Guo and I. Matta. Search Space Reduction in QoS Routing. Technical Report NUCCS -98-09, College of Computer Science, Northeastern University, October 1998. Available from http://www.ccs.neu.edu/home/matta/publications.html.

....complexity of CAO is O(t(A) Theta jRj) where A is the algorithm used to find unicast paths. The original version of CAO uses a constrained breadth first search algorithm, thus its time complexity can be exponential in some cases. However, even with an efficient unicast routing heuristic (e.g. [8]) it may still need a much longer time than QDMR to form a tree. In Section 5, we compare the various heuristics in terms of actual execution time via extensive simulations. Our results show that QDMR is the fastest in generating multicast trees that are competitive in terms of tree cost. This ....

....may fall back on using leastdelay paths (or segments of them) so as to find a feasible tree. A more sophisticated search may yield lower cost paths that are also feasible. To that end, we will investigate the use of our recently proposed heuristic to find low cost QoS constrained (unicast) paths [8]. An interesting question here is whether the gain in tree cost will justify the additional computational cost. It is worth mentioning that our QDMR algorithm, as well as all the other algorithms presented in this paper, assumes that information regarding the state of each link (i.e. link cost and ....

L. Guo and I. Matta. Search Space Reduction in QoS Routing. Technical Report NU-CCS-98-09, College of Computer Science, Northeastern University, October 1998.

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L. Guo and I. Matta. Search Space Reduction in QoS Routing. Computer Networks: The Int. Journal of Comp. and Tel. Networking, 41(1):73--88, 2003.

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L. Guo and I. Matta. Search space reduction in qos routing. In In Proc. of the International Conference on Distributed Computing Systems, pages 142--149, May 1999.

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