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ABSTRACT: Network QoS is essential for supporting real time interactive services such as VoIP. In the differentiated services framework QoS is provided by marking packets to receive preferential forwarding treatment, at each network node. This per hop forwarding treatment at each node may however be ineffective in providing the delay and jitter guarantees unless bounds are also imposed on the number of hops in the service routing paths. Interactive services also require minimal interruptions from network disruptions. Routing on hop limited paths may however have an adverse impact on the proportion of network capacity dedicated for protection to guarantee recovery from failures. In this paper we analyze this tradeoff in the context of MPLS fast reroute when protection capacities are pre-provisioned. We show that the underlying optimization problem is NP hard. We design almost best possible approximation algorithms for the problem and show that they work well in practice as well.
Quality of Service, 2007 Fifteenth IEEE International Workshop on; 07/2007
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ABSTRACT: Supporting fast restoration for general mesh topologies with minimal network over-build is a technically challenging problem. Traditionally, ring-based SONET networks have offered close to 50 ms restoration at the cost of requiring 100% over-build. Recently, fast (local) reroute has gained momentum in the context of MPLS networks. Fast reroute, when combined with pre-provisioning of protection capacities and bypass tunnels, enables faster restoration times in mesh networks. Pre-provisioning has the additional advantage of greatly simplifying network routing and signaling. Thus, even for protected connections, online routing can now be oblivious to the offered protection, and may only involve single shortest path computations. In this paper, we are interested in the problem of reserving the least amount of the network capacity for protection, while guaranteeing fast (local) reroute-based restoration for all the supported connections. We show that the problem is NP-complete, and we present efficient approximation algorithms for the problem. The solution output by our algorithms is guaranteed to use at most twice the protection capacity, compared to any optimal solution. These guarantees are provided even when the protection is for multiple link failures. In addition, the total amount of protection capacity reserved by these algorithms is just a small fraction of the amount reserved by existing ring-based schemes (e.g., SONET), especially on dense networks. The presented algorithms are computationally efficient, and can even be implemented on the network elements. Our simulation, on some standard core networks, show that our algorithms work well in practice as well
IEEE/ACM Transactions on Networking 05/2007; · 2.03 Impact Factor
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ABSTRACT: Multihop infrastructure wireless mesh networks offer increased reliability, coverage, and reduced equipment costs over their single-hop counterpart, wireless local area networks. Equipping wireless routers with multiple radios further improves the capacity by transmitting over multiple radios simultaneously using orthogonal channels. Efficient channel assignment and routing is essential for throughput optimization of mesh clients. Efficient channel assignment schemes can greatly relieve the interference effect of close-by transmissions; effective routing schemes can alleviate potential congestion on any gateways to the Internet, thereby improving per-client throughput. Unlike previous heuristic approaches, we mathematically formulate the joint channel assignment and routing problem, taking into account the interference constraints, the number of channels in the network, and the number of radios available at each mesh router. We then use this formulation to develop a solution for our problem that optimizes the overall network throughput subject to fairness constraints on allocation of scarce wireless capacity among mobile clients. We show that the performance of our algorithms is within a constant factor of that of any optimal algorithm for the joint channel assignment and routing problem. Our evaluation demonstrates that our algorithm can effectively exploit the increased number of channels and radios, and it performs much better than the theoretical worst case bounds
IEEE Journal on Selected Areas in Communications 12/2006; 24(11):1960-1971. · 3.41 Impact Factor
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ABSTRACT: We introduce a novel scheme that flexibly distributes the differential delays in virtual concatenation (VCAT) paths in SONET/SDH networks. We show that this increases the utilization of the network in carrying dynamic traffic and reduces the total buffer requirements.
Optical Fiber Communication Conference, 2005. Technical Digest. OFC/NFOEC; 04/2005
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ABSTRACT: Supporting fast restoration for general mesh topologies with minimal network over build is a technically challenging problem. Traditionally, ring based SONET networks have offered 50 ms restoration at the cost of requiring 100% over-build. Recently, fast (local) reroute has gained momentum in the context of MPLS networks. Fast reroute, when combined with preprovisioning of protection capacities and bypass tunnels, comes close to providing fast restoration for mesh networks. Preprovisioning has the additional advantage of greatly simplifying network routing and signaling. Thus even for protected connections, online routing can now be oblivious to the offered protection, and may only involve single shortest path computations. In this paper we are interested in the problem of reserving the least amount of the network capacity for protection, while guaranteeing fast restoration to all the supported connections. We show that the problem is NP-complete, and we present efficient approximation algorithms for the problem. These guarantees are provided even when the protection is for multiple link failures. In addition, the total amount of protection capacity reserved by these algorithms is just a small fraction of the amount reserved by existing ring-based schemes (e.g. SONET), especially on dense networks. The presented algorithms are computationally efficient, and can even be implemented on the network elements. Our simulation on some standard core networks, show that our algorithms work well in practice as well.
INFOCOM 2004. Twenty-third AnnualJoint Conference of the IEEE Computer and Communications Societies; 04/2004
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ABSTRACT: Network design tools are routinely used in practice to design optical networks that can carry a given set of traffic demands at the least cost The criteria used to route demands during design are often different from those used while routing in the operational network. As a result, the routes computed may be different during design and operations, leading to over- or under- utilization of portions of the network and even failure to route some demands. In this paper, we propose a general solution for this problem, which handles any combination of routing criteria. It works by enhancing the designed network with minimal additional capacity such that it can carry the demands during operations. We also provide experimental results evaluating the performance of this technique and the operational effectiveness of various design algorithms.
Global Telecommunications Conference, 2003. GLOBECOM '03. IEEE; 01/2004
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ABSTRACT: Fast shared restoration is critical to the success of WDM mesh networking. A restricted form of sharing called K-sharing was recently proposed, which allows rapid, signaling-free restoration. However, the routing and design algorithms used for traditional shared restoration do not work for this scheme. Also, K-sharing can potentially increase capacity requirements in the network because it limits sharing. In this paper, we present novel routing and design algorithms for K-shared networks. We also show that a practical version of the routing problem is NP-hard and present heuristics to solve it. We also summarize experimental results demonstrating that the additional capacity requirements imposed by K-sharing are in fact minimal in practice.
Global Telecommunications Conference, 2003. GLOBECOM '03. IEEE; 01/2004
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ABSTRACT: The last decade has witnessed wide-scale deployment of optical networks to support the growing data traffic. This success can be traced back to advances in optical transmission systems such as dense wavelength-division multiplexing, Raman amplification, etc., which allow a single fiber to carry several wavelengths very far, while sharing expensive equipment. However, these cutting-edge technologies require careful placement of amplifiers and other network elements to ensure error-free propagation of the signal and to minimize costs. In practice, it is common to use a set of constraints to ensure valid configurations for deployment. It is nontrivial to identify the optimal configuration under all but the simplest constraints. In this paper, we consider a set of constraints with varying flexibilities and present algorithms for efficiently computing the cost-optimal configuration under them. We also present experimental and theoretical results to evaluate the various constraints and algorithms.
Journal of Lightwave Technology 12/2003; 21(11):2499- 2510. · 2.78 Impact Factor
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ABSTRACT: Deploying an Optical Line System involves minimizing costs while obeying OSNR limits and other constraints. This paper studies the impact of various types of constraints on network costs and presents efficient algorithms for finding the least-cost configurations under those constraints.
Optical Communication, 2002. ECOC 2002. 28th European Conference on; 10/2002
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ABSTRACT: Location tracking has several applications in mobile (cellular or ad hoc) networks, such as location-based routing algorithms and consumer services. It is often difficult to compute the location of a node precisely because of the infrastructure costs and the errors inherent in most tracking techniques. Furthermore, this accuracy differs amongst nodes based on the scattered availability of equipment such as GPS. We focus on heterogeneous mobile networks, wherein some nodes know their locations more precisely than others and there is a short-range peer-to-peer communication channel such as Bluetooth or 802.11. We consider a generalized notion of location, called vicinity, which is the set of potential locations for a node. We formulate a hierarchy of distance constraints that can be applied in a network and devise efficient distributed techniques for computing the most optimal (smallest) vicinities under various constraint classes. In particular, our algorithms use both proximity and non-proximity relationships between the nodes. We present simulation results establishing the effectiveness of using these different types of constraints.
Global Telecommunications Conference, 2004. GLOBECOM '04. IEEE;
