Routing In All-optical Networks Research Articles

On Nash Equilibria in Non-Cooperative All-Optical Networks

We consider the problem of determining a routing in all-optical networks, in which some couples of nodes want to communicate. In particular, we study this problem from the point of view of a network provider that has to design suitable payment functions for non-cooperative agents, corresponding to the couples of nodes wishing to communicate. The network provider aims at inducing stable routings (i.e., routings corresponding to Nash equilibria) using a low number of wavelengths. We consider three different kinds of local knowledge that agents may exploit to compute their payments, leading to three corresponding information levels. Under complete information, the network provider can design a payment function, inducing the agents to reach a Nash equilibrium mirroring any desired routing. If the price to an agent is computed only as a function of the wavelengths used along connecting paths (minimal level) or edges (intermediate level), the most reasonable functions either do not admit Nash equilibria or admit very inefficient ones, i.e., with the largest possible price of anarchy. However, by suitably restricting the network topology, a constant price of anarchy for chains and rings and a logarithmic one for trees can be obtained under the minimal and intermediate levels, respectively.

Routing in All-Optical Networks Using Recursive State Space Technique

In this paper, we have minimized the effects of failures on network performance, by using suitable Routing and Wavelenghth Assignment(RWA) method without disturbing other performance criteria such as blocking probability(BP) and network management(NM). The computation complexity is reduced by using Kalaman Filter(KF) techniques. The minimum reconfiguration probability routing (MRPR) algorithm must be able to select most reliable routes and assign wavelengths to connections in a manner that utilizes the light path(LP) established efficiently considering all possible requests.

Mixing Convergence and Deflection Strategies for Packet Routing in All-Optical Networks

We present two routing algorithms based on deflection and convergence, which are able to provide high bandwidth and an ending guarantee for the end-to-end delay in a core network. We study the performance of these routing techniques by using simulations, and we prove the bounds on the delay.

OSNR model to consider physical layer impairments in transparent optical networks

We propose a model that considers several physical impairments in all-optical networks based on optical signal-to-noise degradation. Our model considers the gain saturation effect and amplified spontaneous emission depletion in optical amplifiers, coherent crosstalk in optical switches, and four-wave mixing in transmission fibers. We apply our model to investigate the impact of different physical impairments on the performance of all-optical networks. The simulation results show the impact of each impairment on network performance in terms of blocking probability as a function of device parameters. We also apply the model as a metric for impairment-constraint routing in all-optical networks. We show that our proposed routing and wavelength assignment algorithm outperforms two common approaches.

Overlap Degree Aware Routing in All-Optical Routing Networks

Dynamic routing and wavelength assignment (RWA) is an attractive method for the efficient use of network resources in all-optical networks. We present a novel fixed alternate routing method referred to as Overlap-Degree Aware (ODA) routing in all-optical networks. A lot of researchers have focused on the shortest path routing and alternate shortest path routing taking into acount link and wavelength usage so as to reduce the consumption of network resources. The authors, however, believe that in order to minimize the blocking probability, it is important to consider not only the consumption of link and wavelength resources but also the existence of the other flows when a routing decision is made. The ODA routing decides routes using the knowledge of ingress-egress node pairs, and tries to prevent future path requests from being blocked unnecessarily by reserving link and wavelength resources for the future requests. Our simulation results show that our new routing algorithm outperforms Fixed-Alternate Routing (FAR) and Weighted Least Congestion Routing (WLCR) from the viewpoint of call blocking probability.

Convergence Routing under Bursty Traffic: Instability and an AIMD Controller

Routing in all optical networks is an important issue. Deflection routing provides a high throughput but suffers from unbounded transportation time. Convergence routing provides ending guarantee to packets entering the network. We focus on the Eulerian routing technique (convergence routing based on an Eulerian directed cycle), and several improvements which increase the throughput. In this paper, we show that these routing algorithms are very unstable when the traffic occurs by bursts. Thus an admission control is needed to maintain a high throughput.

Link-State-Based Algorithms for Dynamic Routing in All-Optical Networks with Ring Topologies

The increased usage of large bandwidth in optical networks raises the problems of efficient routing to allow these networks to deliver fast data transmission with low blocking probabilities. Due to limited optical buffering in optical switches and constraints of high switching speeds, data transmitted over optical networks must be routed without waiting queues along a path from source to destination. Moreover, in optical networks deprived of wavelength converters, it is necessary for each established path to transfer data from source to destination by using only one wavelength. To solve this NP-hard problem, many algorithms have been proposed for dynamic optical routing like Fixed-Paths Least Congested (FPLC) routing or Least Loaded Path Routing (LLR). This paper proposes two heuristic algorithms based on former algorithms to improve network throughput and reduce blocking probabilities of data transmitted in all-optical networks with regard to connection costs. We also introduce new criteria to estimate network congestion and choose better routing paths. Experimental results in ring networks show that both new algorithms achieve promising performance.

Randomized path coloring on binary trees

Motivated by the problem of WDM routing in all-optical networks, we study the following NP-hard problem. We are given a directed binary tree T and a set R of directed paths on T. We wish to assign colors to paths of R, in such way that no two paths that share a directed arc of T are assigned the same color, and the total number of colors used is minimized. Our results are expressed in terms of the depth of the tree and of the maximum load l of R, i.e. the maximum number of paths that go through a directed arc of T. So far, only deterministic greedy algorithms have been presented for the problem. The best known algorithm colors any set R of maximum load l using at most 5l/3 colors. Alternatively, we say that this algorithm has performance ratio 5 3 . It is also known that no deterministic greedy algorithm can achieve a performance ratio better than 5 3 . In this paper we define the class of greedy algorithms that use randomization. We study their limitations and prove that, with high probability, randomized greedy algorithms cannot achieve a performance ratio better than 3 2 when applied for binary trees of depth Ω(l) , and 1.293− o(1) when applied for binary trees of constant depth. Exploiting inherent properties of randomized greedy algorithms, we obtain the first randomized algorithm for the problem that uses at most 7l/5+ o(l) colors for coloring any set of paths of maximum load l on binary trees of depth O(l 1/3−ε) , with high probability. We also present an existential upper bound of 7l/5+ o(l) that holds on any binary tree. For the analysis of our bounds we develop tail inequalities for random variables following hypergeometrical probability distributions that might be of their own interest.

A Virtual Wavelength Translation Scheme for Routing in All-Optical Networks

This paper considers wavelength routed WDM networks where multiple fibers are used for each communication link. For such networks, the effect of wavelength translation can be achieved without explicit use of wavelength translators. We call this as virtual wavelength translation and study the routing issues considering dynamic lightpath allocation. Using multiple (or a bundle of) fibers for each link also allows us to have bundles of varying sizes to accommodate anticipated differences in traffic through different communication links of the network. The paper considers the blocking probabilities of all-optical networks when centralized and distributed lightpath allocation schemes are used.

Algorithms for Dynamic Routing in All-Optical Networks

In this paper, we have studied a number of algorithms for routing in all-optical wavelength routed networks. We have considered situations where a lightpath is dynamically created in response to a request for communication and the WDM channels constituting the lightpath are reclaimed when the communication is over. We have looked at two schemes for dynamic wavelength allocation. In the first scheme we have assumed the existence of a central agent to maintain a database of existing lightpaths where the central agent attempts to generate a new lightpath in response to a request for communication. In the second scheme, we attempt to generate a new lightpath using a distributed algorithm. In the first scheme we have exploited the existence of multiple paths between any pair of nodes in a network in order to reduce the blocking probability. For the second scheme, we have proposed three distributed strategies to determine, if possible, a lightpath when there is a request for communication. Each of these strategies have their advantages and disadvantages in terms of the expected blocking probability and the set-up time. We have studied the performances of both the schemes using Monte Carlo simulation.

Ondashline routing in all-optical networks

The paper deals with ondashline routing in wavelength division multiplexing (WDM) optical networks. A sequence of requests arrives over time, each is a pair of nodes to be connected by a path. The problem is to assign a wavelength and a path to each pair, so that no two paths sharing a link are assigned the same wavelength. The goal is to minimize the number of wavelengths used to establish all connections. Raghavan and Upfal (Proc. 26th Annual Symp. on Theory of Computing, 1994, pp. 133–143) considered the off-line version of the problem, which was further studied in Aumann and Rabani (Proc. 6th ACM-SIAM Symp. on Discrete Algorithms, 1995, pp. 567–576), Kaklamanis and Persiano (Proc. 4th Annual European Symp. on Algorithms, Lecture Notes in Computer Science, vol. 1136, Springer, Berlin, 1996, pp. 460–470), Mihail et al. (Proc. 36th IEEE Annual Symp. on Foundations of Computer Science, 1995, pp. 548–557), Rabani, (Proc. 37th Annual Symp. on Foundations of Computer Science, 1996, pp. 400–409). For a line topology, the problem is the well-studied interval graph coloring problem. Ondashline algorithms for this problem have been analyzed in Kierstead and Trotter (Congr. Numer. 33 (1981) 143–153). We consider trees, trees of rings, and meshes topologies, previously studied in the off-line case. We give ondashline algorithms with competitive ratio O(log n) for all these topologies. We give a matching Ω(log n) lower bound for meshes. We also prove that any algorithm for trees cannot have competitive ratio better than Ω(log n/log log n). We also consider the problem where every edge is associated with parallel links. While in WDM technology, a fiber link requires different wavelengths for every transmission, space division multiplexing technology allows parallel links for a single wavelength, at an additional cost. Thus, it may be beneficial in terms of network economics to combine between the two technologies (this is indeed done in practice). For arbitrary networks with Ω(log n) parallel links we give an ondashline algorithm with competitive ratio O(log n).

Adaptive wavelength routing in all-optical networks

We consider routing and wavelength assignment in wavelength-routed all-optical networks (WAN) with circuit switching. The conventional approaches to address this issue consider the two aspects of the problem disjointly by first finding a route from a predetermined set of candidate paths and then searching for an appropriate wavelength assignment. We adopt a more general approach in which we consider all paths between a source-destination (s-d) pair and incorporate network state information into the routing decision. This approach performs routing and wavelength assignment jointly and adaptively, and outperforms fixed routing techniques. We present adaptive routing and wavelength assignment algorithms and evaluate their blocking performance. We obtain an analytical technique to compute approximate blocking probabilities for networks employing fixed and alternate routing. The analysis can also accommodate networks with multiple fibers per link. The blocking performance of the proposed adaptive routing algorithms are compared along with their computational complexity.