Search

We consider path-based survivable service provisioning in transparent optical networks with the constraints of wavelength continuity and a limited number of add/drop ports at each OXC node in the presence of limited tunability of transmitters. We develop simple but valid analytical models to estimate the effects of number of add/drop ports and transmitter tunability on survivable service provisioning performance. We propose effective algorithms for the assignments of wavelength resources and add/drop ports for each survivable connection service and conduct simulations to evaluate the impacts of number of add/drop ports and transmitter tunability on path-based survivable service provisioning and further to examine the validity of the analytical models. It is found that a certain system add/drop ratio is required at each node so as to eliminate the blocking due to the lack of free add/drop ports. A network with a higher density requires a larger relative number of add/drop ports (i.e.. add/drop ratio) for a given overall blocking objective. A network with a higher density benefits more in blocking from transmitter tunability. Finally, the analytical models are verified to be able to qualitatively predict the trends and effects of all the related constraints on the performance of survivable service provisioning. [ABSTRACT FROM AUTHOR]

Dense wavelength division multiplexing (DWDM)-based optical networks that are assumed to employ exactly two working fibers uniformly on every span are matter of recent interest in the field of telecommunication. An interesting and highly efficient strategy for protection of such networks is to use, if possible, a single dark-Fiber p-cycle formed on a Hamiltonian cycle. It has been showed that in a homogeneous Hamiltonian network, a Hamiltonian p-cycle is the most efficient overall solution, although interestingly it does not always correspond to the individually most efficient p-cycle that can be formed. The article also considers p-cycle planning in non-Hamiltonian but homogeneous networks and introduce the concept of a semi-homogenous network, specifically linked to the p-cycle concept. The proposed semi-homogeneous class of network actually realizes the theoretical lower bound on span-restorable networks in terms of network redundancy. Such networks also provide a strategy to accommodate certain patterns of capacity growth beyond a homogenous network without any increase in protection capacity. The work also demonstrates and explains why a single Hamiltonian p-cycle is not as efficient as a specifically optimized set of individual p-cycles in a "capacitated" network where the working capacity on each span varies in a general way.

At present we see only one basic approach being considered by implementors and standards organizations for provisioning of dynamic protected lightpath services that make efficient use of shared protection capacity. This is the paradigm of a primary working path protected end-to-end by a disjoint backup path using shared spare capacity. Sharing, is arranged among the backup paths associated with other primary paths that are failure-disjoint from the current primary path.[SUP1] This approach, called shared backup path protection (SBPP), has many advantages, but also requires a great deal of network state information to be available and current in every node. It also makes the arrangement of protection a per-connection task, rather than a user-selectable service option supported by the network itself. We propose an alternative paradigm for consideration, partly summed up as provisioning over protected capacity, rather than provisioning protection. Under a given distribution of spare capacity; locally acting protection or restoration schemes create an "envelope" of protected working channels. Dynamic provisioning within this envelope is simplified to a shortest path routing problem and (depending on the mode of operation) requires little or no dissemination of state changes on a per-connection basis. We explain how existing "static" capacity design methods can be adapted to the dimensioning of such a working capacity envelope and the envelope dimensions further adapted online to track evolution of the overall pattern of random demand. An important property is that nothing needs to be done to arrange protection for services on the per-connection timescale other than routing the service itself. Arbitrarily fast-paced demand arrivals and departures can be accommodated within a static distribution of spare capacity. Adjustments to the envelope itself are required only on the timescale on which the statistical parameters of the random demand changes. [ABSTRACT FROM AUTHOR]

This work introduces a significant extension to the method of p-cycles for network protection. The main advance is the generalization of the p-cycle concept to protect path segments of contiguous working flow, not only spans that lie on the cycle or directly straddle the p-cycle. This effectively extends the p-cycle technique to include path protection or protection of any flow segment along a path, as well as the original span protecting use of p-cycles. It also gives an inherent means of protecting working flows that transit a failed node. We use integer linear programming as a research tool to study the new concept and determine its inherent capacity requirements relative to prior p-cycle designs and other types of efficient mesh-survivable networks. Results show that path-segment-protecting p-cycles ("flow p-cycles" for short) have capacity efficiency near that of the shared backup path-protection (SBPP) scheme currently favored for optical networking. But because its protection paths are fully preconnected and because it protects path segments (not entire paths) it has the potential for both higher speed and higher availability than SBPP. We also develop capacity optimization models to support 100% restoration of transiting flows through failed nodes. It is found that only a very small additional spare capacity is needed to achieve both 100 % span and intermediate node-failure restorabilities, and a very high transiting traffic restorability can be accomplished for node failure restorability given spare capacity only for span-failure protection. An immediate practical application of the work is to suggest the use of flow p-cycles to protect transparent optical express flows through a regional network. [ABSTRACT FROM AUTHOR]