Multi-granularity Network Research Articles

Multi-Layer, Multi-Dimensional and Multi-Granularity Network Model to Measure Network Security

Multi-Layer, Multi-Dimensional and Multi-Granularity Network Model to Measure Network Security

Hierarchical traffic grooming: A tutorial

Traffic grooming is concerned with the design, operation, and control of networks with multigranular bandwidth demands. As the number of resources in a multigranular network increases rapidly with the network size, wavelength capacity, and load, a scalable framework for managing these entities becomes essential. Hierarchical traffic grooming facilitates the control and management of multigranular WDM networks. In this paper, we present a survey of traffic grooming schemes for optical networks that make use of architectures, algorithms and design techniques that impose a hierarchical structure on the network topology.

Fully-elastic multi-granular network with space/frequency/time switching using multi-core fibres and programmable optical nodes

We present the first elastic, space division multiplexing, and multi-granular network based on two 7-core MCF links and four programmable optical nodes able to switch traffic utilising the space, frequency and time dimensions with over 6000-fold bandwidth granularity. Results show good end-to-end performance on all channels with power penalties between 0.75 dB and 3.7 dB.

Time Shared Optical Network (TSON): a novel metro architecture for flexible multi-granular services

This paper presents the Time Shared Optical Network (TSON) as metro mesh network architecture for guaranteed, statistically-multiplexed services. TSON proposes a flexible and tunable time-wavelength assignment along with one-way tree-based reservation and node architecture. It delivers guaranteed sub-wavelength and multi-granular network services without wavelength conversion, time-slice interchange and optical buffering. Simulation results demonstrate high network utilization, fast service delivery, and low end-to-end delay on a contention-free sub-wavelength optical transport network. In addition, implementation complexity in terms of Layer 2 aggregation, grooming and optical switching has been evaluated.

Offline Impairment Aware RWA Algorithms for Cross-Layer Planning of Optical Networks

Transparent optical networks are the enabling infrastructure for converged multi-granular networks in the future Internet. The cross-layer planning of these networks considers physical impairments in the network layer design. This is complicated by the diversity of modulation formats, transmission rates, amplification and compensation equipments, or deployed fiber links. Thereby, the concept of quality of transmission (QoT) attempts to embrace the effects of the physical layer impairments, to introduce them in a multi-criterium optimization and planning process. This paper contributes in this field by the proposal and comparative evaluation of two novel offline impairment aware planning algorithms for transparent optical networks, which share a common QoT evaluation function. The first algorithm is based on an iterative global search driven by a set of binary integer linear programming formulations. Heuristic techniques are included to limit the binary programming complexity. The second algorithm performs different pre-orderings of the lightpath demand, followed by a sequential processing of the lightpath demands. The performance and the scalability of both approaches are investigated. Results reveal great scalability properties of the global search algorithm, and a performance similar to or better than the sequential schemes.

Cloud method of multi-granularity network security situation analysis

This paper employs the uncertainty reasoning method in the Cloud Theory to solve the problem of network security perception.On the basis of the analysis of the existing models for security evaluation and their key technologies,the author proposed a situation awareness model using the knowledge base as well as the multi-granularity method.This model has three advantages over the conventional evaluation mechanisms:the dynamic updated knowledge base,multi-granularity method for security representation and visualization of the whole situation offers higher rate in accuracy and lower information redundancy.In addition,an extended cloud reasoning algorithm was designed and implemented to get both the qualitative and quantitative results of the monitored network and thus offers a more perceptible and scalable security situation.At last,experiments are done on the campus network of Wuhan University,and the results indicate that the feasibility and efficiency of our design.

On Hierarchical Traffic Grooming in WDM Networks

The traffic grooming problem is of high practical importance in emerging wide-area wavelength division multiplexing (WDM) optical networks, yet it is intractable for any but trivial network topologies. In this work, we present an effective and efficient hierarchical traffic grooming framework for WDM networks of general topology, with the objective of minimizing the total number of electronic ports. At the first level of hierarchy, we decompose the network into clusters and designate one node in each cluster as the hub for grooming traffic. At the second level, the hubs form another cluster for grooming intercluster traffic. We view each (first- or second-level) cluster as a <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">virtual</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">star</i> , and we present an efficient near-optimal algorithm for determining the logical topology of lightpaths to carry the traffic within each cluster. Routing and wavelength assignment is then performed directly on the underlying physical topology. We demonstrate the effectiveness of our approach by applying it to two networks of realistic size, a 32-node, 53-link topology and a 47-node, 96-link network. Comparisons to lower bounds indicate that hierarchical grooming is efficient in its use of the network resources of interest, namely, electronic ports and wavelengths. In addition to scaling to large network sizes, our hierarchical approach also facilitates the control and management of multigranular networks.

Dynamic routing and wavelength assignment in multi-granularity WDM networks

For the purpose of reducing the complexity and cost of optical large-scale cross-connect, wavelengths are grouped into wavebands or fiber to be switched as a single entity, which is called multi- granularity switching. However, it introduces more complexity into the routing and wavelength assignment problem. In this paper, we propose a novel graph model for describing the states of the multi-granularity switching WDM networks. Based on the model, the dynamic routing and wavelength assignment problems for multi-granularity traffic can be solved jointly, and different on-line wavelength grooming policies can be achieved simultaneously. By simulation, we compared the performance of our algorithms under different policy and different percent of fibers for fiber switching. The result proved that our algorithms yield better performance than those deal with the routing and wavelength assignment separately.

Protection in multigranular waveband networks

Feature Issue on Waveband Switching, Routing, and Grooming As the number of wavelengths in wavelength-division-multiplexed (WDM) systems continues to increase, the switching fabrics of optical cross connects (OXCs) will become increasingly complex. This complexity can be reduced by introducing multigranular optical cross connects (MG-OXCs) into the network. A MG-OXC is capable of switching an entire group of wavelengths through a single switch port, thereby reducing the required number of switching ports and the complexity of the switch fabric. We consider the problem of establishing active and backup paths for connections in networks with MG-OXCs. The problem of establishing protected connections for a given traffic demand in multigranular networks differs from the protection problem in standard wavelength-routed networks in that the primary objective in multigranular networks is to minimize the number of switch ports in the network. The mode of protection (dedicated or shared) affects the ability to aggregate and route traffic together. We formulate the problems of dedicated and shared protection in the form of Integer Linear Programs (ILPs) to optimize the total number of ports. Since solving the ILPs for large networks is intractable, we propose a graph-based heuristic that attempts to solve the problem of routing and waveband assignment in an integrated manner. The heuristic reduces the total number of ports in the multigranular network. We also study the effect of shared protection on the port count.