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Heuristic Approaches for Cache Node Placement in Content-Centric Networking Under Maximum Link Traffic Minimization
(2026-01-01)
Pavarangkoon, Praphan
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Nakajima, Shohei
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Kitsuwan, Nattapong
This paper proposes heuristic approaches for cache node placement in Content-Centric Networking (CCN) with the objective of minimizing maximum link traffic. The work builds on an exact Integer Linear Programming (ILP) formulation from our earlier study, which jointly models routing and caching decisions but becomes computationally expensive for large-scale networks. To address this limitation, we develop scalable heuristic algorithms that approximate the ILP solution while requiring much lower computation time. We introduce four heuristic approaches, comprising two Linear Programming (LP)-based local search algorithms, 2Swap and GreedySwap, which exploit the fractional solution of the LP relaxation, and two proxy-based heuristics, Population-Weighted Closeness (PWC) and Population-Weighted Betweenness (PWB), which estimate cache utility using population-weighted centrality measures without solving any optimization model. Experimental evaluations on four network topologies show that the LP-based heuristics remain within 0-6% of the ILP optimum while reducing computation time by factors ranging from about 40× to more than 160×. Compared with the proxy-based heuristics, the LP-based heuristics consistently yield lower maximum link traffic across all settings. These results indicate that the proposed heuristic approaches provide effective and scalable solutions for cache node placement in practical CCN deployments.
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Cache Node Placement Scheme Considering Maximum Traffic in Content-Centric Networks
(2023-01-01)
Pavarangkoon, Praphan
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Nakajima, Shohei
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Kitsuwan, Nattapong
This paper proposes a cache node placement scheme considering the maximum traffic in content-centric networks (CCNs). The cache node placement problem is considered to satisfy the user's requirement in CCNs. Traffic utilization is one of the most common requirements. Reduced traffic allows more additional traffic on links. In this paper, a scheme to minimize the maximum traffic and the number of hops is proposed. The mathematical model for the cache node placement problem is formulated. The dynamic routing is considered in this model. Numerical result shows that the proposed scheme outperforms the conventional scheme. It suggests that the proposed scheme provides reference values to support the implementation of heuristic algorithms for the cache node placement problem.
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Reducing Bandwidth Blocking Rate in Elastic Optical Networks Through Scale-Based Slicer Placement Strategy
(2023-01-01)
Kitsuwan, Nattapong
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Pavarangkoon, Praphan
In this paper, we present a scale-based slicer placement strategy aimed at decreasing the bandwidth blocking rate (BBR) in elastic optical networks (EONs). EONs adopt slicing-and-stitching technology to bypass the requirement of consecutive spectrum slots on the same link for a single request. This is achieved through the use of slicers to split the requested spectrum band into multiple sub-spectrum components. However, a uniform distribution of slicers across all nodes may not guarantee low BBR due to varying traffic volumes on each node. Our proposed scale-based policy determines the necessary number of slicers for each node based on our investigation. Simulation results demonstrate that our strategy leads to a 91% reduction in BBR compared to conventional methods.
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Spectrum Slicer Placement for Elastic Optical Network With Sparse Slicers
(2023-01-01)
Pavarangkoon, Praphan
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Akaki, Kaito
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Kitsuwan, Nattapong
This paper investigates spectrum slicer placement problem under a spectrum allocation scheme that considers the splitting process to minimize the blocking probability for elastic optical network with sparse slicers. Unlike the conventional elastic optical network without slicers, the elastic optical network with slicers is able to split a spectrum band into several spectrum components by replicating the original spectrum band and filtering out an unwanted signal on each spectrum band. The largest L-shape fit allocation algorithm, which allocates a request to available slot areas with L-shape, is utilized to reduce the request blocking probability. We evaluate the performance of our scheme with various centrality policies on elastic optical network with sparse slicers, where the number of slicers is given. Simulation results show that our scheme with betweenness centrality significantly outperforms that with random centrality, degree centrality, and closeness centrality in terms of bandwidth blocking rate.
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Scale-Based Slicer Placement in Elastic Optical Networks
(2023-01-01)
Kitsuwan, Nattapong
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Pavarangkoon, Praphan
This paper proposes a scale-based slicer placement scheme to reduce bandwidth blocking rate (BBR) in elastic optical networks (EONs). In EONs, a slicing-stitching technology is adopted to overcome a spectrum slot allocation rule that the spectrum slots of the same request must be consecutive on the same link. This technology is done by slicers to split a spectrum band into multiple sub-spectrum components. In EONs with limited slicers, determining equally the number of slicers on every node may not result in a low BBR since the traffic volume on each node is not the same. We investigate and determine the number of slicers needed for each node as a scale-based policy. The simulation results show that our scheme achieves a BBR reduction of 91%, compared to the conventional scheme.
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Resolving Load Imbalance State for SDN by Minimizing Maximum Load of Controllers
(2021-10-01)
Srisamarn, Ukrist
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Pradittasnee, Lapas
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Kitsuwan, Nattapong
This paper proposes a scheme to practically resolve the load imbalance state for orchestrated multiple controllers architecture in software-defined networks (SDN). Multiple controllers architecture is crucial to SDN implementation in large scale networks because this architecture provides efficient performance for end-to-end services, such as reliability and scalability in SDN networks. However, when there are multiple SDN controllers in the network, a load imbalance state may occur. The load imbalance problem can notably degrade service level in some parts of the network because the SDN controllers in those network areas have much higher amount of processing load. Existing works solved the load imbalance problem by migrating the load to multiple SDN controllers in order to maintain an acceptable level of load in all SDN controllers. Nevertheless, most of these works did not consider propagation delay and processing time in their load definition. In large-scale networks, high propagation delay is likely to cause late response from the SDN controller, which may result in a degraded performance in the SDN networks. In this paper, a new load balancing scheme is proposed. The proposed scheme is formulated as an integer linear programming problem (ILP). It defines SDN controller’s load based on propagation delay, processing time at the controller and the number of request messages in order to provide an accurate representation of load in practical environments. Generally, ILP may take a long period of time to process. Therefore, a heuristic algorithm that bases on the proposed load balancing scheme is also developed to provide shorter processing time. Computer simulations and practical implementation in Pica8 switch show that the proposed scheme reduces the average maximum load by at least 9.85%, compared to a conventional scheme.
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Spectrum allocation scheme considering spectrum slicing in elastic optical networks
(2021-07-01)
Kitsuwan, Nattapong
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Akaki, Kaito
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Pavarangkoon, Praphan
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Nag, Avishek
Recent advances in physical layer optics have made slicing of optical bands into multiple subbands with different bandwidths possible. Due to this development, spectrum allocation has become easier in elastic optical networks (EONs). More specifically, owing to the slicing technology, the defragmentation problem in EONs can be addressed easily, i.e., more demands can be fit into empty spectrum slots by breaking the demands as needed using the slicing technology. This paper proposes a spectrum allocation scheme considering the slicing process at any nodes, e.g., source node and intermediate nodes, in EONs. Slicing-and-stitching technology is applied to break the contiguous-spectrum constraint in an EON so that spectrum fragmentation is reduced. While slicing a demand from one node to another, the following questions must be answered: (1) Which parts of the spectrum band should be sliced? (2) In which node(s) along the path of a demand should the slicings be done to reduce the bandwidth blocking rate? To answer the above questions, we formulate a mixed-integer linear programming (MILP) model that jointly addresses the above questions as well as minimizes the total number of slicers in a network. To measure the performance of the MILP, we used the bandwidth blocking ratio (BBR) of the network as a performance metric. Our results from the MILP show that introducing slicing at every node in the network improves the BBR by as much as 68% compared to a conventional case where slicing a demand is allowed only at the source node.
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Large L-shape Fit Spectrum Allocation for Elastic Optical Network with Spectrum Slicing
(2021-01-13)
Akaki, Kaito
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Pavarangkoon, Praphan
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Kitsuwan, Nattapong
A slicing and stitching technology has been invented to relax the consecutive constraint of spectrum slot allocation in elastic optical network (EON). This technology splits a spectrum band into several signal bands, called optical components, by making a copy of the original spectrum band and filtering out an unwanted signal on each spectrum band. The remaining optical components are injected into a transmission channel. At the destination, the optical components are recovered by using phase preserving wavelength conversion. Therefore, a request is able to allocate to dis-consecutive groups of slots. A conventional spectrum allocation scheme with this technology adopts slicing devices, called spectrum slicers, at only a source node. There is a problem of allocation patterns due to lack of flexibility since slicing at intermediate nodes is not considered. In this paper, we propose a spectrum allocation scheme considering slicers at both source node and intermediate nodes. Performance of the proposed scheme is evaluated by a computer simulation. The results show that the proposed scheme with 20 slicers reduces 45% of request blocking probability compared to the conventional scheme in COST239 topology when the traffic is 300 Erlang.
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Elastic optical network for fragmented bandwidth allocation with limited slicers
(2021-01-01)
Akaki, Kaito
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Pavarangkoon, Praphan
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Kitsuwan, Nattapong
A fragmentation problem increases bandwidth blocking in an elastic optical network (EON). A technique to reduce bandwidth fragmentation is important. The routing and spectrum allocation (RSA) approach is one of the techniques to reduce bandwidth fragmentation. A slicing-and-stitching technology is adopted in EON to relax a consecutive slot constraint for the spectrum allocation process. A slicer is used to split a signal of a spectrum band into several spectrum components, as a slicing process. The split spectrum components are transmitted to the destination before recovering the original signal at the destination, as a stitching process. An RSA algorithm for EON with this technology is applied. As a result, the request blocking is reduced. Slicers are applied to all nodes in the network. The implementation cost is high. Reducing the number of slicers in the network degrades the performance in terms of bandwidth blocking. This paper investigates bandwidth blocking when the number of slicers is limited. Some nodes in the network are selected to place slicers. A betweenness centrality (BC) value is used to select the nodes to place the slicers. The result from a simulation shows that placing a small number of slicers per node for a large number of nodes has better performance than placing a large number of slicers per node for a small number of nodes.
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Elastic optical network with spectrum slicing for fragmented bandwidth allocation
(2020-09-01)
Kitsuwan, Nattapong
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Pavarangkoon, Praphan
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Nag, Avishek
Elastic Optical Networks (EONs) allow the channel spacing and the spectral width of an optical signal to be dynamically adjusted and hence have become an important paradigm in managing the heterogeneous bandwidth demands of optical backbone networks. The entire available optical spectrum is divided into some spectrum slots which define the smallest granularity of bandwidth and optical signals with variable bandwidths can occupy different number of such slots. The constraints imposed by the physical layer of an EON require that the slots occupied by an optical signal from source to destination have to be consecutive and contiguous in terms of their relative position in the optical spectrum. Furthermore, the same spectrum slots need to be reserved throughout the entire optical signal's path from its source to destination. The above constraints make the routing and spectrum allocation (RSA) in EONs very challenging because unavailability of enough spectrum slots that together equals the spectral width of the optical signal associated with an end-to-end request, will result in blocking of the request. Recent developments in the physical layer technologies have made all-optical ‘slicing’ of a request possible and make the request to be ‘fit’ into multiple non-consecutive spectral slots in an EON. But these all-optical ‘slicers’ employ complex technologies and can be very costly to employ. In this paper, we propose a spectrum allocation scheme for an EON node architecture with these ‘slicers’ and we also formulate a modified RSA scheme for EONs employing slicers, both as a mixed-integer linear programming (MILP) model and a heuristic algorithm. Our main aim is to analyze the tradeoff between the number of slicers that can be used per node versus the spectrum utilization and bandwidth blocking rate. The numerical results show that the proposed scheme with slicers can significantly improve bandwidth blocking rate, compared to the conventional scheme without slicer.

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