We propose a simple configuration for colorless and directionless (CD) reconfigurable optical add/drop multiplexers that enables contention-free add/drop operation to be achieved. In the configuration, we apply a combination of multiple small-port-count CD add/drop banks (CD banks) and round-robin CD bank assignment. Evaluation results show that the proposed configuration can substantially reduce intra-node contention.

The fine two-phase routing (F-TPR) scheme, an IP finely-distributed load-balanced routing scheme based on two-phase routing over shortest paths, was previously presented to improve routing performances. F-TPR distributes traffic from a source node to intermediate nodes simply by using IP tunnels. F-TPR provides comparable routing performance to the sophisticated traffic engineering (TE) scheme of Multi-Protocol Label Switching (MPLS-TE). However, in practice, most routers will not be able to handle the complexity of determining and implementing uneven traffic distributions with any form of precision. This paper investigates non-split F-TPR, where traffic from a source node to a destination node is not split over multiple routes, in other words, it goes via only one intermediate node to the destination node. The problem solved by non-split F-TPR is formulated as an integer linear programming (ILP) problem. Since it is difficult to solve the ILP problem within a practical time, this paper introduces two heuristic algorithms against the ILP problem. We compare non-split F-TPR against split F-TPR and MPLS-TE. Numerical results show that non-split F-TPR matches the routing performance of F-TPR and MPLS-TE with an error of 1%, when network size is enough large.

This paper proposes a simple shortest-path-based load-balanced Internet-Protocol (IP) routing scheme based on the hose model. The proposed scheme is an extension of the Smart-OSPF (S-OSPF) scheme. The proposed scheme, the same as S-OSPF, splits traffic demand only at source edge nodes and transmits the traffic along the shortest path routes. In S-OSPF, the split ratios are determined for each source-destination edge node pair by assuming that the traffic demand between all source-destination edge node pairs are known, in other words, the exact traffic matrix is completely given. This, however, is difficult to measure and predict accurately because of the measurement costs and rapid traffic fluctuations. On the other hand, in the proposed scheme, we assume the use of the hose model; in this model, only the total amount of traffic that a node injects into the network and the total amount of traffic it receives from the network are known. This simplicity makes it easy for network operators to apply the hose model for IP routing. This is because measuring just the total amount of traffic is less expensive than measuring the traffic demands between all source-destination edge node pairs. In addition, the aggregated traffic exhibits less fluctuation and is easier to predict than the traffic demand between each source-destination pair. Any extension of the Linear Programming (LP) formulation that optimizes S-OSPF to suit the hose model cannot be solved as a simple LP problem, because the traffic matrix is not known. By introducing a duality theorem, we successfully formulate our problem as an LP formulation that can be easily solved yielding the desired split ratios. Numerical results show that the proposed scheme dramatically reduces the network congestion ratio compared to the classical shortest path routing scheme and it provides performance close to that provided by the sophisticated traffic-engineering (TE) scheme of Multi-Protocol Label Switching (MPLS)-TE.

This paper proposes a simple shortest-path-based load-balanced IP routing scheme for the hose model. The proposed scheme is an extension of the Smart-OSPF scheme. The proposed scheme, the same as S-OSPF, splits traffic demand only at source edge nodes and transmits the traffic along the shortest path routes. In S-OSPF, the split ratios are determined for each source-destination edge node pair by assuming that the traffic demand between all source-destination edge node pairs are known, in other words, the exact traffic matrix is completely given. On the other hand, in the proposed scheme, we assume the use of the hose model; in this model, only the total amount of traffic that a node injects into the network and the total amount of traffic it receives from the network are known. Any extension of the linear programming (LP) formulation to suit the hose model cannot be solved as a simple LP problem, because the traffic matrix is not known. By introducing a duality theorem, we successfully formulate our problem as an LP formulation that can be easily solved yielding the desired split ratios. Numerical results show that the proposed scheme dramatically reduces the network congestion ratio compared to the classical shortest path routing scheme and it provides performance close to that provided by the sophisticated traffic-engineering (TE) scheme of multi-protocol label switching (MPLS)-TE.

This paper proposes an IP finely-distributed load- balanced routing scheme based on two-phase routing over shortest paths, where the traffic matrix is given. It is called the fine two-phase routing (F-TPR) scheme. In F-TPR, traffic is distributed from a source node to intermediate nodes more finely, compared to the original TPR. F-TPR determines the distribution ratios to intermediate nodes for each source-destination node pair independently. To determine an optimum set of the distribution ratios, a linear programming (LP) formulation is derived. We compare the F-TPR scheme against the TPR scheme and the sophisticated traffic engineering (TE) scheme of multi-protocol label switching (MPLS-TE). Numerical results show that F-TPR greatly reduces the network congestion ratio compared to TPR. In addition, F-TPR provides almost the same network congestion ratio as that of MPLS-TE, the difference is surprisingly less than 0.1% for various experimented network topologies.

This paper presents an optimization of IP load-balanced routing for the hose model. We present an IP load-balanced routing scheme based on the two-phase routing over shortest paths. It is called a fine two-phase routing (F-TPR) scheme. In F-TPR, traffic is distributed from a source node to intermediate nodes more finely, compared to the original TPR. F-TPR introduces the distribution ratio to node m that is determined for each source-destination pair of (p, q), kmpq. To determine an optimum set of kmpq, an linear programming (LP) formulation is first derived. However, the formulation is difficult to solve as a simple LP problem. This is because each element of the traffic matrix is not determined because of the hose model and there are too many possible parameters for us to consider. By introducing a duality theorem , we successfully formulate our problem a quadratic constraint programming (QCP) formulation that can be solved to determine the split ratios by using a mathematical programming solver. We compare F-TPR with TPR and the multi-protocol label switching (MPLS)-traffic engineering (TE). Numerical results show that F-TPR reduces the network congestion ratio compared to TPR. Numerical results show that F-TPR greatly reduces the network congestion ratio compared to TPR , and provides the network congestion ratio close to that of MPLS-TE within the difference of 6%.