Mohammad Nurujjaman

Design of Resilient Ethernet Ring Protection (ERP) Mesh Networks With Improved Service Availability

Ethernet Ring Protection (ERP) has recently emerged to provide protection switching for Ethernet ring topologies with sub-50 ms failover capabilities. ERPs promise to provide protection in mesh packet transport networks positions Ethernet as a prominent competitor to conventional SONET/SDH and as the technology of choice for carrier networks. Higher service availability, however, in ERP has been challenged by the issue of network partitioning and contention for shared capacity caused by concurrent failures. In this paper, we show that in a network designed to withstand single-link failure, the service availability, in the presence of double link failures, depends on the designed ERP scheme, i.e., the RPL placement as well as the selection of ring hierarchy. Therefore, we present a study for characterizing service outages and propose a design method which strikes a balance between capacity requirement and service availability (i.e., the number of service outages resulting from concurrent failures). We observe that through effective design, remarkable reduction in service outages is obtained at a modest increase in capacity deployment.

Optimal capacity planning and RPL placement in carrier Ethernet mesh network design

Ethernet Ring Protection (ERP) has recently emerged to provide protection switching for Ethernet ring topologies with sub-50 ms failover capabilities. ERPs promise to also provide protection in multi-ring mesh packet transport networks will position Ethernet as a serious competitor to conventional SONET/SDH and the technology of choice for carrier networks. Operating ERP in multi-ring mesh networks however comes with unique challenges. This paper presents an optimal ERP capacity design formulation by jointly solving the problem of routing, RPL placement, and ring hierarchy selection. When prior work relied on exhaustive enumeration, our current design is formulated as an integer linear program (ILP) which is shown to be both more capacity and computationally efficient.

Multi-Ring ERP Network Design: A Traffic Engineering Approach

The recent Ethernet Ring Protection (ERP) method brings new challenges into the design of next generation Ethernet carrier networks. This letter addresses one of the design challenges that may confront a network operator in its migration to provide ERP capabilities over an existing network. The objective of the design is to properly allocate network resources to maximize the service providers revenue given the per-link deployed capacity. We formulate this problem of resource allocation as an optimization model with the objective of maximizing the network flow using the well-known max-min approach. Our proposed model ensures fairness among the admissible flows and the design of a proper protection plan to survive against any single link failure. Numerical results show that the proposed design approach can increase the overall network flow by up to 44.7% in comparison to an arbitrarily designed ERP network while it allocates bandwidth 29.3% more fairly among the sessions.

Optimal and Efficient Design of Ring Instances in Metro Ethernet Networks

Ethernet Ring Protection (ERP) switching has emerged to provide sub-50 ms of restoration times, allowing Ethernet technologies to expand beyond enterprises to next generation metro and backbone networks, providing much needed services to interconnect for instance dispersed and high-bandwidth data centers. This paper considers the problem of efficiently designing and planning an Ethernet-based metro network with ERP protection method. While previous recent work has addressed such design problem, none has considered the capabilities of exploiting multiple ERP instances, leaving behind some advantages that network providers could tap into to provide their customers with desirable quality of service support. Resource planning in ERP-based Ethernet network is, however, a complex problem due to the challenges associated with the logical link block selection as well as ring hierarchy selection. ERP instances add, however, another dimension of combinatorial complexity, making the design problem completely intractable. To address this issue, we resort to large scale optimization tools and present a novel primal-dual decomposition of the original problem using column generation. We show that our method is very scalable and obtain several design insights on various representative network instances.

A Max-Flow Design Approach for Improved Service Availability in Multi-Ring ERP Networks

Ethernet Ring Protection (ERP) has recently emerged to provide protection switching for Ethernet ring topologies with sub-50 ms failover capabilities. In addition to Ethernets cost-effectiveness and simplicity, ERPs promise to also provide protection in mesh packet transport networks positions Ethernet as a prominent competitor to conventional SONET/SDH and the technology of choice for carrier networks. Higher service availability, however, in ERP mesh networks has been challenged by the issue of network partitioning and the contention for protection resources which may be caused by concurrent failures. In this paper, we show that in a mesh network designed to withstand only single failure situations, network services usually suffer from two outage categories subject to concurrent dual-link failures. We address the problem of minimal capacity network design to provide high service availability against concurrent dual-link failures. We cast this combinatorially complex design problem as an optimization one and show that higher service availability can be achieved by proper RPL (Ring Protection Link) placement and ring hierarchy selection. The objective is to maximize the network flow under any dual-link failure scenario. Our design achieves minimal capacity allocation that minimizes the number of service outages (up to 37%) therefore achieving higher service availability. Numerical evaluation and comparative study show that the joint desgin approach of the ILP model provisions 8% less capacity than the sequential two-step approach to achieve similar service availability.

Fast and efficient network protection method using path pre-cross-connected trails

This paper investigates design methods of protection schemes in survivable WDM networks using the path protection p-trail in order to provide better capacity efficiency by eliminating the rigidness of the protection structure of the well-accepted protection scheme, the failure independent path protection (FIPP) pre-configured protection cycle (p-cycle). The flexibility in the protection structure yields lower cost in terms of spare capacity allocation while maintaining the high speed of protection switching. We develop two design approaches, the fully pre-cross-connected path protection trail (fpp-trail) and the partially pre-cross-connected path protection trail (ppp-trail), based on the degree of pre-cross-connectivity of the protection structure. In order to obtain optimally designed trails, we develop an optimization model based on a large-scale optimization technique, namely, column generation. Numerical results show that fpp-trails significantly improve the spare capacity efficiency compared to the FIPP p-cycle, and ppp-trails strike a balance between capacity redundancy and recovery delay. We observe that ppp-trails can achieve as low capacity redundancy as shared backup path protection (SBPP), while the recovery delay is kept lower than in SBPP and slightly higher than FIPP p-cycles by using selective signaling through a control plane that is aware of the location of the cross-connects that are not pre-configured in advance.

Optimal capacity provisioning for survivable next generation Ethernet transport networks

Ethernet ring protection (ERP) has recently emerged to provide protection switching for Ethernet ring topologies with sub-50-ms failover capabilities. ERPs promise to also provide protection in multi-ring mesh packet transport networks will position Ethernet as a serious competitor to conventional synchronous optical networking (SONET)/synchronous digital hierarchy (SDH) and the technology of choice for carrier networks. Operating ERP in multi-ring mesh networks, however, comes with unique challenges. This paper reveals some limitations of prior work which relied on exhaustive enumeration and proposes some modifications to overcome these subtle limitations. We also present an optimal ERP design formulation by jointly solving the problem of ring protection link placement and ring hierarchy selection whose objective is to minimize the overall capacity requirement. Our design approach is formulated as an integer linear program, which is shown to provide optimal capacity provisioning and be computationally scalable.

Joint scheduling and spectrum allocation in wireless networks with frequency-agile radios

We study the benefits of optimal spectrum allocation in a wireless network with frequency agile radios and we present a cross-layer problem formulation for the joint routing and link scheduling under non-uniform spectrum allocation. We present a primal-dual decomposition to provide an exact solution for this complex optimization problem. Given the difficulty associated with such design, we propose a heuristic approach based on simulated annealing to solve the dual subproblem of the decomposed model. Numerical results revealed that up to 44% improvement in network performance is obtained when variable-width spectrum band allocation is used, as opposed to the best fixed-width spectrum band allocation for larger networks. Numerical results also confirm that the primal-dual decomposition method using simulated annealing to solve the dual sub-problem, substantially reduces the computation time and achieves near optimal solutions.

Green Packet Optical Transport Networks (P-OTNs) Based on Photonic PBB-TE Switches and Minimized EEE Overhead

Carrier Ethernet exhibits an enormous potential to be a cost-effective and less complex replacement of SONET/SDH especially after the ratification of IEEE standard 802.1Qay Provider Backbone Bridge-Traffic Engineering (PBB-TE). The recent IEEE standard 802.3az Energy Efficient Ethernet (EEE) presents another opportunity for service providers to select Ethernet as a technology of choice in the backbone while leveraging on its promise for achieving green transport network. In this paper, we propose two novel architectures of photonic PBB-TE core and edge switches, which enhance the usability of PBB-TE networks by reducing power consumption in individual switches in conjunction with passive optical bypassing and EEE. We also formulate the problem of energy-aware scheduling as an optimization problem whose objective is to minimize the overall energy consumption for transmitting Ethernet frames while satisfying their delay requirements. This model will be used as a benchmark while evaluating the performance of packet coalescing, a promising and recently proposed approach, as well as the performance of EEE.

Minimizing EEE Overhead in Green Packet Optical Transport Networks (P-OTNs)

Carrier Ethernet exhibits an enormous potential to be a cost-effective and less complex replacement of SONET/SDH especially after the ratification of IEEE standard 802.1Qay Provider Backbone Bridge-Traffic Engineering (PBB-TE). The recent IEEE standard 802.3az Energy Efficient Ethernet (EEE) presents another opportunity for service providers to select Ethernet as a technology of choice in the backbone while leveraging on its promise for achieving green transport networks. In this paper, we propose two novel architectures of Photonic PBB-TE (PPBB-TE) core and edge switches, which enhance the usability of PBB-TE networks by reducing power consumption in individual switches in conjunction with passive optical bypassing and EEE. We also formulate the problem of energy-aware scheduling as an optimization problem whose objective is to minimize the overall energy consumption for transmitting Ethernet frames while satisfying their delay requirements. This model will be used as a benchmark for evaluating the performance of packet coalescing, a recently proposed performance-enhancing technique, as well as the performance of EEE.