### A pure framework for cost-effective virtual ring based traffic grooming in WDM optical networks

- Research Article in 2nd International ICST Conference on Broadband Networks
- Authors
- Yufeng Xin, Mark Shayman, Richard J. La, Steven I. Marcus
- Abstract
This paper presents a cost-effective virtual topology design framework based on virtual rings in both ring and mesh optical WDM networks. The traffic grooming problem is solved in separate steps, in which different objectives are considered. The nodes are first grouped into clusters, each cluster f…

more »This paper presents a cost-effective virtual topology design framework based on virtual rings in both ring and mesh optical WDM networks. The traffic grooming problem is solved in separate steps, in which different objectives are considered. The nodes are first grouped into clusters, each cluster forms a ring with the self healing property, then hub nodes are decided such that the number of hub nodes is minimized. The author shows that the second and third step are both NP-complete. The reconfiguration of virtual rings is also studied and a virtual ring based network control and management protocol is briefly described

### On the complexity of path traffic grooming

- Research Article in 2nd International ICST Conference on Broadband Networks
- Authors
- Prashant Iyer, Rudra Dutta, Carla D. Savage
- Abstract
Traffic grooming is known to be an inherently difficult problem. It has been shown to be NP-complete for path networks, a simple topology in which wavelength assignment is tractable. In this paper, we explore the borderline between tractability and intractability by considering grooming in unidirec…

more »Traffic grooming is known to be an inherently difficult problem. It has been shown to be NP-complete for path networks, a simple topology in which wavelength assignment is tractable. In this paper, we explore the borderline between tractability and intractability by considering grooming in unidirectional path networks in which all traffic requests are destined for a single egress node. It is an open question whether the complete grooming problem is NP-hard with this restriction or not. We show that at least the problem of routing traffic on a given virtual topology to minimize electronic switching (NP-hard for path networks with arbitrary traffic matrices) becomes polynomial on the egress model. We also show that in the egress model, if the capacity constraint is relaxed, the entire problem becomes polynomial. If, in addition, traffic requests are uniform, there is an explicit combinatorial formula for the optimum solution. For the case of finite capacity and unit traffic requests, we can find in polynomial time a feasible solution which, under certain assumptions, is optimal

### A time and cost efficient dynamic traffic grooming algorithm for optical mesh networks

- Research Article in 2nd International ICST Conference on Broadband Networks
- Authors
- Thanh-Thao Nguyen Thi , Trung Tran Minh, Quang-Dzung Ho, Man-Seop Lee
- Abstract
Traffic grooming is an efficient technique to utilize network resources by packing low speed traffic streams onto a high speed lightpath. Since many existing traffic grooming algorithms still have very high complexities, and do not consider the costs paid for network systems; in this paper, we prop…

more »Traffic grooming is an efficient technique to utilize network resources by packing low speed traffic streams onto a high speed lightpath. Since many existing traffic grooming algorithms still have very high complexities, and do not consider the costs paid for network systems; in this paper, we propose a time and cost efficient dynamic traffic grooming algorithm (TCGA). The novelty of this heuristic algorithm is that it can reduce the complexity by removing redundant nodes when constructing the reachability graph. Then, from the graph established, we propose the cost functions to determine the optimal grooming path for a new connection request with the minimum cost. The simulation results show that our algorithm has a lower complexity, while still ensuring a comparable blocking performance, compared with other existing approaches

### Single shortest path-based logical topologies for grooming IP traffic over wavelength-routed networks

- Research Article in 2nd International ICST Conference on Broadband Networks
- Authors
- Gaurav Agrawal, Deep Medhi
- Abstract
We consider the problem of designing logical topologies for grooming IP traffic over wavelength-routed networks; in particular non-bifurcated minimum hop routing is used to route IP traffic. We present two approaches to solve this problem. The first approach is a two-step approach where in the firs…

more »We consider the problem of designing logical topologies for grooming IP traffic over wavelength-routed networks; in particular non-bifurcated minimum hop routing is used to route IP traffic. We present two approaches to solve this problem. The first approach is a two-step approach where in the first step we solve a mixed integer linear programming (MILP) formulation to determine an initial single shortest path logical topology; this is followed by a pruning approach to find an improved logical topology in the second step. Our second approach is a heuristic solution for moderate size networks. We then consider different performance measures to show the effectiveness of our solution approaches in generating minimum average packet hop-based logical topology

### Physical layer limitations in high-speed electro/optical nodes. The European approach

- Research Article in 2nd International ICST Conference on Broadband Networks
- Authors
- S. Sales , P. Beneit, C. Politi
- Abstract
The aim of this paper is to present the technologies that will enable future nodes for optical networks to upgrade. The limitations of these technologies are also presented. Finally, the investments of the European research projects that are being carried out to improve the current nodes are outlin…

more »The aim of this paper is to present the technologies that will enable future nodes for optical networks to upgrade. The limitations of these technologies are also presented. Finally, the investments of the European research projects that are being carried out to improve the current nodes are outlined

### Physical layer impairments in WDM core networks: a comparison between a North-American backbone and a Pan-European backbone

- Research Article in 2nd International ICST Conference on Broadband Networks
- Authors
- Sawsan AL ZAHR, Maurice GAGNAIRE, Nicolas PUECH, Mohamed KOUBAA
- Abstract
In the absence of all-optical 3R regenerators, the quality of transmission has a strong impact of the feasibility of all-optical long-haul transmission. Four main physical layer impairments degrade the quality of an optical analog signal, namely chromatic dispersion (CD), polarization mode dispersi…

more »In the absence of all-optical 3R regenerators, the quality of transmission has a strong impact of the feasibility of all-optical long-haul transmission. Four main physical layer impairments degrade the quality of an optical analog signal, namely chromatic dispersion (CD), polarization mode dispersion (PMD), optical signal to noise ratio (OSNR), and nonlinear phase shift (PhiNL). In most previous studies, a Q factor evaluates the quality of transmission in considering the aforementioned parameters individually (Qi with i isin {1,2,3,4}). In this paper, we propose a tool implementing a global Q factor that takes into account the interaction between the four impairments and from which we derive the bit error rate (BER). This new factor referenced as Q8 enables to study the suitability of optical transparency in transport networks. By means of numerical applications, we compare two backbone networks: the North-American NSF network (NSFNET) and the Pan-European backbone (EBN)

### Analysis of quality of service provisioning in passive optical networks

- Research Article in 2nd International ICST Conference on Broadband Networks
- Authors
- Djafar K. Mynbaev
- Abstract
Today, tremendous pressure falls on the local networks to provide customers with access to the global telecom infrastructure. To ease this pressure, various versions of broadband access networks have been developed. Among them, the optical access networks provide the most promising immediate and fu…

more »Today, tremendous pressure falls on the local networks to provide customers with access to the global telecom infrastructure. To ease this pressure, various versions of broadband access networks have been developed. Among them, the optical access networks provide the most promising immediate and future solution to the access problem. These optical access networks are mostly implemented today in the form of passive optical networks (PONs). This paper analyzes the quality of service (QoS) provided by the PONs. We start with an introduction to the principle of PON operation, the architectures, topologies, protocols and standards, design issues, and network management and services. Through this introduction, we consider provisioning such QoS parameters as bandwidth allocation, delay (response) time, security, and availability. We also discuss PON lifeline service and survivability and compare the QoS provisioning in ATM-based and Ethernet-based PONs

### Evaluation of the dimensioning and economical benefits of intelligent optical networks

- Research Article in 2nd International ICST Conference on Broadband Networks
- Authors
- K. Casier, S. Verbrugge, A. Groebbens, D. Colle , I. Lievens, M. Pickavet, P. Demeester
- Abstract
In order to cope with the increasing capacity requirements in the optical backbone network, the introduction of optical cross connects (OXC) and intelligent optical networking (ION) capable components such as ASON (automatically switched optical networking) or GMPLS (generalized multi-protocol labe…

more »In order to cope with the increasing capacity requirements in the optical backbone network, the introduction of optical cross connects (OXC) and intelligent optical networking (ION) capable components such as ASON (automatically switched optical networking) or GMPLS (generalized multi-protocol label switching) might become a necessity. In this paper we study the benefits of the introduction of such ION-capable components in the network, using a multi-purpose dimensioning tool (DT) developed within the scope of the ITEA TBONES (transparent optical backbone network simulator) project. The introduction of ION-capable components in the network allows to use the capacity in the network more efficiently, especially when considering a highly dynamic traffic. The enhanced flexibility of the ION-capable components also allows to optimize the capacity-usage in case of network-failures. Optimization of the logical topology could further reduce the capacity-requirements for incorporating a specific resilience scheme in the network. In the light of the ongoing traffic growth in the backbone network, these capacity savings could also result in network cost savings, depending on the moment and price for the introduction of a new OXC in each specific node. By optimizing this estimated cost of the network, an optimal schedule for the introduction of the OXCs can be proposed

### Evaluation of routing algorithms for distributed lightpath establishment in wavelength-routed networks

- Research Article in 2nd International ICST Conference on Broadband Networks
- Authors
- Shinichi Arakawa, Takahiro Toku, Masayuki Murata
- Abstract
Optical networks, where all-optical wavelength channels (called lightpaths) convey traffic, have been considered to effectively utilize WDM technology. In distributed lightpath networks, each node sets up and tears down the lightpath between a pair of communicating nodes. Therefore, conflicts about…

more »Optical networks, where all-optical wavelength channels (called lightpaths) convey traffic, have been considered to effectively utilize WDM technology. In distributed lightpath networks, each node sets up and tears down the lightpath between a pair of communicating nodes. Therefore, conflicts about wavelength reservations during signaling operations may occur because of a lack of precise link-state information. In this paper, we evaluate effects of delayed link-state information on reservation protocols and routing algorithms through some simulations. More specifically, we evaluated the average path setup time for routing algorithms in distributed networks, and found how the frequency of link-state information exchange affects the precision of collected link-state information. From simulation results, we conclusively confirmed that a backward reservation-protocol lessens the effect delayed link-state information has. The effect is less than 0.2% increase of blocking probability with the backward reservation protocol, while the forward reservation protocol increases the blocking probability more than 15%. We also confirm the proposed alternate routing algorithm shortens lightpath setup time about 20% than the least loaded routing algorithm assuming ideal conditions

### Graph theoretic approaches for routing and wavelength assignment of scheduled lightpath demands in WDM optical networks

- Research Article in 2nd International ICST Conference on Broadband Networks
- Authors
- Chava Vijaya Saradhi, Mohan Gurusamy
- Abstract
In WDM optical networks, depending on the offered services the service provider will have precise information for some traffic demands such as the number of required lightpaths and the instants at which these lightpaths must be set-up and torn-down. These types of traffic demands are called as sche…

more »In WDM optical networks, depending on the offered services the service provider will have precise information for some traffic demands such as the number of required lightpaths and the instants at which these lightpaths must be set-up and torn-down. These types of traffic demands are called as scheduled lightpath demands (SLDs). It may so happen that in a given set of SLDs, some of the demands are not simultaneous in time, and hence the same network resource could be used to satisfy several demands at different times. In this paper we develop two complementary algorithms-independent sets algorithm (ISA) and time window algorithm (TWA), based on circular arc graph theory, which respectively capture time-disjointness or time-overlap that could exist among SLDs. These two algorithms are complementary in the sense that, ISA divides the set of SLDs into subsets of time-disjoint demands, whereas, TWA divides the set of SLDs into subsets of time-overlapping demands; before routing them. We conduct extensive simulation experiments on ARPANET, USANET, mesh 8 times 8, mesh 10 times 10, and mesh 12 times 12 networks. In simulation experiments, we consider two different cases: 1) non-blocking case: where the number of wavelengths on each link is set to infinity and 2) blocking case: where the number of wavelengths on each link is set to a certain number. We compare and evaluate the algorithms based on the number of wavelengths required, number of reused wavelengths, average call acceptance ratio, and the reuse factor: the ratio of reused wavelengths to the sum of number of wavelengths used and the reused wavelengths. The numerical results obtained from simulation experiments indicate that TWA reuses significant number of wavelengths (reuse factor up to 53%) followed by ISA (reuse factor up to 14%). By reusing the wavelengths these algorithms reduce the total number of wavelengths required, and hence increase the average call acceptance ratio. Algorithm TWA performs better than - - ISA w.r.t. all parameters except the number of wavelengths required. Further, we observe that as the size of the network increases the number of reused wavelengths for TWA increases