Krzysztof Wajda

Quality of resilience as a network reliability characterization tool

With the increased role of resilience in modern networks, the existing quality of service is required to be expanded with service availability and maintainability. Recently, studies have shown the strong limitation of the common availability metrics for measuring the users quality of experience. In this article a joint specification of QoS definitions with a sophisticated service resilience characterization is proposed, and a concept called quality of resilience is defined. In this unified performance metric, the frequency and length of service interruption are evaluated. It can be used as a tool for characterization of network reliability, as well as comparison and selection of recovery methods. Additionally, by including it in service level agreements, new and more complex requirements of commercial applications can be guaranteed.

Positioning of the RPR standard in contemporary operator environments

This article deals with the fundamentals and current standardization efforts for IEEE 802.17 resilient packet ring. Its special resilience features make this technology robust against outages of the network infrastructure. The goals of this article are threefold. First, the fundamentals of RPR and the standardization process carried out under the auspices of IEEE and ITU are overviewed. Second, potentially hazardous situations involving traffic assignments are defined and illustrated. Finally, possible situations where the simplicity, enhanced throughput, and automatic resilience features of RPR may be advantageous for network operators are identified.

General framework for techno-economic analysis of next generation access networks

A large variety of access network technologies and architectures that provide wide service portfolio to the customer are available for the network operators. Each of the potential access network architectures and technologies varies in complexity, network functionality, services supported and overall network costs. A detailed comparison of the economic viability of different access network scenarios is crucial for operators due to the high cost of this network segment. This paper identifies all essential elements of a general framework for the techno-economic analysis of different access network technologies and architectures, as well as describes some specific issues/problems related to the techno-economic evaluation of next generation (NG) access networks. The goal is to have at operators disposal a methodology allowing the techno-economic comparison of the proposed access network solutions and their introduction/rollout.

A survey on methods to provide multipath transmission in wired packet networks

IP networks were designed to provide general connectivity. At their advent, routing methods focused only on finding one optimal path between given endpoints. Although many solutions to sending traffic via multiple paths have appeared over time, the majority of current IP networks are still managed to support only single-path transmissions. This survey examines various approaches which can provide multipath transmissions in existing IP networks. Firstly, the most recognizable solutions are presented, and later, less well-known proposals are introduced. We show how it is possible to realize multipath transmission in source and hop-by-hop routing, multi-topology routing, bio-inspired routing solutions, Valiants routing, Multi-Protocol Label Switching, Software-Defined Networks, Flow-Aware Multi-Topology Adaptive Routing, Shortest-Path Bridging, Transparent Interconnection of Lots of Links, network virtualization, and Multipath TCP. Moreover, the mentioned approaches are compared, contrasted and subjectively assessed. The goal of the survey is to show that multipath transmissions can be achieved in the current IP networks and in many different ways.

Geometric versus geographic models for the estimation of an FTTH deployment

Optical access networks provide a future proof platform for a wide range of services, and today, several operators are deploying fibre to the home (FTTH) networks. Installing an FTTH infrastructure, however, involves very high investment cost. Therefore, a good estimation of the investment cost is important for building a successful business strategy and, consequently, to speed up the FTTH penetration. In this paper, for calculating the amount of cable and fibre in the outside plant together with the associated civil works, and the number of required network elements, two different approaches are investigated: (1) geometric modelling of the fibre plant based on approximate mathematical models and (2) geographic modelling of the fibre plant based on map-based geospatial data. The results obtained from these two approaches can then be used as input for preliminary investment cost calculations and/or techno-economic evaluations. Compared to more complex and accurate geographic modelling, we verify that especially with uneven population density and irregular street system, simple geometric models do not provide accurate results. However, if no geospatial data is available or a fast calculation is desired for a first estimation, geometric models definitely have their relevance. Based on the case studies presented in this paper, we propose some important guidelines to improve the accuracy of the geometric models by eliminating their main distortion factors.

Experimental Evaluation of PCE-Based Batch Provisioning of Grid Service Interconnections

If dynamic bandwidth-guaranteed connections between distributed services (e.g., grid services) are provisioned through a centralized system, the policy to serve connection requests might heavily impact both the success in and the time required for setting up user services (e.g., grid-enabled applications). In this paper, the implementation of a batch queue in the centralized system is proposed. By implementing different service policies for the queued requests, connections and, in consequence, user services can be set up with different guarantees. In this study, a bulk-service policy is proposed and implemented to maximize connection set up success. The experimental evaluation results show that the utilization of the proposed policy brings advantages in terms of percentage of accepted connection requests as the number of requests served in one batch increases. Moreover, the achieved improvement does not impact the time required to set up the connections because of the specific LSP set up procedures implemented in the utilized commercial routers.

A multi-layer recovery strategy in FAN over WDM architectures

Network operators are migrating towards IP over WDM architectures. In such multi-layer networks, it is necessary to efficiently use the resources available from both layers in order to provide coordinated recovery strategies. Thanks to the development of the control plane (GMPLS and ASON), it is feasible to set up and tear down lightpaths automatically, so the WDM layer itself can support failure recovery. This paper describes a multi-layer recovery strategy in a FAN/WDM (Flow-Aware Networking/Wavelength Division Multiplexing) architecture. We propose using the EHOT (Enhanced Hold-Off Timer) algorithm to control network operation after link or node failure. Although FAN operates only on the IP level, the presented analysis shows that it is possible to ensure sufficiently low (less than 50 ms) recovery times in FAN working over an intelligent optical layer. Additionally, the paper shows the motivation for FAN networks and presents the results of carefully selected simulation experiments which allow for evaluating the duration of outages in data transmission under various conditions.

Towards optical packet switched MANs: Design issues and tradeoffs

Metropolitan Area Networks (MANs) are considered one of the best arenas for an early introduction of optical packet switching technologies. However, there is still no clear definition of how these technologies should be exploited in the design of innovative MANs. In this paper we consider different architectures that have been studied in the framework of the European Network of Excellence e-Photon/ONe and analyze their advantages and limitations. The main contribution of this work is the proposal of an analytical framework to compare these architectures in terms of resource demand when dimensioning them for a given traffic matrix and, from this analysis, discuss issues and trade-offs arising in the design of optical packet MANs.

Economic analysis of future access network deployment and operation

In this paper we take into account the business aspects of building wireless and optical access networks. A detailed view on broadband access network deployment costs, including both capital (CapEx) and operational expenditures (OpEx) is given. Main cost components of optical and wireless access networks have been identified, and the deployment costs of different architectures have also been presented.

Reliability analysis of resilient packet rings

Resilient Packet Ring is a novel metro access standard. Here, we analyze it from the reliability viewpoint. The reliability function, availability as well as Mean Time to Failure metrics are analyzed. Simulation experiments are performed to confirm that the formulas obtained on the theoretical basis are correct.