Monika Jaeger

Pan-European Optical Transport Networks: An Availability-based Comparison

The traffic to be carried by todays European backbone networks increases very rapidly. An important portion of this traffic consists of data traffic (mainly IP-related). In the future data traffic is expected to become the abundantly dominant traffic type, while voice traffic will only account for a very small portion of the total traffic volume. In this paper, some network topologies for such a pan-European fiber-optic backbone network are presented (more details can be found in [1]). These topologies are compared in terms of the efficiency of the network design both from a cost and capacity point of view and in terms of the availability of the connections routed over this network. In order to be able to assess the network topologies under realistic circumstances, the expected traffic demand is forecasted. This enables to make the comparison for the current traffic volume as well as for the traffic patterns of the future. As not all types of (data) traffic require the same degree of survivability and in order to leverage the total capacity cost of the network design, a distinction is made between different recovery options in the optical layer for the different traffic types considered.

Cost vs. reliability performance study of fiber access network architectures

Fiber to the home is the future-proof technology for broadband access networks. Several fiber access network architectures have been developed (e.g., point-to-point, active optical network, and passive optical network). PON is considered the most promising solution due to the relatively low deployment cost and high resource efficiency. Meanwhile, because of the growing demand for reliable service delivery, fault management is becoming more significant in all parts of communications networks. However, there is a trade-off between the cost of protection and the level of service reliability. Since economical aspects are most critical in the access part of networks, improving reliability performance by duplication of network resources (and capital expenditures) could be too expensive. Therefore, recent work has focused on PON protection schemes with reduced CAPEX. The future trend will probably migrate toward minimizing operational expenditures during the access network lifetime. The main contributions of this article include providing a general method for CAPEX and OPEX analysis that can be applied to any type of fiber access network with consideration of changed component cost in time and variable take rates, and comparing the total cost (i.e., sum of CAPEX and OPEX) for the selected representative architectures with and without protection for business and residential users in relation to reliability performance. The aim is to give a guideline for the design of the most cost-effective protection schemes, while maintaining acceptable service reliability.

General availability model for multilayer transport networks

This paper reports the initiative taken within the IST-project NOBEL to define a general availability model and collect general availability numbers for several network equipment types, independent from vendor specific product information. The model includes optical layer equipment as well as IP and SDH equipment, described using a triplet-representation for each of the availability measures with optimistic, nominal and conservative values. The availability model has been applied to different typical transport network scenarios. Several case studies were performed to compare the end-to-end connection availability and the required network capacity for different resilience mechanisms.

Evaluation of novel resilience schemes in dynamic optical transport networks

Today, Wavelength Division Multiplexing (WDM) transmission systems are deployed extensively in transport networks. They are used mainly for static point-to-point connections. With the availability of fast reconfigurable Optical Cross Connects (OXC) and the introduction of a control plane in the Optical Transport Network (OTN), optical channel based logical networks can be built for dynamic WDM networks. Resilience in current transport networks is mainly based on static SONET/SDH dedicated and shared protection. Distributed control planes allow new, flexible protection mechanisms (e.g. GMPLS reroute and fast reroute). To evaluate future distributed control concepts and new resilience schemes in transport networks, we have implemented a dynamic OTN simulation model. Several case studies have been performed using different protection and restoration methods. Different failure scenarios (single or multiple link failures) were used. The paper evaluates the case studies in terms of scalability, recovery time criteria, capacity use (efficiency) and availability. It is shown that the new and flexible resilience schemes are a promising alternative to traditional statically preplanned protection in transport networks. Furthermore, they provide increased network availability in multiple failure cases.

Network migration cost study

In this paper a cost analysis case study of migrating services from an SDH network platform into a packet based transport network is presented. The Net Present Value (NPV) of the costs of actively migrating the services is compared with the NPV of the costs of operating the SDH platform for the regular duration of all remaining services. Different cost contributors, including Capital Expenditures and Operational Expenditures, as well as different traffic scenarios are analyzed based on a realistic scenario. Different migration strategies are considered. In most cases active service migration is cost efficient. It can be shown that cost savings can be optimized if the traffic scenario, the migration time window and the migration speed are aligned.

Quantitative evaluation of architectures for multilayer transport networks

This paper evaluates different architectures for multilayer IP transport networks. The evaluation is based on an exemplary network dimensioning of a reference IP backbone network topology, connecting 63 points of presence (PoPs) in Germany. The network dimensioning results are used for a techno-economic analysis of the different network architectures, taking into account hypothetical but realistic cost models.

Service cost model and cost comparative studies

Purpose – The purpose of this paper is to propose a service cost model which can be used to evaluate the impact of different management functionalities or network platforms to the service cost.Design/methodology/approach – Following the validation of the importance that OpEx has on the overall TCO, a classification of the costs is proposed, based on their relation to the network. Two main types of costs have been identified: network based costs and service based costs. Both cost types have been modeled as a set of interconnected processes based on the network and service life cycle respectively. Network and service cost models have been integrated into a single framework. These models have been implemented as Markov chains, which include the dynamic behavior of services. Two different methods for the implementation (analytical versus non‐analytical) have been compared from the implementation and computation time point of view. The proposed service model has been used in two case studies: cost comparison o...

Network Architectures for Future Optical Networks

The suitability and efficiency of network architectures strongly depend on the service requirements and the mixture of services at different network levels. A case study has been performed in which five different service scenarios have been defined considering the characteristics of network operators. Starting with a service scenario which assumes only Layer 3 IP services, the amount of Layer 2 (Ethernet) and Layer 2 services (leased line) have been increased subsequently in the remaining four scenarios. Moreover, Layer 1 services have been differentiated with respect to broadband leased lines and narrowband services. The service scenarios have been applied to assess network architectures based on IP/MPLS, Ethernet and flexible and static optical systems, respectively. The impact of control plane implementations, i.e. GMPLS and ASON, have been analyzed. Ethernet is making its way into metro and core networks. The development of Ethernet services and technology and their integration into MPLS/GMPLS based networks is still hampered by open issues. Evolutions in this area will be a key differentiator for network architecture evolutions

Assessment of network architecture with respect to different service scenarios

The suitability and efficiency of network architectures strongly depend on the service requirements and the mixture of services at different network levels. A case study has been performed in which five different service scenarios have been defined considering the characteristics of network operators. Starting with a service scenario which assumes only Layer 3 IP services, the amount of Layer 2 (Ethernet) and Layer 2 services (leased line) have been increased subsequently in the remaining four scenarios. Moreover, Layer 1 services have been differentiated with respect to broadband leased lines and narrowband services. The service scenarios have been applied to assess network architectures based on IP/MPLS, Ethernet and flexible and static optical systems, respectively. The impact of control plane implementations, i.e GMPLS and ASON, have been analyzed. Ethernet is making its way into metro and core networks. The development of Ethernet services and technology and their integration into MPLS/GMPLS based networks is still hampered by open issues. Evolutions in this area will be a key differentiator for network architecture evolutions.

Service Availability in Optical Network Design

The paper explores survivability concepts for the migration to carrier class next generation IP services over optical transport networks. Design criteria for highly available optical networks are proposed and tradeoffs of different approaches are analyzed.