Abstract
A dynamic Optical Transport Network (OTN) has the advantage of being able to adjust the connection capacity on demand in order to respond to variations on traffic patterns or to network failures. This feature has the potential to reduce operational costs and at the same time to optimize networks resources. Virtual Concatenation (VCAT) and Link Capacity Adjustment Scheme (LCAS) are two techniques that when properly combined can be used to provide improved dynamism in OTN networks. These techniques have been previously standardized in the context of Next Generation SDH/SONET networks. VCAT is used to tailor the capacity of network connections according to service requirements, while LCAS can adjust dynamically that capacity in a hitless manner. This paper presents an overview of the application of VCAT/LCAS techniques in the context of OTN. It explains in detail how these techniques can be employed to resize the connection capacity and analyses its use in network protection solutions. Furthermore, a detailed analysis of the time delays associated with different operations is provided and its application to some reference networks is undertaken. The obtained results provide an idea about the time delays of the capacity adjustment processes and define potential scenarios for implementing VCAT/LCAS techniques.
Highlights
In order to support the constant growing of network traffic and the increasing heterogeneity of services/applications the transport infrastructure of telecommunication networks is facing a series of new challenges
We considered three network topologies: Figure 7(a) the 24-node North American backbone network (UBN), which has 42 bidirectional links and all links are shorter than 3,000 km, Figure 7(b) the 19-node European Optical Network (EON) with 36 bidirectional links, and the longest link is about 2,000 km, and Figure 7(c) the Pan-European test network (COST 239), which comprises 11 nodes and 26 bidirectional links, and all links are shorter than 1,000 km
The maximum Link Capacity Adjustment Scheme (LCAS) delays were computed using the shortest path between the two farthest network nodes, while the mean LCAS delays require the knowledge of the mean value of the shortest-paths computed between all network node pairs
Summary
In order to support the constant growing of network traffic and the increasing heterogeneity of services/applications the transport infrastructure of telecommunication networks is facing a series of new challenges. To obtain a container of variable size, there are two techniques available: Flexible Rate ODU (ODUflex) and Virtual Concatenation (VCAT) [4] [5]. In order to adjust in a flexible mode, the capacity allocated to connections, the network must be capable of dynamically changing the size of the containers in a hitless manner, i.e. without affecting the service. The resizing of ODUflex containers can be accomplished using the protocol Hitless Adjustment of ODUflex (HAO), while the members of a VCG can be added or removed through the Link Capacity Adjustment Scheme (LCAS). Both techniques have their own advantages and drawbacks.
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