Ciena Cable Landing Station Network Convergence …

1 Cable Landing Station Network CONVERGENCEW hitepaperWGlobal demand for bandwidth continues to increase unabated, and is forecasted to grow at a compound rate of nearly 50 percent annually for the foreseeable future. Although the increasing popularity of video-centric streaming content is the primary driver, an increasing number of subscribers at ever-multiplying per-subscriber access rates are also fueling this growth. Increases in continental bandwidth growth inevitably affect the submarine networks interconnecting the continents, as accessed content can be located anywhere on Earth a situation that will only be compounded with the advent of cloud services that centralize content at a few select geographic locations. Unfortunately, the steady increase in bandwidth demand is also associated with steady price erosion for intercontinental submarine capacity. The main concern facing submarine Cable operators today and in the coming years is how to significantly reduce the operating costs of their networks.

2 Cable Landing Stations are now being considered a key area in the submarine Network where significant reductions in power consumption, space allocation, management and equipment complexity, and operating costs can be a Cable Landing Station , submarine networks interconnect to terrestrial networks, usually via a backhaul Network into the carrier s inland Point of Presence (PoP). This distinct demarcation point was created primarily due to business, political, geographic, and technological factors. However, a steady Convergence of optical networking technologies used in both submarine and terrestrial networks is blurring this demarcation point and putting its physical existence into question. Maintaining an ongoing distinct Network demarcation point only serves to make Network equipment redundant within the Cable Landing Station , leading to increased capital and operating expenses.

3 These costs can be significantly reduced by leveraging the Convergence of optical networking technologies and exploiting Network node consolidation. Successful global service providers must operate efficient end-to-end optical networks, managing their submarine and terrestrial networks assets as a single omnipresent entity and negating the need for a distinct demarcation Submarine Networking Business DriversThe submarine networking community traditionally chose technological paths different from their terrestrial networking brethren, leading to a distinct, and relatively inefficient, interconnection point between networks. Traditional builders of submarine networks were consortia composed of national incumbents operating as peers in the construction and ongoing maintenance of submarine cables. Differentiated service offerings were not a main priority due to the absence of competition.

4 To ensure sovereignty between the services of each of the consortium members, Cable Landing Station demarcation points were constructed to be inflexible by design, such that the shared submarine Network was not integrated into a consortium member s terrestrial Network . This led to managing submarine networks as distinct and separate Network entities. When services were primarily low-growth voice services, this Network business model was indeed economically viable. However, as traffic shifts towards connectionless high-speed data services, coupled with steady increases in competition both nationally and internationally, this legacy business model and the associated demarcated Network design become less economically viable. Both consortia and single-owner Cable operators must find innovative ways to significantly reduce the costs of their Network assets wherever possible. The Cable Landing Station is an excellent place to start especially legacy stations that are still being served by inefficient Network Networking Technology Evolution and ConvergenceCompared to terrestrial networks, submarine networks face significant challenges due to their unique operating environment in which active electronic devices lie at the bottom of oceans, often spanning thousands of kilometers.

5 The location of the wet plant entails repairs that are extremely costly and time-consuming, with the resulting loss of traffic often being costlier than the repair operation itself. The submarine Network s mean time to repair pales in comparison to terrestrial networks because the latter is far easier to access in an expedient and cost-effective manner. As a result, submarine Network assets are typically designed to operate for 25 years, and thus will continue to use technologies that are specifically tailored to harsh submarine operating environments. However, equipment located in land-based Cable Landing Stations can fully leverage the more rapid technological advances of terrestrial optical networks and associated cost savings from higher production technological advances in submarine networks have already occurred. Single-channel fiber optic submarine cables using electrical regenerators were replaced with multi-wavelength Dense Wavelength Division Multiplexing (DWDM) fiber-optic-based submarine cables and Erbium-Doped Fiber Amplifiers (EDFAs).

6 Point-to-point networks were replaced with ring-based topologies to improve Network survivability. PDH signal formats were replaced by 5 Gb/s proprietary signals to increase submarine Cable -carrying capacity. The adoption of SDH, DWDM techniques, and Optical Add/Drop Multiplexer (OADM) technologies not only increased submarine Network flexibility but, more importantly, converged with terrestrial networks for simplified Network interconnections. As this steady Convergence of optical networking technology continues, redundant inefficiencies call the legacy requirement for a distinct submarine-to-terrestrial Network demarcation point into Landing Station EvolutionFigure 1 illustrates the traditional configuration, where the Cable Landing Station served as the junction point between the submarine wet plant and the terrestrial dry plant. The equipment facing the terrestrial Network was primarily based on SDH, with line rates ranging from Gb/s to 10 Gb/s.

7 The equipment facing the submarine side was proprietary, with line rates typically up to 5 Gb/s. Proprietary solutions facing the wet plant were necessary at the time, because each submarine link required maximum optimization given the distances and harsh operating environments of the wet plant. This architecture is highly inefficient, and thus cost-ineffective, compared to the optical networking technologies available today. There are numerous limitations and inefficiencies with this legacy Network demarcation architecture, summarized below:> Inefficient hand-off between the submarine and terrestrial networks via back-to-back optical tributaries> Substantial amount of Network equipment required, much of it redundant> Significant physical space and power consumption requiring larger Cable Landing Stations> Translation to/from proprietary and standards-based signal formats> Complex Cable management required to interconnect numerous pieces of Network equipment> Separate Network Management Systems (NMS) for less effective Network maintenance> Limited and unintelligent bandwidth management> Significant equipment/ Cable sparing complexities and associated costsIt should be noted that the adopted networking solutions were innovative at the time, producing effective and reliable solutions that served associated business models quite well.

8 However, today s market forces have rendered this legacy Network design inefficient and cost-prohibitive based on current competition-based business Equipment and Integration Due to telecom deregulation and the initial localization of the Internet within the , terrestrial optical networks were the first networks subjected to fierce competition. Fueled by investor capital and bandwidth growth, startup and traditional equipment vendors developed innovative new solutions 2 Figure 1. Legacy submarine-terrestrial Network demarcation configurationFacing Terrestrial NetworkFacing Submarine NetworkDWDM CouplersDWDM-based SubmarineLine Terminating EquipmentTerrestrially ManagedSubmarine ManagedDWDM CouplersDWDM-based TerrestrialLine Terminating EquipmentTerrestrial Facing Network Protection EquipmentSubmarine FacingNetwork Protection Equipmentapplicable to the terrestrial-facing side of the Landing Station , as shown in Figure 2.

9 Integration of duplicated Network protection equipment allowed for improved protection schemes such as Transoceanic Protocol Switching (TOPS), which is a modified implementation of terrestrial ring-based protection switching. Terrestrial-facing DWDM optical interfaces also were integrated, along with pre/post optical amplifiers to further reduce the complexity of the demarcation point. Although networking equipment facing the wet plant is still clearly demarcated, the continual drive toward integration yielded several additional advantages and efficiencies, some of which are listed below:> Integrated DWDM optical transceivers, eliminating inefficient client-side tributary hand-offs> Integrated switch fabric, enabling a broader range of agile service offerings> Reduced amount of networking equipment and associated optical cables to manage and spare> Increased integration, resulting in reduced overall power and cooling requirements> Reduced Cable Landing Station rack and floor space requirements> Achieved substantial savings in overall capital and operational expenditures This level of continued integration also demonstrates ongoing Convergence of terrestrial and submarine equipment, resulting in savings in space, power, and cost, complemented by increased reliability, flexibility, and manageability.

10 Advances on the submarine side include faster line rates and higher channel counts for increased capacity. The Network Protection Equipment (NPE), along with switching/grooming, can now be managed as an integral part of the terrestrial NMS for improved operations, administration, maintenance, and provisioning. For a variety of political and technological reasons, the networking equipment facing the wet plant is likely to be the last portion of the Network demarcation point to be integrated. However, with the advent of innovative optical transmission technologies such as coherent modems, this last piece of networking equipment housed in a Cable Landing Stations inevitably will be integrated, since the benefits are simply too attractive to Fully Integrated Cable Landing StationThe complete integration of networking equipment into a single unified Network node will maximize realized benefits from both capital and operational viewpoints.