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Introducing Open Wave Restoration

portrait of Teresa Monteiro

February 8, 2024
By Teresa Monteiro
Director of Solutions, Software and Automation

Network resiliency for an open networking future

Network downtime impacts businesses, individuals, and emergency services, disrupting all types of activities and leading to revenue losses, user frustration, and even lives lost. But despite the great care taken by network operators, equipment manufacturers, and fiber suppliers to minimize network outages, with 4 billion kilometers of fiber optic cable deployed all around the globe (over 13 times the distance to the sun and back!), fiber cuts and other network failures are bound to happen. They can be caused by humans (construction work, vandalism), by animals (monkeys, squirrels, sharks…or maybe not), or by natural disasters (storms, earthquakes, wildfires).

While networks are often designed to mitigate up to two simultaneous network failures, in discussions with key network operators, we have encountered cases where anywhere from five to 23 simultaneous fiber failures have been experienced at a given time. Network operators in Africa as well as the Asia Pacific and Latin America regions are some of the most impacted by fiber cuts – many own very large fiber deployments, and a combination of geographical factors and local resources and practices make fiber more vulnerable in these areas of the globe. The good news is, even in cases where fiber cuts are common, the combination of advanced restoration techniques with protection, applied at the right network layers, means most networks can operate at very high levels of availability and keep customers satisfied. Let’s see how.

How to survive network failures: protection vs. restoration

Network protection and restoration solutions have been commonly used to improve service survivability. In both protection and restoration schemes, network failures, regardless of their cause, are automatically detected, and the impacted services are transmitted, as long as possible, via alternative routes that bypass the affected areas or resources.

Protection (or strictly speaking 1+1 protection, the most common protection technique) is achieved by duplicating the routes for protected services, with dedicated resources reserved and preconfigured but useless until a failure happens. This is the case, for example, in Y-cable protection, where the client signal is split in two and fed into two different transponder cards, with the corresponding optical signals generated and routed independently through the network. 1+1 protection schemes guarantee resilience to single failures and are very fast, offering detection and switching times below 50 ms – but protection is costly due to the high number of redundant resources required.

Restoration, on the other hand, uses network resources in a more flexible manner for more cost-effective resiliency. Restoration routes for a restorable service can be preplanned: in this case, the routes are defined in the management system and assigned to a service ahead of any event, so-called backup routes. In pre-planned restoration, restoration resources can be strictly reserved for one backup route to guarantee that they are available when needed, as in protection, but they can also be shared among several backup routes (1:N redundancy).

Alternatively, restoration routes can be computed and assigned dynamically on the fly upon failure, depending on real-time network status and resource availability. While this does not always guarantee restoration resource availability, a network operator can find the right compromise between solution cost and network resilience level by choosing the number and the location of redundant resources to deploy and reserving them if and where appropriate.

Properly designed restoration can offer the required resilience against many simultaneous failures in the network, with very efficient use of resources. However, restoration is slower than protection because resource configuration happens only after a rerouting decision has been taken.

Network resiliency for an open networking future

Several restoration solutions on the market today offer Layer 1 (L1) restoration, implemented in GMPLS control planes. Those solutions work well in single-vendor networks with an abundance of OTN switches because it is at these switches that the L1 services can be redirected.

But networks are moving away from traditional OTN switching, with the OTN switching market flattening and IP taking over:

  • Router evolution has provided the market with IP routers that are highly scalable, are able to meet demanding service-level agreements, and have improved on power consumption.
  • The annual bandwidth growth on the order of 20% to 30% that service providers have been witnessing has been driven by an immense surge of IP traffic, while the amount of OTN traffic remains relatively flat over time.
  • IP traffic is increasingly being routed over DWDM networks with the adoption of coherent optical pluggables inserted directly in routers (known as IPoDWDM).

It is time to reconsider pure L1 restoration. In a modern network landscape, where the optical network has become very flexible, consisting mostly of colorless-directionless ROADMs, restoration at Layer 0 (L0), i.e., reestablishing optical channels via different routes, is the most natural, economical choice. For fast switching and increased availability, L0 restoration can be combined with IP layer protection or with optical protection, while the L0 restoration engine works in the background to find a route to recover the working path.

Combined optical protection and restoration (1+1+R)

Combined optical protection and restoration (1+1+R)

Additionally, with open optical networking gaining traction, restoration solutions are required to work across equipment from multiple vendors. Despite standardization attempts, GMPLS control plane has continued to rely on proprietary signaling mechanisms and doesn’t make the cut.

Introducing Open Wave Restoration

These considerations were key in the development of Infinera’s restoration solution: Open Wave Restoration, a future-looking application that delivers high service availability in open optical networks, ensuring optimal restoration routes, prioritizing critical services, and minimizing failed restoration attempts, in a flexible yet operationally simple manner.

The Open Wave Restoration application is enabled by Infinera’s Transcend Network Automation Suite software.

Transcend control plane has network-wide awareness, which means the restoration engine knows the full network connectivity and optical performance. It knows the status of all network resources and services at any given point in time and can optimize rerouting. This visibility over the whole network is important because it allows the most efficient network use.

Upon failure(s), a single restoration engine is responsible for orchestrating the restoration of all impacted services, ensuring there are no time-wasting failed restoration attempts and crank-backs, which would occur if multiple parallel restoration processes were competing for the same resources.

Open Wave Restoration works primarily at L0 – this means it will attempt to restore optical channels, supporting wavelength conversion; however, if this is not enough, it will then try to restore L1 services using existing wavelengths.

Complex restoration constraints can be supported, and so can complex restoration triggers, resulting from combining different information reported by different network objects at different network layers – or even outside the network. Is there a site that is at high risk of losing power in case of floods? Why not reroute traffic out of that site when the rain starts to get heavy?

First things first

Also, if you suffer simultaneous failures and have finite restoration resources, which services should be restored first? Since Transcend knows the priorities and service-level agreements (SLAs) of all client and line services in the network, the restoration engine can prioritize the most valuable services in case of resource contention.

The Open Wave Restoration application is readily available for networks based on Infinera’s GX Series, but it can also be deployed in open optical networks controlled by Open Wave Manager, Infinera’s holistic, multi-vendor optical domain controller, relying on open interfaces and common data models. The advantages of restoration are extended to the disaggregated, multi-vendor networks of the future – including IPoDWDM networks.

Open Wave Restoration is highly scalable, aligned with the increasing adoption of SDN-enabled automation in our industry. It will help you minimize the impact of network failures and gain differentiation with highly resilient networks that your customers can trust.

Interested in learning more? Let’s discuss, and we will quantify what Open Wave Restoration can do for your network!