Resilience, a necessity in today’s connected world?

Resilience is currently a trendy word, used in at least one conversation per day. But what does the term really mean? According to Wikipedia and some other sources, in computer networking it is: the ability to provide and maintain an acceptable level of service in the face of faults and challenges to normal operation.

This morning I learned personally what resilience means and how important it can be. As usual, I logged in to work from home and started reading my mail and doing other regular morning check-ins. Suddenly the optical fiber network was down! Immediately I realized that this must be what the Internet provider meant with the warning about the possible one-hour downtime when moving my services to another server during the week. And I had a meeting in 5 minutes! But my resilient network came to the rescue. I used my mobile phone and connected my computer via the mobile network. In less than one minute, I was connected again and could continue working.

Another example on a larger scale of how to increase resilience in a fiber network is when you set up a parallel microwave link due to the lower cost compared to a different optical path. It might not offer the same maximum capacity, but it secures connectivity for high-priority services. Last summer, on Independence Day, American Samoa experienced such a case when their 130 km long undersea fiber-optic cable was suddenly cut off. A long-distance microwave link was the much-appreciated backup with its 1 Gbps capacity to enable continued communication.

Since I work with microwave products for telecom networks, it seems natural to focus on how these products can help our customers build more resilient transport networks. Lately, it has become clear that it is not only the occasional thunderstorm and equipment failure that may require a re-routing in the network for services to be maintained. Other more violent things may occur that disrupt equipment or optical fiber connections.

So, what is required to make a network connection resilient?

Resilience with dual paths, where a microwave hop is added as redundancy for fiber.

Here are some possible solutions:

• Alternative paths
  Alternative paths will protect against broken fiber or other equipment failures along the original path. If dual optical fiber paths are used, they need to employ a different geographical path in order to protect the connection. Another possibility is one fiber and one microwave path, which can be along the same geographical path since radio waves are not easily cut off.
• Dual controllers and multiple radios
  They secure connectivity also when vital HW equipment fails.
• Ring or Mesh topologies in the network
  In this case, each site will have more than one connection to the rest of the network, preferably in different physical directions.
• Multiple synch sources available
  Modern networks require high precision stable time, and phase sync. Therefore, synch should be available from sources in different directions. Combined with local GNSS receivers at some sites, these sites can be secondary synch sources for the rest of the network.

Resilience with a ring network, where a microwave hop is used to close a fiber ring, in case fiber laying is difficult or too costly.

There are also more specific types of microwave related resilience features that will help make the link more robust:

• Adaptive modulation
  Traditional static modulation was of the type on/off – it either worked or not. The adaptive modulation will offer whatever capacity is possible at all times. This means more capacity when everything is fine, but more importantly, continued connectivity also when the traditional solutions stopped working. Misaligned antennas may reduce the system gain below the planned availability target, but you may still have some connectivity left with adaptive modulation. Adaptive modulation will increase the robustness of the link.
• Radio-link bonding
  When you have more than one link available, all the capacity is pooled into one common resource. Based on QoS settings, the high priority traffic takes precedence in whatever capacity is available. Therefore, a modern 2+0 link with adaptive modulation and radio-link bonding can be much more resilient than a traditional 1+1 link ever was.
• Traffic-Aware Power Saving
  When there is a major network problem, it is not unusual that it may also be a problem with the power supply and that the battery backup needs to function as long as possible. That is where TAPS helps – power usage is dependent on traffic needs instead of using the same power all the time. This can reduce used power and prolong the battery backup time, thus increasing the chance that power comes back in time to charge the batteries.
• Emergency unlock
  Modern products are more often than not based on SW licensing that defines their capacity and capability. In a network scenario with fire on some sites and cut off connections on other sites, using what is left to the maximum may be necessary. That is when the Emergency unlock function comes into play. All capability and capacity get unlocked with one command for a limited time until the issue is permanently solved.
• Remote management
  When the reorganization of the network is needed due to an emergency, you do not want to plan for a series of site visits. Therefore, it is vital to have a safe and secure DCN connection over which all changes can be made.

The good news is that modern microwave equipment supports all of the above mentioned requirements!

The bad news is that they also seem to be needed! Now more than ever.

Want to learn more?

Microwave - MINI-LINK 6000, microwave family for cost-efficient mobile transport networks

Microwave long haul

American Samoa connected via long microwave backhaul link