pendent on mobile communications services, requiring upgrading the reliability of these services. In addition, over time more and more mission-critical services have migrated to the public mobile network, including first responders, hospitals, and more recently smart city appli- cations. Initial studies of 5G identified ultra-reliable services as one of the vertical markets that needed to be addressed. In this subsection we will consider two related topics, availability and packet loss of the transport network. Availability is beyond doubt the most important characteristic of any communication service, since a non-available service is of no use. The golden standard for 6 Enabling Technologies telephony service has always been 5 nines, which translates to less than 4 and a half minutes of downtime per month. Some cloud-based services now promise 6 nines, that is, less than half a minute of downtime per month. Additionally, the 4 minutes and 23 seconds of 5 nines, or even the 26 seconds of 6 nines, are not allowed to occur in a single duration. The golden standard here is 50 ms from failure detection to repair. High reliability and fast repair is obtained in transport networks today by one of two self-healing mechanisms, which we may term automatic protection switching (APS) and fast reroute (FRR), respectively. With APS, supported by Carrier Ethernet and MPLS Trans- port Profile (MPLS-TP), one prepares an alternative disjoint E2E path, which is called the backup path in contrast to the working path (ITU-T G.808.1). A prevalent special case of APS utilizes rings, where one way around the ring is the working path and the opposite direction is the standby path (ITU-T G.808.2). Non-ring scenarios are often referred to as linear protection. Upon detection of a failure of the working path (e.g. through physical layer indications or via loss of several consecutive OAM continuity check [CC] messages), the traffic is sent over the backup path. In order to conform to 50 ms repair times, CC messages are often sent at rates o