Service providers and network operators must meet stringent frequency and phase/time synchronization requirements in 5G mobile transport networks. To succeed, they need new tools that will enable them to simplify and automate the configuration, provisioning and management of the synchronization layer network.

Many telecommunications equipment vendors have developed synchronization solutions based on Synchronous Ethernet (SyncE) and the Precision Time Protocol (PTP) to address the accuracy and protocol performance challenges posed by the transition to 5G. But the configuration of the synchronization layer is often manual and done on a node-by-node basis using a command line interface or the graphical user interface (GUI) of a traditional element management system (Figure 1).

During configuration, manual tasks increase the possibility of errors because they can be cumbersome or require expert knowledge of the PTP parameters. A misconfiguration can result in timing islands or inaccurate advertisements of time/phase information, which can cause a cascade of errors throughout the network. By implementing new applications that automate these tasks, service providers and network operators can simplify the provisioning and management of the end-to-end synchronization chain.

Figure 1: Topology view of synchronization across nodes

Monitoring synchronization performance can be difficult

While the IEEE Std 1588-2008 (Precision Clock Synchronization Protocol for Networked Measurement and Control Systems) and ITU-T G.8275.1 (PTP telecom profile with full timing support) standards define the architecture and protocols for time synchronization over packet networks, they offer limited alarm and performance monitoring capabilities.

Similarly, although SyncE has been widely deployed, vendors have not strictly followed Recommendation ITU-T G.781 (Synchronization layer functions for frequency). Instead, they have chosen to implement proprietary alarms and performance management parameters. This has led to a lack of homogeneity across solutions, which makes it difficult to get a holistic view of the synchronization layer.

The new ITU-T Sync OAM standard can help

Fortunately, there are new standardized methods of monitoring synchronization layer networks. These methods are determined in part by ITU-T G Suppl.68, also known as ITU-T Sync OAM, which defines the requirements for synchronization fault management and performance monitoring information.

As shown in Figure 2, the ITU-T’s synchronization OAM functional diagram accounts for two different synchronization layers – the frequency synchronization layer and the time synchronization layer. Each of these layers has its own features and OAM functional requirements. But the two layers are linked because time synchronization performance relies in part on frequency synchronization performance.

Figure 2: ITU-T Sync OAM functional diagram

The ITU-T Sync OAM framework simplifies the monitoring and OAM processes for synchronization layer networks while enabling homogeneity across different vendor implementations. This framework also makes it easier to monitor the synchronization service and resolve service level specification compliance issues. Nokia packet-optical transport systems implement the alarms and performance monitoring parameters defined in ITU-T G Suppl. 68 for the frequency (SyncE) and phase/time (PTP) domains.

Recently introduced ITU-T standards provide new capabilities that help operators configure and monitor timing distribution within packet transport networks. These capabilities include inherent mechanisms and algorithms that allow for the protection, resiliency and OAM of the synchronization signal, such as alarm reporting and consequent actions in response to network synchronization status. Nokia has incorporated these capabilities into the WaveSuite Synchronizer application, which provides network-layer management to improve synchronization OAM through abstraction, simplification and automation.

Putting the Sync OAM standard to work  

By fully implementing and complying with the latest versions of existing ITU-T standards, Nokia packet and optical transport systems deliver new capabilities that help network operators perform the OAM tasks required to manage synchronization distribution networks. These systems incorporate Recommendation ITU-T G.8275.1 PTP telecom profile (edition 2.1) features such as better path traceability, monitoring of timing signal failures (synchronization uncertain indication), and limits to the length of the synchronization chain (max steps removed). They also enable improved traceability of eEEC and mixed EEC/eEEC chains in accordance with the latest amended versions of Recommendation ITU-T G.8264/G.781.

Nokia packet-optical transport solutions go beyond the standards by providing enhanced management, monitoring and supervision capabilities. These solutions include a powerful network-layer synchronization management application that allows operators to manage time and frequency synchronization distribution in packet transport networks while delivering Synchronization as a Service (SyncaaS). The solutions also include custom templates that help reduce provisioning effort and time, making the creation of PTP and/or SyncE services an efficient process.

A more intuitive approach to synchronization management

The advanced network element functionalities defined in the new standards, coupled with the addition of the synchronization application to the Nokia Network Services Platform (NSP), simplify the tedious procedures involved in configuring and managing synchronization networks node by node. With an efficient and intuitive GUI representation of the synchronization layer, the synchronization management application offers a holistic view of synchronization services and topology while providing the same look and feel as any other layer in the network (Figure 3).

The application provides a network-wide health summary of the network equipment and services, including a geographical view of the sync topology that makes it simple to trace PTP and SyncE status.

Figure 3: Service templates and intuitive maps

Service providers and network operators can use these intuitive synchronization OAM tools to ensure that they meet the stringent frequency and phase/time synchronization requirements of mobile transport networks. The new tools enable them to automate the planning, provisioning, operation and maintenance of the synchronization distribution network. This automation simplifies network operations and improves synchronization performance.

The new tools also augment the capabilities of the Nokia network management systems NFM-P for IP/MPLS and NFM-T for packet-optical networks. For synchronization these systems provide a centralized view of timing synchronization across the network. They also provide visibility into a common list of master and slave synchronization peers in a synchronization domain. Network operators can use these capabilities to assign path monitors to peers between network elements configured with SyncE EEC/eEEC clocks and IEEE 1588 PTP clocks.

Find out more

Read our Synchronization transport operations and management white paper to learn more about how our packet-optical transport systems support the recent ITU-T synchronization standards. This paper also describes how the new Nokia WaveSuite Synchronizer network application manages frequency and phase/time distribution to enable SyncaaS.