Synchronisation and precise timing in packet networks

Download “Synchronisation and precise timing in packet networks” white-paper

Executive summary

IP/MPLS and Ethernet packet optical networks are now a widely deployed technology and are being applied in all network segments and should therefore be able to support all types of network applications. Replacing the circuit switched synchronous SDH/SONET networks does however represent a number of challenges, where delay and synchronization are among the most prominent. E.g. mobile networks have strict requirements to accuracy of both frequency and time references. In synchronous networks this is solved using inherent synchronization mechanism of the network. In packet networks however, delay becomes unpredictable because of the asynchronous nature of these networks. Depending on the specific application, mechanisms and several standards and variants of standards exist for supporting the different synchronization requirements in packet networks. Rather than solving the timing problem for specific applications, a network should be designed more general, being able to support both current as well as future network applications. TransPacket brings a general and future proof solution to the delay and synchronization problem in packet networks through its novel fusion network technology (also known as integrated hybrid). The technology is based on Ethernet packet transport, but as for the synchronous SDH/SONET circuit networks, transport is fully predictable, enabling synchronization and zero packet loss. The technology is still fully compatible with Ethernet, with the throughput and cost efficiency known from the packet networks.
This whitepaper gives an overview of synchronization and delay requirements for a selection of applications. In light of this, the implications on the network design and requirements to equipment are discussed. We then explain the basics of mechanisms that typically are applied in pure packet networks, synchronous Ethernet (SyncE) which is physical layer (L1) based, and the Precision Time Protocol (PTP, IEEE 1588, G.8265) which relies on packet layer synchronization. We then show how TransPacket brings a more general and future proof solution with the fusion network technique, meeting synchronization and stringent timing challenges as well as other future challenges related to supporting circuit properties in packet optical networks.