Time Synchronization

 Time synchronization requirements for 5G/6G mobile networks and other use cases are evolving. Synchronization implementations must keep pace with the increasing precision, complexity, scale, and security requirements. This year, we implemented new time synchronization test cases for the EANTC interoperability testing to verify the accuracy, stability, and interoperability of different time synchronization mechanisms and devices. All tests were based on ITU-T and IEEE standards and O-RAN Alliance specifications.
           
This year, nine vendors participated in the Time Synchronization test area: Arrcus, Calnex Solutions, Ciena, Ericsson, Huawei, Juniper Networks, Keysight Technologies, Microchip Technology, and H3C Technologies. Their time synchronization solutions were extensively tested and validated through a series of predetermined test cases.

Time Synchronization in SRv6-Enabled 5G x-Haul

In traditional Centralized Radio Access Networks (C-RAN) architectures, fronthaul and mid-haul ("x-Haul") connections consisted of direct fiber cables running Ethernet framing without intermediate switches. The Open Radio Access Network (O-RAN) disaggregation enables fully switched/routed x-haul infrastructures, enabling better RAN transport scaling, more flexible component placement, and seamless transport network management. For the first time at EANTC, we validated timing over a 5Gx-Haul using a SRv6 architecture. This test was performed to see if the time synchronization performance in an O-RAN 5G network with SRv6 would still fulfill the requirements of 1100 ns (nanoseconds) maximum absolute time error ( i.e. max|TEL | ≤1100 ns) from the Telecom Grandmaster to the output of the access nodes while having a relative time error of less than 130 ns between the access nodes' outputs. This test was performed with and without congested links. During this test, we had two types of traffic: best-effort background traffic and strict priority O-RAN eCPRI traffic.

When the links were congested, we observed packet drops; however,  only the background traffic was dropped, not O-RAN eCPRI traffic, and no timing packets, proving that PTP prioritization worked correctly.

Secure PTP Transport

The Precision Time Protocol (PTP) is a mission-critical technology targeted by denial of service and other attacks. So far, all PTP traffic worldwide runs unencrypted. MACsec, a technology that encrypts Ethernet links, has been around for a long time. PTP over MACsec, while not sounding necessarily complex, introduces performance challenges: PTP relies heavily on accurate packet timestamping to maintain synchronization within a network.
However, MACsec requires insertion and removal of the 24-to-32-byte long MACsec header on all or some of the link frames, and the encryption and decryption can cause delay variations between the egress timestamping point and the physical link.  
           
This year we successfully tested inter-vendor MACsec in a back-to-back scenario for the first time beating the challenges MACsec introduces to time synchronization.
         
In addition, we conducted PTP tests over DWDM interfaces, holdover/failover test scenarios, simulated GNSS disruption tests, delay asymmetry detection/measurement, interworking protocol tests, and Time Synchronization over 800G links. Where applicable, the clocks involved complied at least with Class C requirements and typically with Class D.
With these and many other tests in the time synchronization area this year, we continued the efforts to validate and optimize the multi-vendor interoperability of a range of advanced time synchronization standards.  

The following test cases have been executed for this test area: