PTP lock issue with LiteON FlexFi FR1 O-RU – E2E O-RAN Testbed

[justinlau21]

Server (Core, CU/DU, LinuxPTP GM)

• Model: ZTE ZXCLOUD R5300 G4
• CPU: 2 × Intel Xeon Gold 6230N
• RAM: 384 GB
• Links: 10G fiber

NICs tested

• Intel X520
• Intel Onboard X722
• Intel E810-DA2 (non-GNSS variant)
  All NICs show identical PTP behavior.

O-RU

• LiteON FlexFi Indoor FR1 Radio Unit
• Sub-6 GHz (n78 / n79)

Additional Lab Equipment (available in lab)

• Ettus Research USRP X310
• Ettus Research USRP B210
• ZTE ZXCTN 6120S
• ZTE ZXCTN 9000
• ZTE ZXR10 8900E
• ZTE ZXR10 5960X
• Trimble GNSS System

PTP Setup

• LinuxPTP (ptp4l) acting as GM

[global]
dataset_comparison		        G.8275.x
G.8275.defaultDS.localPriority	128
maxStepsRemoved			        255
logAnnounceInterval		        -3
logSyncInterval			        -4
logMinDelayReqInterval		    -4
serverOnly			            1
G.8275.portDS.localPriority	    128
domainNumber			        24


#
# Transport options.
#
ptp_dst_mac             AA:BB:CC:DD:EE:FF
p2p_dst_mac             AA:BB:CC:DD:EE:FF
uds_address             /var/run/ptp4l
network_transport       L2
delay_mechanism         E2E
time_stamping           hardware
tsproc_mode             filter
delay_filter            moving_median
delay_filter_length     10
egressLatency           0
ingressLatency          0

#
# Clock description.
#
clockClass              6
clock_type              OC
clockAccuracy           0x20

• I've also tried using the MAC: 01:80:C2:00:00:0E

Observed Behavior

• O-RU detects PTP
• RU sends Delay_Req
• PTP sends Sync / Follow_Up
• ptp4l repeatedly logs bad message warnings
• Same behavior across X520, X722, and E810

Traffic confirmed with tcpdump

• RU enters SYNCHRONIZING
• RU never reaches LOCK

DPDK Status

• I am not using DPDK, as VFIO binding fails on my system:

dpdk-devbind.py --bind=vfio-pci <device>
Error: Cannot bind to driver vfio-pci: Invalid argument (Error 22)

Current testing is kernel networking + LinuxPTP only.
Main Questions

• Is Intel E810-DA2 without GNSS expected to work for achieving PTP lock with a LiteON O-RU when using LinuxPTP?
• Does i need a GNSS-disciplined NIC?
• Is DPDK required for correct PTP behavior with this RU?

Has the LiteON FlexFi FR1 RU been validated with:

• LinuxPTP as GM
• no GNSS
• Is a PTP-aware switch / boundary clock (e.g. ZXCTN 6120S acting as BC) effectively required between DU and RU?

What I’m Trying to Clarify
I want to understand whether the root cause is:

• NIC capability (E810 without GNSS),
• LinuxPTP limitations as a GM,
• Missing timing elements (BC / SyncE / GNSS), or an expected dependency on DPDK.

Any clarification on expected timing hardware assumptions or validated NIC requirements would be very helpful, Thanks.