Assisted Partial Timing Support on ACX7024 and ACX7024X Routers
SUMMARY Assisted Partial Timing Support (APTS) is a GNSS backed by PTP delivers accurate timing and synchronization in mobile backhaul networks. This topic talks about the APTS support on ACX7024 and ACX7024X routers.
This feature is supported on Junos OS Evolved Release 24.2R2 only.
ACX7024 and ACX7024X routers act as Telecom Boundary Cloud for Assisted partial timing
support (T-BC-A). The router locks to GNSS as a primary source. When GNSS loses lock, it
operates in a frequency or phase backup mode from deriving time information from a
G8275.2 packet timeReceiver. If GNSS loses lock and PTP is unavailable, the system moves
into a holdover state with the internal clock and continues to be in that state until
the holdover timer expires (default value of 5 minutes). You can configure the holdover
time using the holdover-in-spec-duration
option under the [set
protocols ptp
] hierarchy. Once GNSS is available, the router locks back
into it. Supported APTS features include:
-
Both G.8275.1 and G8275.2 timeTransmitter ports are supported, however only a single G.8275.2 slave port can be configured as the backup path for APTS.
- Up to 512 PTPoIPv4 and PTPoE timeTransmitter streams are supported simultaneously.
-
A single PTPoIPv4 timeReceiver stream is supported when APTS is configured.
-
PTPoIPv4 timeReceiver configuration is supported for interfaces that belong to a routing-instance.
-
APTS is supported for 100G, 50G, 40G, 25G, 10G, 1G ports.
Configuration
To support this feature on ACX7024 and ACX7024X, you need an APTS node with GNSS source configured at the [
edit chassis synchronization
] hierarchy level and PTP boundary clock configured at the [edit protocols ptp
] hierarchy level as shown below.Configure
ptp-mode
to enable PTP functionality:set chassis fpc 0 pic 0 ptp-mode
- Configure GNSS
settings:
set chassis synchronization network-option option-1 set chassis synchronization enable-extended-ql-tlv set chassis synchronization esmc-transmit interfaces all set chassis synchronization gnss-receiver 0 interface set chassis synchronization gnss-receiver 0 receiver-type tb-1 set chassis synchronization gnss-receiver 0 constellation gps l1ca
Configure PTP. Note that the
clock-mode
is set to boundary clock and the base profile is set to G.8275.1 in this configuration for downstream timeReceivers. The configuration [set protocols ptp apts
] is required when configuring boundary clock with APTS.set protocols ptp clock-mode boundary set protocols ptp profile-type g.8275.1 set protocols ptp ipv4-dscp 54 set protocols ptp slave delay-request -4 set protocols ptp slave sync-interval -4 set protocols ptp slave grant-duration 500 set protocols ptp slave interface et-0/0/18.0 unicast-mode transport ipv4 set protocols ptp slave interface et-0/0/18.0 unicast-mode clock-source 192.168.1.2 local-ip-address 192.168.1.10 set protocols ptp master interface et-0/0/0.0 unicast-mode transport ipv4 set protocols ptp master interface et-0/0/0.0 unicast-mode clock-client 10.0.0.2 local-ip-address 10.0.0.10 set protocols ptp master interface et-0/0/2.0 multicast-mode transport ieee-802.3 set protocols ptp master interface et-0/0/10.0 multicast-mode transport ieee-802.3 set protocols ptp apts
You can enable PTP on an interface that belongs to a routing instance:
set protocols ptp slave interface et-0/0/0.0 unicast-mode clock-source 192.168.1.2 local-ip-address 192.168.1.10 set routing-instances PTP-VRF instance-type virtual-router set routing-instances PTP-VRF interface et-0/0/0.0
(Optional) Configure
holdover-in-spec-duration
settings:set protocols ptp holdover-in-spec-duration 10
Verification
- Verify the PTP
configuration:
user@host> show ptp global-information PTP Global Configuration: Domain number : 24 Clock mode : Boundary Profile: G.8275.1 Priority Level1 : 128 Priority Level2 : 128 Local Priority : 128 Path Trace : Disabled ESMC QL From Clock Class: Enabled Clock Class/ESMC QL : 6 / (QL PRC/SSM 0x2) SNMP Trap Status : Disabled PHY Time Stamping : Enabled UTC Leap Seconds : 37 Transparent-clock-config : DISABLED Transparent-clock-status : N/A APTS : Enabled APTS Domain : 44 APTS Unicast Negotiation : Enabled Holdover-in-spec Duration: 4 Hours Slave Parameters: Sync Interval : -6 (64 packets per second - unicast request) Delay Request Interval: -6 (64 packets per second - unicast request) Announce Interval : 0 (1 packet per second - unicast request) Announce Timeout : 3 Grant Duration : 300 Master Parameters: Sync Interval : -4 (16 packets per second) Announce Interval : -3 (8 packets per second) Delay Request Timeout : <not applicable> Clock Step : one-step Arbitrary Mode : FALSE Master Parameters (G.8275.2.enh): Min Announce Interval : -3 (8 packets per second) Max Announce Interval : 0 (1 packets per second) Min Sync Interval : -7 (128 packets per second) Max Sync Interval : 0 (1 packet per second) Min Delay Response Interval : -7 (128 packets per second) Max Delay Response Interval : 0 (1 packet per second) Number of Slaves : 1 Number of Masters : 3 Number of Stateful : 0
Verify PTP lock status:
When GNSS and PTP are active:
user@host> show ptp lock-status detail Lock Status: Lock State : FREERUN/INITIALIZING State since : 2023-11-27 05:34:56 PST (00:00:54 ago) Source Details: Current Source : NONE Primary Source : GNSS Active, Ready or Not Ready/Inactive Secondary Source : PTP Active, Ready or Not Ready/Inactive
When system is locking to GNSS:
user@host> show ptp lock-status detail Lock Status: Lock State : ACQUIRING State since : 2023-11-27 05:34:56 PST (00:00:54 ago) Source Details: Current Source : GNSS Primary Source : GNSS Active, Ready Secondary Source : PTP Active, Ready/Not Ready Selected PTP Master Details: Upstream Master address : 50.1.1.1 Slave interface : et-0/0/50.0
When system is locked to GNSS:
user@host> show ptp lock-status detail Lock Status: Lock State : PHASE ALIGNED Phase offset : x ns --- offset wrt GNSS State since : 2023-11-27 05:34:56 PST (00:00:54 ago) Source Details: Current Source : GNSS Primary Source : GNSS Active, Ready Secondary Source : PTP Active, Ready/Not Ready Selected PTP Master Details: Upstream Master address : 50.1.1.1 Slave interface : et-0/0/50.0
When GNSS is lost and the system falls back to PTP:
user2host> show ptp lock-status detail Lock Status: Lock State : PHASE ALIGNED/ACQUIRING Phase offset : x ns --- offset wrt PTP State since : 2023-11-27 05:34:56 PST (00:00:54 ago) Source Details: Current Source : PTP Primary Source : GNSS Inactive Secondary Source : PTP Active, Ready/Not Ready Selected PTP Master Details: Upstream Master address : 50.1.1.1 Slave interface : et-0/0/50.0
When both GNSS and PTP are inactive:
user@host> show ptp lock-status detail Lock Status: Lock State : HOLDOVER Holdover state: In-specification/ Out-of-specification Phase offset : x ns (last known offset) State since : 2023-11-27 05:34:56 PST (00:00:54 ago) Source Details: Current Source : NONE Primary Source : GNSS Inactive Secondary Source : PTP Inactive Selected PTP Master Details: Upstream Master address : 50.1.1.1 Slave interface : et-0/0/50.0
Verify PTP clock detail:
user@host> show ptp clock detail Clock Details: Slot Number : 0 (CB) Default Data: Two-step Clock : FALSE Clock Identity : 00:cc:34:ff:fe:88:bd:5d Total Ports on Device : 128 Clock Class : 248 Clock Accuracy : 254 Log Variance : 65535 Clock Priority1 : 128 Clock Priority2: 128 UTC Offset : 37 Leap59 : FALSE Leap61 : FALSE Time Traceable : FALSE Frequency Traceable : FALSE Time Source : 160 Delay Req Sending Time: 0 Steps Removed : 0 Slave-only : FALSE Parent Data: Parent Id : 00:cc:34:ff:fe:88:bd:5d GMC Id : 00:cc:34:ff:fe:88:bd:5d GMC Class : 6 GMC Accuracy : 33 GMC Variance : 20061 GMC Priority1 : 128 GMC Priority2 : 128 Global Data: UTC Offset : 37 Leap-59 : FALSE Leap-61 : FALSE Time traceable : TRUE Freq Traceable : TRUE Time Scale : TRUE Time source : 32 Path Trace count : 0
Verify PTP timeTransmitter details:
user@host> show ptp all-master-clock detail Upstream Masters: Slot : 2 Parent Id : e4:23:3c:ff:fe:0c:e1:74 GMC Id : e4:23:3c:ff:fe:0c:e1:74 GMC Class : 248 GMC Accuracy : 254 GMC Variance : 65535 GMC Priority1 : 128 GMC Priority2 : 128 UTC Offset : 37 Leap-59 : FALSE Leap-61 : FALSE Time traceable : FALSE Freq Traceable : FALSE Time Scale : TRUE Time source : 160 Unicast : FALSE UTC Valid : FALSE Two Step : FALSE Alternate Master : FALSE Steps Removed : 0 Parent SourcePort Id : 2 ANN msg Interval : -3 Interface : et-2/0/0.0 PTP Stream ID : 0
- Verify the PTP
configuration: