Precision Time Protocol - PTP

Cumulus Linux supports IEEE 1588-2008 Precision Timing Protocol (PTPv2), which defines the algorithm and method for synchronizing clocks of various devices across packet-based networks, including Ethernet switches and IP routers.

PTP is capable of sub-microsecond accuracy. The clocks are in a master-slave hierarchy, where the slaves synchronize to their masters, which can be slaves to their own masters. The best master clock (BMC) algorithm, which runs on every clock, creates and updates the hierarchy automatically. The grandmaster clock is the top-level master. To provide a high-degree of accuracy, a Global Positioning System (GPS) time source typically synchronizes the grandmaster clock.

In the following example:

• Boundary clock 2 receives time from Master 1 (the grandmaster) on a PTP slave port, sets its clock and passes the time down from the PTP master port to Boundary clock 1.
• Boundary clock 1 receives the time on a PTP slave port, sets its clock and passes the time down the hierarchy through the PTP master ports to the hosts that receive the time.

Cumulus Linux and PTP

PTP in Cumulus Linux uses the linuxptp package that includes the following programs:

• ptp4l provides the PTP protocol and state machines
• phc2sys provides PTP Hardware Clock and System Clock synchronization
• timemaster provides System Clock and PTP synchronization

Cumulus Linux supports:

• PTP boundary clock mode only (the switch provides timing to downstream servers; it is a slave to a higher-level clock and a master to downstream clocks).
• Both IPv4 and IPv6 UDP PTP encapsulation.
• Only a single PTP domain per network.
• PTP on layer 3 interfaces, layer 3 bonds, trunk ports, and switch ports belonging to a VLAN.
• Multicast, unicast, and mixed message mode.
• End-to-End delay mechanism only. Cumulus Linux does not support Peer-to-Peer.
• Two-step clock correction mode, where PTP notes the time when the packet goes out of the port and sends the time in a separate (follow-up) message. Cumulus Linux does not support one-step mode.
• Hardware time stamping for PTP packets. This allows PTP to avoid inaccuracies caused by message transfer delays and improves the accuracy of time synchronization.

Basic Configuration

Basic PTP configuration requires you:

• Enable PTP on the switch.
• Configure PTP on at least one interface; this can be a layer 3 routed port, switch port, or trunk port. You do not need to specify which is a master interface and which is a slave interface; the PTP Best Master Clock Algorithm (BMCA) determines the master and slave.

The basic configuration shown below uses the default PTP settings:

• The clock mode is Boundary. This is the only clock mode that Cumulus Linux supports.
• The PTP clock domain is 0.
• PTP Priority1 and Priority2 are both 128.
• The DSCP is 46 for both general and event messages.
• The PPT interface transport mode is IPv4.
• Announce messages from any master are accepted.
• The PTP Interface Message Mode is multicast.
• The delay mechanism is End-to-End (E2E), where the slave measures the delay between itself and the master. The master and slave send delay request and delay response messages between each other to measure the delay.
• The hardware packet time stamping mode is two-step.

To configure optional settings, such as the PTP profile, domain, priority, and DSCP, the PTP interface transport mode and timers, and PTP monitoring, see the Optional Configuration sections below.

cumulus@switch:~$ nv set service ptp 1 enable on
cumulus@switch:~$ nv set interface swp1 ip address 10.0.0.9/32
cumulus@switch:~$ nv set interface swp2 ip address 10.0.0.10/32
cumulus@switch:~$ nv set interface swp1 ptp enable on
cumulus@switch:~$ nv set interface swp2 ptp enable on
cumulus@switch:~$ nv config apply

cumulus@switch:~$ nv set service ptp 1 enable on
cumulus@switch:~$ nv set bridge domain br_default
cumulus@switch:~$ nv set bridge domain br_default type vlan-aware
cumulus@switch:~$ nv set bridge domain br_default vlan 10-30
cumulus@switch:~$ nv set bridge domain br_default vlan 10 ptp enable on
cumulus@switch:~$ nv set interface vlan10 type svi
cumulus@switch:~$ nv set interface vlan10 ip address 10.1.10.2/24
cumulus@switch:~$ nv set interface vlan10 ptp enable on
cumulus@switch:~$ nv set interface swp1 bridge domain br_default
cumulus@switch:~$ nv set interface swp1 bridge domain br_default vlan 10
cumulus@switch:~$ nv set interface swp1 ptp enable on
cumulus@switch:~$ nv config apply

cumulus@switch:~$ nv set service ptp 1 enable on
cumulus@switch:~$ nv set bridge domain br_default
cumulus@switch:~$ nv set bridge domain br_default type vlan-aware
cumulus@switch:~$ nv set bridge domain br_default vlan 10-30
cumulus@switch:~$ nv set bridge domain br_default vlan 10 ptp enable on
cumulus@switch:~$ nv set interface vlan10 type svi
cumulus@switch:~$ nv set interface vlan10 ip address 10.1.10.2/24
cumulus@switch:~$ nv set interface swp2 bridge domain br_default
cumulus@switch:~$ nv set interface swp2 bridge domain br_default access 10
cumulus@switch:~$ nv set interface swp2 ptp enable on
cumulus@switch:~$ nv config apply

Optional Global PTP Configuration

PTP Profiles

PTP profiles are a standardized set of configurations and rules intended to meet the requirements of a specific application. Profiles define required, allowed, and restricted PTP options, network restrictions, and performance requirements.

Cumulus Linux supports the following predefined profiles:

• IEEE 1588 is the profile specified in the IEEE 1588 standard. This profile addresses some common applications and does not have any network restrictions.
• ITU 8275.1 is the PTP profile for use in telecom networks that require phase or time-of-day synchronization. Each device in the network must participate in the PTP protocol.

The following table shows the default parameter values for the predefined profiles.

The switch has a predefined default profile of each profile type, one for IEEE1588 and one for ITU8275.1. You can configure the switch to use a predefined profile or you can create a custom profile. You can change the profile settings of the predfined profiles, such as the announce rate, sync rate, domain, priority, transport, and so on. These changes conform to the ranges and allowed values of the profile type. You can also configure these parameters for individual PTP interfaces. When you configure parameters for an individual interface, the configuration takes precedence over the profile configuration. The interface is not part of the profile.

To set a predefined profile:

cumulus@switch:~$ nv set service ptp 1 current-profile default-itu-8275-1
cumulus@switch:~$ nv config apply

cumulus@switch:~$ nv set service ptp 1 current-profile default-1588
cumulus@switch:~$ nv config apply

cumulus@switch:~$ sudo nano /etc/ptp4l.conf
...
[global]
#
# Default Data Set
#
slaveOnly                      0
priority1                      128
priority2                      128
domainNumber                   24

twoStepFlag                    1
dscp_event                     46
dscp_general                   46
dataset_comparison             G.8275.x
G.8275.defaultDS.localPriority 128
G.8275.portDS.localPriority    128
ptp_dst_mac                    01:80:C2:00:00:0E
network_transport              L2

#
# Port Data Set
#
logAnnounceInterval            -3
logSyncInterval                -4
logMinDelayReqInterval         -4
announceReceiptTimeout         3
delay_mechanism                E2E

offset_from_master_min_threshold   -50
offset_from_master_max_threshold   50
mean_path_delay_threshold          200

#
# Run time options
#
logging_level                  6
path_trace_enabled             0
use_syslog                     1
verbose                        0
summary_interval               0

#
# servo parameters
#
pi_proportional_const          0.000000
pi_integral_const              0.000000
pi_proportional_scale          0.700000
pi_proportional_exponent       -0.300000
pi_proportional_norm_max       0.700000
pi_integral_scale              0.300000
pi_integral_exponent           0.400000
pi_integral_norm_max           0.300000
step_threshold                 0.000002
first_step_threshold           0.000020
max_frequency                  900000000
sanity_freq_limit              0

#
# Default interface options
#
time_stamping                  software


# Interfaces in which ptp should be enabled
# these interfaces should be routed ports
# if an interface does not have an ip address
# the ptp4l will not work as expected.

[swp1]
udp_ttl                 1
masterOnly              0
delay_mechanism         E2E
network_transport       L2

[swp2]
udp_ttl                 1
masterOnly              0
delay_mechanism         E2E
network_transport       L2

cumulus@switch:~$ sudo systemctl restart ptp4l.service

cumulus@switch:~$ sudo nano /etc/ptp4l.conf
[global]
#
# Default Data Set
#
slaveOnly                      0
priority1                      128
priority2                      128
domainNumber                   0

twoStepFlag                    1
dscp_event                     46
dscp_general                   46
dataset_comparison             ieee1588

#
# Port Data Set
#
logAnnounceInterval            1
logSyncInterval                0
logMinDelayReqInterval         0
announceReceiptTimeout         3
delay_mechanism                E2E

offset_from_master_min_threshold   -50
offset_from_master_max_threshold   50
mean_path_delay_threshold          200

#
# Run time options
#
logging_level                  6
path_trace_enabled             0
use_syslog                     1
verbose                        0
summary_interval               0

#
# servo parameters
#
pi_proportional_const          0.000000
pi_integral_const              0.000000
pi_proportional_scale          0.700000
pi_proportional_exponent       -0.300000
pi_proportional_norm_max       0.700000
pi_integral_scale              0.300000
pi_integral_exponent           0.400000
pi_integral_norm_max           0.300000
step_threshold                 0.000002
first_step_threshold           0.000020
max_frequency                  900000000
sanity_freq_limit              0

#
# Default interface options
#
time_stamping                  software


# Interfaces in which ptp should be enabled
# these interfaces should be routed ports
# if an interface does not have an ip address
# the ptp4l will not work as expected.

[swp1]
udp_ttl                 1
masterOnly              0
delay_mechanism         E2E
network_transport       UDPv4

[swp2]
udp_ttl                 1
masterOnly              0
delay_mechanism         E2E
network_transport       UDPv4

cumulus@switch:~$ sudo systemctl restart ptp4l.service

To create a custom profile:

cumulus@switch:~$  nv set service ptp 1 profile CUSTOM1 
cumulus@switch:~$  nv set service ptp 1 profile CUSTOM1 profile-type itu-g-8275-1  
cumulus@switch:~$  nv set service ptp 1 profile CUSTOM1 domain 28
cumulus@switch:~$  nv set service ptp 1 profile CUSTOM1 announce-timeout 3
cumulus@switch:~$  nv set service ptp 1 current-profile CUSTOM1
cumulus@switch:~$  nv config apply

cumulus@switch:~$ sudo nano /etc/ptp4l.conf
[global]
#
# Default Data Set
#
slaveOnly                      0
priority1                      128
priority2                      128
domainNumber                   28

twoStepFlag                    1
dscp_event                     46
dscp_general                   46
dataset_comparison             G.8275.x
G.8275.defaultDS.localPriority 128
G.8275.portDS.localPriority    128
ptp_dst_mac                    01:80:C2:00:00:0E
network_transport              L2

#
# Port Data Set
#
logAnnounceInterval            5
logSyncInterval                -4
logMinDelayReqInterval         -4
announceReceiptTimeout         3
delay_mechanism                E2E

offset_from_master_min_threshold   -50
offset_from_master_max_threshold   50
mean_path_delay_threshold          200

#
# Run time options
#
logging_level                  6
path_trace_enabled             0
use_syslog                     1
verbose                        0
summary_interval               0

#
# servo parameters
#
pi_proportional_const          0.000000
pi_integral_const              0.000000
pi_proportional_scale          0.700000
pi_proportional_exponent       -0.300000
pi_proportional_norm_max       0.700000
pi_integral_scale              0.300000
pi_integral_exponent           0.400000
pi_integral_norm_max           0.300000
step_threshold                 0.000002
first_step_threshold           0.000020
max_frequency                  900000000
sanity_freq_limit              0

#
# Default interface options
#
time_stamping                  software


# Interfaces in which ptp should be enabled
# these interfaces should be routed ports
# if an interface does not have an ip address
# the ptp4l will not work as expected.

[swp1]
udp_ttl                 1
masterOnly              0
delay_mechanism         E2E
network_transport       L2

[swp2]
udp_ttl                 1
masterOnly              0
delay_mechanism         E2E
network_transport       L2

cumulus@switch:~$ sudo systemctl restart ptp4l.service

To show the current PTP profile setting, run the nv show service ptp <ptp-instance> command:

cumulus@switch:~$ nv show service ptp 1
                             operational  applied             description
---------------------------  -----------  ------------------  --------------------------------------------------------------------
enable                       on           on                  Turn the feature 'on' or 'off'.  The default is 'off'.
current-profile                           default-itu-8275-1  Current PTP profile index
domain                       24           0                   Domain number of the current syntonization
ip-dscp                      46           46                  Sets the Diffserv code point for all PTP packets originated locally.
priority1                    128          128                 Priority1 attribute of the local clock
priority2                    128          128                 Priority2 attribute of the local clock
two-step                     on           on                  Determines if the Clock is a 2 step clock
...

To show the settings for a profile, run the nv show service ptp 1 profile <profile-name> command:

cumulus@switch:~$ nv show service ptp 1 profile CUSTOM1
                    operational  applied         description
------------------  -----------  ------------    ----------------------------------------------------------------------
announce-interval                -3              Mean time interval between successive Announce messages.  It's spec...
announce-timeout                 5               The number of announceIntervals that have to pass without receipt o...
delay-mechanism                  end-to-end      Mode in which PTP message is transmitted.
delay-req-interval               -4              The minimum permitted mean time interval between successive Delay R...
domain                           19              Domain number of the current syntonization
local-priority                   128             Local priority attribute of the local clock
priority1                        128             Priority1 attribute of the local clock
priority2                        128             Priority2 attribute of the local clock
profile-type                     itu-g-8275-1    The profile type
sync-interval                    -4              The mean SyncInterval for multicast messages.  It's specified as a...
transport                        802.3           Transport method for the PTP messages.

Clock Domains

PTP domains allow different independent timing systems to be present in the same network without confusing each other. A PTP domain is a network or a portion of a network within which all the clocks synchronize. Every PTP message contains a domain number. A PTP instance works in only one domain and ignores messages that contain a different domain number.

You can specify multiple PTP clock domains. PTP isolates each domain from other domains so that each domain is a different PTP network. You can specify a number between 0 and 127.

The following example commands configure domain 3:

cumulus@switch:~$ nv set service ptp 1 domain 3
cumulus@switch:~$ nv config apply

cumulus@switch:~$ sudo nano /etc/ptp4l.conf
[global]
#
# Default Data Set
#
slaveOnly               0
priority1               128
priority2               128
domainNumber            3
...

cumulus@switch:~$ sudo systemctl restart ptp4l.service

PTP Priority

The BMC selects the PTP master according to the criteria in the following order:

1. Priority 1
2. Clock class
3. Clock accuracy
4. Clock variance
5. Priority 2
6. Port ID

Use the PTP priority to select the best master clock. You can set priority 1 and 2:

• Priority 1 overrides the clock class and quality selection criteria to select the best master clock.
• Priority 2 identifies primary and backup clocks among identical redundant Grandmasters.

The range for both priority1 and priority2 is between 0 and 255. The default priority is 128. For the boundary clock, use a number above 128. The lower priority applies first.

The following example commands set priority 1 and priority 2 to 200:

cumulus@switch:~$ nv set service ptp 1 priority1 200
cumulus@switch:~$ nv set service ptp 1 priority2 200
cumulus@switch:~$ nv config apply

cumulus@switch:~$ sudo nano /etc/ptp4l.conf
[global]
#
# Default Data Set
#
slaveOnly               0
priority1               200
priority2               200
domainNumber            3
...

cumulus@switch:~$ sudo systemctl restart ptp4l.service

DSCP

You can configure the DiffServ code point (DSCP) value for all PTP IPv4 packets originated locally. You can set a value between 0 and 63.

cumulus@switch:~$ nv set service ptp 1 ip-dscp 22
cumulus@switch:~$ nv config apply

cumulus@switch:~$ sudo nano /etc/ptp4l.conf
[global]
#
# Default Data Set
#
slaveOnly               0
priority1               200
priority2               200
domainNumber            3

twoStepFlag             1
dscp_event              22
dscp_general            22
...

cumulus@switch:~$ sudo systemctl restart ptp4l.service

Optional PTP Interface Configuration

Transport Mode

By default, Cumulus Linux encapsulates PTP messages in UDP/IPV4 frames. To encapsulate PTP messages on an interface in UDP/IPV6 frames:

cumulus@switch:~$ nv set interface swp1 ptp transport ipv6
cumulus@switch:~$ nv config apply

cumulus@switch:~$ sudo nano /etc/ptp4l.conf
...
# Default interface options
#
time_stamping           hardware

# Interfaces in which ptp should be enabled
# these interfaces should be routed ports
# if an interface does not have an ip address
# the ptp4l will not work as expected.

[swp1]
udp_ttl                 1
masterOnly              0
delay_mechanism         E2E
network_transport       UDPv6

[swp2]
udp_ttl                 1
masterOnly              0
delay_mechanism         E2E
network_transport       UDPv6
...

cumulus@switch:~$ sudo systemctl restart ptp4l.service

Forced Master Mode

By default, PTP ports are in auto mode, where the BMC algorithm determines the state of the port.

You can configure Forced Master mode on a PTP port so that it is always in a master state and the BMC algorithm does not run for this port. This port ignores any Announce messages it receives.

cumulus@switch:~$ nv set interface swp1 ptp forced-master on
cumulus@switch:~$ nv config apply

cumulus@switch:~$ sudo nano /etc/ptp4l.conf
...
# Default interface options
#
time_stamping           hardware

# Interfaces in which ptp should be enabled
# these interfaces should be routed ports
# if an interface does not have an ip address
# the ptp4l will not work as expected.

[swp1]
udp_ttl                 1
masterOnly              1
delay_mechanism         E2E
network_transport       UDPv4
...

cumulus@switch:~$ sudo systemctl restart ptp4l.service

Message Mode

Cumulus Linux supports the following PTP message modes:

• Multicast, where the ports subscribe to two multicast addresses, one for event messages with timestamps and the other for general messages without timestamps. The Sync message that the master sends is a multicast message; all slave ports receive this message because the slaves need the time from the master. The slave ports in turn generate a Delay Request to the master. This is a multicast message that the intended master for the message and other slave ports receive. Similarly, all slave ports in addition to the intended slave port receive the master’s Delay Response. The slave ports receiving the unintended Delay Requests and Responses need to drop the packets. This can affect network bandwidth if there are hundreds of slave ports.
• Unicast, where you configure the port as a unicast client or server. The client sends out requests for Announce, Sync and Delay Response from its list of servers (masters) from the Unicast Master Table. The servers respond, then start sending Announce Messages. The client uses the Announce Messages to run the BMCA and to choose the best master. You typically use PTP unicast when multicast is not an option in the network or when sending multicast traffic to unintended devices is not desirable.
• Mixed, where Sync and Announce messages are multicast messages but Delay Request and Response messages are unicast. This avoids the issue seen in multicast message mode where every slave port sees Delay Requests and Responses from every other slave port.

Multicast and Mixed Mode

Multicast mode is the default setting; when you enable PTP on an interface, the message mode is multicast.

To change the message mode to mixed on swp1:

cumulus@switch:~$ nv set interface swp1 ptp mixed-multicast-unicast on
cumulus@switch:~$ nv config apply

cumulus@switch:~$ nv set interface swp1 ptp mixed-multicast-unicast off
cumulus@switch:~$ nv config apply

cumulus@switch:~$ sudo nano /etc/ptp4l.conf
...
# Default interface options
#
time_stamping           hardware

# Interfaces in which ptp should be enabled
# these interfaces should be routed ports
# if an interface does not have an ip address
# the ptp4l will not work as expected.

[swp1]
Hybrid_e2e              1
...

cumulus@switch:~$ sudo systemctl restart ptp4l.service

Unicast Mode

You can configure a PTP interface on the switch to be a unicast client or a unicast server. Unicast mode reduces the amount of bandwidth consumed.

To configure a PTP interface to be the unicast client:

• Configure the unicast master table. You must configure at least one unicast master table on the switch. If you configure more than one unicast master table, each table must have a unique ID.
  • Set the unicast table ID; a unique ID that identifies the unicast master table.
  • Set the unicast master address. You can set more than one unicast master address, which can be an IPv4, IPv6, or MAC address.
  • Set the IP address for peer delay requests. You can set an IPv4 or IPv6 address.
  • Optional: Set the unicast master query interval, which is the mean interval between requests for announce messages. Specify this value as a power of two in seconds. You can specify a value between -3 and 4. The default value is -0 (2 power).
• On the PTP interface:
  • Set the table ID of the unicast master table you want to use.
  • Set the unicast service mode to client.
  • Optional: Set the unicast request duration; the service time in seconds requested during discovery. The default value is 300 seconds.

The following example commands configure a unicast master table with ID 1. The commands set the unicast master address and the peer address to 10.10.10.1, the query interval to 4, the unicast service mode to client, and the unicast request duration to 20 in the unicast master table.

cumulus@switch:~$ nv set service ptp 1 unicast-master 1 address 10.10.10.1
cumulus@switch:~$ nv set service ptp 1 unicast-master 1 peer-address 10.10.10.1
cumulus@switch:~$ nv set service ptp 1 unicast-master 1 query-interval 4
cumulus@switch:~$ nv set interface swp1 ptp unicast-master-table-id 1
cumulus@switch:~$ nv set interface swp1 ptp unicast-service-mode client
cumulus@switch:~$ nv set interface swp1 ptp unicast-request-duration 20
cumulus@switch:~$ nv config apply

To configure a PTP interface to be the unicast server:

• Set the unicast table ID and the unicast master address. You can set more than one unicast master address, which can be an IPv4, IPv6, or MAC address.
  • Set the IP address for peer delay requests. You can set an IPv4 or IPv6 address.
  • Optional: Set the unicast master query interval, which is the mean interval between requests for announce messages. Specify this value as a power of two in seconds. You can specify a value between -3 and 4. The default value is -0 (2 power).
• On the PTP interface:
  • Set the table index of the unicast master table you want to use.
  • Set the unicast service mode to server.

The following example commands set the unicast table ID to 1, the unicast master address and the peer address to 10.10.10.1, the query interval to 4, and the unicast service mode to server.

cumulus@switch:~$ nv set service ptp 1 unicast-master 1 address 10.10.10.1
cumulus@switch:~$ nv set service ptp 1 unicast-master 1 peer-address 10.10.10.1
cumulus@switch:~$ nv set service ptp 1 unicast-master 1 query-interval 4
cumulus@switch:~$ nv set interface swp1 ptp unicast-master-table-id 1
cumulus@switch:~$ nv set interface swp1 ptp unicast-service-mode server
cumulus@switch:~$ nv config apply

Show Unicast Master Information

To show the unicast master table configuration on the switch, run the nv show service ptp <instance-id> unicast-master <table-id> command:

cumulus@switch:~$ nv show service ptp 1 unicast-master 1
                operational  applied     description
--------------  -----------  ----------  ----------------------------------------------------------------------
peer-address                 10.10.10.1  IP address for Peer Delay request
query-interval               4           Mean interval between requests for Announce messages. It is specifi...
[address]                    10.10.10.1  ipv4, ipv6 or mac address

To show information about a specific unicast master, run the nv show service ptp <instance-id> unicast-master <table-id> address <ip-mac-address-id> command:

cumulus@switch:~$ nv show service ptp 1 unicast-master 1 address 10.10.10.1

TTL for a PTP Message

To restrict the number of hops a PTP message can travel, set the TTL on the PTP interface. You can set a value between 1 and 255.

cumulus@switch:~$ nv set interface swp1 ptp ttl 20
cumulus@switch:~$ nv config apply

cumulus@switch:~$ sudo nano /etc/ptp4l.conf
...
# Default interface options
#
time_stamping           hardware

# Interfaces in which ptp should be enabled
# these interfaces should be routed ports
# if an interface does not have an ip address
# the ptp4l will not work as expected.

[swp1]
udp_ttl                 20
masterOnly              1
delay_mechanism         E2E
network_transport       UDPv4
...

cumulus@switch:~$ sudo systemctl restart ptp4l.service

PTP Interface Timers

You can set the following timers for PTP messages.

• To set the timers with NVUE, run the nv set interface <interface> ptp timers <timer> <value> command.
• To set the timers with Linux commands, edit the /etc/ptp4l.conf file and set the timers in the Default interface options section.

cumulus@switch:~$ nv set interface swp1 ptp timers announce-interval -1
cumulus@switch:~$ nv config apply

cumulus@switch:~$ nv set interface swp1 ptp timers sync-interval -5
cumulus@switch:~$ nv config apply

cumulus@switch:~$ sudo nano /etc/ptp4l.conf
...
# Default interface options
#
time_stamping           hardware

# Interfaces in which ptp should be enabled
# these interfaces should be routed ports
# if an interface does not have an ip address
# the ptp4l will not work as expected.

[swp1]
logAnnounceInterval     -1
logSyncInterval         -5
udp_ttl                 20
masterOnly              1
delay_mechanism         E2E
network_transport       UDPv4
...

cumulus@switch:~$ sudo systemctl restart ptp4l.service

Acceptable Master Table

The acceptable master table option is a security feature that prevents a rogue player from pretending to be the Grandmaster to take over the PTP network. To use this feature, you configure the clock IDs of known Grandmasters in the acceptable master table and set the acceptable master table option on a PTP port. The BMC algorithm checks if the Grandmaster received on the Announce message is in this table before proceeding with the master selection. Cumulus Linux disables this option by default on PTP ports.

The following example command adds the Grandmaster clock ID 24:8a:07:ff:fe:f4:16:06 to the acceptable master table and enable the PTP acceptable master table option for swp1:

cumulus@switch:~$ nv set service ptp 1 acceptable-master 24:8a:07:ff:fe:f4:16:06
cumulus@switch:~$ nv config apply

cumulus@switch:~$ nv set service ptp 1 acceptable-master 24:8a:07:ff:fe:f4:16:06 alt-priority 2

cumulus@switch:~$ nv set interface swp1 ptp acceptable-master on
cumulus@switch:~$ nv config apply

cumulus@switch:~$ sudo nano /etc/ptp4l.conf
...
#
# Default interface options
#
time_stamping           hardware


[acceptable_master_table]
maxTableSize 16
acceptable_master_clockIdentity 248a07.fffe.f41606
...

cumulus@switch:~$ sudo nano /etc/ptp4l.conf
...
#
# Default interface options
#
time_stamping           hardware


[acceptable_master_table]
maxTableSize 16
acceptable_master_clockIdentity 248a07.fffe.f41606 2

...
# Default interface options
#
time_stamping           hardware

# Interfaces in which ptp should be enabled
# these interfaces should be routed ports
# if an interface does not have an ip address
# the ptp4l will not work as expected.

[swp1]
udp_ttl                 20
masterOnly              1
delay_mechanism         E2E
network_transport       UDPv4
acceptable_master       on
...

cumulus@switch:~$ sudo systemctl restart ptp4l.service

Optional Monitor Configuration

Cumulus Linux monitors clock correction and path delay against thresholds, and generates counters that show in the nv show interface swp5 ptp command output and log messages when PTP reaches the thresholds. You can configure the following monitor settings:

cumulus@switch:~$ nv set service ptp 1 monitor path-delay-threshold 300
cumulus@switch:~$ nv config apply

cumulus@switch:~$ sudo nano /etc/ptp4l.conf
...
global]
#
# Default Data Set
#
slaveOnly               0
priority1               128
priority2               128
domainNumber            0

twoStepFlag             1
dscp_event              46
dscp_general            46

offset_from_master_min_threshold   -50
offset_from_master_max_threshold   50
mean_path_delay_threshold          300
...

Delete PTP Configuration

To delete PTP configuration, delete the PTP master and slave interfaces. The following example commands delete the PTP interfaces swp1, swp2, and swp3.

cumulus@switch:~$ nv unset interface swp1 ptp
cumulus@switch:~$ nv unset interface swp2 ptp
cumulus@switch:~$ nv unset interface swp3 ptp
cumulus@switch:~$ nv config apply

cumulus@switch:~$ sudo nano /etc/ptp4l.conf
...
# Default interface options
#
time_stamping           hardware

# Interfaces in which ptp should be enabled
# these interfaces should be routed ports
# if an interface does not have an ip address
# the ptp4l will not work as expected.

cumulus@switch:~$ sudo systemctl restart ptp4l.service

To disable PTP on the switch and stop the ptp4l and phc2sys processes:

cumulus@switch:~$ nv set service ptp 1 enable off
cumulus@switch:~$ nv config apply

cumulus@switch:~$ sudo systemctl stop ptp4l.service phc2sys.service
cumulus@switch:~$ sudo systemctl disable ptp4l.service phc2sys.service

Troubleshooting

PTP Configuration and Status

To show a summary of the PTP configuration on the switch, run the nv show service ptp <instance> command:

cumulus@switch:~$ nv show service ptp 1

---------------------------  -----------  -------  --------------------------------------------------------------------
enable                       on           on       Turn the feature 'on' or 'off'.  The default is 'off'.
domain                       0            0        Domain number of the current syntonization
ip-dscp                      46           46       Sets the Diffserv code point for all PTP packets originated locally.
priority1                    128          128      Priority1 attribute of the local clock
priority2                    128          128      Priority2 attribute of the local clock
two-step                     on           on       Determines if the Clock is a 2 step clock
monitor
  max-offset-threshold       50           50       Maximum offset threshold in nano seconds
  max-timestamp-entries                   400      Maximum timestamp entries allowed
  max-violation-log-entries               8        Maximum violation log entries per set
  max-violation-log-sets                  8        Maximum violation logs sets allowed
  min-offset-threshold       -50          -50      Minimum offset threshold in nano seconds
  path-delay-threshold       200          200      Path delay threshold in nano seconds
  violation-log-interval                  0        violation log intervals in seconds
...

You can drill down with the following nv show service ptp <instance> commands:

• nv show service ptp <instance> acceptable-master shows a collection of acceptable masters.
• nv show service ptp <instance> monitor shows PTP monitor configuration.
• nv show service ptp <instance> current shows the local states learned during PTP message exchange.
• nv show service ptp <instance> clock-quality shows the clock quality status.
• nv show service ptp <instance> parent shows the local states learned during PTP message exchange.
• nv show service ptp <instance> time-properties shows the clock time attributes.

To check configuration and counters for a PTP interface, run the nv show interface <interface> ptp command:

cumulus@leaf03:mgmt:~$ nv show interface swp1 ptp
                           operational  applied     description
-------------------------  -----------  ----------  ----------------------------------------------------------------------
enable                                  on          Turn the feature 'on' or 'off'.  The default is 'off'.
acceptable-master                       off         Determines if acceptable master check is enabled for this interface.
delay-mechanism            end-to-end   end-to-end  Mode in which PTP message is transmitted.
forced-master              off          off         Configures PTP interfaces to forced master state.
instance                                1           PTP instance number.
mixed-multicast-unicast                 off         Enables Multicast for Announce, Sync and Followup and Unicast for D...
transport                  ipv4         ipv4        Transport method for the PTP messages.
ttl                        1            1           Maximum number of hops the PTP messages can make before it gets dro...
unicast-request-duration                300         The service time in seconds to be requested during discovery.
timers
  announce-interval        0            0           Mean time interval between successive Announce messages.  It's spec...
  announce-timeout         3            3           The number of announceIntervals that have to pass without receipt o...
  delay-req-interval       -3           -3          The minimum permitted mean time interval between successive Delay R...
  sync-interval            -3           -3          The mean SyncInterval for multicast messages.  It's specified as a...
peer-mean-path-delay       0                        An estimate of the current one-way propagation delay on the link wh...
port-state                 master                   State of the port
protocol-version           2                        The PTP version in use on the port
counters
  rx-announce              0                        Number of Announce messages received
  rx-delay-req             0                        Number of Delay Request messages received
  rx-delay-resp            0                        Number of Delay response messages received
  rx-delay-resp-follow-up  0                        Number of Delay response follow upmessages received
  rx-follow-up             0                        Number of Follow up messages received
  rx-management            0                        Number of Management messages received
  rx-peer-delay-req        0                        Number of Peer Delay Request messages received
  rx-peer-delay-resp       0                        Number of Peer Delay Response messages received
  rx-signaling             0                        Number of singnaling messages received
  rx-sync                  0                        Number of Sync messages received
  tx-announce              2639                     Number of Announce messages transmitted
  tx-delay-req             0                        Number of Delay Request messages transmitted
  tx-delay-resp            0                        Number of Delay response messages transmitted
  tx-delay-resp-follow-up  0                        Number of Delay response follow upmessages transmitted
  tx-follow-up             21099                    Number of Follow up messages transmitted
  tx-management            0                        Number of Management messages transmitted
  tx-peer-delay-req        0                        Number of Peer Delay Request messages transmitted
  tx-peer-delay-resp       0                        Number of Peer Delay Response messages transmitted
  tx-signaling             0                        Number of singnaling messages transmitted
  tx-sync                  21099                    Number of Sync messages transmitted

To view PTP status information, including the delta in nanoseconds from the master clock:

cumulus@switch:~$ sudo pmc -u -b 0 'GET TIME_STATUS_NP'
sending: GET TIME_STATUS_NP
    7cfe90.fffe.f56dfc-0 seq 0 RESPONSE MANAGEMENT TIME_STATUS_NP
        master_offset              12610
        ingress_time               1525717806521177336
        cumulativeScaledRateOffset +0.000000000
        scaledLastGmPhaseChange    0
        gmTimeBaseIndicator        0
        lastGmPhaseChange          0x0000'0000000000000000.0000
        gmPresent                  true
        gmIdentity                 000200.fffe.000005
    000200.fffe.000005-1 seq 0 RESPONSE MANAGEMENT TIME_STATUS_NP
        master_offset              0
        ingress_time               0
        cumulativeScaledRateOffset +0.000000000
        scaledLastGmPhaseChange    0
        gmTimeBaseIndicator        0
        lastGmPhaseChange          0x0000'0000000000000000.0000
        gmPresent                  false
        gmIdentity                 000200.fffe.000005
    000200.fffe.000006-1 seq 0 RESPONSE MANAGEMENT TIME_STATUS_NP
        master_offset              5544033534
        ingress_time               1525717812106811842
        cumulativeScaledRateOffset +0.000000000
        scaledLastGmPhaseChange    0
        gmTimeBaseIndicator        0
        lastGmPhaseChange          0x0000'0000000000000000.0000
        gmPresent                  true
        gmIdentity                 000200.fffe.000005

PTP Violations

You can check PTP violations:

• To show the collection of violation logs, run the nv show service ptp <instance> monitor timestamp-log command.
• To show PTP violations, run the nv show service ptp <instance> monitor violations command.

The following example shows that there are no violations:

cumulus@switch:~$ nv show service ptp 1 monitor violations
                  operational  applied  description
----------------  -----------  -------  -----------------------------------------------
last-max-offset                         Time at which last max offest violation occurred
last-min-offset                         Time at which last min offest violation occurred
last-path-delay                         Time at which last path delay violation occurred
max-offset-count  0                     Number of maximum offset violations
min-offset-count  0                     Number of min offset violations
path-delay-count  0                     Number of Path delay violations

PTP Show Commands

• To see the list of NVUE show commands for PTP, run the nv list-commands service ptp command.
• To show the list of show commands for a PTP interface, run the nv list-commands interface command, then scroll to see PTP.

cumulus@switch:~$ nv list-commands service ptp
nv show service ptp
nv show service ptp <instance-id>
nv show service ptp <instance-id> acceptable-master
nv show service ptp <instance-id> acceptable-master <clock-id>
nv show service ptp <instance-id> unicast-master
nv show service ptp <instance-id> unicast-master <table-id>
nv show service ptp <instance-id> unicast-master <table-id> address
nv show service ptp <instance-id> unicast-master <table-id> address <ip-mac-address-id>
nv show service ptp <instance-id> profile
nv show service ptp <instance-id> profile <profile-id>
nv show service ptp <instance-id> monitor
nv show service ptp <instance-id> monitor timestamp-log
nv show service ptp <instance-id> monitor violations
nv show service ptp <instance-id> monitor violations log
nv show service ptp <instance-id> monitor violations log acceptable-master
nv show service ptp <instance-id> monitor violations log forced-master
nv show service ptp <instance-id> monitor violations log max-offset
nv show service ptp <instance-id> monitor violations log min-offset
nv show service ptp <instance-id> monitor violations log path-delay
nv show service ptp <instance-id> current
nv show service ptp <instance-id> clock-quality
nv show service ptp <instance-id> parent
nv show service ptp <instance-id> parent grandmaster-clock-quality
nv show service ptp <instance-id> time-properties
...

cumulus@switch:~$ nv list-commands interface
...
nv show interface <interface-id> ptp
nv show interface <interface-id> ptp timers
nv show interface <interface-id> ptp counters
...

Example Configuration

In the following example, the boundary clock on the switch receives time from Master 1 (the grandmaster) on PTP slave port swp1, sets its clock and passes the time down through PTP master ports swp2, swp3, and swp4 to the hosts that receive the time.

The following example configuration assumes that you have already configured the layer 3 routed interfaces (swp1, swp2, swp3, and swp4) you want to use for PTP.

cumulus@switch:~$ nv set service ptp 1 enable on
cumulus@switch:~$ nv set service ptp 1 priority2 254
cumulus@switch:~$ nv set service ptp 1 priority1 254
cumulus@switch:~$ nv set service ptp 1 domain 3
cumulus@switch:~$ nv set interface swp1 ptp enable on
cumulus@switch:~$ nv set interface swp2 ptp enable on
cumulus@switch:~$ nv set interface swp3 ptp enable on
cumulus@switch:~$ nv set interface swp4 ptp enable on
cumulus@switch:~$ nv config apply

cumulus@switch:~$ sudo cat /etc/nvue.d/startup.yaml
- set:
    interface:
      lo:
        ip:
          address:
            10.10.10.1/32: {}
        type: loopback
      swp1:
        ptp:
          enable: on
        type: swp
      swp2:
        ptp:
          enable: on
        type: swp
      swp3:
        ptp:
          enable: on
        type: swp
      swp4:
        ptp:
          enable: on
        type: swp
    service:
      ptp:
        '1':
          domain: 3
          enable: on
          priority1: 254
          priority2: 254

cumulus@switch:~$ sudo cat /etc/ptp4l.conf
...
[global]
#
# Default Data Set
#
slaveOnly               0
priority1               254
priority2               254
domainNumber            3

twoStepFlag             1
dscp_event              46
dscp_general            46

offset_from_master_min_threshold   -50
offset_from_master_max_threshold   50
mean_path_delay_threshold          200

#
# Run time options
#
logging_level           6
path_trace_enabled      0
use_syslog              1
verbose                 0
summary_interval        0

#
# Default interface options
#
time_stamping           hardware

# Interfaces in which ptp should be enabled
# these interfaces should be routed ports
# if an interface does not have an ip address
# the ptp4l will not work as expected.

[swp1]
udp_ttl                 1
masterOnly              0
delay_mechanism         E2E
network_transport       UDPv4

[swp2]
udp_ttl                 1
masterOnly              0
delay_mechanism         E2E
network_transport       UDPv4

[swp3]
udp_ttl                 1
masterOnly              0
delay_mechanism         E2E
network_transport       UDPv4

[swp4]
udp_ttl                 1
masterOnly              0
delay_mechanism         E2E
network_transport       UDPv4

Considerations

Spanning Tree and PTP

PTP frames are affected by STP filtering; events, such as an STP topology change (where ports temporarily go into the blocking state), can cause interruptions to PTP communications.

If you configure PTP on bridge ports, NVIDIA recommends that the bridge ports are spanning tree edge ports or in a bridge domain where spanning tree is disabled.