Reset Search
 

 

Article

How To: EXOS PTP Boundary and Ordinary Clock Configuration

« Go Back

Information

 
TitleHow To: EXOS PTP Boundary and Ordinary Clock Configuration
Objective
Explain the procedure required to configure a PTP boundary clock and a PTP ordinary clock in EXOS
Environment
  • EXOS 15.3 and higher
  • PTP
Procedure

Topology 

In this example two EXOS PTP capable switches are connected as shown to a third-party PTP Grand Master Clock (GMC).  The first of the two EXOS switches will serve as a PTP boundary clock, the second a PTP ordinary clock.  
PTP Example Topology
In EXOS, PTP clocks communicate with other PTP clocks via a loopback interface. In order to ensure that loopback interfaces are reachable by other clocks, routing must be established.  In this example, OSPF is used to dynamically propagate routes.  Static routing, or other dynamic routing protocols, could be used as well.  A VLAN common to all devices, VLAN timing, will be used to establish OSPF neighborship and advertise routes.

Boundary Clock Configuration

Boundary clocks bridge upstream master clocks with downstream slave clocks.  They serve as an intermediary and improve time synchronization in larger networks where there are multiple non-PTP hops.  In EXOS, a boundary clock requires two loopback interfaces.  One loopback interface will exchange PTP messages with the upstream master clock, the other will exchange PTP messages with downstream slave(s).

In this example VLAN "lpbk-to-GMC" serves as the loopback interface for the PTP master clock communication and "lpbk-to-Slave" serves as the loopback interface for slave clock communication.  The VLAN configuration for the switch is provided below.
#
# Module vlan configuration.
#
configure vlan default delete ports all
create vlan "lpbk-to-GMC"
configure vlan lpbk-to-GMC tag 10
enable loopback-mode vlan lpbk-to-GMC
create vlan "lpbk-to-Slave"
configure vlan lpbk-to-Slave tag 20
enable loopback-mode vlan lpbk-to-Slave
create vlan "timing"
configure vlan timing tag 99
configure vlan timing add ports 1, 10 untagged 
configure vlan timing ipaddress 10.0.2.2 255.255.255.0
enable ipforwarding vlan timing
configure vlan lpbk-to-GMC ipaddress 10.0.1.1 255.255.255.255    #Loopback Interface that communicates with GMC
enable ipforwarding vlan lpbk-to-GMC
configure vlan lpbk-to-Slave ipaddress 10.0.1.2 255.255.255.255  #Loopback Interface that communicates with Slaves
enable ipforwarding vlan lpbk-to-Slave

As stated previously, OSPF is used to dynamically advertise the routes for the loopback interfaces.  A simple OSPF configuration is provided below.
#
# Module ospf configuration.
#
enable ospf   #OSPF or some other static routes or routing protocol is required for routing between loopbacks and timing VLAN
configure ospf add vlan lpbk-to-GMC area 0.0.0.0 passive
configure ospf add vlan lpbk-to-Slave area 0.0.0.0 passive
configure ospf add vlan timing area 0.0.0.0
In EXOS, an end-to-end-transparent clock must be created and configured for the physical ports associated with the PTP timing network.  This is required for both boundary and ordinary clocks.  

The loopback interfaces for the master and slave clocks must then be configured and their respective slave clocks and master clocks added.

Boundary Clock  Procedure

1. Create the end-to-end-transparent clock, add timing enabled physical ports, enable the ports:
create network-clock ptp end-to-end-transparent
configure network-clock ptp end-to-end-transparent add ports <PORT_LIST>
enable network-clock ptp end-to-end transparent ports <PORT_LIST>
2. Create the PTP boundary clock and enable it:
create network-clock ptp boundary 
enable network-clock ptp boundary
3.  Add the loopback interface for the communication with the master clock and configure the IP address of the master clock:
Note: This is a slave clock interface to the upstream master clock.  The other loopback interface will be a master clock interface for the downstream slave clocks.
configure network-clock ptp boundary add vlan <VLAN> one-step slave-only  
configure network-clock ptp boundary add unicast-master <IP_ADDRESS_MASTER_CLOCK> query-interval 3 vlan <LOOPBACK_INTERFACE_VLAN> 
4. Add the loopback interface for communication with the slave clock(s) and configure the IP addresses of the slave clock(s):
configure network-clock ptp boundary add vlan <SLAVE_LOOPBACK_VLAN> one-step master-only
configure network-clock ptp boundary add unicast-slave <SLAVE_CLOCK_IP> vlan <SLAVE_LOOPBACK_VLAN>
The complete example configuration can be found below:
#
# Module ptpV2 configuration.
#
create network-clock ptp end-to-end-transparent
#Physical ports participating in PTP are added to transparent clock and enabled
configure network-clock ptp end-to-end-transparent add ports 1 one-step
enable network-clock ptp end-to-end-transparent ports 1
configure network-clock ptp end-to-end-transparent add ports 10 one-step
enable network-clock ptp end-to-end-transparent ports 10
create network-clock ptp boundary domain 0
enable network-clock ptp boundary
configure network-clock ptp boundary add vlan lpbk-to-GMC one-step slave-only
configure network-clock ptp boundary add vlan lpbk-to-Slave one-step master-only
configure network-clock ptp boundary add unicast-master 10.0.2.1 query-interval 3 vlan lpbk-to-GMC  # IP here is of GMC
configure network-clock ptp boundary add unicast-slave 10.0.1.3 vlan lpbk-to-Slave   #IP here is for Slave Clock

Ordinary Clock Configuration

Ordinary clocks exist at the edge of the timing network.  Technically speaking an ordinary clock can be either a master clock (GMC) or a slave clock.  In the EXOS implementation, ordinary clocks can only act as slave clocks.  Ordinary clock configuration is very similar to the boundary clock configuration.  The main difference being that there is only one loopback interface created.  That interface is then configured to communicate with the upstream master clock.

In this example "lpbk-to-mstr" will serve as the loopback VLAN for the ordinary clock.
#
# Module vlan configuration.
#
configure vlan default delete ports all
create vlan "lpbk-to-mstr"
configure vlan lpbk-to-mstr tag 30
enable loopback-mode vlan lpbk-to-mstr
create vlan "timing"
configure vlan timing tag 99
configure vlan timing add ports 1, 10 untagged 
configure vlan timing ipaddress 10.0.2.3 255.255.255.0
enable ipforwarding vlan timing
configure vlan lpbk-to-mstr ipaddress 10.0.1.3 255.255.255.255
enable ipforwarding vlan lpbk-to-mstr
OSPF has been setup on the ordinary clock as well.  This allows for dynamic advertisement of routes.
#
# Module ospf configuration.
#
enable ospf
configure ospf add vlan lpbk-to-mstr area 0.0.0.0 passive
configure ospf add vlan timing area 0.0.0.0

Ordinary Clock Procedure 

1. Create end-to-end-transparent clock, add timing enabled physical ports, enable the ports:
create network-clock ptp end-to-end-transparent
configure network-clock ptp end-to-end-transparent add ports <PORT_LIST>
enable network-clock ptp end-to-end transparent ports <PORT_LIST>
 2. Create the PTP boundary clock and enable it:
create network-clock ptp ordinary
enable network-clock ptp ordinary
3.  Add the loopback interface for the communication with the master clock and configure the IP address of the master clock:
Note: In this example the master clock for the ordinary clock will be the boundary clock that has just been configured.  An ordinary clock could also communicate directly with a GMC.
configure network-clock ptp boundary add vlan <VLAN> one-step slave-only  
configure network-clock ptp boundary add unicast-master <IP_ADDRESS_MASTER_CLOCK> query-interval 3 vlan <LOOPBACK_INTERFACE_VLAN> 
The complete example configuration can be found below:
#
# Module ptpV2 configuration.
#
create network-clock ptp end-to-end-transparent
configure network-clock ptp end-to-end-transparent add ports 1 one-step
create network-clock ptp ordinary domain 0
enable network-clock ptp ordinary
configure network-clock ptp ordinary add vlan lpbk-to-mstr one-step slave-only
configure network-clock ptp ordinary add unicast-master 10.0.1.2 query-interval 3 vlan lpbk-to-mstr #IP of parent/master clock for this clock



 
Additional notes
For information on validating PTP configuration please see the following article:
How to troubleshoot PTP Boundary Clock Configuration

Current EXOS PTP Limitations:

  • Layer 2 transport is not supported.
  • IPv6-UDP transport is not supported.
  • Multicast event messages are not supported.
  • One-step timestamp functionality is not supported on 1G Fiber ports, 10G ports on CSR switches, and stacking ports.
  • Peer-to-peer delay mechanism is not supported.
  • PTP datasets are not maintained for end-to-end transparent clocks.
  • Domain number cannot be assigned to end-to-end transparent clocks.
  • Boundary clock does not support synchronizing clocks across multiple domains.
  • Distributing clock frequency recovered from SyncE or from BITS or from a TDM port over PTP is not supported.
  • Ordinary clock master (Grandmaster) mode is not supported.
  • Synchronizing system time with the time recovered from PTP event messages is not supported.
  • Time of Day (ToD) output and inputs are not supported.
  • Unicast message negotiation on clock ports is not supported.
  • PTP cannot be used if network clock source is configured as BITS.

Feedback

 

Was this article helpful?


   

Feedback

Please tell us how we can make this article more useful.

Characters Remaining: 255