Supported Platforms
Precision Time Protocol Overview
Increase in bandwidth requirements on wireless backhaul networks and the need to reduce costs and to improve flexibility have triggered the need for a packet-based backhaul infrastructure. Traditional metro deployments do not cater to the delivery of synchronization services, and this leaves operators with no other choice than to keep older parallel infrastructure. Physical layer–based Synchronous Ethernet and packet-based Precision Time Protocol (PTP) enable MX Series and ACX Series routers to deliver synchronization services that meet the requirements of today’s mobile network, as well as future Long Term Evolution (LTE)–based infrastructures. Physical layer–based technologies function regardless of network load, whereas packet-based technologies require careful architecture and capacity planning. For information about Synchronous Ethernet, see Synchronous Ethernet Overview.
PTP, also known as IEEE 1588v2, is a packet-based technology that enables the operator to deliver synchronization services on packet-based mobile backhaul networks. IEEE 1588 PTP (Version 2) clock synchronization standard is a highly precise protocol for time synchronization that synchronizes clocks in a distributed system. The time synchronization is achieved through packets that are transmitted and received in a session between a master clock and a slave clock.
The system clocks can be categorized based on the role of the node in the network. They are broadly categorized into ordinary clocks and boundary clocks. The master clock and the slave clock are known as ordinary clocks. The boundary clock can operate as either a master clock or a slave clock. The following list explains these clocks in detail:
- Master clock—Also called the grandmaster clock, the master clock is located in the PTP server (also called master or master node). The master clock transmits the messages to the PTP clients (also called slave node or boundary node). This allows the clients to establish their relative time distance and offset from the master clock (which is the reference point) for phase synchronization. Delivery mechanism to the clients is either unicast or multicast packets over Ethernet or UDP.
- Slave clock—Located in the PTP client (also called slave or slave node), the slave clock performs clock and time recovery operations based on the received and requested timestamps from the master clock.
- Boundary clock—The boundary clock operates as a combination of the master and slave clocks. The boundary clock endpoint acts as a slave clock to the master clock, and also acts as the master to all the slaves reporting to the boundary endpoint.
For more information about configuring PTP, see Configuring Precision Time Protocol and Example: Configuring Precision Time Protocol.
The Table 1 summarizes the first Junos OS release that supports PTP on the various Juniper routers and their components:
Table 1: Precision Time Protocol Support
Routers and components | Junos OS Release |
|---|---|
MX80 3D Universal Edge Routers with model number MX80-P | 12.2 |
MX-MPC2E-3D-P on MX240, MX480, and MX960 routers | 12.2 |
Ethernet Modular Interface Cards (MICs) on MX240, MX480, and MX960 routers | 12.2 |
ACX Series Universal Access Routers | 12.2 |
 | Note: Unified in-service software upgrade (unified ISSU) is currently not supported when clock synchronization is configured for PTP on the MICs and Enhanced MPCEs on MX240, MX480, and MX960 routers. |
| Note: To switch between the PTP and Synchronous Ethernet modes, you must first deactivate the configuration for the current mode and then commit the configuration. Wait for a short period of 30 seconds, configure the new mode and its related parameters, and then commit the configuration. |
