Overview of 1588 ATR

Definition

1588 Adaptive Time Recovery (ATR) is a PTP-based technology that allows routers to establish clock links and implement time synchronization over a third-party network using PTP packets in Layer 3 unicast mode.

1588 ATR is an advancement compared to 1588v2, the latter of which requires 1588v2 support on all network devices.

1588 ATR is a client/server protocol through which servers communicate with clients to achieve time synchronization.

When the time server (such as the SSU2000) supports only the 1588v2 unicast negotiation mode, the client sends a negotiation request to the server, and the server sends time synchronization packets to the client after the negotiation is established. The client is configured with the 1588 ATR hop-by-hop mode and interconnected with the time server to achieve time synchronization in 1588v2 unicast negotiation mode. After that, the client can function as a BC to provide time synchronization for downstream NodeBs.

Purpose

1588v2 is a software-based technology used to achieve frequency and time synchronization and can support hardware timestamping to provide greater accuracy. However, 1588v2 requires support from all devices on the live network.

To address this disadvantage, 1588 ATR is introduced to allow time synchronization over a third-party network that includes 1588v2-incapable devices. On the live network, 1588v2 is preferred for 1588v2-capable devices, and 1588 ATR is used when 1588v2-incapable devices exist.

Benefits

This feature offers the following benefits to carriers:

Does not require 1588v2 to be supported by all network devices, reducing network construction costs.
Fits for more network applications that meet time synchronization requirements.

Features Supported

The 1588 ATR features supported by NetEngine 8000 Fs are as follows:

An NetEngine 8000 F that functions as a 1588 ATR server can synchronize time information with upstream devices using the BITS source and transmit time information to downstream devices.
An NetEngine 8000 F that functions as a 1588 ATR server can synchronize time information with upstream devices using 1588v2/G.8275.1 and transmit time information to downstream devices.
The NetEngine 8000 F functioning as a 1588 ATR client supports time synchronization with upstream and downstream devices in 1588 ATR hop-by-hop mode.

An NetEngine 8000 F can function only as the 1588 ATR server. The following restrictions apply to network deployment:

When 1588 ATR is used to implement time synchronization over a third-party network, reduce the packet delay variation (PDV) and the number of devices on the third-party network as much as possible in order to ensure time synchronization performance on clients. For details, see performance specifications for clients.
The server and client communicate with each other through PTP packets which can be either Layer 3 IP packets or single-VLAN-tagged packets. The PTP packets cannot carry two VLAN tags or the MPLS label.
The interface used to send PTP packets on the server needs to be support 1588v2.

The NetEngine 8000 F supports the 1588 ATR client. Network deployment has the following restrictions:

When the 1588 ATR client in hop-by-hop mode is interconnected with the time source in 1588v2 unicast negotiation mode, the NetEngine 8000 F must be directly connected to the time source.