System Basics Introduction
Page 200 7210 SAS D, E, K OS Basic System Configuration Guide
IEEE 1588v2 PTP
NOTE: This feature is applicable only to the 7210 SAS-D ETR device and 7210 SAS-K (both
ETR and non-ETR).
The Precision Time Protocol (PTP) is a timing-over-packet protocol defined in the IEEE 1588v2
standard 1588 PTP 2008.
PTP may be deployed as an alternative timing-over-packet option to ACR. PTP provides the
capability to synchronize network elements to a Stratum-1 clock or primary reference clock (PRC)
traceable source over a network that may or may not be PTP-aware. PTP has several advantages
over ACR. It is a standards-based protocol, has lower bandwidth requirements, can transport both
frequency and time, and can potentially provide better performance.
There are four basic types of PTP devices, as listed below:
• Ordinary clock
• Boundary clock
• End-to-end transparent clock
• Peer-to-peer transparent clock
The 7210 SAS supports the ordinary clock in slave mode or the boundary clock. The boundary
clock and ordinary clock slave can be used for both frequency and time distribution. 7210 SAS
does not support ordinary clock in master mode, end-to-end transparent clock and peer-to-peer
transparent clock.
The 7210 SAS communicates with peer 1588v2 clocks; see Figure 20. These peers can be ordinary
clock slaves or boundary clocks. Each peer is identified by the IPv4 address to be used for
communications between the two clocks. There are two types of peers: configured and discovered.
The 7210 SAS operating as an ordinary clock slave or as a boundary clock should have configured
peers for each PTP neighbor clock from which it might accept synchronization information. The
7210 SAS initiates unicast sessions with all configured peers. A 7210 SAS operating as an
boundary clock will accept unicast session requests from external peers. If the peer is not a
configured peer, then it is considered a discovered peer. The 7210 SAS can deliver
synchronization information toward discovered peers (that is, slaves).
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