Specifications

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Cisco MWR 2941 Mobile Wireless Edge Router Release 3.5 Software Configuration Guide, Cisco IOS Release 15.1(3)MR
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Chapter 16 Configuring Clocking and Timing
Network Clocking Overview
When configured as a multicast PTP router, the Cisco MWR 2941 selects the best path toward a
Rendezvous Point (RP) using the active routing protocol, sends a Cisco Protocol Independent Multicast
(PIM) join message to the RP, and forwards PTP multicast messages to the PTP client. The
Cisco MWR 2941 also supports PIM forwarding. For instructions on how to configure PTP redundancy
using multicast, see Configuring PTP Redundancy, page 16-10.
Hot Standby Master Clock
The Cisco MWR 2941 supports a hot standby master clock for PTP clocking; the Cisco MWR 2941
selects the best clock source between two PTP master clocks and switches dynamically between them if
the clock quality of the standby clock is greater than that of the current master clock. For instructions on
how to configure a hot standby master clock, see Configuring PTP Clocking.
Hybrid Clocking
The Cisco MWR 2941 supports a hybrid clocking mode that uses clock frequency obtained from the
synchronous Ethernet port while using phase (ToD or 1PPS) obtained using PTP. For instructions on how
to configure hybrid clocking, see Configuring PTP Clocking.
Pseudowire-Based Clocking
Pseudowire-based clocking allows the Cisco MWR 2941 router to
• Transmit and receive clocking information over a pseudowire interface
• Receive clocking over a virtual pseudowire interface.
The Cisco MWR 2941 can transmit clocking information within packet headers (in-band) or as a
separate packet stream (out-of-band).
Pseudowire-based clocking also supports adaptive clock recovery (ACR), which allows the
Cisco MWR 2941 to recover clocking from the headers of a packet stream. For instructions on how to
configure pseudowire-based clocking, see Configuring Clocking and Timing.
Synchronous Ethernet
Synchronous Ethernet is a timing technology that allows the Cisco MWR 2941 to transport frequency
and time information over Ethernet. Because frequency and time are embedded in Ethernet packets,
synchronous Ethernet must be supported by each network element in the synchronization path.
Synchronous Ethernet is defined in the ITU-T G.781, G.8261, G.8262, and G.8264, Telcordia
GR-253-CORE, and Telcordia GR-1244-CORE standards.
You can use synchronous Ethernet in conjunction with an external timing technology such as GPS to
synchronize timing across the network. For instructions on how to configure synchronous Ethernet, see
Configuring Clocking and Timing.
Synchronous Ethernet ESMC and SSM
The Cisco MWR 2941 supports Ethernet Synchronization Message Channel (ESMC) and
Synchronization Status Message (SSM) to provide clock synchronization on Synchronous Ethernet. For
more information about Ethernet ESMC and SSM, see Chapter 17, “Configuring Synchronous Ethernet
ESMC and SSM.”