•
If the 1-Port 10-Gigabit Ethernet LAN/WAN PHY SPA is on LAN or WAN mode at one end, it must
run on the same mode (LAN or WAN) at the remote end as well. However, SPA-1X10GE-WL-V2
(configured in LAN mode) is compatible with the SPA-1X10GE-L-V2 (LAN SPA).
Synchronous Ethernet
Synchronous Ethernet (SyncE) is a procedure in which a physical layer interface is used to pass timing from
node to node in the same way that timing is passed in SONET or SDH. SyncE, defined by ITU-T standards,
such as G.8261, G.8262, G.8264, and G.781, leverages the PHY layer of Ethernet to transmit frequency to
remote sites. SyncE over Ethernet provides a cost-effective alternative to the networks. For SyncE to work,
each network element must, along with the synchronization path, support SyncE.
The 2-Port Gigabit Synchronous Ethernet SPA has a dedicated external interface known as the BITS interface
to recover the clock from a SSU. The Cisco ASR 1000 Series Routers use this clock for SyncE. The BITS
interface supports E1 (European SSUs) and T1 (American BITS) framing. The following table lists the framing
modes for the BITS interface on a 2-Port Gigabit Synchronous Ethernet SPA.
Table 17: Framing Modes for BITS Interface
Rx Port
Tx Port
SSM or QL support
Framing Modes
Supported
BITS or SSU
Interface Support
Matrix
Yes
Yes
Yes
T1 ESF
T1
Yes
Yes
No
T1 SF
T1
Yes
Yes
Yes
E1 CRC4
E1
Yes
Yes
No
E1 FAS
E1
Yes
No
No
E1 CAS
E1
Yes
No
Yes
E1 CAS CRC4
E1
Yes
Yes
No
2048kHz
2048kHz
You can implement SyncE on the 2-Port Gigabit Synchronous Ethernet SPA, with four different configurations:
•
Clock Recovery from SyncE: The system clock is recovered from the SyncE clocking source (Gigabit
and Ten gigabit interfaces only). The router uses this clock as the Tx clock for other SyncE interfaces
or ATM or CEoP interfaces.
•
Clock Recovery from External Interface: The system clock is recovered from a BITS clocking source
or a GPS interface.
•
Line to External: The system clock received from an Ethernet is forwarded to an external Synchronization
Supply Unit (SSU). During a synchronization chain, the received clock may have unacceptable wander
and jitter. The router recovers the clock from the SyncE interface, converts it to the format required for
Cisco ASR 1000 Series Aggregation Services Routers SIP and SPA Software Configuration Guide, Cisco IOS XE
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Overview of the Ethernet SPAs
Synchronous Ethernet