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The Clock Recovery System recovers the service clock using Adaptive Clock Recovery (ACR) and Differential Clock Recovery (DCR).
Information About Clock Recovery
 Note |
Framing type should be maintained same in all routers end to end. |
Effective Cisco IOS XE Everest 16.5.1, ACR is supported on the 8-port T1/E1 interface module.
Note |
Framing type should be maintained same in all routers end to end. |
Customer-edge devices (CEs) can have different clock from that of the Provide-edge devices (PEs).
|
IM Card |
Pseudowires Supported (Number of Clocks Derived) |
|---|---|
|
T1 CEM Interface Module |
1476 |
The clock of interface modules must be used as service clock.
CEM must be configured before configuring the global clock recovery.
RTP must be enabled for DCR in CEM, as the differential clock information is transferred in the RTP header.
The reference clock source is used and locked to a single clock.
The clock ID should be unique for a particular interface module for ACR or DCR configuration.
When CEM group is configured, dynamic change in clock source is not allowed.
ACR clock configuration under each controller should be performed before configuring CEM group.
Before configuring Adaptive Clock Recovery, CEM must be configured. Below are the guidelines to configure clock recovery:
The node (chassis) on which the DS1 is configured for ACR, must have its own clock derived from BITS/GPS/Stratum clock.
The minimum packet size of CEM pseudowires on the network that delivers robust clock recovery is 64 bytes.
enable
configure terminal
controller t1 0/4/0
cem-group 0 unframed
clock source recovered 1
exit
recovered-clock 0 1
clock recovered 1 adaptive cem 1 0
exit
Note |
The clock configuration on controller must be done before configuring the clock recovery on global configuration mode. |
To remove the clock configuration in ACR and DCR, you must remove the recovery clock configuration in global configuration mode and then remove the controller configuration.
Before configuring Adaptive Clock Recovery, CEM must be configured. Below are the guidelines to configure clock recovery:
The node (router) on which the interface module is configured for ACR, must have its own clock derived from BITS/GPS/Stratum clock.
The minimum packet size of CEM pseudowires on the network that delivers robust clock recovery is 256 bytes.
enable
configure terminal
controller t3 0/4/12
cem-group 0 unframed
clock source recovered 1
exit
recovered-clock 0 1
clock recovered 1 adaptive cem 1 0
exit
Note |
The clock configuration on controller must be done before configuring the clock recovery on global configuration mode. |
To remove the clock configuration in ACR and DCR, you must remove the recovery clock configuration in global configuration mode and then remove the controller configuration.
Use the show recovered-clock command to verify the adaptive clock recovery of T3 interfaces for SAToP:
Router# show recovered-clock
Recovered clock status for subslot 0/1
---------------------------------------
Clock Type Mode CEM Status Frequency Offset(ppb) Circuit-No
0 DS3 ADAPTIVE 0 ACQUIRED n/a 12 (Port)Use the show running-config | section command to verify the configuration of adaptive clock of T3 interfaces:
Router# show running-config | section 0/4/12
controller MediaType 0/4/12
mode t3
controller T3 0/4/12
cem-group 0 unframed
clock source recovered 1
cablelength 224
interface CEM 0/4/12
no ip address
cem 0Use the show running-config | section recovered-clock command to verify the recovery of adaptive clock of T3 interfaces:
Router# show running-config | section recovered-clock
recovered-clock 0 0
clock recovered 1 adaptive cem 12 0Before you start configuring DCR, RTP must be enabled on the CEM interface. The RTP is used to carry the differential time.
The minimum packet size of CEM pseudowires on the network that delivers robust clock recovery is 256 bytes.
To configure differential clock recovery on T3 interface for SAToP in controller mode:
enable
configure terminal
controller t3 0/4/12
cem-group 0 unframed
clock source recovered 1
exit
To configure RTP header under interface, use the following commands:
interface cem 0/4/12
cem 0
rtp-present
To configure differential clock recovery of T3 interface in global configuration mode, use the following commands:
recovered-clock 0 1
clock recovered 1 differential cem 12 0
exit
Note |
The clock configuration on controller must be done before configuring the clock recovery on global configuration mode. |
Starting from Cisco IOS XE Bengaluru 17.4.1, ACR and DCR are supported on STS-1e controller for framed SAToP.
To configure the clock on STS-1e controller for framed SAToP on the T3 mode, enter the following commands:
enable
configure terminal
controller STS-1e slot/bay/port
sts-1 1
mode t3
t3 framing c-bit
cem-group 0 framed
t3 clock source recovered 1
To configure the clock on STS-1e controller for framed SAToP on the CT3 mode, enter the following commands:
enable
configure terminal
controller STS-1e slot/bay/port
sts-1 1
clock source internal
mode ct3
t3 framing c-bit
t1 1 cem-group 0 framed
t1 1 clock source recovered 1
To configure the clock on STS-1e controller for framed SAToP on the VT-15 mode, enter the following commands:
enable
configure terminal
controller STS-1e slot/bay/port
sts-1 1
mode vt-15
vtg 1 t1 1 cem-group 0 framed
vtg 1 t1 1 clock source recovered 2
The following example shows how to configure the clock on STS-1e controller for framed SAToP on the T3 mode:
enable
configure terminal
controller STS-1e 0/8/12
sts-1 1
mode t3
t3 framing c-bit
cem-group 0 framed
t3 clock source recovered 1
The following example shows how to configure the clock on STS-1e controller for framed SAToP on the CT3 mode:
enable
configure terminal
controller STS-1e 0/8/12
sts-1 1
clock source internal
mode ct3
t3 framing c-bit
t1 1 cem-group 0 framed
t1 1 clock source recovered 1
The following example shows how to configure the clock on STS-1e controller for framed SAToP on the VT-15 mode:
enable
configure terminal
controller STS-1e 0/8/12
sts-1 1
mode vt-15
vtg 1 t1 1 cem-group 0 framed
vtg 1t1 1 clock source recovered 2
The commands used to configure adaptive clock recovery and differential clock recovery are:
|
Commands |
URL |
|---|---|
|
clock recovered adaptive cem |
|
|
clock recovered differential cem |
|
|
cem-group |
|
|
recovered-clock |
|
|
controller t1/e1 |
|
|
clock-source |
|
|
network-clock input-source |
http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/interface/command/ir-cr-book/ir-l2.html |
|
Related Topic |
Document Title |
|---|---|
|
Cisco IOS commands |
|
Standard/RFC |
Title |
|---|---|
|
ITU -T G.8261 |
Timing and synchronization aspects in packet networks |
|
MIB |
MIBs Link |
|---|---|
|
— |
To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL: |
|
Description |
Link |
|---|---|
|
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