Cisco Cisco XR 12000 12000 1-Port OC-48c STM-16c POS SDH ISE Line Card
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Packet-Over-SONET Line Card Installation and Configuration
78-16412-02
Configuring and Troubleshooting Line Card Interfaces
For more information on troubleshooting and diagnostics, refer to the installation and configuration
guide that came with your Cisco 12000 Series Router.
guide that came with your Cisco 12000 Series Router.
Note
If you perform online insertion or removal of the GBIC or SFP without shutting down the interface, a
warning message is displayed on the console device.
warning message is displayed on the console device.
SONET/SDH Clocking Issues
This section provides an overview of SONET/SDH clocking issues. A POS line card supports both line
and internal clocking functions. Line clocking is derived from the incoming signal from a given port.
Internal clocking is derived from the clock that is internal to the line card.
and internal clocking functions. Line clocking is derived from the incoming signal from a given port.
Internal clocking is derived from the clock that is internal to the line card.
Each port can be configured independently of any other in a line-timed setup, going back as far as the
first payload processor. However, on a POS line card, the second level of payload processing ties the
ports to a common clock source which is timed from only one port. This can result in pointer
justifications if the remaining ports are not synchronous. However, with a properly configured router,
these pointer justifications can be limited to provide the same performance as a SONET cross-connect
device.
first payload processor. However, on a POS line card, the second level of payload processing ties the
ports to a common clock source which is timed from only one port. This can result in pointer
justifications if the remaining ports are not synchronous. However, with a properly configured router,
these pointer justifications can be limited to provide the same performance as a SONET cross-connect
device.
Note
Pointer justifications do not affect data throughput. All configurations of a POS line card provide total
data throughput regardless of pointer justifications. Under no circumstances does any data loss occur.
All configurations provide 100 percent error-free data flow.
data throughput regardless of pointer justifications. Under no circumstances does any data loss occur.
All configurations provide 100 percent error-free data flow.
The line card uses Stratum3 (S3) as the internal clock reference. However, if one of the ports is Stratum1
(S1) accurate, it can be used as the local reference for the system clock. In this case, pointer justifications
are very limited. If the system clock is timed from an S1 clock source, from a valid SONET network,
then there will be no pointer justifications on any synchronous interface. There are minimal pointer
justifications (limited to S1 pointer justifications) on any asynchronous interface if it is on another
SONET network. Pointer justification in this case is proportional to the accuracy of the other port clock.
(S1) accurate, it can be used as the local reference for the system clock. In this case, pointer justifications
are very limited. If the system clock is timed from an S1 clock source, from a valid SONET network,
then there will be no pointer justifications on any synchronous interface. There are minimal pointer
justifications (limited to S1 pointer justifications) on any asynchronous interface if it is on another
SONET network. Pointer justification in this case is proportional to the accuracy of the other port clock.
A POS line card has the ability to select an input port as the source of synchronization for the system
clock. This eliminates pointer justifications on any port that is synchronous with the selected port. Any
other port on that line card that is not synchronous to the selected reference port will encounter pointer
justifications at a rate proportional to clock accuracy of the port.
clock. This eliminates pointer justifications on any port that is synchronous with the selected port. Any
other port on that line card that is not synchronous to the selected reference port will encounter pointer
justifications at a rate proportional to clock accuracy of the port.
If the port is locally timed, it is Stratum3. If the port is line-timed, it depends on the attached network.
It could be another Stratum3 clock, a Stratum1, or something much worse. This issue only applies to
multiport cards and can be avoided if all ports on the line card are connected to the same SONET/SDH
network.
It could be another Stratum3 clock, a Stratum1, or something much worse. This issue only applies to
multiport cards and can be avoided if all ports on the line card are connected to the same SONET/SDH
network.
Configuring and Troubleshooting Line Card Interfaces
The following sections detail how to configure and troubleshoot line card interfaces:
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