Specifications

Channelized and Electrical Interface Line Card Installation and Configuration

78-16417-02

Configuring and Troubleshooting Line Card Interfaces

SONET/SDH Clocking Issues

This section provides an overview of SONET/SDH clocking issues and is applicable to the 1-port

channelized OC-48/STM-16 ISE and 4-port channelized OC-12/STM-4 ISE line cards. These line cards

support 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.

Each port can be configured independently of the other in a line-timed setup, going back as far as the

first payload processor. However, on the 1-port channelized OC-48/STM-16 ISE and 4-port channelized

OC-12/STM-4 ISE line cards, the second level of payload processing ties the ports to a common clock

source that 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 the1-port channelized

OC-48/STM-16 ISE and 4-port channelized OC-12/STM-4 ISE line cards 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.

These line cards use 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.

Note When using the show controller pos command, Positive Stuff Event (PSE) and Negative Stuff Event

(NSE) values can be safely ignored.

The 1-port channelized OC-48/STM-16 ISE and 4-port channelized OC-12/STM-4 ISE line cards can

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.

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

multi-port 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

This section provides procedures for configuring and troubleshooting the channelized and electrical

interface line card:

• Configuring the 1-Port Channelized OC-12/STM-4 (DS1/E1) ISE Line Card, page 41

• Configuring the 1-Port Channelized OC-48/STM-16 ISE and 4-Port Channelized OC-12/STM-4

ISE Line Cards, page 42

• Configuring the 1-Port Channelized OC-12/STM-4 (OC-3) Line Card, page 44