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The IEEE C37.94 standard defines the communication of protection relays with communication equipment inside a substation using optical fibers.
The IEEE defines the C37.94 standard as N * 64 kbps optical fiber interface to provide transparent communications between tele-protection relays and multiplexers equipments. The C37.94 standard describes the interconnection details for the variable N, (where N = 1, 2…12), which describes a multiple of 64 kilobit per second connections at which the communication link is to operate.
The C37.94 interface module supports four ports from port number 0 to 3.
The 4-Port C37.94 interface module is supported on the RSP2 module of the Cisco ASR 902 and ASR 903 routers.
This following section provides information about configuring C37.94 interface module on the Cisco ASR 903 Series Router.
The C37.94 interface module supports smart grid tele-protection.
Smart Grid refers to the electricity delivery system from the point of generation to the point of consumption using analog or digital information and the communication technology for gathering and acting on the information.
Tele-protection refers to the mechanism to quickly switch on alternative routes using tele-protection equipment when a malfunction occurs. The switchover is to improve the performance of the electric grid.
The IEEE standard defines a data frame format for C37.94 interface module. The frame format is designed to allow the passage of information in packet format from the multiplexer to the tele-protection equipment and from the tele-protection equipment to the multiplexer equipment.
The features of 4-Port C37.94 Interface Module are:
Supports 4 independent C37.94 interfaces
Provides low latency connection over pseudowires
Supports allocation of timeslot. Timeslot ranges from 1 to 12
Supports Online Insertion and Removal (OIR)
Supports traffic switch from active to standby
Provides quick switchover to alternative route at the time of a route failure
Populates the C37.94 controller indexes in IfTable; the IfTable is defined in IF-MIB
The channelization of N * 64 kbps channels of C37.94 interface is not supported
The bandwidth of N * 64 kbps (N ranges from 1 to 12) is supported
Pseudowire configuration between local and remote PE with different time slots is not supported
Pseudowire configuration is supported only when C37.94 interface is configured on both PE nodes
Provides low latency connection to C37.94 interfaces
Supports multiple interface modules on single chassis
Tele-protection relay checks a failure and thus provides reliable, robust and safe electric grid
Provides quick switchover to an alternative route of any route failure
Prevents damage to the network and power outages
Before you configure CEM class, configure payload size and dejitter buffer values on CEM.
enable configure terminal class cem mycemclass payload-size 64 dejitter-buffer 20 idle-pattern 0x55 end
![]() Note |
Before you configure CEM group cross-connect, configure the C37.94 controller.
enable configure terminal controller c3794 0/0/0 cem-group 0 timeslots 12 exit interface cem 0/0/0 no ip address cem 0 cem class mycemclass xconnect 10.10.10.10 200 encapsulation mpls exit
![]() Note | The controller is auto-configured when the interface module is inserted. |
You use the following show commands to verify the configuration of 4-Port C37.94 interface module:
Use the show running-config command to view the configurations.
Router# show running-config | sec 0/0/0 controller C3794 0/0/0 cem-group 0 timeslots 12 interface CEM0/0/0 no ip address cem 0 xconnect 10.10.10.10 200 encapsulation mpls
Use the show xconnect command to verify the configuration of cross connect between the controllers.
Router# show xconnect all Legend: XC ST=Xconnect State S1=Segment1 State S2=Segment2 State UP=Up DN=Down AD=Admin Down IA=Inactive SB=Standby HS=Hot Standby RV=Recovering NH=No Hardware XC ST Segment 1 S1 Segment 2 S2 ------+---------------------------------+--+---------------------------------+-- UP pri ac CE0/0/0:0(CESoPSN Basic) UP mpls 10.10.10.10 200 UP
Use the show cem circuit command to verify the CEM configurations.
Router# show cem circuit detail CEM0/0/0, ID: 0, Line: UP, Admin: UP, Ckt: ACTIVE Controller state: up, T1/E1 state: up Idle Pattern: 0xFF, Idle CAS: 0x8 Dejitter: 5 (In use: 0) Payload Size: 96 Framing: Framed (DS0 channels: 1-12) CEM Defects Set None Signalling: No CAS RTP: No RTP Ingress Pkts: 26669 Dropped: 0 Egress Pkts: 26669 Dropped: 0 CEM Counter Details Input Errors: 0 Output Errors: 0 Pkts Missing: 0 Pkts Reordered: 0 Misorder Drops: 0 JitterBuf Underrun: 0 Error Sec: 0 Severly Errored Sec: 0 Unavailable Sec: 0 Failure Counts: 0 Pkts Malformed: 0 JitterBuf Overrun: 0
Use the show controllers command to verify the controller configurations.
Router# show controllers c3794 0/0/0 C3794 0/0/0 - (A900-IMA4C3794) is up Configured Channels: 1 Peer Channels : 1 Alarm : Nil Sending Y-Alarm to Peer Device : No Receiving Y-Alarm from Peer Device : No Transceiver Rx Optical Power :-15 db
Commands |
URL |
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cem-group |
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xconnect |
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loopback |
You use the following to troubleshoot C37.94 controllers:
The 4-Port C37.94 interface module supports the following alarms during failure:
The scenario when the receiver end receives two or more errors in eight consecutive framing patterns within 1 millisecond, the Loss of Signal (LOS) alarm is declared.
The receiver end should clear LOS after receiving eight consecutive correct framing patterns.
During the LOS condition at its optical receive port
At Tele-protection Equipment
At Multiplexer Equipment
Replaces the data bits over the higher order communications link with “All Ones,” which is commonly referred to as Alarm Indication Signal (AIS).
Changes the “Yellow” bit in the transmitted optical output frames from “0” to “1”
During the loss of the higher order communications link, the multiplexer should replace the data bits in the transmitted optical output frames with “All Ones.”
The scenario is declared as path yellow when three consecutive received frames have the “Yellow” bit = 1 and the received signal is OK (no LOS).
The receiver clears path yellow when three consecutive received frames have the “Yellow” bit = 0 or the received signal is bad (LOS).
You can use the following loopbacks on the C37.94 interfaces.
Loopback |
Description |
---|---|
loopback local line |
Loops the incoming signal in the interface using the framer’s line loopback mode. The framer does not reclock or reframe the incoming data. All incoming data is received by the interface driver. |
loopback local payload |
Loops the incoming signal back in the interface using the payload loopback mode of the framer. The framer reclocks and reframes the incoming data before sending it back out to the network. |
loopback network line |
Sets the loopback toward the network before going through the framer (line). |
loopback network payload |
Sets the loopback toward the network after going through the framer (payload). |
Before you configure loopback, you must configure the controller and the CEM.
enable configure terminal controller c3794 0/0/0 loopback local line exit
enable configure terminal controller c3794 0/0/0 loopback network payload exit
![]() Note | To remove a loopback, use the no loopback command. |
You use the following show command to verify the loopback configuration of 4-Port C37.94 interface module:
Related Topic |
Document Title |
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Cisco IOS commands |
Standard/RFC |
Title |
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— |
There are no standards and RFCs for this feature. |
MIB |
MIBs Link |
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IF-MIB |
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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