Table Of Contents

VISM/VISM-PR Clocking

Description of Network Clocking

Clocking Sources

Revertive and Nonrevertive Clocking

VISM/VISM-PR Card as a Clocking Source

PXM Card as Clocking Source

PXM1 Card as a Clocking Source

PXM1E or PXM45 Card as Clocking Source

VISM/VISM-PR Clocking

---

This section explains the clocking options in the following sections:

• Description of Network Clocking

• Clocking Sources

• Revertive and Nonrevertive Clocking

• VISM/VISM-PR Card as a Clocking Source

• PXM Card as Clocking Source

Description of Network Clocking

Network clocking means that a clock signal is generated or derived and distributed through a node to ensure a synchronized network operation.

If a clocking problem occurs on the voice circuits, calls can be dropped. Voice quality can be diminished because of the possible echoing and "hissing" problems.

VISM/VISM-PR typically interfaces to TDM devices (for example, public or private voice switches). These voice switches usually demand a robust clocking schema in which the clock supplied to each voice switch is traceable to the clock source of every other voice switch in the network.VISM must be introduced into this kind of network in a manner which does not breakdown the clocking integrity.

Typically, a local and remote VISM/VISM-PR must be provided with clock sources which are traceable to each other and traceable to the voice switches to which they interconnect. Failure to properly set up this clocking can result in dropped calls and frequent voice quality problems.

To avoid these problems, time the entire voice network, including the VISMs and MGX switches, to a single clock source that is propagated throughout the network.

Clocking Sources

To ascertain the optimum single clock source for the network, examine the entire configuration of the MGX 8000 Series platform.

The MGX 8850 supports the following types of internal and external clock sources.

•Building Integrated Timing Supply (BITS) clock—This type is an external clock source connected to one of two RJ-48 female connectors on the PXM-UI-S3 back card (see Figure A-1).

•Synchronous Equipment Timing Source (SETS) clock—This type is an external clock source connected to one of two RJ-48 female connectors on the PXM-UI-S3 back card (see Figure 3-1).

•External clock—This clock is derived from a service module line (for example, a VISM/VISM-PR line).

•Internal clock—This clock consists of a Stratum 3 clock circuit in the internal clock oscillator on the PXM back card - PXM-UI-S3. This clock source is distributed to all cards in the gateway.

---

Note The PXM-UI supports only Stratum 4 clock.

---

Revertive and Nonrevertive Clocking

PXM1E and PXM45 support revertive or nonrevertive clocking. If your MGX switch is configured for a clock source from a BITS source or PXM line source and the source line goes into the alarm state, a revertive or nonrevertive recovery occurs.

•Revertive clocking—If a node is configured and the clock source fails (due to a physical failure such as a loss of signal or the clock frequency drifting out of specification), the node abandons the clock source and finds an alternative clock source. When the original clock source is repaired, the node automatically reverts to using the original clock source without manual intervention from a network operator.

•Nonrevertive clocking—Similar to revertive clocking, except that when the original clock source is repaired, the node does not automatically revert to the original clock source.

The choice of revertive or nonrevertive clocking depends upon the processor module back card used and the clocking source specified. See Table 3-1 to ascertain if your clocking is revertive or nonrevertive in your network configuration.

Table 3-1 Revertive/Nonrevertive Clocking and PXM Back Card Support 

Processor Module Back Card	Using External Clock	Using Inband/Service Module Clock
PXM-UI	For loss of service: revertive For bad frequency/drift: nonrevertive	For loss of service: revertive For bad frequency/drift: nonrevertive
PXM-UI-S3	For loss of service: revertive For bad frequency/drift: nonrevertive	For loss of service: revertive For bad frequency/drift: nonrevertive

To make a nonrevertive clock source usable after it has failed, you must use the cnfclksrc command on the PXM card to remove the configuration of that particular clock source, and then use the cnfclksrc command again to configure it back.

VISM/VISM-PR Card as a Clocking Source

Figure 3-1 shows the VISM card primary clocking source option, in which the clock originates at the VISM side of the VISM/PXM interface. This figure also applies to VISM-PR cards.

Figure 3-1 VISM Configured for Loop Clocking

With the VISM/VISM-PR card option, clocking originates from one of the T1 or E1 lines on one of the VISM/VISM-PR cards.

If the VISM/VISM-PR is the primary clocking source, the clocking originates on one of the VISM/VISM-PR T1 or E1 lines. The line that is providing the clock source must be configured for loop clocking. All remaining T1 or E1 lines on all of the VISM/VISM-PR cards in the shelf must be configured for local clocking.

To configure the VISM/VISM-PR card as the primary or secondary clocking source, complete the following steps:

---

Step 1 Log in to the VISM/VISM-PR card.

Step 2 To configure the first line for loop clocking, enter the cnfln command.

---

Note On VISM-PR cards you can configure the clock source on any line. On VISM cards you can configure only line 1 as the clock source.

---

nodename.1.27.VISM8.a > cnfln <line_number> <line_code> <line_len> <clk_src> <line_type> <loopback_detection> |<circuit_identifier>|




---

Note You must include all argument values when using the cnfln command; however, the <line_number> and <clk_src> are the only relevant arguments for configuring the clocking source on your VISM/VISM-PR cards.

---

Replace the cnfln arguments with the values listed in Table 3-2.

Table 3-2 Parameters for cnfln Command 

Parameter	Description
line_number	Line number is in the range 1-8.
line_code	Line coding method is specified by one of the following values: •2 = B8ZS (T1) •3 = HDB3 for E1 lines •4 = AMI for T1 or E1 lines
line_len	Line length is specified by one of the following values: •8 = For E1 cards with an SMB back card •9 = For E1 cards with an RJ-48 back card •10 = 0-131 feet for T1 •11 = 131-262 feet for T1 •12 = 262-393 feet for T1 •13 = 393-524 feet for T1 •14 = 524-655 feet for T1 •15 = More than 655 feet for T1
clk_src	Clock source. •1 = Loop clock. Clocking comes from the T1/E1 line. –If the clocking source is from a line on a VISM card, configure line 1 as loop clock. Configure all remaining lines on all remaining VISM cards for local clock. –If the clocking source is from a line on a VISM-PR card, configure the appropriate line (range 1-8) for loop clock. Configure all remaining lines on all remaining VISM-PR cards for local clock. •2 = Local clock. Clocking comes from the PXM card. If the clocking source to the VISM/VISM-PR cards is derived from the PXM card, configure all lines on all VISM/VISM-PR cards as local.
line_type	Line type is specified by one of the following values: •1 = dsx1ESF •2 = dsx1D4 •3 = E1 •4 = E1CRC •5 = E1MF •6 = E1MFCRC •7 = E1 Clear •8 = E1Q50 •9 = E1Q50CRC
loopback_detection	Loopback detection is specified by one of the following values: •1 = Disabled •2 = Enabled (This value is not applicable to E1 lines.)
circuit_identifier	(Optional) Name of the circuit in ASCII format. Range is 1-64 characters.

The following example shows sample syntax for adding loop clock to line 1.

nodename.1.27.VISM8.a > cnfln 1 3 9 1 3 1




nodename.1.27.VISM8.a >




---

Note You cannot delete a line that is configured as the clock source. You must first configure the line to not be the clock source, and then you can delete the line.

---

See Chapter 10, "CLI Commands" for more information on VISM/VISM-PR commands.

Step 3 To display the clocking option that you configured in Step 2, enter the dspln command.

The following example shows the resulting display:

nodename.1.27.VISM8.a > dspln 1




LineNum: 1

LineConnectorType: RJ-48

LineEnable: Modify

LineType: dsx1E1CCS

LineCoding: dsx1HDB3

LineLength: G.703 120 ohm

LineXmtClockSource: LoopTiming

LineLoopbackCommand: NoLoop

LineSendCode: NoCode

LineUsedTimeslotsBitMap: 0x2

LineLoopbackCodeDetection: codeDetectDisabled

LineSignalingType: No Signaling

LineCcsChannels: 0x0

LineTrunkConditioning: disable

LineBearerBusyCode: 255

CircuitIdentifier:

TxDigitOrder: dnisThenAni

TonePlanRegion:

TonePlanVersion: 0

RingingTO: 180

RingBackTO: 180

BusyTO: 30

ReorderTO: 30

DialTO: 16

StutterDialTO: 16

OffHookAlertTO: 5

RemoteRingbackMethod: proxy




Step 4 To configure the remaining T1 or E1 lines for local clocking, enter the cnfln command.

Step 5 To display the clocking source for all of the lines on the VISM/VISM-PR card, enter the dsplns command.

The following example shows the resulting display:

nodename.1.27.VISM8.a > dsplns




Line Conn Type Status/Coding Length XmtClock Alarm

Type Source

---- ----- ------------ ------ -------- ------------- -------- -----

27.1 RJ-48 dsx1E1CCS Mod/dsx1HDB3 G.703 120 ohm LoopTimi No

27.2 RJ-48 dsx1E1CCS Mod/dsx1HDB3 G.703 120 ohm LocalTim No

27.3 RJ-48 dsx1E1CCS Mod/dsx1HDB3 G.703 120 ohm LocalTim Yes

27.4 RJ-48 dsx1E1CCS Mod/dsx1HDB3 G.703 120 ohm LocalTim Yes

27.5 RJ-48 dsx1E1CCS Mod/dsx1HDB3 G.703 120 ohm LocalTim Yes

27.6 RJ-48 dsx1E1CCS Mod/dsx1HDB3 G.703 120 ohm LocalTim Yes

27.7 RJ-48 dsx1E1CCS Mod/dsx1HDB3 G.703 120 ohm LocalTim Yes

27.8 RJ-48 dsx1E1CCS Mod/dsx1HDB3 G.703 120 ohm LocalTim Yes




LineNumOfValidEntries: 8




Step 6 Log in to the PXM card.

Step 7 To configure the VISM/VISM-PR card as a primary clocking source, enter the cnfclksrc command with the following parameters:

nodename.1.7.PXM.a > cnfclksrc <slot.port> P




Replace <slot.port> with the VISM/VISM-PR card slot number and line number of the loop clock. The P indicates that the VISM/VISM-PR card is configured as a primary clocking source.

Step 8 To display the configured clock on the PXM card, enter the dspclkinfo command.

The following example shows the service module as the clocking source:

cvgmgx1a.1.7.PXM.a > dspclkinfo




****** Clock HW registers ********

SEL_T1 = t1 SEL100 = ON SEL120 = OFF SEL75 = OFF

NOEXTCLK = ON NOEXTCLK2 = OFF




priMuxClockSource = SERVICE_MODULE_PRI_CLK

prevPriMuxClockSource = INTERNAL_OSC

primaryInbandClockSourceLineNum = 1

secMuxClockSource = INTERNAL_OSC

prevSecMuxClockSource = INTERNAL_OSC

secondaryInbandClockSourceLineNumber = 1

currentClockSetReq = primary

currentClockHwStat = primary

StratumLevel = STRATUM4

PreviousClockHwStat = none

extClock1Present = No

extClock2Present = No

extClkConnectorType = RJ45

extClkSrcImpedance = 100 Ohms

internal Clock Status=0, Primary Clock Status=0

Secondary Clock Status=0, Last inband Clock State=0

last Inband Clock state= 0, Last External Clock Present = 1

Last External Clock2 Present = 1




Step 9 To configure the VISM/VISM-PR as a secondary clocking source, enter the cnfclksrc command with the following parameters:

nodename.1.7.PXM.a > cnfclksrc <slot.port> S




Replace <slot.port> with the VISM/VISM-PR card slot number and line number. The S indicates that the VISM card is configured as a secondary clocking source.

Step 10 To display the configured clock on the PXM card, enter the dspclkinfo command.

The following example shows the service module as a secondary clock source:

nodename.1.7.PXM.a > dspclkinfo




****** Clock HW registers ********

SEL_T1 = t1 SEL100 = ON SEL120 = OFF SEL75 = OFF

NOEXTCLK = ON NOEXTCLK2 = OFF




priMuxClockSource = SERVICE_MODULE_PRI_CLK

prevPriMuxClockSource = SERVICE_MODULE_PRI_CLK

primaryInbandClockSourceLineNum = 1

secMuxClockSource = SERVICE_MODULE_SEC_CLK

prevSecMuxClockSource = INTERNAL_OSC

secondaryInbandClockSourceLineNumber = 1

currentClockSetReq = primary

currentClockHwStat = secondary

StratumLevel = STRATUM4

PreviousClockHwStat = primary

extClock1Present = No

extClock2Present = No

extClkConnectorType = RJ45

extClkSrcImpedance = 100 Ohms

Internal Clock Status=0, Primary Clock Status=0

Secondary Clock Status=0, Last inband Clock State=0

last Inband Clock state= 0, Last External Clock Present = 1

Last External Clock2 Present = 1




---

PXM Card as Clocking Source

You can configure the PXM cards for clocking as described in the following sections:

• PXM1 Card as a Clocking Source

• PXM1E or PXM45 Card as Clocking Source

The PXM card option makes the PXM the clock source for the all cards in the chassis. The VISM/VISM-PR cards then use this clocking to provide clocking for their associated T1 or E1 lines.

PXM1 Card as a Clocking Source

Figure 3-2 shows the PXM1 card clocking source option, in which the clock originates at the PXM1 side of the VISM/PXM interface.

Figure 3-2 VISM Configured for Local Clocking

The PXM1 card option allows you to use one of the following sources:

•An external BITS clock on the PXM1 T1 or E1 back card port.

•An external signal on a PXM1 back card port.

•The PXM1 card internal crystal (default). The internal crystal is the default and is set as the primary clock source automatically when power is applied to the chassis.

To use one of the other two clocking sources, complete the following steps:

---

Step 1 Log in to the active PXM card.

Step 2 To configure the clocking source, enter the cnfclksrc command.

nodename.1.7.PXM.a > cnfclksrc <slot.port> <clktyp>




Replace <slot.port> with the card slot number and line number.

---

Note Between the slot and port argument values, type the period with no spaces on either side.

---

Replace <clktyp> with one of the following values:

•P = Primary

•S = Secondary

•T = Tertiary

•N = Null (no external clocking source)

Specify the cnfclksrc command argument values according to the following rules:

•If the clock source is the external BITS clock (a T1 or E1 port on the PXM1 back card), specify the configuration as:

nodename.1.7.PXM.a > cnfclksrc 7.35 P




Type 7 for the slot number, regardless of the PXM1 card location in the chassis.

Type 35 for the port number. The BITS port is always port 35.

•If the clock source is an external signal on one of the PXM1 ports, specify the configuration as:

nodename.1.7.PXM.a > cnfclksrc 7.n P




Type 7 for the slot number, regardless of the PXM1 card location in the chassis.

Replace the n port parameter with the port number in the range 1-4.

•If the clock source is the PXM1 internal crystal and no other clock source has been specified, do not configure the clock source. The crystal is the automatic default.

•If you want to change the clocking source from external to the PXM1 card's internal crystal, specify the configuration as:

nodename.1.7.PXM.a > cnfclksrc 7.n N




Type 7 for the slot number, regardless of the PXM1 card location in the chassis.

Replace n with the port number 35 or the port number, depending on which is the current source.

Type N to cancel the previous configuration and to return the clocking source to the default internal crystal.

•If the clock source is from a line on a VISM/VISM-PR card, specify the configuration as:

nodename.1.7.PXM.a > cnfclksrc y.z P




Replace the y value with the slot number of the VISM/VISM-PR card.

For VISM cards, replace z with 1 for the line argument value.

For VISM-PR cards, replace z with the line number of the clock source. Line range is 1-8.

Step 3 To display the configured clock on the PXM card, enter the dspclkinfo command.

nodename.1.7.PXM.a > dspclkinfo




****** Clock HW registers ********

SEL_T1 = t1 SEL100 = ON SEL120 = OFF SEL75 = OFF

NOEXTCLK = ON NOEXTCLK2 = OFF




priMuxClockSource = INTERNAL_OSC

prevPriMuxClockSource = INTERNAL_OSC

primaryInbandClockSourceLineNum = 1

secMuxClockSource = INTERNAL_OSC

prevSecMuxClockSource = INTERNAL_OSC

secondaryInbandClockSourceLineNumber = 0

currentClockSetReq = primary

currentClockHwStat = primary

StratumLevel = STRATUM4

PreviousClockHwStat = primary

extClock1Present = No

extClock2Present = No

extClkConnectorType = RJ45

extClkSrcImpedance = 100 Ohms

Internal Clock Status=0, Primary Clock Status=0

Secondary Clock Status=0, Last inband Clock State=0

last Inband Clock state= 0, Last External Clock Present = 1

Last External Clock2 Present = 1




Step 4 Log in to the VISM/VISM-PR card.

Step 5 To configure a VISM/VISM-PR line for local clocking, enter the cnfln command.

nodename.1.27.VISM8.a > cnfln <line_number> <line_code> <line_length> <clk_src> <line_type> <loopback_detection> |<circuit_identifier>|




---

Note You must include all argument values when using the cnfln command; however, the <line_number> and <clk_src> are the only relevant arguments for configuring the clocking source on your VISM/VISM-PR cards.

---

Replace the cnfln arguments with the values listed in Table 3-3.

Table 3-3 Parameters for cnfln Command 

Parameter	Description
line_number	Line number is in the range 1-8.
line_code	Line coding method is specified by one of the following values: •2 = B8ZS (T1) •3 = HDB3 for E1 lines •4 = AMI for T1 or E1 lines
line_length	Line length is specified by one of the following values: •8 = AX-SMB-8E1 and AX-R-SMB-8E1 back card types •9 = AX-RJ48-8E1 and AX-R-RJ48-8E1 back card types •10 = T1 for 000-131 ft •11 = T1 for 131-262 ft •12 = T1 for 262-393 ft •13 = T1 for 393-524 ft •14 = T1 for 524-655 ft •15 = T1 for 655 and greater ft
clk_src	Clock source. •1 = Loop clock. Clocking comes from the T1/E1 line. –If the clocking source is from a line on a VISM card, configure line 1 as loop clock. Configure all remaining lines on all remaining VISM cards for local clock. –If the clocking source is from a line on a VISM-PR card, configure the appropriate line (range 1-8) for loop clock. Configure all remaining lines on all remaining VISM-PR cards for local clock. •2 = Local clock. Clocking comes from the PXM1 card. If the clocking source to the VISM/VISM-PR cards is from the PXM1 card, configure all lines on all VISM/VISM-PR cards as local.
line_type	Line type is specified by one of the following values: •1 = dsx1ESF •2 = dsx1D4 •3 = E1 •4 = E1CRC •5 = E1MF •6 = E1MFCRC •7 = E1 Clear •8 = E1Q50 •9 = E1Q50CRC
loopback_detection	Loopback detection is specified by one of the following values: •1 = Disabled •2 = Enabled (This value is not applicable to E1 lines.)
circuit_identifier	(Optional) Name of the circuit in ASCII format. Range is 1-64 characters.

The following example shows sample syntax for adding local clock to line 1.

nodename.1.27.VISM8.a > cnfln 1 3 9 2 3 1




nodename.1.27.VISM8.a >




Step 6 Repeat Step 5 for all other lines on the VISM/VISM-PR card.

Step 7 To display the clocking source for all of the lines on the VISM card, enter the dsplns command.

nodename.1.27.VISM8.a > dsplns

Line Conn Type Status/Coding Length XmtClock Alarm

Type Source

---- ----- ------------ ------ -------- ------------- -------- -----

27.1 RJ-48 dsx1E1CCS Mod/dsx1HDB3 G.703 120 ohm LocalTim No

27.2 RJ-48 dsx1E1CCS Mod/dsx1HDB3 G.703 120 ohm LocalTim No

27.3 RJ-48 dsx1E1CCS Mod/dsx1HDB3 G.703 120 ohm LocalTim Yes

27.4 RJ-48 dsx1E1CCS Mod/dsx1HDB3 G.703 120 ohm LocalTim Yes

27.5 RJ-48 dsx1E1CCS Mod/dsx1HDB3 G.703 120 ohm LocalTim Yes

27.6 RJ-48 dsx1E1CCS Mod/dsx1HDB3 G.703 120 ohm LocalTim Yes

27.7 RJ-48 dsx1E1CCS Mod/dsx1HDB3 G.703 120 ohm LocalTim Yes

27.8 RJ-48 dsx1E1CCS Mod/dsx1HDB3 G.703 120 ohm LocalTim Yes




LineNumOfValidEntries: 8




---

For more information about PXM1 card clocking, refer to the Cisco MGX 8850 Edge Concentrator Installation and Configuration, Release 1.1.3 and to the Cisco MGX 8800 Series Switch Command Reference, Release 1.1.3.

PXM1E or PXM45 Card as Clocking Source

The PXM1E and PXM45 cards have two clock source configuration options:

•Manual clocking sources

•NCDP clocking sources

---

Note NCDP is not addressed in the VISM/VISM-PR documentation. For more information on NCDP, refer to the Cisco MGX 8850 (PXM1E/PXM45), Cisco MGX 8950, and Cisco MGX 8830 Configuration Guide, Release 5.1.

---

The clock source ports on the PXM-UI-S3 and PXM-UI-S3/B cards can be used to receive clock signals from either T1 or E1 lines; the card does not support both line types simultaneously. These clock ports support stratum levels 1 to 3.

---

Note The PXM45 and PXM1E cards support T1 data (1.544Mbps) and E1 data (2.048Mbps) clock sources, and the PXM1/B supports both T1 and E1 data types and an E1 sync (2.048MHz) line as a clock input. The E1 sync line is not supported on switches with PXM45 and PXM1E cards.

---

The following procedure describes how to configure the switch to use clock sources on the BITS ports.

---

Step 1 Establish a configuration session using a user name with GROUP1 privileges or higher.

Step 2 To configure a primary or secondary BITS clock source, enter the cnfclksrc command:

nodename.7.PXM.a > cnfclksrc <priority> [shelf.]slot.port -bits {e1|t1} [-revertive {enable|disable}]




Table 3-4 describes the parameters for this command.

Table 3-4 Parameters for cnfclksrc Command 

Parameter	Descriptions
priority	Priority is the type of clock source that is primary or secondary. The default is primary.
shelf	Shelf value is always 1 and is optional.
slot	For the BITS clock, the slot number is 7 for a Cisco MGX 8850 (PXM1E/PXM45) or slot 1 for a Cisco MGX 8830 switch.
port	Port number that identifies the line on the PXM1E-UI-S3 or PXM1E-UI-S3/B back card to which the BITS clock is connected and the type of line connected. •Port 35 = upper line •Port 36 = lower line
-bits	This option specifies whether the clock source line is an E1 or T1.
-revertive	This option enables or disables the revertive feature for all clock sources.

---

Note Manual clock distribution provides a revertive function that can apply when the primary clock source fails and is subsequently restored. A failure is a loss of the primary clock source after the switch has locked on to that clock source. If the primary clock source recovers and revertive mode is enabled, the switch automatically reverts to the primary source

---

The following command example shows how to configure a primary E1 external clock source at the upper connector of the PXM1E-UI-S3. Note the command punctuation.

nodename.7.PXM.a > cnfclksrc primary 7.35 -bits e1




The next example configures a primary network clock source and enables the revertive option.

nodename.7.PXM.a > cnfclksrc primary 7.36 -bits e1 -revertive enable




The last example disables the revertive function for an E1 BITS clock.

nodename.7.PXM.a > cnfclksrc primary 7.36 -bits e1 -revertive disable




Step 3 To display the parameter configuration of the BITS clock sources, enter the dspclkparms command as shown in the following example:

nodename.8.PXM.a > dspclkparms

BITS Cable Type : Twisted Pair

BITS Signal Type : Data Mode




The above example shows the default BITS clock configuration parameters. The cable type can be either twisted pair or coax. The signal type can be either data mode or sync mode.

Step 4 If you need to change the BITS clock configuration parameters, enter the cnfclkparms command as follows:

nodename.8.PXM.a > cnfclkparms <signal type> <cable type>




Replace the signal type variable with 1 to select data or with 2 to select sync. Replace the cable type variable with 1 to select twisted pair cabling or with 2 to select coaxial cabling.

Step 5 To configure an additional BITS clock source, repeat Step 2 using the correct parameters for the additional source. The clock parameters configured in Steps 3 and 4 apply to both BITS clock inputs.

Step 6 To display the clock source configuration, enter the dspclksrcs command.

---

Posted: Mon Apr 16 14:25:58 PDT 2007
All contents are Copyright © 1992--2007 Cisco Systems, Inc. All rights reserved.
Important Notices and Privacy Statement.