Cisco 10000 Series Router Software Configuration Guide
Configuring Link Noise Monitoring
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Table Of Contents

Configuring Link Noise Monitoring

About Link Noise Monitoring

Feature History of Link Noise Monitoring

Restrictions for Link Noise Monitoring

Configuration Tasks for Link Noise Monitoring

Enabling Syslog Messages

Configuration Examples for Link Noise Monitoring

Example of LNM Configuration on a Line Card

Example of LNM Configuration on a Shared Port Adapter

Example of a Syslog Message

Verification Example for Link Noise Monitoring


Configuring Link Noise Monitoring

About Link Noise Monitoring

Link Noise Monitoring (LNM) feature monitors noise associated with T1/E1 communication links between a base transceiver station (BTS) and the aggregation node (AN).

T1/E1 links are leased spans (lines) from service providers. Noise in these lines causes data loss. Significant data loss affects the voice quality. When notified of such issues the system operator can move the faulty span out of service.

The LNM feature monitors link noise by determining whether the error parameter associated with the selected link has exceeded its predefined threshold.

The LNM feature is described in the following sections:

•Feature History of Link Noise Monitoring

•Restrictions for Link Noise Monitoring

•Configuration Tasks for Link Noise Monitoring

•Verification Example for Link Noise Monitoring

Feature History of Link Noise Monitoring

Cisco IOS Release
Description
Required PRE

12.2(33)XNE

This feature was introduced on the Cisco 10000 series router for the following line cards.

•1-port Channelized OC-12 line card

•4-port Channelized OC-3/STM-1 line card

•2-port Channelized OC-12 shared port adapter (SPA)

PRE3 and PRE4


Restrictions for Link Noise Monitoring

The LNM feature has the following restrictions and limitations:

•The LNM feature is supported only on T1/E1 links.

•The use of a repeater removes errors at the physical layer (Layer 1) before passing the data, and renders the LNM feature ineffective.

•LNM provides the option of monitoring errors through LCV or PCV values, or both. If the LCV value is specified, the router calculates the PCV value by a liner extrapolation of the Gaussian Curve. Because of the extrapolation, the calculated PCV value can be the same for two close LCV values.

•LNM can be enabled to issue a minor warning, a major warning or a removal. You cannot simultaneously configure a major warning and a removal on the same T1/E1 link. The removal functionality only works when the link is part of a multilink bundle.

Note We do not recommend link removals. The reason being, if two end points of a T1/E1 link disagree about the status of the last T1 link, there exists the possibility of each end point independently concluding that it is safe to remove the remaining links. This could result in the last link being removed.

•We do not recommend a low duration (set to a level as low as 4 seconds, when the default is set to 10). If the errors on the links fluctuate, the low duration value that is set triggers more events from the line card (LC) to the route processor (RP). The flood of syslog messages (if enabled) generated by the RP increases the load on the router CPU and the syslog server. A low duration value averages out errors and leads to inaccurate results.

•The Cisco 10000 series router only supports a maximum of 4000 TI links. An LC supports 336 T1 links and a SPA supports 772 T1 links.

•When many events are exchanged between the LC and RP, some events can get lost. The LNM feature does not account for lost events sent from the LC or SPA to the RP.

•If LNM is disabled on the T1/E1 link that is removed from the multilink bundle, the link can be added to the bundle through the LNM feature.

•If the ppp multilink links minimum num mandatory command is configured on an MLP bundle with LNM enabled on a member T1/E1 link, all links get removed from the bundle through LNM.

Note If this command is configured, there is the danger of all links being removed from the bundle.

•The 2-port Channelized OC12/DS0 SPA only monitors the PCV count for LNM.

Configuration Tasks for Link Noise Monitoring

The LNM feature can be configured on theT1/E1 links of a line card or a SPA.

To configure T1/E1 links on a SPA (2-port Channelized OC12 SPA) refer chapter "Configuring a Channelized SPA" in the Cisco 10000 Series Router SIP and SPA Software Configuration Guide.

To configure T1/E1 links on a line card (1-port Channelized OC12 or 4-port Channelized OC3/STM-1 line cards) refer chapters "1-Port Channelized OC-12/STM-4 Line Card Configuration" and "4-Port Channelized OC-3/STM-1 Line Card Configuration" in the Cisco 10000 Series Router Line Card Configuration Guide.

To configure the Link Noise Monitoring feature on a T1 link of a line card, perform the following configuration tasks:

 
Command
Description

Step 1 

t1 t1-number channel-group channel-group-number timeslots list-of-timeslots

Example:

Router(config-controller)# t1 1 channel-group 0 timeslots 1-24

Specifies the channel group and timeslots on a T1 interface.

•t1-number—The T1 interface number from 1 to 28.

•Channel-group channel-group-number—Identifies the channel group with any number from 0 to 23

•Timeslots list-of-timeslots—T1 is divided into 24 timeslots (or DS0s).

Step 2 

t1 t1-number span {minor-warn | {remove | major-warn}} [{[lcv value [pcv value]] [duration seconds]} set | clear]

Example:

Router(config-controller)# t1 1 span minor-warn lcv 20 pcv 10 duration 10 set

Generates a minor-warn, a major-warn or a remove event based on the defined thresholds, for the T1 interface.

•t1-number—The T1 interface number from 1 to 28.

•minor-warn—Enables link warning (minor) monitoring on the link.

•major-warn—Enables link warning (major) monitoring on the link.

•remove—Enables Link Removal monitoring on the link.

•lcv value—The Line Code Violation (LCV) threshold value in bit error per second. The valid range on a T1 link is 5 to 1544 seconds. The valid range on an E1 link is 7 to 2048 seconds.

–The default LCV value for minor-warn on a T1 link is 154 seconds and an E1 link is 205 seconds.

–The default LCV value for major-warn or removal on a TI link is 1544 seconds and an E1 link is 2048 seconds.

 

•pcv value—Number of time slots in error per second. If not specified, this value is calculated from the LCV threshold based on a Gaussian distribution.

–The default PCV value for minor-warn on a T1 link is 145 seconds and an E1 link is 205 seconds.

–The default PCV value for major-warn or removal on a TI link is 320 seconds and an E1 link is 832 seconds.

•duration seconds—The number of consecutive seconds that a threshold is exceeded or improved for a condition to occur. The valid range on a T1/E1 link is 4 to 600 seconds. The default value for T1 and E1 links is 10 seconds.

•set—Specifies the set condition. Set is the default when no conditions are specified.

•clear— Specifies the clear condition.

Enabling Syslog Messages

To enable the generation of syslog messages on a particular T1/TE1 link use the following command syntax. Use the no form of the command to disable generation of syslog messages.

 
Command
Description

Step 1 

Router# t1 <1-28> span syslog

Router# e1 <1-21> span syslog

Example:

Router# t1 3 span syslog

Generates syslog messages for the specified T1 link. A T1 link has 28 channels. An E1 link has 21 channels.

Step 2 

Router# no [e1 <1-21> span syslog]

Router# no [t1 <1-21> span syslog]

Example:

Router# no e1 3 span syslog

Disables generation of syslog messages for the specified T1/E1link.

For more information on the Link Noise Monitoring feature, see the Link Noise Monitoring feature guide.

Configuration Examples for Link Noise Monitoring

This section provides the following configuration examples:

•Example of LNM Configuration on a Line Card

•Example of LNM Configuration on a Shared Port Adapter

•Example of a Syslog Message

Example of LNM Configuration on a Line Card

Example 1 shows how to configure the LNM feature on the 4-port Channelized OC-3/STM-1 and 1-port Channelized OC-12 line cards.

Example 1 Sample Output of LNM Configuration on a Line Card 

Router# configure terminal

Router(config)# controller soNET 7/0/0

Router(config-controller)# framing sonet 

Router(config-controller)# clock source internal 

Router(config-controller)# path 1 controller t3

Router(config-controller)# exit

Router(config)# controller t3 7/0/0.1

Router(config-controller)# t1 1 channel-group 0 timeslots 1-24

! Once a T1/E1 is created, LNM can be configured using 'span' CLI

Router(config-controller)# t1 1 ?

  bert           Start BERT test

  channel-group  Specify a channel-group mapping on a T1 interface

  clock          Specify the clock source for a T1

  fdl            Specify the Facility Data Link for a T1

  framing        Specify the type of Framing on a T1

  loopback       Put the T1 line into loopback

  span           Noise monitor for managing noisy T1 spans   

Router(config-controller)# t1 1 span

Example of LNM Configuration on a Shared Port Adapter

Example 2 shows how to configure the LNM feature ona 2-port Channelized OC12/DS0 SPA.

Example 2 Sample Output of LNM Configuration on a SPA 

Router# configure terminal

Router(config)# controller soNET 5/1/0

Router(config-controller)# framing sonet 

Router(config-controller)# clock source internal 

Router(config-controller)# sts-1 1

Router (config-ctrlr-sts1)# mode ct3

Router (config-ctrlr-sts1)# t1 1 channel-group 0 timeslots 1-24

! Once a T1/E1 is created, LNM can be configured using 'span' CLI

Router (config-ctrlr-sts1)# t1 1 ?

  channel-group  Specify the timeslots to channel-group mapping for an T1

                 interface

  clock          Specify the clock source for a T1

  fdl            Specify the Facility Data Link for a T1

  framing        Specify the type of Framing on a T1

  loopback       Put the T1 line into loopback

  shutdown       Shut down a T1 interface (send AIS)

  span           Noise monitor for managing noisy T1 spans  <Ð=

  yellow         Yellow Alarm Configuration for a T1

Example of a Syslog Message

The following is a sample output of a generated fault notification on a serial interface:

LNM-3- MINWARNEXCEED: Interface Serial7/0/0.1/1:0, noise exceeded above minor warning threshold.

Verification Example for Link Noise Monitoring

Example 3 shows the sample output when the LNM feature is configured. Use the show controllers t3 command to view the configuration information.

Example 3 Sample Output for Verifying LNM Configuration 

Router# show controllers t3 7/0/0.1 lnm 


Channel    Monitoring type                Thresholds (lcv/pcv/duration)

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

 1      minor-warn (syslog disabled)   Set(154 /145 /10  ) Clear(154 /145 /10  )

        remove     (syslog disabled)   Set(1544/320 /10  ) Clear(1544/320 /10  )

 2      Channel not configured for E1/T1

 3      Channel not configured for E1/T1

 4      Channel not configured for E1/T1

 5      minor-warn (syslog disabled)   Set(154 /145 /10  ) Clear(154 /145 /10  )

 6      Link Noise Monitoring is disabled

 7      Channel not configured for E1/T1

 8      Channel not configured for E1/T1

 9      Channel not configured for E1/T1

 10     Channel not configured for E1/T1

 11     Channel not configured for E1/T1

 12     Channel not configured for E1/T1

 13     Channel not configured for E1/T1

 14     Channel not configured for E1/T1

 15     Channel not configured for E1/T1

 16     Channel not configured for E1/T1