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Configuring RTP-Based VoIP Operations

Last Updated: March 22, 2011

This module describes how to configure an IP Service Level Agreements (SLAs) Real-Time Transport Protocol (RTP)-based Voice over IP (VoIP) Operation feature to set up and schedule a test call for using Voice gateway digital signal processors (DSPs) to gather network performance-related statistics for the call. Available statistical measurements for VoIP networks include jitter, frame loss, Mean Opinion Score for Conversational Quality (MOS-CQ), and Mean Opinion Score for Listening Quality (MOS-LQ).

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information Table at the end of this document.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Prerequisites for IP SLAs RTP-Based VoIP Operations

  • Both the source and destination routers must be running Cisco IOS Release 12.4(4)T or later releases.
  • Both the source and destination routers must be running a Cisco IOS image with the Cisco IOS IP Voice or higher grade feature package.
  • The source router must have a network module with a c5510 or c549 DSP. The destination router need not have a network module with a DSP.
  • The IP SLAs Responder must be enabled on the destination gateway.

Restrictions for IP SLAs RTP-Based VoIP Operations

  • The IP SLAs RTP-based VoIP operation gathers statistical information only from the DSP of the source router.
  • For source-to-destination measurements, the RTP-based VoIP operation does not obtain statistical information from DSPs.
  • Depending on the type of DSP, the statistics measured by the IP SLAs RTP-based VoIP operation will vary. For more information, see the “Statistics Measured by the IP SLAs RTP-Based VoIP Operation” section.
  • The voice port used by the IP SLAs RTP-based VoIP operation will not be available for other calls.

Information About IP SLAs RTP-Based VoIP Operations

Benefits of the IP SLAs RTP-Based VoIP Operation

The IP SLAs RTP-Based VoIP Operation feature provides the following key benefits:

  • End-to-end performance measurements using DSPs for determining voice quality in VoIP networks.
  • Proactive threshold violation monitoring through Simple Network Management Protocol (SNMP) trap notifications and syslog messages.

Statistics Measured by the IP SLAs RTP-Based VoIP Operation

The IP SLAs RTP-based VoIP operation provides an enhanced capability to measure voice quality using DSP-based calculations to determine MOS scores. For customer scenarios where the destination gateway does not have DSP hardware, statistical information is gathered only from the DSP of the source gateway. In this case, the RTP data stream is looped back from the destination to the source gateway.

The statistics gathered by the IP SLAs RTP-based VoIP operation will vary depending on the type of DSP module (see the tables below).

Table 1 Statistics Gathered by the RTP-Based VoIP Operation for c549 DSPs

Statistics

Description

Interarrival jitter (destination-to-source and source-to-destination)

Interarrival jitter is the mean deviation (smoothed absolute value) of the difference in packet spacing for a pair of packets.

The source-to-destination value is measured by sending RTP packets to the IP SLAs Responder. No values are obtained from the DSP for this measurement.

For more information about interarrival jitter, see RFC 3550 (RTP: A Transport Protocol for Real-Time Applications ).

Estimated R factor (destination-to-source and source-to-destination)

Estimated transmission rating factor R.

This value is based on one-way transmission delay and standard default values. No values are obtained from the DSP to calculate the estimated transmission rating factor R.

For more information about the estimated R factor, see International Telecommunication Union Telecommunication Standardization Sector (ITU-T) Recommendation G.107 (The E-model, a computational model for use in transmission planning ).

MOS-CQ (destination-to-source and source-to-destination)

Mean Opinion Score for Conversational Quality.

This value is obtained by conversion of the estimated R factor to Mean Opinion Score (MOS) using ITU-T Recommendation G.107 conversion tables.

The source-to-destination value is measured by sending RTP packets to the IP SLAs Responder. No values are obtained from the DSP for this measurement.

Round-trip time (RTT) latency

Round-trip time latency for an RTP packet to travel from the source to the destination and back to the source.

Packet loss (destination-to-source and source-to-destination)

Number of packets lost.

The source-to-destination value is measured by sending RTP packets to the IP SLAs Responder. No values are obtained from the DSP for this measurement.

Packets missing in action (source-to-destination)

Number of missing packets.

The source-to-destination value is measured by sending RTP packets to the IP SLAs Responder. No values are obtained from the DSP for this measurement.

One-way latency (destination-to-source and source-to-destination)

Average, minimum, and maximum latency values.

These values are measured by sending RTP packets to IP SLAs Responder. The RTP data stream is then looped back from the destination to the source gateway.

Table 2 Statistics Gathered by the RTP-Based VoIP Operation for c5510 DSPs

Statistics

Description

Interarrival jitter (destination-to-source and source-to-destination)

Interarrival jitter is the mean deviation (smoothed absolute value) of the difference in packet spacing for a pair of packets.

The source-to-destination value is measured by sending RTP packets to the IP SLAs Responder. No values are obtained from the DSP for this measurement.

For more information on how this value is calculated, see RFC 1889 (RTP: A Transport Protocol for Real-Time Applications ).

Estimated R factor (destination-to-source and source-to-destination)

Estimated transmission rating factor R.

This value is based on one-way transmission delay and standard default values, as well as values obtained from the DSP.

For more information about how to calculate the estimated R factor, see International Telecommunication Union Telecommunication Standardization Sector (ITU-T) Recommendation G.107 (The E-model, a computational model for use in transmission planning ).

MOS-CQ (destination-to-source and source-to-destination)

Mean Opinion Score for Conversational Quality.

This value is obtained by conversion of the estimated R factor to Mean Opinion Score (MOS) using ITU-T Recommendation G.107 conversion tables.

The source-to-destination value is measured by sending RTP packets to the IP SLAs Responder. No values are obtained from the DSP for this measurement.

Round-trip time (RTT) latency

Round-trip time latency for an RTP packet to travel from the source to the destination and back to the source.

Packet loss (destination-to-source and source-to-destination)

Number of packets lost.

The source-to-destination value is measured by sending RTP packets to the IP SLAs Responder. No values are obtained from the DSP for this measurement.

Packets missing in action (source-to-destination)

Number of missing packets.

The source-to-destination value is measured by sending RTP packets to the IP SLAs Responder. No values are obtained from the DSP for this measurement.

One-way latency (destination-to-source and source-to-destination)

Average, minimum, and maximum latency values.

These values are measured by sending RTP packets to IP SLAs Responder. The RTP data stream is then looped back from the destination to the source gateway.

Frame loss (destination-to-source)

Number of DSP frame loss events.

A frame loss can occur due to such events as packet loss, late packets, or a jitter buffer error.

MOS-LQ (destination-to-source)

Mean Opinion Score for Listening Quality.

How to Configure IP SLAs RTP-Based VoIP Operations

Configuring and Scheduling an IP SLAs RTP-Based VoIP Operation

Perform this task to configure and schedule an IP SLAs RTP-based VoIP operation.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    ip sla operation-number

4.    voip rtp {destination-ip-address | destination-hostname} source-ip {ip-address | hostname} source-voice-port {slot [/ subunit / port : ds0-group-number]} [codec codec-type] [duration seconds] [advantage-factor value]

5.    frequency seconds

6.    history history-parameter

7.    owner text

8.    tag text

9.    threshold milliseconds

10.    timeout milliseconds

11.    exit

12.    ip sla reaction-configuration operation-number react monitored-element [action-type option] [threshold-type {average [number-of-measurements] | consecutive [occurrences] | immediate | never | xofy [x-value y-value]}] [threshold-value upper-threshold lower-threshold]

13.    ip sla schedule operation-number [life {forever | seconds}] [start-time {hh : mm[: ss] [month day | day month] | pending | now | after hh : mm : ss}] [ageout seconds] [recurring]

14.    exit

15.    show ip sla configuration [operation-number]


DETAILED STEPS
 Command or ActionPurpose
Step 1 enable


Example: 
Router> enable
 

Enables privileged EXEC mode.

  • Enter your password if prompted.
 
Step 2 configure terminal


Example: 
Router# configure terminal
 

Enters global configuration mode.

 
Step 3 ip sla operation-number


Example: 
Router(config)# ip sla 1
 

Begins configuration for an IP SLAs operation and enters IP SLA configuration mode.

 
Step 4 voip rtp {destination-ip-address | destination-hostname} source-ip {ip-address | hostname} source-voice-port {slot [/ subunit / port : ds0-group-number]} [codec codec-type] [duration seconds] [advantage-factor value]


Example: 
Router(config-ip-sla)# voip rtp 10.2.3.4 source-ip 10.5.6.7 source-voice-port 1/0:1 codec g711alaw duration 30 advantage-factor 5
 

Enters IP SLAs VoIP RTP configuration mode and configures the IP SLAs operation as an RTP-based VoIP operation.

 
Step 5 frequency seconds


Example: 
Router(config-ip-sla-voip-rtp)# frequency 90
 

(Optional) Sets the rate at which a specified IP SLAs operation repeats. The default frequency value is 60 seconds.

 
Step 6 history history-parameter


Example: 
Router(config-ip-sla-voip-rtp)# history buckets-kept 25
 

(Optional) Specifies the parameters used for gathering statistical history information for an IP SLAs operation.

 
Step 7 owner text


Example: 
Router(config-ip-sla-voip-rtp)# owner 10.16.1.1 cwb.cisco.com John Doe RTP 555-1212
 

(Optional) Configures the SNMP owner of an IP SLAs operation.

 
Step 8 tag text


Example: 
Router(config-ip-sla-voip-rtp)# tag testoperation
 

(Optional) Creates a user-specified identifier for an IP SLAs operation.

 
Step 9 threshold milliseconds


Example: 
Router(config-ip-sla-voip-rtp)# threshold 10000
 

(Optional) Sets the upper threshold value for calculating network monitoring statistics created by an IP SLAs operation.

 
Step 10 timeout milliseconds


Example: 
Router(config-ip-sla-voip-rtp)# timeout 10000
 

(Optional) Sets the amount of time an IP SLAs operation waits for a response from its request packet.

 
Step 11 exit


Example: 
Router(config-ip-sla-voip-rtp)# exit
 

Exits IP SLAs VoIP RTP configuration submode and returns to global configuration mode.

 
Step 12 ip sla reaction-configuration operation-number react monitored-element [action-type option] [threshold-type {average [number-of-measurements] | consecutive [occurrences] | immediate | never | xofy [x-value y-value]}] [threshold-value upper-threshold lower-threshold]


Example: 
Router(config)# ip sla reaction-configuration 1 react frameLossDS action-type traponly threshold-type consecutive 3
 

(Optional) Configures certain actions to occur based on events under the control of Cisco IOS IP SLAs.

 
Step 13 ip sla schedule operation-number [life {forever | seconds}] [start-time {hh : mm[: ss] [month day | day month] | pending | now | after hh : mm : ss}] [ageout seconds] [recurring]


Example: 
Router(config)# ip sla schedule 1 start-time now life forever
 

Specifies the scheduling parameters for an IP SLAs operation.

 
Step 14 exit


Example: 
Router(config)# exit
 

(Optional) Exits global configuration mode and returns to privileged EXEC mode.

 
Step 15 show ip sla configuration [operation-number]


Example: 
Router# show ip sla configuration 10
 

(Optional) Displays configuration values including all defaults for all IP SLAs operations or a specified operation.

 

Troubleshooting Tips

  • If the IP SLAs operation is not running and generating statistics, add the verify-data command to the configuration of the operation (while configuring in IP SLA configuration mode) to enable data verification. When enabled, each operation response is checked for corruption. Use the verify-data command with caution during normal operations because it generates unnecessary overhead.
  • Use the debugipsla trace and debug ip sla error commands to help troubleshoot issues with an IP SLAs operation.

What to Do Next

To view and interpret the results of an IP SLAs operation use the show ip sla statistics and show ip sla statistics aggregatedcommands. Checking the output for fields that correspond to criteria in your service level agreement will help you determine whether the service metrics are acceptable.

Configuration Examples for IP SLAs RTP-Based VoIP Operations

Example Configuring an IP SLAs RTP-Based VoIP Operation

The following example shows how to configure an IP SLAs RTP-based VoIP operation:

ip sla 1
 voip rtp 10.2.3.4 source-ip 10.5.6.7 source-voice-port 1/0:1 codec g711alaw duration 30 advantage-factor 5
!
ip sla reaction-configuration 1 react FrameLossDS action-type traponly threshold-type consecutive 3
!
ip sla schedule 1 start-time now life forever

Use the show ip sla statistics command in privileged EXEC mode to display the current operational status and statistics for an IP SLAs operation. Use the show ip sla statistics aggregated command in privileged EXEC mode to display the aggregated hourly status and statistics for an IP SLAs operation.

Additional References

The following sections provide references related to the IP SLAs RTP-Based VoIP Operation feature.

Related Documents

Related Topic

Document Title

Cisco IOS IP SLAs UDP-based VoIP operations for VoIP networks

Configuring UDP Jitter Operations for VoIP chapter of the Cisco IOS IP SLAs Configuration Guide

Cisco IOS commands

Cisco IOS Master Commands List, All Releases

Cisco IOS IP SLAs commands

Cisco IOS IP SLAs Command Reference

Standards

Standard

Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

--

MIBs

MIB

MIBs Link

CISCO-RTTMON-MIB

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

http://www.cisco.com/go/mibs

RFCs

RFC

Title

No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.

--

Technical Assistance

Description

Link

The Cisco Technical Support & Documentation website contains thousands of pages of searchable technical content, including links to products, technologies, solutions, technical tips, and tools. Registered Cisco.com users can log in from this page to access even more content.

http://www.cisco.com/techsupport

Feature Information for IP SLAs RTP-Based VoIP Operations

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Table 3 Feature Information for IP SLAs RTP-Based VoIP Operations

Feature Name

Releases

Feature Information

IP SLAs RTP-Based VoIP Operation

12.4(4)T

The Cisco IOS IP Service Level Agreements (SLAs) Internet Control Message Protocol (ICMP) jitter operation provides the capability to generate a stream of ICMP packets to gather network performance-related statistics. Available statistical measurements for the IP SLAs ICMP jitter operation include latency, round-trip time, jitter (interpacket delay variance), and packet loss between a Cisco device (source) and any other IP device (destination).

IP SLAs RTP-Based VoIP Operation Enhancements

12.4(6)T

New statistical measurement options for the source-to-destination data path were added.

Cisco and the Cisco Logo are trademarks of Cisco Systems, Inc. and/or its affiliates in the U.S. and other countries. A listing of Cisco's trademarks can be found at www.cisco.com/go/trademarks. Third party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1005R)

Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.