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Table Of Contents
VoIP Call Admission Control Using RSVP
Related Features and Technologies
Supported Standards, MIBs, and RFCs
Configuring Synchronization and the Reservation Timer
Configuring Slow Connect for VoIP Globally
Configuring Slow Connect for a Specific Dial Peer
Monitoring and Maintaining RSVP Call Admission Control
H.323 Slow Connect by Voice Service Example
H.323 Slow Connect by Dial Peer Example
debug call rsvp-sync func-trace
VoIP Call Admission Control Using RSVP
Document Update Alert
This document was originally produced for Cisco IOS Release 12.1(5)T. This feature has been updated in subsequent releases, and more recent documentation is available.
If you are using Cisco IOS Release 12.3 or higher, refer to the following documentation in the Quality of Service for Voice guide, Cisco IOS Voice Configuration Library, Release 12.3:
If you are using Cisco IOS Release 12.2 or higher, refer to the following documentation in the Configuring Quality of Service for Voice chapter of the Cisco IOS Voice, Video, and Fax Configuration Guide, Release 12.2:
Feature History
This feature module describes enhancements to call admission control using Resource Reservation Protocol (RSVP) in Cisco H.323 Voice over IP (VoIP) networks. This feature synchronizes RSVP procedures with H.323 Version 2 (Fast Connect) setup procedures to ensure that the required Quality of Service (QoS) for a call is maintained across the IP network.
This document includes the following sections:
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Supported Standards, MIBs, and RFCs
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Feature Overview
RSVP is the IP service that allows applications to request end-to-end QoS guarantees from the network. Cisco VoIP applications use RSVP for call admission control, limiting the accepted voice load on the IP network to guarantee the QoS levels of calls. The VoIP Call Admission Control using RSVP feature synchronizes RSVP signaling with H.323 Version 2 signaling to ensure that the bandwidth reservation is established in both directions before a call moves to the alerting phase (ringing). This ensures that the called party phone rings only after the resources for the call have been reserved. Using RSVP-based admission control, VoIP applications can reserve network bandwidth and react appropriately if bandwidth reservation fails.
Prior to Cisco IOS Release 12.1(3)XI and 12.1(5)T, VoIP gateways used H.323 Version 1 (Slow Connect) procedures when initiating calls requiring bandwidth reservation. This feature, which is enabled by default, allows gateways to use H.323 Version 2 (Fast Connect) for all calls, including those requiring RSVP. To enable backward compatibility, commands are available to force the originating gateway to initiate calls using Slow Connect procedures if the terminating gateway is running Cisco IOS Release 12.1(1)T or later. You can configure Slow Connect globally for all VoIP calls by using the h323 call start voice-service command, or configure Slow Connect per the individual VoIP dial-peer by using the call start voice-class command.
A timer can be set by using the call rsvp-sync resv-timer command to limit the number of seconds that the terminating gateway waits for bandwidth reservation setup before proceeding with the call setup or releasing the call, depending on the configured QoS level in the dial peers.
Note
Synchronized RSVP is attempted for an IP call when the requested (desired) QoS for the associated dial peer is set to controlled-load or guaranteed-delay, as long as RSVP has been enabled for the interface by using the ip rsvp bandwidth command. If the requested QoS level is set to the default of best-effort, or RSVP is not enabled, bandwidth reservation is not attempted.
If RSVP reservation is attempted but fails, the acceptable QoS for the dial peer determines the outcome of the call. When the acceptable QoS is configured for best effort, the call setup proceeds but without any bandwidth reservation in place. When the acceptable QoS on either gateway is configured for other than best effort, and the RSVP reservation fails, the call is released. The requested QoS and acceptable QoS are configured through Cisco IOS software by using the req-qos and acc-qos dial-peer configuration commands, respectively.
Table 1 summarizes the results of nine call setup scenarios using Fast Connect, based on the QoS levels configured in the VoIP dial peers at the originating and terminating gateways. This table does not include cases where the requested QoS is best-effort and the acceptable QoS is other than best effort because those configurations are considered invalid.
Note
For detailed descriptions and instructions on configuring the requested and acceptable QoS levels, see the Cisco IOS Multiservice Applications Command Reference, Cisco IOS Release 12.1.
Benefits
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Restrictions
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Related Features and Technologies
RSVP-based resource admission control is related to the existing RSVP feature, which is documented in the Cisco IOS Quality of Service Solutions Configuration Guide, Cisco IOS Release 12.1.
Related Documents
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Supported Platforms
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The VoIP Call Admission Control Using RSVP feature runs on all platforms that support Cisco IOS Release 12.1(3)XI or 12.1(5)T, and H.323-based VoIP.
Determining Platform Support Through Cisco Feature Navigator
Cisco IOS software is packaged in feature sets that support specific platforms. To get updated information regarding platform support for this feature, access Cisco Feature Navigator. Cisco Feature Navigator dynamically updates the list of supported platforms as new platform support is added for the feature.
Cisco Feature Navigator is a web-based tool that enables you to determine which Cisco IOS software images support a specific set of features and which features are supported in a specific Cisco IOS image. You can search by feature or release. Under the release section, you can compare releases side by side to display both the features unique to each software release and the features in common.
To access Cisco Feature Navigator, you must have an account on Cisco.com. If you have forgotten or lost your account information, send a blank e-mail to cco-locksmith@cisco.com. An automatic check will verify that your e-mail address is registered with Cisco.com. If the check is successful, account details with a new random password will be e-mailed to you. Qualified users can establish an account on Cisco.com by following the directions at http://www.cisco.com/register.
Cisco Feature Navigator is updated regularly when major Cisco IOS software releases and technology releases occur. For the most current information, go to the Cisco Feature Navigator home page at the following URL:
Availability of Cisco IOS Software Images
Platform support for particular Cisco IOS software releases is dependent on the availability of the software images for those platforms. Software images for some platforms may be deferred, delayed, or changed without prior notice. For updated information about platform support and availability of software images for each Cisco IOS software release, refer to the online release notes or, if supported, Cisco Feature Navigator.
Supported Standards, MIBs, and RFCs
Standards
No new or modified standards are supported by this feature.
MIBs
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To obtain lists of supported MIBs by platform and Cisco IOS release, and to download MIB modules, go to the Cisco MIB website on Cisco.com at the following URL:
http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml
RFCs
No new or modified RFCs are supported by this feature.
Prerequisites
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Cisco IOS IP and IP Routing Configuration Guide, Cisco IOS Release 12.1.•
Software Configuration Guide for Cisco 3600 and Cisco 2600 Series Routers or Configuring H.323 VoIP Gateway for Cisco Access Platforms.•
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Cisco IOS Multiservice Applications Command Reference, Cisco IOS Release 12.1.
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Configuration Tasks
The following sections describe optional configuration tasks for the VoIP Call Admission Control Using RSVP feature. The tasks in the first section are for configuring synchronization:
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Use the following tasks only if you require backward compatibility with Version 2 (Slow Connect) gateways running a release earlier than Cisco IOS Release 12.1(3)XI or 12.1(5)T (must be Cisco IOS Release 12.1(1)T or later):
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Configuring Synchronization and the Reservation Timer
Synchronization between RSVP and the H.323 voice signaling protocol is enabled by default; no configuration tasks are required to enable this feature. To reenable the feature if the no call rsvp sync command was used to disable it, perform the following steps in global configuration mode:
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Configuring Slow Connect for VoIP Globally
To make an H.323 gateway backward compatible with a destination gateway that is running Cisco IOS Release 12.1(1)T or later (up to Cisco IOS Release 12.1(3)XI), perform the following steps beginning in global configuration mode. This procedure is optional and selects Slow Connect globally for all VoIP services.
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Configuring Slow Connect for a Specific Dial Peer
To make an H.323 gateway backward compatible with a destination gateway that is running Cisco IOS Release 12.1(1)T or later (up to Cisco IOS Release 12.1(3)XI), perform the following steps beginning in global configuration mode. This procedure is optional and selects Slow Connect for a specific VoIP dial peer.
Step 1
Router(config)# voice class h323 tag
Enters voice-class configuration mode and creates a voice class for H.323 attributes.
Step 2
Router(config-class)# call start slow
orRouter(config-class)# call start system
Forces the H.323 gateway to use Slow Connect procedures.
The default is system, which causes the H.323 gateway to use the connect procedure that is configured by using the h323 call start voice-service configuration command (see "Configuring Slow Connect for VoIP Globally").
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Step 3
Router(config-class)# exit
Exits voice-class configuration mode and returns to global configuration mode.
Step 4
Router(config)# dial-peer voice number voip
Enters dial-peer configuration mode for the VoIP dial peer.
Step 5
Router(config-dial-peer)# voice-class h323 tag
Assigns the voice class attributes to the dial peer, including the H.323 connect procedure that was selected in Step 2.
Verifying Configuration
To verify that RSVP-based call admission control is configured correctly, enter the show running-config privileged EXEC command to display the command settings for the router, as shown in the "Configuration Examples" section.
Monitoring and Maintaining RSVP Call Admission Control
To display the configuration parameters for RSVP synchronization and to display statistics for calls that initiate RSVP, use the following privileged EXEC commands.
Displays the RSVP synchronization configuration.
show call rsvp-sync stats
Displays statistics for calls that attempted RSVP reservation.
Configuration Examples
The following examples display the screen output using the show running-config command:
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RSVP Synchronization Examples
The following examples show that calls can be made in either direction between gateway A and
gateway B, which are connected to POTS phones, with phone numbers 711 and 712 respectively. The requested QoS indicates that RSVP setup must complete before the destination phone rings. The acceptable QoS indicates that the call is released if the RSVP setup fails or does not complete within the allotted time.
H.323 Slow Connect by Voice Service Example
The following example shows that Slow Connect is configured globally for all VoIP calls because the h323 call start slow command is used in the voice service configuration:
!dial-peer voice 712 voipdestination-pattern 712session target ipv4:10.10.107.108req-qos controlled-loadacc-qos controlled-load!voice service voiph323 call start slow
!The following example shows the same basic configuration but demonstrates that when the call start system command is used in the voice class configuration, the gateway defaults to the connect procedure that is configured in the voice service; otherwise the dial peer configuration takes precedence (see the H.323 Slow Connect by Dial Peer Example).
!dial-peer voice 712 voipvoice-class h323 2destination-pattern 712session target ipv4:10.10.107.108req-qos controlled-loadacc-qos controlled-load!voice class h323 2H.323 Slow Connect by Dial Peer Example
The following example shows that calls from VoIP dial peer 712 use Slow Connect procedures because the call start slow command is configured in the voice class assigned to the dial peer:
!dial-peer voice 712 voiph323 call start fast!
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Command Reference
This section documents new commands. All other commands used with this feature are documented in the Cisco IOS Release 12.1 command reference publications.
call rsvp-sync
To enable synchronization between Resource Reservation Protocol (RSVP) signaling and the voice signaling protocol, use the call rsvp-sync global configuration command. To disable synchronization, use the no form of this command.
call rsvp-sync
no call rsvp-sync
Syntax Description
This command has no keywords or arguments.
Defaults
Synchronization is enabled between RSVP and the voice signaling protocol (for example, H.323).
Command Modes
Global configuration
Command History
Usage Guidelines
The call rsvp-sync command is enabled by default. To enable RSVP, the ip rsvp bandwidth command must be configured on the related interface.
Examples
The following example enables synchronization between RSVP and the voice signaling protocol:
call rsvp-syncRelated Commands
call rsvp-sync resv-timer
To set the timer on the terminating VoIP gateway for completing RSVP reservation setups, use the call rsvp-sync resv-timer global configuration command. To restore the default value, use the no form of this command.
call rsvp-sync resv-timer seconds
no call rsvp-sync resv-timer
Syntax Description
seconds
Number of seconds in which the reservation setup must be completed, in both directions. Value range is 1 to 60 seconds. Default is 10.
Defaults
10 seconds
Command Modes
Global configuration
Command History
Usage Guidelines
The reservation timer is started on the terminating gateway when the session protocol receives an indication of the incoming call. This timer is not set on the originating gateway because the resource reservation is confirmed at the terminating gateway. If the reservation timer expires before the RSVP setup is complete, the outcome of the call depends on the acceptable QoS level configured in the dial peer; the call either proceeds without any bandwidth reservation or it is released. The timer must be set long enough to allow calls to complete but short enough to free up resources. The optimum number of seconds depends on the number of hops between the participating gateways and the delay characteristics of the network.
Examples
The following example sets the reservation timer to 30 seconds:
call rsvp-sync resv-timer 30Related Commands
call start
To force the H.323 Version 2 gateway to use Fast Connect or Slow Connect procedures for a dial peer, use the call start voice-class configuration command. To restore the default condition, use the no form of this command.
call start {fast | slow | system}
no call start
Syntax Description
Defaults
system
Command Modes
Voice-class configuration
Command History
Usage Guidelines
In Cisco IOS Release 12.1(3)XI and later, H.323 VoIP gateways by default use H.323 Version 2 (Fast Connect) for all calls including those initiating RSVP. Previously, gateways used only Slow Connect procedures for RSVP calls. To enable Cisco IOS Release 12.1(3)XI gateways to be backward compatible with earlier releases of Cisco IOS Release 12.1 T, the call start command allows the originating gateway to initiate calls using Slow Connect.
This call start command is configured as part of the voice class assigned to an individual VoIP dial peer. It takes precedence over the h323 call start voice-service configuration command, which applies globally to all VoIP calls, unless the system keyword is selected. If the system keyword is used for the call start voice-class command, the gateway defaults to the voice-service configuration.
Examples
The following example selects Slow Connect for voice class 1000:
voice class h323 1000call start slow!dial-peer voice 210 voipvoice-class h323 1000Related Commands
h323 call start
To force the H.323 Version 2 gateway to use Fast Connect or Slow Connect procedures for all H.323 calls, use the h323 call start voice-service configuration command. To restore the default condition, use the no form of this command.
h323 call start {fast | slow}
no h323 call start
Syntax Description
fast
Gateway uses H.323 Version 2 (Fast Connect) procedures.
slow
Gateway uses H.323 Version 1 (Slow Connect) procedures.
Defaults
fast
Command Modes
Voice-service configuration
Command History
Usage Guidelines
In Cisco IOS Release 12.1(3)XI and later, H.323 VoIP gateways by default use H.323 Version 2 (Fast Connect) for all calls including those initiating RSVP. Previously, gateways used only Slow Connect procedures for RSVP calls. To enable Cisco IOS Release 12.1(3)XI gateways to be backward compatible with earlier releases of Cisco IOS Release 12.1 T, the h323 call start command forces the originating gateway to initiate calls using Slow Connect.
This h323 call start command is configured as part of the global voice-service configuration for VoIP services. It does not take effect unless the call start system voice-class configuration command is configured in the VoIP dial peer.
Examples
The following example selects Slow Connect procedures for the gateway:
voice service voiph323 call start slowRelated Commands
show call rsvp-sync conf
To display the configuration settings for RSVP synchronization, use the show call rsvp-sync conf privileged EXEC command.
show call rsvp-sync conf
Syntax Description
This command has no arguments or keywords.
Defaults
No default behavior or values
Command Modes
Privileged EXEC
Command History
Examples
The following example shows sample output from the show call rsvp-sync conf command:
Router# show call rsvp-sync confVoIP QoS: RSVP/Voice Signaling Synchronization config:Overture Synchronization is ONReservation Timer is set to 10 secondsTable 2 describes the fields shown in the display.
Related Commands
show call rsvp-sync stats
To display statistics for calls that attempted RSVP reservation, use the show call rsvp-sync stats privileged EXEC command.
show call rsvp-sync stats
Syntax Description
This command has no arguments or keywords.
Defaults
No default behavior or values
Command Modes
Privileged EXEC
Command History
Examples
The following example shows sample output from the show call rsvp-sync stats command:
Router# show call rsvp-sync statsVoIP QoS:Statistics Information:Number of calls for which QoS was initiated : 18478Number of calls for which QoS was torn down : 18478Number of calls for which Reservation Success was notified : 0Total Number of PATH Errors encountered : 0Total Number of RESV Errors encountered : 0Total Number of Reservation Timeouts encountered : 0Table 3 describes the fields shown in the display.
Related Commands
Debug Commands
This section documents new debug commands. All other debug commands used with this feature are documented in the Cisco IOS Release 12.1 command reference publications.
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debug call rsvp-sync events
To display events that occur during RSVP setup, use the debug call rsvp-sync events privileged EXEC command. To restore the default condition, use the no form of this command.
debug call rsvp-sync events
no debug call rsvp-sync events
Syntax Description
This command has no arguments or keywords.
Defaults
No default behavior or values
Command History
Usage Guidelines
It is highly recommended that you log the output from the debug call rsvp-sync events command to a buffer, rather than sending the output to the console; otherwise, the size of the output could severely impact the performance of the gateway.
Examples
The following example shows a portion of sample output for a call initiating RSVP when using the debug call rsvp-sync events command:
00:03:25: Parameters: localip: 10.19.101.117 :localport: 1666000:03:25: Parameters: remoteip: 10.19.101.116 :remoteport: 1756800:03:25: QoS Primitive Event for Call id 0x1 : QoS Listen00:03:25: Lookup to be done on hashkey 0x1 in hash table 0x61FC249800:03:25: Hashed entry 0x1 in call table 0x61FC249800:03:25: Entry Not found00:03:25: Parameters: localip: 10.19.101.11700:03:25: remoteip: 10.19.101.11600:03:25: QoSpcb : 0x61FC34D800:03:25: Response Status : 0Starting timer for call with CallId 0x1 for 10000 secs00:03:25: Handling QoS Primitive QoS Listen00:03:25: Establishing RSVP RESV state : rsvp_request_reservation()00:03:25: For streams from 10.19.101.116:17568 to 10.19.101.117:1666000:03:25: RSVP Confirmation required00:03:25: QoS Primitive Event for Call id 0x1 : QoS Resv00:03:25: Lookup to be done on hashkey 0x1 in hash table 0x61FC249800:03:25: Hashed entry 0x1 in call table 0x61FC249800:03:25: Initiating RVSP PATH messages to be Sent : reg_invoke_rsvp_advertise_sender()00:03:25: Advertizing for streams to 10.19.101.116:17568 from 10.19.101.117:1666000:03:25: RESV notification event received is : 200:03:25: Received RESVCONFIRM00:03:25: RESV CONFIRM message received from 10.19.101.116 for RESV setup from 10.19.101.11700:03:25: RESV event received is : 000:03:25: RESV message received from 10.19.101.116:17568 for streams from 10.19.101.117:1666000:03:25: RESERVATIONS ESTABLISHED : CallId: 1 Stop timer and notify Session Protocol of Success (ie. if notification requested)00:03:25: Invoking spQoSresvCallback with SuccessRelated Commands
debug call rsvp-sync func-trace
To display messages about software functions called by RSVP, use the debug call rsvp-sync func-trace privileged EXEC command. To restore the default condition, use the no form of this command.
debug call rsvp-sync func-trace
no debug call rsvp-sync func-trace
Syntax Description
This command has no arguments or keywords.
Defaults
No default behavior or values
Command History
Usage Guidelines
It is highly recommended that you log the output from the debug call rsvp-sync func-trace command to a buffer, rather than sending the output to the console; otherwise, the size of the output could severely impact the performance of the gateway.
Examples
The following example shows a portion of sample output for a call initiating RSVP when using the debug call rsvp-sync func-trace command in conjunction with the debug call rsvp-sync events command:
00:03:41: Entering Function QoS_Listen00:03:41: Parameters:localip:10.10.101.116 :localport:1756800:03:41:remoteip:10.10.101.117 :remoteport:000:03:41: Entering Function qos_dequeue_event00:03:41: Entering Function process_queue_event00:03:41: QoS Primitive Event for Call id 0x2 :QoS Listen00:03:41: Entering Function get_pcb00:03:41: Entering Function hash_tbl_lookup00:03:41:Lookup to be done on hashkey 0x2 in hash table 0x61FAECD800:03:41: Entering Function hash_func00:03:41:Hashed entry 0x2 in call table 0x61FAECD800:03:41:Entry Not found00:03:41: Entering Function qos_dequeue_pcb00:03:41: Entering Function qos_initialize_pcb00:03:41: Parameters:localip:10.10.101.11600:03:41: remoteip:10.10.101.11700:03:41: QoSpcb :0x61FAFD1800:03:41: Response Status :000:03:41: Entering Function hash_tbl_insert_entry00:03:41: Entering Function hash_func00:03:41: Handling QoS Primitive QoS Listen00:03:41: Entering Function qos_dequeue_hash_port_entry00:03:41: Entering Function qos_port_tbl_insert_entry00:03:41: Entering Function hash_func00:03:41: Doing RSVP Listen :rsvp_add_ip_listen_api()Related Commands
Glossary
acceptable QoS—Minimum level of QoS that is required for a call, or the call is released.
Call Admission Control—Procedures that determine whether to admit a VoIP call based on the available bandwidth in the IP network. There must be sufficient bandwidth to support the new VoIP call with the required QoS, while also maintaining the required QoS of already established VoIP calls.
desired QoS—Requested level of QoS that is preferred for a call. The desired QoS is typically equal to or higher than the acceptable QoS for the call.
Fast Connect—Allows H.323 endpoints to establish media channels without waiting for a separate H.245 connection to be opened. This streamlines the number of messages that are exchanged and the amount of processing that must be done before endpoint connections can be established.
gateway—An H.323 endpoint on the LAN that provides real-time, two-way communication between H.323 terminals on the LAN, other ITU-T terminals in the WAN, or to another H.323 gateway. A gateway allows H.323 terminals to communicate with non-H.323 terminals by converting protocols. A gateway is the point where a circuit-switched call is encoded and repackaged into IP packets.
H.323—An International Telecommunication Union (ITU-T) standard that describes packet-based video, audio, and data conferencing. H.323 is an umbrella standard that describes the architecture of the conferencing system and refers to a set of other standards (H.245, H.225.0, and Q.931) to describe its actual protocol.
QoS—Quality of Service. The performance of a transmission across a network. To ensure that receivers get the quality they expect, for example a video image that is smooth rather than choppy, various strategies have been developed that enable routers to give preference to one set of packets over others that arrive at the routers at the same moment. These strategies are known as Quality of Service features.
RSVP—Resource reSerVation Protocol. An IETF protocol used for signalling requests (setting up reservations) for Internet services by a customer, before that customer is permitted to transmit data over that portion of the network.
VoIP—Voice over IP. The ability to carry normal telephone-style voice over an IP-based Internet with POTS-like functionality, reliability, and voice quality. VoIP is a blanket term, that generally refers to the Cisco standards-based (for example H.323) approach to IP voice traffic.
VoIP dial peer—Dial peer connected by a packet network; in the case of Voice over IP, this is an IP network. VoIP peers point to specific VoIP devices.
