Downloads |
 Feedback
|
Table Of Contents
Prerequisites for SIP: Busy Out Support
Information About SIP: Busy Out Support
SIP: Busy Out Support Functionality
Options Message Requests Sent to an Active SIP Server or Servers
Options Message Requests Sent to a Server Not Responding
Benefit of the SIP: Busy Out Support Feature
How to Configure the SIP: Busy Out Support Feature
Configuring the SIP: Busy Out Support Feature
Configuration Examples for SIP: Busy Out Support
Feature Information for SIP: Busy Out Support
SIP: Busy Out Support
First Published: February 27, 2006Last Updated: February 27, 2006The SIP: Busy Out Support feature introduces, at the SIP level, a generic keepalive mechanism that allows the SIP gateway to monitor the status of the SIP servers and provide the option of busying-out the associated voice ports upon total keepalive failure.
Note
Generic means that the keepalive mechanism work with any SIP server, not just Cisco equipment.
Finding Feature Information in This Module
Your Cisco IOS software release may not support all of the features documented in this module. To reach links to specific feature documentation in this module and to see a list of the releases in which each feature is supported, use the "Feature Information for SIP: Busy Out Support" section.
Finding Support Information for Platforms and Cisco IOS Software Images
Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at the login dialog box and follow the instructions that appear.
Contents
•
•
•
•
•
Prerequisites for SIP: Busy Out Support
For information about configuring voice functionality, see the Cisco IOS Voice Configuration Library.
•
•
•
•
Information About SIP: Busy Out Support
In order to use the SIP Busy Out feature, you should understand the following concepts:
•
•
SIP: Busy Out Support Functionality
The SIP: Busy Out Support feature allows you to configure a SIP gateway to monitor the status of the SIP server by using a keepalive mechanism. When a lack of keepalive responses from a SIP server indicate a failure, the configured voice ports present a seized or busied-out condition to the attached private branch exchange (PBX) or other customer premises equipment (CPE). The SIP: Busy Out Support feature causes calls to fallback to another means of connection more quickly in the event of a failure than if the feature were not enabled. For example, if the connection between the client and a SIP server goes down and a call is made, an INVITE message request is not sent to the downed SIP server, instead, the system sees that the link is down and looks for alternate routes. The PBX or CPE then attempts to select an alternate route. When a voice port is busied out, the SIP gateway resumes the keepalive mechanism and unbusys the associated voice ports upon receipt of a message response.
The SIP: Busy Out Support feature differs from existing connection admission control (CAC) mechanisms because it works at the SIP level and does not require any proprietary capabilities on the remote SIP server. The SIP: Busy Out Support feature works over channel associated signaling (CAS), Primary Rate Interface (PRI), and Foreign Exchange Station (FXS). In addition, the SIP: Busy Out Support feature adds a new command at the dial-peer level to prevent registration of selected plain old telephone service (POTS) dial-peers.
The SIP: Busy Out Support feature involves the following events that help explain how the feature works:
•
•
Options Message Requests Sent to an Active SIP Server or Servers
The keepalive target command must be enabled within the SIP UA configuration mode, so that the SIP gateway can send Options message requests as a keepalive mechanism to active SIP servers. The SIP gateway sends Options message requests to the specified SIP servers at the rate specified by the timers keepalive active command active timer. As long as the SIP gateway receives responses to these Options message requests and the command is not disabled, the SIP gateway continues sending Options message requests at this rate.
However, if the configured SIP servers fail to respond to an Options message request by the time the configurable retry keepalive count has been exhausted, the configured voice port or ports, are busied out and the SIP gateway begins sending Options message requests at the rate specified under the timers keepalive down command.
Busy Voice Ports
Voice ports are made busy in a manner similar to that used with gatekeeper monitoring in H.323 (Enhanced Features for Local and Advanced Voice Busyout). When the keepalive mechanism fails and the SIP servers are in the down state, the gateway. cycles through the voice ports and shuts down voice ports that are configured to monitor SIP keepalives.
The callback register invokes the voice port busyout action and sets the ABCD bit to reflect busy in the case of channel associated signaling (CAS) and generates busy D signal in common channel signaling (CCS). If no voice ports have busyout monitor keepalive configured, the Options message request are sent as long as the keepalive target command is configured, but no voice ports are busied or unbusied.
Options Message Requests Sent to a Server Not Responding
When the SIP servers fail to respond in the down state, the Options message requests continue to be sent, at the rate specified by the timers keepalive down command. At the time of failure, the voice ports are cycled through, and any voice ports with busyout monitor command keepalive configured are busied out. When the SIP gateway receives a sufficient configurable number of Options message responses, the Options message requests resumed at the rate specified by the timers keepalive active command. When the servers resume the active state, the configured voice ports are unbusied. The SIP gateway does not unbusy the ports until the number of sequential responses specified via the keepalive trigger command are received. This prevents flapping or repeatedly busying and unbusying the ports.
Unbusy Voice Ports
The voice ports are removed from the unbusy state in a manner similar to that used in gatekeeper monitoring in H.323 (Enhanced Features for Local and Advanced Voice Busyout). When the keepalive mechanism becomes active (from the down state), the voice ports that were busied because of keepalive failurea are unbusied. Ports with a matching busyout type are unbusied. This callback handles setting the ABCD bit and D channel signal to reflect not-busy in the case of CAS and CCS, respectively.
Benefit of the SIP: Busy Out Support Feature
The SIP: Busy Out Support feature makes fallback seamless to the user.
For example; you have two dial peers configured for calling 555-1212. One of the dial peers routes the outbound call to 555-1212 through SIP server A, and the other routes it through SIP server B (both routes end up in the same place). If SIP server A has a higher preference than SIP server B, it is always tried first when someone dials 555-1212, and it fails, the SIP gateway tries SIP server B via the other dial peer. However, if the SIP: Busy Out Support feature is implemented and it detects a failure in the connection with SIP server A, it marks that connection as unavailable (before anyone dials the number) so that it is skipped when the number is dialed, going straight to the second dial peer (SIP server B), thus saving the time of waiting for the call through SIP server A to fail. The end result is that someone placing an outbound call does not have to wait as long for the call to complete if there are multiple routes available for that particular call, and one route is down.
How to Configure the SIP: Busy Out Support Feature
This section contains the following procedure:
•
Configuring the SIP: Busy Out Support Feature
Configuring the SIP: Busy Out Support feature involves the following general steps, which are provided in summary form and in detailed form in this section:
•
•
•
•
•
•
SUMMARY STEPS
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
DETAILED STEPS
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
voice-port port
Example:Router(config)# voice-port 2/2
Enters voice-port configuration mode. To find the port argument for your router, see the Cisco IOS Voice Command Reference, Release 12.4T.
Step 4
busyout monitor keepalive
Example:Router(config-voiceport)# busyout monitor keepalive
Selects a voice port to be busied-out in case of a keepalive failure.
Step 5
sip-ua
Example:Router(config-dial-peer)# sip-ua
Enters SIP user-agent configuration mode.
Step 6
keepalive target {ipv4:address[:port] | dns:hostname} [tcp [tls] | udp] [secondary]
Example:Router(config-sip-ua)# keepalive target ipv4:172.16.0.2 tcp secondary
Sets the keepalive target to either primary, secondary, or both depending on how many are configured.
•
•
•
•
•
•
•
Step 7
timers keepalive active seconds
Example:Router(config-sip-ua)# timers keepalive active 20
(Optional) Sets the keepalive active timer value in seconds.
•
Step 8
retry keepalive count
Example:Router(config-sip-ua)# retry keepalive 5
(Optional) Sets the retry count for keepalive retransmissions.
•
Step 9
keepalive trigger count
Example:Router(config-sip-ua)# keepalive trigger 5
(Optional) Sets the keepalive trigger count.
•
Step 10
exit
Example:Router(config-sip-ua)# exit
Exits the current mode.
Step 11
show voice busyout
Example:Router# show voice busyout
(Optional) Displays information about the voice-busyout states.
Examples
The following sample output of the show voice busyout command shows which voice ports are in busy out state:
Router# show voice busyoutIf following network interfaces are down, voice port will be put into busyout stateATM0Serial0Voice port busyout will be triggered by the following network states1/0/0 busyout monitor keepaliveThe following voice ports are in busyout state1/1 is forced into busyout state1/2 is in busyout state caused by network interfaces1/3 is in busyout state caused by ATM01/4 is in busyout state caused by network interfaces1/5 is in busyout state caused by Serial0Configuration Examples for SIP: Busy Out Support
The following shows examples of the SIP: Busy Out Support feature when enabled.
Examples of keepalive information shown are as follows:
•
•
•
•
•
version 12.4service timestamps debug datetime msecservice timestamps log datetime msecno service password-encryption!hostname chef!boot-start-markerboot-end-marker!no logging buffered!no aaa new-model!resource policy!clock timezone GMT 5clock summer-time Gmt recurring!!--More--ip cefip domain name sip.comip name-server 172.18.192.48!!voice call debug full-guid!voice service voipsipregistrar server expires max 600 min 60!!voice class codec 2codec preference 1 g729r8codec preference 2 g711ulawcodec preference 3 g711alaw!!--More--!applicationservice voipapp tftp://172.18.207.15/gw-tcl-scripts/mirinda/mirinda_regress_server.tcl!!username jsmith password 0 jsmithusername cisco password 0 lab!!interface FastEthernet0/0ip address 172.18.193.120 255.255.255.0duplex autospeed autoip rsvp bandwidth 7500 7500!--More--interface FastEthernet0/1no ip addressshutdownduplex autospeed auto!ip http server!ip route 0.0.0.0 0.0.0.0 172.18.193.1!ip rtcp report interval 200!!control-plane!call treatment on!!call filter match-list 1 voiceincoming dialpeer 125outgoing signaling remote ipv4 172.16.0.4--More--voice-port 1/0/0! Busyout monitor command with keepalive option selectedbusyout monitor keepalive!voice-port 1/0/1!voice-port 1/1/0!voice-port 1/1/1!voice-port 2/0/0!voice-port 2/0/1!!dial-peer cor custom!!dial-peer voice 1 potsdestination-pattern 36602--More--port 2/0/0! Unregistered dial peer command required for the keepalive mechanism to functionno sip-register!dial-peer voice 6 voipdestination-pattern 36601modem passthrough nse codec g711ulawsession protocol sipv2session target ipv4:172.18.193.98:5060incoming called-number 36602dtmf-relay rtp-ntecodec g711ulaw!dial-peer voice 5 voipdestination-pattern 5550199session protocol sipv2session target ipv4:172.18.197.182codec g711ulaw!dial-peer voice 4 voipdestination-pattern 9002session protocol sipv2session target ipv4:172.18.193.87!--More--dial-peer voice 9001 voipdestination-pattern 9001session protocol sipv2session target ipv4:172.18.195.49!dial-peer voice 31 voipdestination-pattern 3100801signaling forward nonesession protocol sipv2session target ipv4:64.102.17.208codec g711ulaw!dial-peer voice 123 voipshutdowndestination-pattern 3100802session protocol sipv2session target ipv4:172.18.193.99codec g711ulaw!dial-peer voice 8 voipdescription stanshutdowndestination-pattern 9876--More--session protocol sipv2session target dns:stan-a.sip.com!dial-peer voice 333 voipdestination-pattern 111session protocol sipv2session target ipv4:172.18.201.177codec g711ulaw!dial-peer voice 2 potspreference 2destination-pattern 362port 2/0/1!dial-peer voice 362 voippreference 1destination-pattern 362session protocol sipv2session target ipv4:172.18.193.120incoming called-number 362fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback cisco!gateway--More--timer receive-rtp 1200!sip-ua! Keepalive target command with a primary server keepalive mechanism using an IP version 4 addresskeepalive target ipv4:172.18.198.184! Keepalive target command with a secondary server keepalive mechanism using a DNS hostnamekeepalive target dns:wendy.sip.com tcp secondary! Keepalive trigger command set to fivekeepalive trigger 5retry invite 2retry response 10retry bye 2retry prack 8retry notify 2retry subscribe 8! Retry keepalive command set to nineretry keepalive 9sip-server dns:sip.com!!telephony-servicemwi relaymax-conferences 8 gain -6transfer-system full-consult!!line con 0--More--exec-timeout 0 0line aux 0line vty 0 4login!!endAdditional References
The following sections provide references related to the SIP: Busy Out Support feature.
Related Documents
Standards
MIBs
RFCs
Technical Assistance
Command Reference
This section documents the following new and modified commands:
busyout monitor
To place a voice port into the busyout monitor state, enter the busyout monitor command in voice-port configuration mode. To remove the busyout monitor state from the voice port, use the no form of this command.
busyout monitor {serial interface-number | ethernet interface-number | keepalive} [in-service]
no busyout monitor {serial interface-number | ethernet interface-number | keepalive}
Syntax Description
Defaults
The voice port does not monitor any interfaces.
Command Modes
Voice-port configuration
Command History
Usage Guidelines
When you place a voice port in the busyout monitor state, the voice port monitors the specified interface and enters the busyout state when the interface is down. This down state forces the rerouting of calls.
The busyout monitor command monitors only the up or down status of an interface—not end-to-end TCP/IP connectivity.
When an interface is operational, a busied-out voice port returns to its normal state.
This feature can monitor LAN, WAN, and virtual subinterfaces.
A voice port can monitor multiple interfaces at the same time. To configure a voice port to monitor multiple interfaces, reenter the busyout monitor command for each additional interface to be monitored.
If you specify more than one monitored interface for a voice port, all the monitored interfaces must be down to trigger busyout on the voice port.
You can combine in-service and out-of-service monitoring on a voice port. The following rule describes the action if monitored interfaces change state. A voice port is busied out if either of the following occurs:
•
•
Examples
The following example shows configuration of analog voice port 1/2 to busy out if serial port 0 or 1 comes into service:
voice-port 1/2busyout monitor serial 0 in-servicebusyout monitor serial 1 in-serviceThe following example shows configuration of digital voice port 1/2/2 on a Cisco 3600 series router to busy out if serial port 0 goes out of service:
voice-port 1/2/2 busyout monitor serial 0The following example shows configuration of the voice port to monitor two serial interfaces and an Ethernet interface. When all these interfaces are down, the voice port is busied out. When at least one interface is operating, the voice port is put back into a normal state.
voice-port 3/0:0busyout monitor ethernet 0/0busyout monitor serial 1/0busyout monitor serial 2/0The following example shows configuration of the voice port to be busied out in case of a keepalive failure:
voice-port 10busyout monitor keepaliveRelated Commands
keepalive target
To identify session initiation protocol (SIP) servers that will receive keepalive packets from the SIP gateway, use the keepalive target command in SIP user agent configuration mode. To disable the keepalive target command behavior, use the no form of this command.
keepalive target {ipv4:address[:port] | dns:hostname} [tcp [tls]] | udp] [secondary]
no keepalive target [secondary]
Syntax Description
Command Default
No keepalives are sent by default from SIP gateway to SIP gateway. The SIP port number is 5060 by default.
Command Modes
SIP user agent configuration
Command History
Usage Guidelines
The primary or secondary SIP server addresses are in the following forms: dns:example.sip.com or ipv4:172.16.0.10.
Examples
The following example sets the primary SIP server address and defaults to the UDP transport:
sip-uakeepalive target ipv4:172.16.0.10The following example sets the primary SIP server address and the transport to UDP:
sip-uakeepalive target ipv4:172.16.0.10 udpThe following example sets both the primary and secondary SIP server address and the transport to UDP:
sip-uakeepalive target ipv4:172.16.0.10 udpkeepalive target ipv4:172.16.0.20 udp secondaryThe following example sets both the primary and secondary SIP server addresses and defaults to the UDP transport:
sip-uakeepalive target ipv4:172.16.0.10keepalive target ipv4:172.16.0.20 secondaryThe following example sets the primary SIP server address and the transport to TCP:
sip-uakeepalive target ipv4:172.16.0.10 tcpThe following example sets both the primary and secondary SIP server addresses and the transport to TCP:
sip-uakeepalive target ipv4:172.16.0.10 tcpkeepalive target ipv4:172.16.0.20 tcp secondaryThe following example sets the primary SIP server address and the transport to TCP and sets security to TLS mode:
sip-uakeepalive target ipv4:172.16.0.10 tcp tlsThe following example sets both the primary and secondary SIP server addresses and the transport to TCP and sets security to the TLS mode:
sip-uakeepalive target ipv4:172.16.0.10 tcp tlskeepalive target ipv4:172.16.0.20 tcp tls secondaryRelated Commands
keepalive trigger
The trigger count represents the number of Options message requests that must consecutively receive responses from the SIP servers when in the down state in order to unbusy the voice ports, use the keepalive trigger command in SIP user agent configuration mode. To restore to the default value of 3 seconds, use the no form of this command.
keepalive trigger count
no keepalive trigger count
Syntax Description
Command Default
The default value for the keepalive trigger is 3.
Command Modes
SIP user agent configuration
Command History
Usage Guidelines
Sets the count to represent the number of Options message requests that must be consecutively receive responses from the SIP servers in order to unbusy the voice ports when in the down state. The default is 3.
Examples
The following example sets a time interval after the number of Options message requests that must consecutively receive responses from the SIP servers in order to unbusy the voice ports when in the down state. The trigger interval is set to 8 in the following example:
sip-uakeepalive trigger 8Related Commands
retry keepalive
To set the retry count for keepalive retransmission, use the retry keepalive command in SIP user agent configuration mode. To restore the retry count to the default value for keepalive retransmission, use the no form of this command.
retry keepalive count
no retry keepalive count
Syntax Description
Command Default
The default value for the retry keepalive retransmission is 6.
Command Modes
SIP user agent configuration
Command History
Usage Guidelines
Sets the keepalive retransmissions retry count.
Examples
The following example sets the retry for the keepalive retransmissions to 8:
sip-uaretry keepalive 8Related Commands
timers keepalive
To set the keepalive timers interval between sending Options message requests when the session initiation protocol (SIP) servers are in the down state, use the timers keepalive command in SIP user agent configuration mode. To restore the keepalive timers to the default value of 120 seconds when active or 30 seconds when down, use the no form of this command.
timers keepalive {active | down} seconds
no timers keepalive {active | down} seconds
Syntax Description
Command Default
The default value for the active state is 120 seconds and the default value for the down state is 30 seconds.
Command Modes
SIP user agent configuration
Command History
Usage Guidelines
Use this command to change the keepalive message time interval in seconds between the sending Options message requests when the SIP server or servers are either in the active or down state.
Examples
The following example sets the keepalive message time interval to 20 seconds when the SIP server is in the active state:
sip-uatimers keepalive active 20The following example sets the keepalive message time interval to 10 seconds when the SIP server is in the down state:
sip-uatimers keepalive down 10Related Commands
Feature Information for SIP: Busy Out Support
Table 1 lists the release history for this feature.
Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.
Cisco IOS software images are specific to a Cisco IOS software release, a feature set, and a platform. Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at the login dialog box and follow the instructions that appear.
Note
Table 1 Feature Information for SIP: Busy Out Support
SIP: Busy Out Support
12.4(6)T
The SIP: Busy Out Support feature introduces, at the SIP level, a generic keepalive mechanism that allows the SIP gateway to monitor the status of the SIP servers and provide the option of busying-out the associated voice ports upon total keepalive failure.
The following sections provide information about this feature:
•
•
•
The following commands were introduced or modified by this feature: busyout monitor, keepalive target, keepalive trigger, retry keepalive, and timers keepalive
CCSP, CCVP, the Cisco Square Bridge logo, Follow Me Browsing, and StackWise are trademarks of Cisco Systems, Inc.; Changing the Way We Work, Live, Play, and Learn, and iQuick Study are service marks of Cisco Systems, Inc.; and Access Registrar, Aironet, BPX, Catalyst, CCDA, CCDP, CCIE, CCIP, CCNA, CCNP, Cisco, the Cisco Certified Internetwork Expert logo, Cisco IOS, Cisco Press, Cisco Systems, Cisco Systems Capital, the Cisco Systems logo, Cisco Unity, Enterprise/Solver, EtherChannel, EtherFast, EtherSwitch, Fast Step, FormShare, GigaDrive, GigaStack, HomeLink, Internet Quotient, IOS, IP/TV, iQ Expertise, the iQ logo, iQ Net Readiness Scorecard, LightStream, Linksys, MeetingPlace, MGX, the Networkers logo, Networking Academy, Network Registrar, Packet, PIX, Post-Routing, Pre-Routing, ProConnect, RateMUX, ScriptShare, SlideCast, SMARTnet, The Fastest Way to Increase Your Internet Quotient, and TransPath are registered trademarks of Cisco Systems, Inc. and/or its affiliates in the United States and certain other countries.
All other trademarks mentioned in this document or Website 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. (0601R)
Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and coincidental.
© 2006 Cisco Systems, Inc. All rights reserved.
