Table Of Contents
SIP Service Handling and Feature Interworking Enhancements
Document Release History
Publication Date Comments
March 20, 2008
Changed the default mode for the sipModeSelectionControl parameter.
March 12, 2007
Initial version of the document.
The SIP Service Handling and Feature Interworking Enhancements feature was introduced on the Cisco MGC software.
This document describes the SIP Service Handling and Feature Interworking Enhancements feature.
This feature is described in the following sections:
This feature introduces into the Cisco MGC, a Back to Back User Agent (B2BUA) mode of operation for SIP-to-SIP calls using the PGW 2200. It also enhances the existing mid-call service handling to better interwork SIP signaling for mid-call services. This feature allows PGW handling of SIP-to-SIP calls, including intrusive replacement of E.164 addresses appearing in various headers and configurable handling of REFER and 3xx redirect messaging. In addition, this feature enhances the PGW 2200 mid-call service handling for interworking of SIP redirection and transfers with SIP to SIP and SIP to other protocols.
The feature provides the following enhancements as well as consolidating the PGW 2200 call-processing infrastructure:
•Configurable selection of SIP-to-SIP call processing mode (B2BUA or Proxy).
•Introduction of B2BUA mode for SIP-to-SIP calls. This mode of operation allows you to align SIP call processing with the existing PGW call model.
•For SIP-to-SIP calls: intrusive modification of E.164 is addressed within various SIP headers.
•On calls involving SIP where rerouting is invoked, rerouting is supported to or from other protocols. Thus redirection scenarios function properly for calls that start as SIP to SIP and are redirected to SIP to H.323 or calls that start as SIP to H.323 calls and are redirected to SIP-to-SIP calls.
•SIP calls correctly use cause analysis.
•Improved CDR records for SIP-to-SIP calls.
•SIP-to-SIP calls can now be controlled by use of Intelligent Network Application Part (INAP).
•Control of redirection behavior is a dialplan configured option so that a service provider can configure the PGW 2200 to pass on or act locally on redirection requests. In addition, redirection is inter-worked correctly with QSIG and DPNSS diversion services.
•REFER inter-operates with QSIG Single Step Call Transfer (SSCT).
For calls involving DPNSS or QSIG, the following support is introduced for Redirection handling:
•Backward notification of redirection when calls are handled locally.
•Generation of redirection information at the originating side.
•Backward indication of call forwarding when a call is executed locally on the terminating side.
This feature provides the following benefits:
•Adds flexibility to B2BUA support with enhanced mid-call service handling on the PGW 2200. A service provider can configure the PGW 2200 to pass or act on redirection requests based on dial plan provisioning.
•Allows redirection scenarios to function properly for calls that start as SIP to SIP and are redirected to SIP to H.323 or calls that start as SIP to H.323 calls and are redirected to SIP-to-SIP calls.
•Allows SIP and INAP to interwork for terminating leg manipulations.
•Allows the PGW 2200 to redirect SIP-to-ISUP calls to SIP-to-SIP calls for announcements and to normalize the A-number on SIP-to-SIP calls.
The B2BUA implementation on the PGW 2200 is a partial B2BUA solution when the sides are treated independently to a degree but certain information is kept relevant to both sides, that is, supporting SIP-SIP transparency via the call model. This is opposed to a full B2BUA solution when both call sides are treated completely independently with regard to CallID, routing information, and so on.
The PGW 2200 cannot support that SIP invokes hold/resume to TDM after a switchover or resumes the held call after a switchover; the PGW 2200 cannot support that SS7 invokes hold/resume to SIP after a switchover or resumes the held SIP call after a switchover.
This document contains information that is related strictly to this feature. The documents that contain additional information related to the Cisco Media Gateway Controller (MGC) are at the following url:
Supported Standards, MIBs, and RFCs
No new or modified standards are supported by this feature.
No new or modified MIBs are supported by this feature.
For more information on the MIBs used in the Cisco MGC software, see the Cisco Media Gateway Controller Software Release 9.5(2) MIBs
This feature supports the following RFCs:
•RFC 3261, SIP: Session Initiation Protocol (partial compliance)
•RFC 3265, SIP NOTIFY Method
•RFC 3311, SIP UPDATE Method
•RFC 3515, SIP REFER Method
•RFC 4028, Session Timers in the Session Initiation Protocol (SIP)
Prerequisites for Using This Feature
The Cisco PGW 2200 must be running Cisco MGC software Release 9.7(3). Prerequisites for this release can be found in the Release Notes for the Cisco Media Gateway Controller Software Release.
XECfgParm.dat Configuration Tasks
This section contains the steps necessary for configuration of the Cisco MGC software to support this feature. If you are installing and configuring the Cisco MGC software on your system for the first time, use the procedures in the Cisco Media Gateway Controller Software Release 9 Installation and Configuration Guide. Return to this section once you encounter the *.sipModeSelectionControl parameter in the XECfgParm.dat file.
Caution Configuration of the Cisco MGC software requires that the system software be shut down. In a simplex system, calls cannot be processed during system shutdown. In a continuous service system, your system loses the ability to maintain calls during a critical event if the system software on one of the PGW hosts is shut down.
To configure the sipModeSelectionControl value, perform the following steps:
Step 1 If you have not already done so, open the /opt/CiscoMGC/etc/XECfgParm.dat file on the active and standby Cisco PGW hosts using a text editor, such as vi.
Step 2 If you have not already done so, ensure that the pom.dataSync parameter is set to false on the active and standby Cisco PGW hosts.
Step 3 Search for the *.sipModeSelectionControl parameter and enter the desired value
(1—B2BUA/optional mode or 2—Fixed Proxy Mode) on the active and standby Cisco PGW hosts.
Step 4 Save your changes and close the text editor.
Verifying the XECfgParm.dat Changes
To verify the XECfgParm.dat settings for this feature, perform the following steps:
Caution Do not modify the other XECfgParm.dat parameters associated with this feature.
Step 1 Log in to the standby Cisco MGC as root and change directories to the etc subdirectory by entering the following UNIX command:cd /opt/CiscoMGC/etc
Step 2 Open XECfgParm.dat using a text editor, such as vi.
Step 3 Search for the *.sipModeSelectionControl parameter and verify that the displayed value (1—B2BUA/optional mode or 2—Fixed Proxy Mode) is correct.
If the value is correct, proceed to Step 4. Otherwise, correct the value and then proceed to Step 4.
Step 4 Save your changes and close the text editor.
Step 5 Manually stop the Cisco MGC software on the standby Cisco MGC by entering the following UNIX command:/etc/init.d/CiscoMGC stop
Step 6 Once the software shutdown is complete, manually start the Cisco MGC software on the standby Cisco MGC by entering the following command:/etc/init.d/CiscoMGC start
Step 7 Log in to the active Cisco MGC, start an MML session, and enter the following command:mml> sw-over::confirm
Site alarms are automatically set until the out-of-service (OOS) Cisco MGC host is returned to an in-service (IS) state.
Step 8 Repeat steps 2 through 7 for the newly standby Cisco MGC host. Once you have verified the settings on both hosts, the procedure is complete.
This section provides a configuration example for the XECfgParm.dat parameter associated with this feature. Additional configuration examples for the Cisco MGC software can be found in the Cisco Media Gateway Controller Software Release 9 Installation and Configuration Guide.
Note Configuration of XECfgParm.dat parameters for this feature is required only when the Cisco PGW 2200 hosts are not in the same subnet.
*.sipModeSelectionControl = 1 # 1 - B2BUA mode, allow later selection of proxy mode via the dialplan, 2 - Fixed Proxy mode, always work in proxy mode.
Dial Plan Examples
This section provides an example of dial plan provisioning for this feature. Additional examples of dial plan provisioning for the Cisco MGC software can be found in the Cisco Media Gateway Controller Software Release 9 Dial Plan Guide.
Provisioning the FACILITY Result Within the B-Digit Tree
The commands numan-add, numan-ed, and numan-dlt are used to provision dial plan result types and their associated data words. The following example illustrates the provisioning of the FACILITY result within the B-Digit tree:
Create the result within a result-set, in the dial plan result table:mml>numan-add:resulttable:custgrpid="1111", name="fac01", resulttype="FACILITY", dw1="2", dw2="2",setname="rset1"
Now assign the result-set at the required point in the B-Digit tree:numan-add:bdigtree:custgrpid="1111",digitstring="612456",callside="originating",setname="r set1"
Proxy mode is required for SIP-to-SIP calls and data word 2 is not allowed here.mml>numan-add:resulttable:custgrpid="1111", name="fac01", resulttype="FACILITY", dw1="1",setname="rset1"
With this combination of dataword1 and dataword 2, the backward transit of the Redirection is not supported so the existing redirection mechanism (that is, into Cause analysis) applies.mml>numan-add:resulttable:custgrpid="1111", name="fac01", resulttype="FACILITY", dw1="2", dw2="1",setname="rset1"
With this combination of dataword1 and dataword2, the backward transit of the redirection is always supported.mml>numan-add:resulttable:custgrpid="1111", name="fac01", resulttype="FACILITY", dw1="2", dw2="2",setname="rset1"
With this combination of dataword1 and dataword2, the backward transit of the Refer is conditionally supported if the received Refer-To header domain in the REFER message (term side) matches the domain in the From header received within the original INVITE on the OCC side.mml>numan-add:resulttable:custgrpid="1111", name="fac01", resulttype="FACILITY", dw1="3",dw2="3",setname="rset1"
Backward Transition of Redirection Handlingnuman-add:resultset:custgrpid="1111",name="facrset"numan-add:resulttable:custgrpid="1111", name="fac01",resulttype="FACILITY",dw1="2",dw2="2",setname="facrset"
Software Changes for this Feature
The following section describes software changes related to this feature:
The XECfgParm.dat file configuration parameter added for this feature is described in Table 1. For information on the other XECfgParm.dat parameters, see the Cisco Media Gateway Controller Software Release 9 Installation and Configuration Guide.
Table 1 XECfgParm.dat Parameter
Configuration Parameter Definition
The XECfgParm parameter sipModeSelectionControl is the highest level means of governing SIP actions. This parameter lets you provision one system-level parameter and maintain your proxy mode functionality for SIP-to-SIP calls. If you are using proxy mode for SIP calls, you do not have to provision a dialplan result for all numbers handled simply to maintain your call processing capability.
At this level there is a choice of operating mode, either the B2BUA/optional mode using the new dial plan result FACILITY as described in the "FACILITY" section or the default Fixed Proxy Mode working. The parameter has two settings:
1 B2BUA/optional mode—With the parameter set to 1, default processing on SIP-to-SIP calls is B2BUA mode and you can select the proxy mode of operation later with the dial plan (A/B analysis).
2 Fixed Proxy Mode—With the parameter set to 2, handling of SIP-to-SIP calls is supported in proxy mode only. Any later selection of B2BUA mode with the dial plan becomes meaningless once you select this value. There is no means to select B2BUA mode in the FACILITY result, only Proxy mode. This means that if you set XECfgParm for proxy mode there is no point in defining FACILITY results for Proxy mode because all SIP-to-SIP calls will already be in proxy mode. This is the default setting for this parameter.
If there is no dialplan result FACILITY or if number analysis is not used, then the variable remains set at value 0 and default Fixed Proxy behavior results.
This section identifies the call detail record (CDR) data added for this feature. For billing interface information for the rest of the Cisco MGC software, see the Cisco Media Gateway Controller Software Release 9 Billing Interface Guide.
Originating Local SIP Host (Tag: 4202)
Terminating Remote SIP Host (Tag: 4242)
Terminating Local SIP Host (Tag: 4243)
The properties in this section are used for this feature. The parent objects for the properties involved in this feature are found in Table 6.
The properties used for this feature are described in Table 7.
Note The four properties listed in Table 7 are existing properties whose definitions were modified for this feature. The valid values and default values have not changed.
Result Type Definitions
Table 8 shows the result type definition added for this feature. For information on other result type definitions for the Cisco MGC software, see the Cisco Media Gateway Controller Software Release 9 Dial Plan Guide.
The FACILITY result provides a means of setting originating and terminating redirection and call transfer behavior. It also can be used to define SIP call handling mode as proxy mode only for this call and can be configured for the source (A-number) or destination (B-number). As long as the parameter sipModeSelectionControl is set to permit selection of either B2BUA or Proxy mode, this FACILITY dialplan result type provides this "per-call" means of selection.
However, the use of this result is expanded beyond just selecting "Proxy-mode" for a call. It also includes provisioned data which indicates the PGW behavior with regard to redirection and SIP Refer handling.
The key thing is to know for which type of action you are provisioning and thus know the various dw1 and dw2 combinations required. Table 9 should help you to understand and determine this.
1 = Proxy Mode required
2 = Originating Redirection treatment action
3 = Originating Call Transfer treatment action
4 = Terminating Redirection treatment action
5 = Originating Redirection Rejection treatment action
This data word has values 1-4 and provides the actions required according to the type given in dw1. If dw1 is set to value 1 (Proxy mode), then this data word is not used.
Call Processing Actions According to FACILITY Configuration
Table 9 provides the call processing treatment applied according to the combinations of parameter sipModeSelectionControl and the dataword values from the FACILITY result-type. Unless otherwise stated, sipModeSelectionControl is set to value 1 (b2bua optional).
Note The sigpath property siprediranalysismethod affects the 302 handling by the PGW. This property defines how the PGW handles the SIP redirection. The valid value for this property is any integer from 0 to 2. The default value for this property is 0.
0—Only analyze the target whose domain matches with the PGW domain
SIP response codes are now saved in the event that backward transit is required on a B2BUA call. For information on other cause and location codes for the Cisco MGC software, see the Cisco Media Gateway Controller Software Release 9 Dial Plan Guide.
Obtaining Documentation, Obtaining Support, and Security Guidelines
For information on obtaining documentation, obtaining support, providing documentation feedback, security guidelines, and also recommended aliases and general Cisco documents, see the monthly What's New in Cisco Product Documentation, which also lists all new and revised Cisco technical documentation at
Table 10 contains definitions of acronyms and technical terms used in this feature module.
This document is to be used in conjunction with the documents listed in the Related Documents section.
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