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Cisco H.323 Signaling Interface User Guide, Release 4.2
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Cisco H.323 Signaling Interface
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Installing and Configuring Cisco HSI Software
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Provisioning the Cisco HSI
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Managing the Cisco HSI
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Troubleshooting Cisco HSI Alarms
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Cisco HSI Backup and Restore Procedures
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MML User Interface and Command Reference
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Skeleton Configuration File
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Example of an HSI Configuration File
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E-ISUP Cause Value-to-Name Lookup
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E-ISUP Name-to-Cause Value Lookup
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H.323 Name-to-Cause Value Lookup
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H.323 Cause Value-to-Name Lookup
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Feedback
Table Of Contents
Introduction to MML Command Operation for HSI
Initiating an MML Session to Enable DTMF on the HSI
Reverting to the Base Configuration
Quick Reference for Important Parameters
Configuring T.38 Fax on the Cisco PSTN Gateway
Configuring T.38 Fax on a Cisco IOS H.323 Gateway
Configuring T.38 Fax on a Cisco IOS MGCP Gateway
HSI INFORMATION Message Support
Enabling Dynamic Packetization
Configuring Clear Channel on the Cisco HSI
Configuring G.726 on the Cisco HSI
Configuring G.729 Annex and G.729 Annex B
Enabling the NON-RAS Mode of Operation on the Cisco HSI
Disabling the Non-RAS Mode of Operation on the Cisco HSI
Provisioning the Cisco HSI
This chapter describes the data that must be provisioned for the Cisco H.323 Signaling Interface (HSI). The data is divided into two areas: system configuration data and H.323 stack data. This chapter contains the following sections:
Cisco HSI Configuration
All configuration data is contained within configuration files. Cisco HSI starts with an initial configuration file in $GWHOME/currentGW/etc/GWmain.conf. This file is created during installation of the software.
The configuration data within the file is defined as dynamic, static, or constant:
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Dynamic data can be modified by a provisioning session (see Appendix A, "MML User Interface and Command Reference"). It can be activated on the currently running Cisco HSI.
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Examples of the use of constant data are given in Appendixes D, E, F, and G. These appendixes determine the mapping of cause values for incoming and outgoing H.323 and Enhanced ISDN User Part (E-ISUP) messages. System technicians can modify these values in the initial configuration file to explicitly choose the mappings for their system.
When a provisioning session creates a new configuration file, it also verifies that provisioned data is within allowable ranges and indicates this in the start of the file. It checksums the configuration file and writes the checksum as $GWHOME/currentGW/var/prov/configname/checksum.dat. When the Cisco HSI starts up, it attempts to read the active configuration, checks that the configuration has been verified, and ensures that the checksum matches. If the active configuration is not verified or if the checksum is faulty, the configuration reverts to using the $GWHOME/currentGW/etc/GWmain.conf file.
All configuration data that can be set in the system is defined in the Skeleton Configuration file (see Appendix B, "Skeleton Configuration File"). The Skeleton Configuration file defines the data names and types (strings or numbers), and defines whether the data is dynamic, static, or constant.
MML Configuration Commands
There are three types of MML configuration command:
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•
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For more information about MML configuration commands, see Appendix A, "MML User Interface and Command Reference."
Note
The configuration export command is prov-exp, which exports the currently provisioned configuration of the Cisco HSI to a file.
Introduction to MML Command Operation for HSI
After the HSI software is installed, you can configure additional items. The following MML command examples show how to enable DTMF capability on the HSI. (For a description of the sys_config_static entry and the dtmf parameters, please see the section (System Configuration Data).
Initiating an MML Session to Enable DTMF on the HSI
The following MML command example shows how to start an MML session and enable DTMF support of the HSI:
Step 1
/etc/init.d/CiscoGW startStep 2
mml
Step 3
prov-sta:srcver=active, dstver=myconf
Note
prov-add:name=sys_config_static, dtmfsupportedtype=dtmfprov-add:name=sys_config_static, dtmfsupporteddirection=bothprov-cpyrestart-softw
Note
Caution
Verifying the Configuration
The following MML command examples show how to verify that configuration changes have been correctly processed:
Step 1
prov-rtrv:list
Note
Step 2
rtrv-configTo display a subset of the configuration, one can issue a command such as the following:
rtrv-config:sys_config_staticStep 3
quit
Reverting to the Base Configuration
The following MML command examples show how to revert to the base HSI configuration:
Step 1
mmlStep 2
restart-softw:init
Note
System Configuration Data
System configuration data can be static or dynamic. Static data can be activated only at startup. Dynamic data can be activated during system run time.
Static System Data
To modify the static system data parameters in Table 3-3, use the sys_config_static MML name variable for the prov-add, prov-dlt, and prov-ed commands. Stop and restart the application to put the changes into effect.
In the following example, the prov-add command adds the static system data parameter VSCA_PORT_NUMBER1 to a static configuration file. The prov-ed command modifies the value of the VSCA_PORT_NUMBER1 parameter. The prov-dlt command deletes the VSCA_PORT_NUMBER1 parameter from the static configuration file.
Example
prov-add:name=sys_config_static,vsca_port_number1=8003prov-ed:name=sys_config_static,vsca_port_number1=8002prov-dlt:name=sys_config_static,vsca_port_number1The parameters in Table 3-3 are written to a static configuration file or to a section within a file.
Table 3-3 Static System Data Parameters
HOST_PORT_NUMBER1
[0-65535]
The first port number to be used by the Cisco HSI. The default value is 0.
Note
HOST_PORT_NUMBER2
[0-65535]
The second port number to be used by the Cisco HSI. The default value is 0.
Note
HOST_IPADDR1
STRING
The primary IP address of HSI.
HOST_IPADDR2
STRING
The secondary IP address of HSI.
Note
VSCA_IPADDR1
STRING
The primary IP address of the primary PGW 2200.
VSCA_IPADDR2
STRING
The secondary IP address of the primary PGW 2200.
Note
VSCB_IPADDR1
STRING
The primary IP address of the secondary PGW 2200.
Note
VSCB_IPADDR2
STRING
The secondary IP address of the secondary PGW 2200.
Note
VSCA_PORT_NUMBER1
[0-65535]
The first port number of the primary PGW 2200.
VSCA_PORT_NUMBER2
[0-65535]
The second port number of the primary PGW 2200.
Note
VSCB_PORT_NUMBER1
[0-65535]
The first port number of the secondary PGW 2200.
Note
VSCB_PORT_NUMBER2
[0-65535]
The second port number of the secondary PGW 2200.
Note
ClipClirSupported
STRING
CLI presentation or restriction is enabled if this parameter is present and set to anything other than "". For example, to enable CLIP/CLIR support, set this parameter explicitly to "Enabled."
Note
RaiSupported
STRING
RAI support is enabled if this parameter is present and set to anything other than "". For example, to enable RAI support, set this parameter to "Enabled."
DtmfSupportedDirection
STRING
This is set to "both", "tx," or "rx". If this parameter is not present or is set to any value other than "both," "tx," or "rx," the DTMF Relay feature is disabled.
DtmfSupportedType
STRING
This is set to "dtmf" or "basicString." If this parameter is not present or set to any other value, the DTMF Relay feature is disabled.
H225PavoSupported
STRING
Pavo support is enabled if this parameter is present and set to anything other than "". For example, set it to "Enabled."
PavoRedirScreeningInd
[0-3]
The value of the Pavo redirecting number screening indicator. (If this parameter is not provisioned, the default is Q.931 zero—user provided, not screened.)
PavoRedirReason
[0-15]
The value of the Pavo redirecting number reason field. This parameter has no default. If this parameter is not provisioned, the redirecting number parameter will not contain the Reason for Redirection field (octet 3b).
PavoRedirPresInd
[0-3]
The value of the Pavo redirecting number presentation indicator. (If this parameter is not provisioned, the default is Q.931 zero—no indication.)
CliInDisplaySupported
STRING
If this parameter is present and set to anything other than "", the Calling Number is also sent in the DISPLAY IE. The NetMeeting endpoint retrieves the calling party number from the DISPLAY IE in the H.225 setup message. To enable this parameter, set it to "Enabled."
T38MaxVal
STRING
The T38MaxVal parameter has the following optional attributes that can be assigned values in a specific range.
Note
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•
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T38Options
STRING
This T.38 Fax parameter is assigned one of the following optional values:
•
•
•
•
•
AsymmetricHandlingSupported
STRING
Asymmetric Codec Treatment support is enabled if this parameter is present and set to anything other than "". To enable Asymmetric Codec Treatment, set this parameter to "Enabled."
UseConfID
STRING
Use this parameter to specify the precedence of extracting the Global Call ID from the Conference ID or the GUID in the H.225 Setup message. The provisioning of this property to a value other than "" gives precedence to the Conference ID. For example, set it to "Enabled." To set the precedence to the GUID field, the crafts person can either delete the property from the config or set it to "".
DualCLISupported
STRING
To enable Dual CLI support (see H.246 Annex C), set this parameter to anything other than "". For example, to explicitly enable Dual CLI support, set this parameter to "Enabled."
InjectPi8
STRING
If this parameter is set to a text value (for example, "enabled" or "true"), the HSI inserts a progress indicator value of 8 into the H.225 alerting message, which allows creation of a backward speech path. To disable this feature, you can delete the parameter using the command prov-dlt or issue the prov-ed command and set the value to "".
Setting the InjectPi8 parameter is required if the PSTN network does not notify the HSI that inband information is available. For instance, when no Optional Backward Call Indicator is present, a backward speech path will not be available.
CC_HC_PortedNumber
STRING
Enable mapping the H.323 cause code 14 (PortedNumber) to a supported EISUP cause code.
Because CC_HC_PortedNumber is a static parameter, after you provision it, you must restart the HSI.
The following provisioning example shows how you might provision CC_HC_PortedNumber:
gw mml> prov-sta::srcver=active,dstver=HCPortedNumgw mml> prov-add::name=CCPackage,CC_HC_PortedNumber=CC_EC_PortedNumbergw mml> prov-cpygw mml> restart-softwConnectedCallsMaxDuration
[0-65535]
Establishes the maximum duration for a connected call.
When a call exceeds the value set for ConnectedCallsMaxDuration, the HSI clears the call.
The value set for ConnectedCallsMaxDuration is in hours. The default value is 0 (zero). If the HSI retains the default value, a call could remain in the connected state indefinitely.
Because CC_HC_PortedNumber is a static element, after you provision it, you must restart the HSI.
The following provisioning example shows how you might provision ConnectedCallsMaxDuration:
gw mml> prov-sta::srcver=active,dstver=connectedDurationgw mml> prov-add::name=CCPackage, ConnectedCallsMaxDuration=100gw mml> prov-cpygw mml> restart-softw
1 PGW = Public Switched Telephone Network (PSTN) Gateway
Changing Static System Data
To change static system data, you must first determine if it is acceptable to stop currently active calls in 20 seconds. If it is acceptable to stop active calls in 20 seconds, change static system data using the following procedure:
Step 1
Step 2
Note
Step 3
This command stops the HSI application in 20 seconds and then restarts it. The restarted HSI application reads the changed static system data parameters.
Step 4
If you wish to change static system data but it is not acceptable to stop active calls in 20 seconds, use the following procedure:
Step 1
Step 2
Step 3
Step 4
Step 5
This command stops the HSI application and then restarts it. The restarted HSI application reads the changed static system data parameters.
Step 6
Dynamic System Data
To modify the dynamic system data parameters in Table 3-4, use the sys_config_dynamic MML name variable for the prov-add, prov-dlt, and prov-ed commands. You need not halt and restart call processing for the changes to take effect.
In the following example, the prov-add command adds the dynamic system data parameter OVLDLEVEL1PERCENT to a dynamic configuration file. The prov-ed command modifies the value of the OVLDLEVEL1PERCENT parameter. The prov-dlt command deletes the OVLDLEVEL1PERCENT parameter from the dynamic configuration file.
Example
prov-add:name=sys_config_dynamic,OVLDLEVEL1PERCENT=20prov-ed:name=sys_config_dynamic,OVLDLEVEL1PERCENT=25prov-dlt:name=sys_config_dynamic,OVLDLEVEL1PERCENTThe MML commands write the parameters in Table 3-4 to a dynamic configuration file or to a section within a file.
Table 3-4 Dynamic System Data Parameters
LOGDIRECTORY
Specifies the directory used when the active log file is created, and also specifies the directory where the rotated log file is stored.
/var/log/
LOGFILENAMEPREFIX
Specifies the filename prefix used when the log files are created or rotated. The .log postfix is appended to the end of the filename to establish the name of the active log file.
platform.log
LOGPRIO
Defines the initial logging levels. By default it is set to TRACE. When the system initializes and is running, the levels set for individual packages (0x0000 to 0xFFFF) determine the log levels. See the "Logging Levels" section on page 4-10.
TRACE
LOGFILEROTATESIZE
Triggers a log file rotation based on the size of the active file. The application regularly checks the current size of the file to determine whether a rotation is required. If a file rotation is triggered by this parameter, the rotated file might be slightly larger than the size specified by this parameter. This parameter triggers a file rotation and also resets the timer associated with the LOGFILEROTATEINTERVAL parameter.
10 Mb
LOGFILEROTATEINTERVAL
Triggers a log file rotation based on the time elapsed since the previous rotation. This timer is reset after any rotation occurs, regardless of the cause or trigger of the rotation.
1440 minutes
(24 hours)IPADDRNMS
Defines the IP address of the network management system.
—
OVLDSAMPLERATE
Defines the frequency of CPU sampling and threshold checking.
3000 millisecond (ms) polling rate
OVLDLEVEL1PERCENT
Indicates what percentage of calls should be rejected when an overload condition occurs. This parameter is used in conjunction with the OVLDLEVEL1FILTER parameter. The overload level 1 value is the lowest level of overload and must be less than or equal to the provisioned values for OVLDLEVEL2PERCENT and OVLDLEVEL3PERCENT.
Note
20
OVLDLEVEL1FILTER
Indicates what call types should be gapped if an overload level 1 condition occurs. The possible values are:
•
•
Note
Normal
OVLDLEVEL1THRESHLOWERCALLS
The number of active calls below which the application load must fall before the system removes the overload level 1 condition.
1800
OVLDLEVEL1THRESHUPPERCALLS
The number of simultaneous active calls that triggers an overload level 1 condition.
1900
OVLDLEVEL1THRESHLOWERCPU
The CPU utilization level below which the application must fall before the system removes the overload level 1 condition.
60
OVLDLEVEL1THRESHUPPERCPU
The level of CPU utilization that triggers an overload level 1 condition.
65
OVLDLEVEL2PERCENT
Indicates what percentage of calls should be rejected when an overload condition occurs. The parameter is used in conjunction with the OVLDLEVEL2FILTER parameter. This is the second level of overload and must be less than or equal to the provisioned value of OVLDLEVEL3PERCENT and greater than or equal to the provisioned value of OVLDLEVEL1PERCENT.
Note
75
OVLDLEVEL2FILTER
Indicates what call types should be gapped if an overload level 2 condition occurs (see OVLDLEVEL1FILTER).
Normal
OVLDLEVEL2THRESHLOWERCALLS
Determines the number of active calls below which the application load must fall in order for the overload level 2 condition to be removed.
2000
OVLDLEVEL2THRESHUPPERCALLS
Determines how many simultaneous active calls trigger an overload level 2 condition.
2200
OVLDLEVEL2THRESHLOWERCPU
Determines the level of CPU utilization below which the application must fall in order for the overload level 2 condition to be removed.
70
OVLDLEVEL2THRESHUPPERCPU
Determines the level of CPU utilization that triggers an overload level 2 condition.
80
OVLDLEVEL3PERCENT
Indicates what percentage of calls should be rejected when an overload condition occurs. The parameter is used in conjunction with the OVLDLEVEL3FILTER parameter. This is the highest level of overload and must be greater than or equal to the provisioned values for OVLDLEVEL1PERCENT and OVLDLEVEL2PERCENT.
Note
90
OVLDLEVEL3FILTER
Indicates what call types should be gapped if an overload level 3 condition occurs (see OVLDLEVEL1FILTER).
Normal
OVLDLEVEL3THRESHLOWERCALLS
Determines the number of active calls below which the application load must fall in order to remove the overload level 3 condition.
2300
OVLDLEVEL3THRESHUPPERCALLS
Determines how many simultaneous active calls trigger an overload level 3 condition.
2400
OVLDLEVEL3THRESHLOWERCPU
Determines the level of CPU utilization below which the application must fall in order to remove the overload level 3 condition.
85
OVLDLEVEL3THRESHUPPERCPU
Determines the level of CPU utilization that triggers an overload level 3 condition.
95
CIAGENTSCANPERIOD
Specifies the frequency with which the CIagent polls the CPU utilization.
—
ALARMDEBOUNCETIME
Specifies the length of time that an alarm condition must persist before being reported, and any associated action taken.
0
CALLREFERENCEUSAGE
Determines which call reference identity is passed on to the PGW 2200 (call reference field or Conference ID).
—
DISKUSAGELIMIT
Represents a percentage of disk occupancy.
The application continually polls the system for disk occupancy, and if the percentage rises above the limit set by DISKUSAGELIMIT, the LOW_DISK_SPACE alarm is raised.
DISKUSAGELIMIT has a default value of 95 percent. The value range is 0-100, inclusive. When dynamically provisioned, the parameter DISKUSAGELIMIT, if not set within that range, is set to the default value (95) and the CONFIGURATION_ FAILURE alarm is raised.
95
RegFailureReleaseCause
This parameter specifies the Q.850 release cause, which the HSI uses after the HSI fails three times to register to a gatekeeper.
This parameter is assigned a value in the range 1—127.
—
UsePayloadTypeMapping
When set to a non-empty value, the HSI negotiates the SDP payload type to be identical to the value received from the Cisco PGW 2200. By default, this parameter is disabled (set to an empty value). In the default case, the HSI uses the payload type that is hardcoded (static) in the HSI.
To enable payload mapping issue the following MML command:
prov-add:name=sys_config_dynamic, UsePayloadTypeMapping="true"To disable payload mapping issue the following MML command:
prov-ed: name=sys_config_dynamic, UsePayloadTypeMapping="""_"
H.323 Stack Configuration
The parameter name is based on the ASN.1 paths; but, in some cases, the parameter name has been shortened for convenience. For example, "capabilities" has been shortened to "caps."
The case of the parameter name reflects exactly the ASN.1 definitions; but case is not important to MML configuration.
Nonprovisionable Data
The parameters in Table 3-5 cannot be altered through MML commands.
MML Provisionable Data
H.323 System Parameters
The parameters in Table 3-6 are required for H.323 stack initialization. To modify the parameters in Table 3-6, use the h323_sys MML name variable for the prov-add, prov-dlt, and prov-ed commands. Stop and restart the application for these changes to take effect.
Note
Q.931 Parameters
To modify the parameters listed in Table 3-7, use the q931 MML name variable for the prov-add, prov-dlt, and prov-ed commands.
In the following example, the prov-add command sets the Q.931 parameter maxCalls to the value 2000.
Example
prov-add:name=q931,maxCalls=2000The Update Type column in Table 3-7 shows when the change to a parameter takes effect once a change is made:
•
•
•
Note
Note
Note
RAS Parameters
The parameters in Table 3-8 are required for RAS stack initialization. To modify the RAS parameters, use the ras MML name variable for the prov-add, prov-dlt, and prov-ed commands.
In the following example, the prov-add command sets the RAS parameter maxfail to the value 3.
Example
prov-add:name=ras,maxfail=3The array index [i] in some of the parameter names in the first column of Table 3-8 must be replaced with a valid braced index from 1 to 20, and must be continuous and unique (that is, it must contain no duplicates).
The Update Type column in Table 3-8 shows when the change to a parameter takes effect after it is modified:
•
•
•
Note
Note
Note
H.245 Parameters
To modify the H.245 parameters listed in Table 3-9, use the h245 MML name variable for the prov-add, prov-dlt, and prov-ed commands.
In the following example, the prov-add command sets the H.245 parameter masterSlave.timeout to the value 5.
Example
prov-add:name=h245,masterSlave.timeout=5The Update Type column in Table 3-9 shows when a change to an H.245 parameter takes effect after it is modified:
•
•
•
Note
Table 3-10, Table 3-11, and Table 3-12 list the parameters and modes related to the configuring of codecs. The array index [i] must be replaced with a valid braced index from 1 to 20. The braced index must be continuous and unique (that is, there must be no duplicates).
Codec Selection
The Cisco HSI negotiates the media stream codec to establish a match between the PSTN MGCP media gateway (for example, the Cisco AS5xxx series or Cisco MGX series) and the H.323 endpoint or gateway. To match codecs, the MGCP gateway must be configured to match what is expected at the H.323 end. Similarly, the Cisco HSI also must be configured with the same codecs.
The Cisco HSI receives a list of codecs from the MGCP gateway and matches the listed codecs to the codecs that are configured on the HSI. The HSI advertises all of the successful matches in the H.245 terminalCapabilitySet messaging with the H.323 endpoint.
It is important to determine and configure the "frames-per-packet" value correctly on the Cisco HSI per codec. If "frames-per-packet" value is incorrect, the codec may not be negotiated successfully between the HSI and the H.323 endpoint.
It is also important to configure the MGCP gateway correctly. The gateway should be configured to provide "static payload" values for the required codecs, rather than dynamic payload types (see Table 4 in RFC 3551, Schulzrinne and Casner).
Quick Reference for Important Parameters
Table 3-13, Table 3-14, Table 3-15, and Table 3-16 can be used in initial HSI configuration. The tables present parameters that you might use frequently to align the Cisco HSI with an existing PSTN or Voice over IP network.
Table 3-13 presents important call control parameters.
The following MML command example shows the command sequence used to provision the call control parameters provided in the preceding table.
Example
mml> prov-sta::srcver=active, dstver=myconf> prov-ed:name=CCPackage, A_CC_ANumDataSI=2> prov-cpy> restart-softwTable 3-14 presents important static system data parameters.
Table 3-14 Common Static System Data Parameters
CarrierCodeMapping
•
•
•
Allows the mapping of a special tech prefix (the format of which is CCxCy) to the DestinationCircuitID "group" field in the ARQ message. This feature works only with IOS Gatekeeper build Release 12.2(15)T10 or above. See the section "Carrier Code Mapping" for more information.
ClipClirSupported
•
•
•
Allows transit of CLI presentation/screening information.
Note
DtmfSupportedType
•
•
Selects the DTMF type during H.245 terminal capabilities exchange.
Note
DtmfSupportedDirection
•
•
•
•
Selects DTMF transit direction.
Note
H225PavoSupported
•
•
•
Allows transit of redirecting number parameter (contained in Cisco CallManager H.225 setup messages—nonStandardControl field).
RaiSupported
For example:
•
•
•
Allows H.225 RAS RAI messages to be sent to the gatekeeper if the E-ISUP link fails or if the HSI is under heavy load.
Note
NotifyMsgEnabled
For example:
•
•
•
Allows transit of connected number, display information, and generic notification indicator in H.225 Notify messages.
VSCB_IPADDR1/2
IP address, for example: "10.10.10.1"
Allows IP address configuration of second PGW.
VSCB_PORT_NUMBER1/2
Port number, for example: 8003
Allows port configuration of second PGW.
The following MML command example shows the command sequence used to provision the static system data parameters provided in the preceding table.
Example
mml> prov-sta::srcver=active, dstver=myconf> prov-ed:name=SYS_CONFIG_STATIC, DtmfSupportedType="dtmf"> prov-cpy> restart-softwTable 3-15 presents common RAS parameters.
Table 3-15 Common RAS Parameters
gateway.prefix[1]
gateway.prefix[2]
For example: 020
HSI prefix (for gatekeeper registration)
timeToLive
Integer (to specify number of seconds)
for example, 45Note
RAS registration time to live.
See Table 3-8.
The following MML command example shows the command sequence used to provision the RAS parameters provided in the preceding table.
Example
mml> prov-sta::srcver=active, dstver=myconf> prov-ed:name=RAS, timeToLive=45> prov-cpy> restart-softwTable 3-16 presents common H.245 parameters for enabling the G.729 codec.
The following MML command example shows the command sequence used to provision the H.245 parameters provided in the preceding table for enabling the G.729 codec. Provisioning the G.729 codec on the Cisco HSI supports passing SS7 calls to the Cisco CallManager through a gateway running the Media Gateway Control Protocol (MGCP).
Example
prov-sta::srcver="active",dstver="g729"prov-add:name="H245",caps.table[4].audio.g729="2"prov-add:name="H245",caps.table[4].entryno="729"prov-add:name="H245",chan[4].audio.g729="2"prov-add:name="H245",chan[4].name="g729"prov-add:name="H245",modes[3].audio.g729=""prov-add:name="H245",modes[3].name="g729"
HSI Feature Configuration
This section describes how to enable the following HSI features:
•
•
•
•
•
Asymmetric Codec Treatment
The Asymmetric Codec Treatment feature averts the potential for inconsistencies in codec selection, which can result if the open channel requests are sent by each endpoint at nearly the same time, so that neither side has received an open channel request prior to sending one. In practice, such asymmetric conditions occur only for slow start calls. When there is a fast start recipient, both channels agree to use the same codec in unison.
The Asymmetric Codec Treatment support is enabled if this parameter is present and set to anything other than "". For example, support is enabled if the parameter is explicitly set to "Enabled." To enable Asymmetric Codec Treatment, enter the following command:
prov-add:name=sys_config_static, asymmetrichandlingsupported = "Enabled"Empty Capability Set
The Empty Capability Set feature enables an H.323 endpoint to send a TCS message with empty capabilities during a call. The TCS message causes the audio channels to close. This action enables the negotiation and opening of new audio channels.
The Empty Capability Set feature is useful if the H.323 endpoint wishes to change the audio codec during a call or if the endpoint needs to divert the media streams to a different location. Typically, the feature is used to place a call on hold to disable the media stream until the user presses the Resume button.
The Empty Capability Set feature on the HSI requires no provisioning.
Note
H.323 Hairpin
The H.323 Hairpin feature can be used to connect a call between two H.323 endpoints without the use of resources on the media gateway. For example, the PGW can respond to the dialed number in an incoming H.323 call by routing the call to another HSI (perhaps the same HSI) rather than routing the call to the PSTN. In this case, the originating and terminating HSIs establish the call normally but pass the H.245 address of the H.323 endpoints. This enables the two endpoints to use H.245 to negotiate media channels with each other directly, independent of the HSI.
The H.323 Hairpin feature on the HSI requires no provisioning. However, to operate throughout the system, H.323 Hairpin must be enabled on the PGW. On the PGW, you enable H.323 Hairpin through a trunk group property by issuing the following commands:
prov-add:trnkgrpprop:name="2000",AllowH323Hairpin="1"prov-add:trnkgrpprop:name="3000",AllowH323Hairpin="1"
Note
Refer to Cisco PGW and Cisco IOS documentation at www.cisco.com for further information on these commands.
T.38 Fax
The T.38 Fax feature enables the HSI to alter a call, initially established for voice, to support a fax transmission.
When a fax call is initiated, a voice call is established. When the terminating gateway detects the fax tone generated by the terminating fax machine, the gateway initiates a T.38 mode request using H.245 procedures from the terminating gateway. If the opposite end of the call acknowledges the T.38 mode request, the initial audio channel is closed and a T.38 fax relay channel is opened.
You enable T.38 Fax for the HSI by specifying static system data parameters. By default, T.38 is provisioned on the HSI by use of the following commands:
prov-add:name=sys_config_static,t38maxval="MaxBit 0x90, FxMaxBuf 0xc8, FxMaxData 0x48"prov-add:name=sys_config_static,t38options="FxFillBit 0, FxTransMMR 0, FxTransJBIG 0, FxRate Trans, FxUdpEC Red"Table 3-3 describes the T.38 static system data parameters. The T.38 parameters for HSI correspond to T.38 parameters proposed in the ITU T.38 recommendation.
Configuring T.38 Fax on the Cisco PSTN Gateway
To enable T.38 Fax throughout the system, you must enable T.38 Fax on the Cisco PGW. On the PGW, T.38 is enabled through a trunk group property by use of the following MML command:
prov-add:trnkgrpprop:name="2000",FaxSupport="1"Configuring T.38 Fax on a Cisco IOS H.323 Gateway
Enable T.38 Fax on a Cisco IOS H.323 gateway by issuing the following IOS commands:
voice service voipfax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback noneConfiguring T.38 Fax on a Cisco IOS MGCP Gateway
Enable T.38 fax on a Cisco IOS MGCP gateway by issuing the following IOS commands:
voice service voipfax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback nonemgcp package-capability fxr-packageRefer to PGW and Cisco IOS documentation at www.cisco.com for further information on these commands.
HSI INFORMATION Message Support
Cisco CallManager uses the H.225 INFORMATION message during transfer to indicate that ringback tone is on or off. The Cisco HSI now supports this message to correctly interoperate with Cisco CallManager.
Support for the H.225 INFORMATION message is enabled by default. A craftsperson can disable H.255 INFORMATION message support through a new property called Information MsgDisabled by issuing the following MML command:
prov-add:name=sys_config_static,informationmsgdisabled = "True"HSI Support for Tech Prefixes
The Cisco HSI now maps the "*" (asterisk, or star) and "#" (number sign, or hash) H.225 prefixes to the PGW for H.323 to PSTN calls as follows:
•
•
•
•
The craftsperson can change these values by issuing the following MML command:
prov-ed:name=ccpackage,hash='C'Cisco HSI now maps the EISUP "B" to "*" and "C" to "#" (Called Party Number) for PSTN to H.323 calls.
H.323 to SIP Interworking
H.323 to SIP and SIP to H.323 interworking supports basic calls between SIP and H.323 based networks, which are connected through the Cisco PGW 2200.
Support for the interoperation of SIP to H.323 is present in the Cisco HSI software, Release 4.2 and the Media Gateway Controller Protocol software running on the Cisco PGW 2200, Release 9.6. See the Release Notes for the Cisco Media Gateway Controller Software Release 9.6.
No additional HSI configuration is needed for support of this interworking functionality.
HSI Notify Support
Cisco Call Manager uses H.225 NOTIFY messages during call transfer to indicate the transferees name and number information to the calling party. That is, when A calls B, and B transfers the call to C, the information about C is sent to A by means of the H.225 NOTIFY message.
The HSI supports this message to correctly interoperate with Cisco Call Manager.
To enable this functionality, enter the following commands in an MML provisioning session:
prov-add:name=sys_config_static, NotifyMsgEnabled=enabledprov-cpyrestart-softwFor this functionality to be disabled, the NotifyMsgEnabled parameter entry must be deleted or set to "", as shown in the following example:
prov-ed:name=sys_config_static, NotifyMsgEnabled=""prov-cpyrestart-softwAdjustable Packetization
The Cisco HSI enables adjusting of the payload size of H.323 calls. The HSI can reduce the packetization from its advertised value to the value advertised by the remote endpoint.
Rather than reject calls, the HSI reduces payload size from what is configured in the HSI to what is proposed by the Terminal Capability Set (TCS). The ability to adjust the packetization value is important for H.323 to H.323 calls when the MGCP gateway is not involved in the call.
The packetization values are provisioned on the HSI because these values are not included in the SDP. Previously, the HSI did not lower a packetization value because some endpoints failed when the RTP packetization differed from the H.245 negotiated value.
Note
Adjustable packetization enables the HSI to negotiate a packetization period that might differ from that provisioned on the Media Gateway. The codec packetization is asymmetric, which can cause problems with some endpoints.
Figure 3-1 illustrates how the HSI synchronizes the packetization value with a remote endpoint.
Figure 3-1 Synchronizing Packetization Values
Enabling Dynamic Packetization
A new parameter is available in Cisco HSI 4.1 Patch 9 that enables the HSI to synchronize the packetization value with the packetization required by a remote endpoint.
The HSI parameter is DynamicPacketizationSupported. To enable Dynamic Packetization Support, issue the following MML command:
prov-add:name=sys_config_dynamic, DynamicPacketizationSupported="enabled"Carrier Code Mapping
Carrier Code Mapping enables routing based on a prefix or carrier identifier. When the HSI receives a called party number with the format CCxCy from the PGW 2200 (in which C is the single overdecadic digit C and x is the single- or multiple-digit carrier code and y is the single- or multiple-digit destination number), the HSI can advise the gatekeeper of the carrier code.
Figure 3-2 illustrates how carrier code mapping works. In this illustration, the call is to 0800123456, and the PGW determines that it is destined to be completed by the carrier numbered 999.
Figure 3-2 Carrier Code Mapping
The HSI inserts y into the e164 destinationInfo field of the ARQ message and into the H.225 SETUP message; it inserts x into the DestinationCircuitID group field in the ARQ message.
The dial plan on the PGW 2200 must be configured to perform the appropriate digit modification to prepend the carrier ID to the called party number in the special CCxCy carrier-code format.
To configure the Cisco HSI to perform carrier code mapping, issue the following MML commands:
prov-add:name=sys_config_static, CarrierCodeMapping="enabled"restart-softw
Note
Configuring Clear Channel on the Cisco HSI
The Clear Channel capability (identified as G.Clear or gclear in this document) enables support for both voice and data calls on a network. However, the end applications are responsible for packet loss and error recovery. For more information, refer to the document G.Clear, GSMFR, and G.726 Codecs and Modem and Fax Passthrough for Cisco Universal Gateways at http://www.cisco.com/en/US/products/sw/iosswrel/ps1839/products_feature_guide09186a00800b3568.html.
Note
The Cisco HSI interoperates with Cisco voice gateways (for example, the Cisco AS54xx series or VISM), which advertises G.Clear capability via MGCP signaling using the following methods: G.Clear, G.nX64, CCD. The Cisco HSI automatically selects the correct method depending on the gateway that originates or terminates the call.
Refer to the Cisco H.323 Signaling Interface User Guide for information regarding the use of HSI MML commands.
Table 3-17 presents examples of configuration commands that may be required to implement a particular G.Clear configuration.
Configuring G.726 on the Cisco HSI
The G.726 codec enables transcoding a PCM channel to or from an ADPCM data stream. The standard supports four data rates:16, 24, 32 and 40 kbit/sec.
Note
G.726 capability is advertised by the Cisco HSI and other H.323 gateways/endpoints in H.225 fast-start elements, in H.245 (tunneled or a separate TCP/IP connection) terminal capability (TCS) messages, and open logical channel (OLC) messages.
Currently, H.323 devices use several different methods to advertise G.726. ITU G.726 Annex B defines one method, referred to in this document as g726-generic. Cisco H.323 gateways (for example, the Cisco AS5400) support an alternate method referred to as g726-cisco. There is another method used by the OpenH323 project; however, the Cisco HSI does not support that method.
MGCP gateways advertise G.726 capability using the method described in RFC 3551 (RTP Profile for Audio and Video Conferences with Minimal Control). The four data rates use dynamic payloads; however, the 32kbit/sec data rate, alternatively, can have a static payload value of 2 (this alternative value is being phased out).
You can configure the Cisco HSI for 32kbit/sec MGCP support using dynamic or static payload values. In addition, you can configure the Cisco HSI to support g726-generic and/or g726-cisco for the H.323 signaling. If possible, it is best to select g726-cisco for your network because it offers additional flexibility.
The g726-generic method cannot indicate the data rate in H.245 TCS messages. The ITU standard specifies that the data rate is only advertised in the OLC messages.
Note
The fact that the g726-generic method cannot indicate the data rate in an H.245 TCS message is not a problem if the MGCP gateway and your network are designed to support all data rates for this codec. However, if all data rates are not supported, it is possible for the remote endpoint/gateway to select a non-preferred or non-supported data rate in the OLC message.
Note
If a data-rate preference list specifies only a single rate (for example, G.726-16kbit/sec), it is not possible to advertise this fact in the TCS message. Subsequently, the remote endpoint may attempt to open the media stream using an unsupported data rate (perhaps, G.726-24kbit/sec).Whenever OLC messages are exchanged and a non-supported G.726 data rate is detected, to prevent unnecessary call clearing, the Cisco HSI always attempts to send the data rate selection to the MGCP gateway. If the MGCP gateway does not support the selected data rate, it sends a message to the Cisco PGW to clear the call.
If a non-preferred G.726 data rate is selected over a higher-preference codec, the HSI will continue with the call using the non-preferred data rate. This is preferable to the alternative (aborting the media stream, invoking an empty capability exchange followed by a re-negotiation of codecs and new OLC messaging). The alternative causes call processing delay and overhead associated with switching media streams.
Note
Refer to the Cisco H.323 Signaling Interface User Guide for information about Cisco HSI MML commands.
Table 3-18 presents examples of configuration commands that may be required to implement a particular G.726 configuration.
Configuring G.729 Annex and G.729 Annex B
Table 3-18 presents examples of configuration commands that may be required to implement a particular configuration of G.729 Annex A or G.729 Annex B.
Non-RAS Mode
The Non-RAS mode feature of the Cisco Media Gateway Controller (MGC) software running on the Cisco PSTN Gateway (PGW) 2200 and Cisco H.323 Signaling Interface (HSI) enables service providers to create a simplified network without a gatekeeper, for networks that do not require gatekeeper features such as security.
In Non-RAS mode, the Cisco MGC converts called numbers into one or more IP addresses in the dial plan to support load sharing over multiple HSIs. This mechanism supports H.323 endpoints that have multiple IP addresses. With such support, when an initial IP address does not work, subsequent attempts are made to the alternative IP addresses for the same endpoint.
If the Cisco MGC sends an IP address to the HSI over E-ISUP, the HSI sends a SETUP directly to the endpoint. In addition, the Cisco MGC stores the H.323 Destination IP address in the Cisco MGC's Call Detail Record (CDR).
Non-RAS mode enables deployment of a Cisco PGW 2200 with a connected Cisco HSI without a gatekeeper in networks that do not require admission, location of the H.323 endpoint, or when selection of the endpoint does not benefit from H.323 mechanisms such as Resource Availability Indication (RAI). Examples of such deployments include Cisco CallManager (CCM), H.323 ITS, or cases in which an H.323 gateway provides the only connection to a PBX.
To enable the Non-RAS mode of operation on the Cisco HSI, the feature must also be enabled on the Cisco PGW 2200.
Note
Enabling the NON-RAS Mode of Operation on the Cisco HSI
To enable Non-RAS mode on the Cisco HSI, enter the following MML command:
prov-add:name=RAS, manualRASDisabling the Non-RAS Mode of Operation on the Cisco HSI
To disable Non-RAS mode, enter the following MML command:
prov-dlt:name=RAS, manualRASFor information on enabling Non-RAS mode on the Cisco PGW 2200, see the feature module document Non-RAS Mode Feature.
