Fax, Modem, and Text Support over IP Configuration Guide, Cisco IOS Release 12.4T
Configuring Fax Rollover
Configuring Fax Rollover
Last Updated: May 4, 2012
This chapter describes configuration for fax rollover on an IP network. Fax rollover occurs when a T.38 fax is configured to roll over to a T.37 fax session when the far end is busy or unreachable.
History for the Fax Rollover Feature
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Prerequisites for Configuring Fax Rollover
This section describes prerequisites for configuring fax rollover.
Restrictions for Configuring Fax Rollover
The following restriction applies to fax rollover:
Information About Fax Rollover
The on-ramp gateway receives fax calls at an E.164 number. The gateway attempts to route fax calls using fax relay. If the attempt fails, the call is forwarded to an SMTP server by a mail transfer agent (MTA) using T.37-standard protocols for store-and-forward fax.
Fax rollover is configured by installing the TCL IVR rollover application to the on-ramp gateway and adding the application to the POTS dial peer that answers T.38 calls.
The TCL IVR application has a procedure for setting up the call, waiting for success, and, upon receiving a busy or gateway-down message, setting up the same call again with new destination parameters. When the call is returned to the originating gateway, the gateway searches for a new VoIP dial peer with the same destination number, and a preference equal to or greater than the first dial peer that it found. If it finds one, it sets up the call again.
Dial peers for the fax rollover application include at least one inbound dial peer to receive calls from the PSTN and at least two outbound dial peers, one for fax relay and one for store-and-forward fax.
The inbound dial peer describes the inbound call leg from the telephony connection to the gateway and is called a plain old telephone service (POTS) dial peer. POTS dial peers define the characteristics of the telephony (PSTN) connection between the sending fax device or voice instrument and the gateway to the IP network. In general, the gateway uses the line characteristics defined by POTS dial peers to determine call type and call destination.
The gateway then finds an outbound dial peer whose configured parameters match these attributes and routes the call to it. You can establish more than one POTS dial peer if you want different incoming calls to receive different handling. The fax rollover application is enabled on the inbound dial peer.
One of the two types of outbound dial peers in the gateway router is the Voice-over-IP (VoIP) dial peer, which describes the fax relay call leg that is outbound from the router.
The second type of outbound dial peer on the on-ramp gateway is the Multimedia-Mail-over-IP (MMoIP) dial peer, which describes an IP call leg for store-and-forward fax. The MMoIP dial peer is configured with the fax_on_vfc_onramp_app IVR application in the outbound mode, which is the standard configuration for store-and-forward fax.
How to Download the Fax Rollover Application File
This section describes how to download the TCL script and default audio prompt files used with the fax rollover application. You must download these files before you can configure the fax rollover application. The script is contained in a zip file on Cisco.com.
The Cisco IOS File System (IFS) reads the files, so any IFS-supported URL can be used as a location for the files. URLs can include TFTP, FTP, or a pointer to a device on the router. For more information, see the TCL IVR API Version 2.0 Programmer's Guide.
1. Log in to the Cisco website and go to http://www.cisco.com/cgi-bin/tablebuild.pl/tclware.
2. Select and download this zip file: TCLware.2.0.1.zip.
3. Unzip the files.
4. Move the application script file to a location that can be accessed by your gateway using a URL address.
How to Configure Fax Rollover
Use the following tasks to configure fax rollover on an on-ramp gateway:
Loading the Fax Rollover Application on the Gateway
Fax rollover is an IVR application that is written in a TCL script. The script must be downloaded from Cisco.com and installed on your network before the fax rollover application can be loaded on the gateway. See the How to Download the Fax Rollover Application File.
Install the script at a location that is accessible by the gateway and load it using a name of your choice. All later commands that refer to the fax rollover application use the name you selected when loading the the application on the gateway.
2. configure terminal
4. service service-name location
Configuring Dial Peers
Configuration of dial peers for fax rollover is described in the following sections:
Configuring Inbound POTS Dial Peers
The inbound POTS dial peers associates a destination pattern and call type with each incoming call so that the call is properly routed to an outbound dial peer. The fax rollover application is enabled on the inbound POTS dial peer.
2. configure terminal
3. dial-peer voice tag pots
4. application application-name
6. incoming called-number string
Configuring One or More Outbound VoIP Dial Peers for T.38 Fax Relay
The purpose of configuring an outbound VoIP dial peer for T.38 fax relay is to enable call handling from the on-ramp gateway to a destination in the packet network. For fax relay, this destination is typically an incoming dial peer on an off-ramp gateway. If you are configuring T.38 fax relay as the fax component of your fax detection application, see the "Configuring One or More Individual VoIP Dial Peers for T.38 Fax Relay" section on page 10 .
Configuring One or More Outbound MMoIP Dial Peers for T.37 Store-and-Forward Fax
The purpose of configuring an outbound MMoIP dial peer for store-and-forward fax is to enable call handling from the on-ramp gateway to a destination in the packet network. For store-and-forward fax, this destination is typically an SMTP or ESMTP server. If you are configuring T.37 store-and-forward fax as the fax component of your fax detection application, see "Configuring One or More Outbound POTS Dial Peers" section on page 28.
Use the following commands to troubleshoot fax rollover:
Configuration Example for Fax Rollover
T.38 Fax Rollover to T.37 Example
The following example shows dial peers configured for T.38 fax rollover to T.37 fax.
. . voice hunt user-busy ! ! Inbound peer for T.38/T.37 on-ramp rollover operation. ! This peer includes the TCL application for rollover operation. dial-peer voice 70 pots application app_lib_rollover incoming called-number 5...... port 1/1:0 ! ! Outbound peer for T.38 ingress gateway. ! This peer requires a lower preference number than the next matching peer. dial-peer voice 71 voip preference 1 destination-pattern 5550119 session target ipv4:10.14.120.109 fax protocol t38 ls_redundancy 0 hs_redundancy 0 ! ! Outbound peer for T.37 on-ramp operation. dial-peer voice 72 mmoip preference 2 ! The application name below must be exactly as shown! application fax_on_vfc_onramp_app out-bound destination-pattern 5550119 session target mailto:$email@example.com information-type fax
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Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.
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