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Cisco BTS 10200 Softswitch T.38 Fax Relay
Feature History
Release Modification
900.03.02.00 This feature was initially introduced on the Cisco BTS 10200 Softswitch
in Release 3.2.
This Feature Module describes the support provided by the Cisco BTS 10200 Softswitch software in
Release 3.2 and 3.3 for ITU-T recommendation T.38 Fax Relay, T.38 Fax Relay is used for transporting
real-time Group 3 Fax documents over the Internet Protocol (IP), commonly used in packet networks.
This feature modul
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Cisco BTS 10200 Softswitch T.38 Fax Relay Introduction Introduction Most current fax devices are Group 3 compliant. Fax Group 3 is a standards-based technology that consists primarily of International Telecommunications Union (ITU) T.4 and T.30 recommendations. ITU T.4 pertains to how the fax image is encoded by a fax device, and ITU T.30 details the facsimile negotiations and communication protocol. T.30 is the standard procedure for fax transmission in the public switched telephone
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Cisco BTS 10200 Softswitch T.38 Fax Relay Introduction When page transmission occurs, a bit rate is used that is substantially higher than the initial 300 bps used in the call setup negotiation. The bit rate used for the page transmission is confirmed during training. Following are some of the common rates used in fax page transmission: – V.27ter – 2400/4800 bps – V.29 – 7200/9600 bps – V.17 – 14400 bps Note The specifications used for page transmission (V.27ter, V.29, V.17) and fax ne
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Cisco BTS 10200 Softswitch T.38 Fax Relay T.38 Benefits Fax Modes Existing H.323-based VoIP networks cannot interoperate with MGCP-controlled media gateways. Starting in this release, the Cisco BTS 10200 Softswitch software provides a gateway interface that supports the H.323 protocol. This allows MGCP-controlled gateways to interwork with H.323 VoIP ports. In the Call Agent (CA)-controlled mode the Cisco BTS 10200 Softswitch can mediate fax control signaling using T.38 fax relay attr
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Cisco BTS 10200 Softswitch T.38 Fax Relay T.38 Benefits connection parameters on the remote H.323 gateway after the logical channels are established. For modifying the connection parameters, H3A implements a mechanism called “sending Empty Capability Set (ECS).” In prior releases of the Cisco BTS 10200 Softswitch software, H3A supported this capability only for IVR applications. Note Any gateway that requires closure of both logical channels after sending ECS is not supported by the
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Cisco BTS 10200 Softswitch T.38 Fax Relay T.38 Benefits The negotiated fax mode is provided in an extension to the LocalConnectionOption (LCO) parameter of the CRCX message that the CA sends to MGCP-controlled gateways, which allows the CA to give the gateway up front instructions on how to handle fax for any given connection. This reduces the number of messages required between the CA and the gateway, which reduces the time to switch to the T.38 media format. The syntax of the fx:
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Cisco BTS 10200 Softswitch T.38 Fax Relay External Interfaces External Interfaces This section contains information about the external operational, management, and administrative interfaces for the T.38 Fax Relay feature, which include the following: • Billing Interface • Alarms/Events • Measurements • Provisioning Billing Interface Three new fields have been added to the Call Data Blocks (CDBs) to support the T.38 fax relay feature: • Fax Indicator—The value of this indicator is depend
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Cisco BTS 10200 Softswitch T.38 Fax Relay External Interfaces Table 2 T.38 Fax Relay Traffic Counters Measurement Name Measurement Description FAX_PAGES_SENT Number of fax pages sent. FAX_PAGES_RECV Number of fax pages received. Provisioning This section describes provisioning changes that resulted from the addition of the T.38 Fax Relay feature to the Cisco BTS 10200 Softswitch software. For more information on provisioning commands, refer to the “Command Reference” section on page 13
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Cisco BTS 10200 Softswitch T.38 Fax Relay External Interfaces Call Flow The following call flow diagram (Figure 1) illustrates the interactions between the Cisco BTS 10200 Softswitch software modules for the CA-controlled T.38 Fax Relay implementation. Figure 1 CA-Controlled T.38 Fax Relay MGA BCM H3A CNM API EstablishCx_ex (PCMU, T38 ) CRCX(PCMU, t38) RTP Cut thru (H323 fast start) SAI CCM OOBINFO REQ RQNT (fxr / t38()) NTFY (fxr / t38(start)) Service feature Ind(fax-start) Ser
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Cisco BTS 10200 Softswitch T.38 Fax Relay External Interfaces The following steps describe in detail the T.38 Fax Relay functionality: Step 1 The BCM checks the gateway profiles for their T.38 fax relay capabilites. It selects a common/preferred capability supported by both the gateways. Prior to establishing a connection, the BCM encodes the T.38 fax Local Connection Option (LCO) in the SAI_CreateCxData_t . The t38fax LCO information is transmitted by the MGA in the CRCX. Step 2 The B
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Cisco BTS 10200 Softswitch T.38 Fax Relay Related Features Related Features The T.38 Fax Relay feature is directly related to the H.323 features introduced in Release 3.1 and 3.2. Note For more information on the H.323 features, refer to the Cisco BTS 10200 Softswitch System Description. Related Documents This Release 3.2 T.38 Fax Relay Feature Module should be used in conjunction with the following Cisco BTS 10200 Softswitch Release 3.1 and 3.2 documents: • Cisco BTS 10200 Softswitch P
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Cisco BTS 10200 Softswitch T.38 Fax Relay Supported Standards 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
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Cisco BTS 10200 Softswitch T.38 Fax Relay Prerequisites Prerequisites The T.38 Fax Relay feature requires that the following prerequisites be completed prior to sending or receiving fax transmissions: • (to be supplied) Configuration Tasks The T.38 Fax Relay feature requires that the following configuration tasks be completed prior to sending or receiving fax transmissions. Each task in the list is identified as either required or optional. • Configure the H.323 Gateway • Configure the
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Cisco BTS 10200 Softswitch T.38 Fax Relay H.323 Gateway • change h323-gw id=gw1@cisco.com; fax-relay-cap=t38-ca-fax; • delete h323-gw id=gw1@cisco.com; Usage Guidelines Primary Key Token(s): id; Add Rule: status=OOS Change Rule: status=OOS Delete Rules: FK constraints, status must be OOS. Token Properties Table 3 lists the token properties that were added to this command for T.38 Fax Relay. Table 3 T.38 Fax Relay Tokens Token Values FAX-RELAY-CAP INBAND—Possible only for G.711 and G.726,
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Cisco BTS 10200 Softswitch T.38 Fax Relay H.323 Trunk Group Profile H.323 Trunk Group Profile The H.323 Trunk Group Profile (h323-tg-profile) table defines the characteristics of each H.323 trunk. A h323-tg-profile id must be created in this table before H.323 trunk group entries can be added. Table Name: H323-TG-PROFILE Table Containment Area: Call Agent Command Types Show, add, change, and delete Examples • show h323-tg-profile id=gw1@cisco.com • add h323-tg-profile id= ras-tg; ras=n;
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Cisco BTS 10200 Softswitch T.38 Fax Relay Media Gateway Profile Media Gateway Profile The Media Gateway Profile (mgw-profile) table provides templates for defining a Media Gateway by hardware vendor. It identifies the specifications and settings necessary for communications between the Call Agent and each type of Media Gateway. An ID must be created in this table before entries can be added to the Media Gateway table. Several tokens have values that can be overwritten after the Call A
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Cisco BTS 10200 Softswitch T.38 Fax Relay Troubleshooting Fax Relay Troubleshooting Fax Relay The purpose of this section is to provide basic troubleshooting procedures for anyone trying to resolve Cisco BTS 10200 Softswitch T.38 fax relay issues. The technical intricacies of faxing and fax relay are not covered in detail, but you will get a basic understanding and be able to perform troubleshooting for a majority of common fax relay issues. It is important to know the following infor
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Cisco BTS 10200 Softswitch T.38 Fax Relay Troubleshooting Fax Relay It is not always required that you have identical configurations on the outgoing and incoming VoIP dial-peers. When you have a fax relay problem though, make sure you have a dedicated incoming VoIP dial-peer on the terminating gateway and that its configuration matches the configuration of the outgoing VoIP dial-peer on the originating gateway. Another method you can use to check dial peer matching is to issue the deb
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Cisco BTS 10200 Softswitch T.38 Fax Relay Troubleshooting Fax Relay If voice calls work in both directions, but fax calls are failing in at least one direction, check that normal faxing between these two machines works across the PSTN. In other words, ensure the fax machines successfully transmit faxes to each other using the PSTN without traversing the packet network. If they do not, one or both fax machines may have problems that need to be addressed before you consider fax relay p
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Cisco BTS 10200 Softswitch T.38 Fax Relay Troubleshooting Fax Relay Step 6 Disable T.38 fax relay and change codec for passthrough. In the previous troubleshooting steps you established that voice calls work, faxes work through PSTN, and all digital interfaces in the fax relay path are free from errors. This step determines whether faxes can go through with T.38 fax relay disabled. Under the dial-peers, enter the following commands on both media gateways: gateway-name(config)#voice-por
