Cisco BTS 10200 Softswitch User Manual - Page 5

Browse online or download pdf User Manual for Switch Cisco BTS 10200 Softswitch. Cisco BTS 10200 Softswitch 29 pages. T.38 fax relay

Print Page

Cisco BTS 10200 Softswitch T.38 Fax Relay

•

The CA-controlled mode for T.38 fax relay provided by this feature also imposes several restrictions:

•

Capability Negotiation

For the CA-controlled media change, capabilities supported by the gateway are advertised in the SDP

exchange during connection establishment. This provides knowledge early and prevents unnecessary

messaging to switch to a media or voice format that is not supported by both gateways.

During the initial bearer path setup, the Cisco BTS 10200 Softswitch negotiates the T.38 Fax Relay

capabilities of both the originating and terminatinggateways (endpoints).

•

Since the H.323 stack in the version 3.2 software does not support T.38 capability exchange during

Fast-start information exchanges, the Cisco BTS 10200 Softswitch initiates a Terminal Capability Set

(TCS) procedure to exchange T.38 Fax Relay capabilities along with DTMF capabilities.

MGCP Gateway Capabilities

The Cisco BTS 10200 Softswitch provides default provisioning parameters in the MGW-PROFILE table

for MGCP-controlled media gateways. The MGWs are also provisioned with static capabilities showing

the types of T.38 Fax Relay supported by the MGW.

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.

Any gateway that requires closure of both logical channels after sending ECS is not

Note

supported by the Cisco BTS 10200 Softswitch.

Clearing the call once the T.38 fax relay is completed—after the fax image transfer, the

connection remains established until one of the endpoints goes onhook, then the call is cleared.

Clearing the call if an H245 request mode rejection is received—if an H245 request mode

rejection is received from the remote media gateway, the call is cleared.

Seamless integration of various features—connection parameters on the remote H.323 gateway

can be modified after the connection is established by sending empty capability set (ECS).

Only partial support of MGCP fax package (fax start, fax stop, fax failure events only).

No voice fall back is supported—

when the fax call completes the call is cleared.

–

if the T.38 fax invocation fails, the call is cleared.

–

CA-controlled mode feature cannot function for H.323-to-H.323 calls transiting the CA.

If there are no common T.38 Fax Relay capabilities, the inband method is chosen.

If both sides have more than one capability in common, the common preferred T.38 mode is used.

If there is a common preferred mode, which is also present among the common capabilities, that

mode is chosen.

If no common preferred T.38 mode is available, then one of the common T.38 mode capabilities is

chosen.

Cisco BTS 10200 Softswitch T.38 Fax Relay Support

T.38 Benefits