INFO: Changes in Brooktrout driver version 6.4.0 update
This Zetafax technical note applies to:
The Brooktrout 6.4.0 driver update contains a number of bug fixes and enhancements and is available to download with the associated updated Zetafax files here.
Below is an extract from the Dialogic release notes of the changes in this release:
- Fixed IPY92754 – Under rare conditions, an IP fax produced a hangup 23 error when receiving IP packets with bad frame checksums, which caused the DIS message to appear to come before the CSI message. This has been corrected.
- Enhancement nhma~40746 – A new T38 parameter t38_v21preamble_repeat has been added to btcall.cfg. Please refer to the Reference Manual for details.
- Interoperating in a network consisting of V.34 T.38 capable devices
- If the equipment you are communicating with includes V.34 T.38 capable devices; for example the Dialogic® 4000 Media Gateway Series, and any other non-V.34 T.38 equipment can correctly negotiate the T.38 fax version, you can change the default settings to support V.34 as follows:
t38_fax_version = 3
t38_max_bit_rate = 33600
- Interoperating with Cisco V.34 T.38 capable devices
- For outbound V.34 T.38 calls (SR140 to Cisco) to succeed without falling back to V.17, the callctrl.cfg parameter media_renegotiate_delay_outbound must be changed to a value equal to or greater than zero. This change implies that the SR140 will initiate a T.38 changeover. The media_renegotiate_delay_outbound parameter is set to -1 by default. In the Configuration tool, this parameter can be found on the ‘T.38 Parameters’ tab of the ‘IP Call Control Modules’ section.
- Cisco IOS versions that support V.34 T.38 have added a new parameter, ‘version’, to the ‘fax protocol t38’ command. This parameter must be set to 3 in order to enable V.34 T.38 operation since the third version of the ITU-T’s T.38 specification added V.34 support. This parameter can be set in the global configuration or an individual dial peer.
- Global configuration example:
voice service voip
fax protocol t38 version 3 ls-redundancy 0 hs-redundancy 0 fallback none
- Dial peer configuration example:
dial-peer voice 4443 voip
session protocol sipv2
session target ipv4:10.10.10.1
session transport udp
voice-class codec 1 fax protocol t38 version 3 ls-redundancy 0 hs-redundancy 0 fallback none
Interoperating with ShoreTel gateways
Interoperating with Avaya gateways, Alcatel gateways and the Broadspeed SIP trunking service
- Enabling redundancy for T.38 causes data errors when using the ShoreTel Gateway Software Release 10 Build 15.6.4207.0. For interoperability, the SR140 requires redundancy for both image and control to be set to 0.
- The ShoreTel Gateway sends a SIP session refresh if it is enabled on the ShoreTel Gateway, even if the SR140 is configured not to use SIP session refresh. This will cause the SR140 to drop the call if a SIP refresh is received. For interoperability, the SR140 must enable SIP session refresh or the ShoreTel Gateway must disable SIP session refresh by using the ShoreWare Director (select Call Control, then Options, then disable the session timer, and set the session interval and the refresher).
- The ShoreTel Gateway does not support V.17 for T.38. The maximum protocol supported is V.29 (9600 bits/sec).
- Due to lack of T.38 Error Correction Mode (ECM) support on these systems, faxes containing errors caused by possible telephone line conditions are more likely to fail and therefore affect the overall fax completion rate under these specific conditions.
Last updated: 28th November 2011 (NT/MW)