Fax use G711 and voice use G729

Question

I am going to have 2821 connecting to PBX T1 for about 10 sites. GK is used to manage the call routing and bandwidth. The codec we choose is G729. Question is: can we meantime use G711 for the fax even H323 dialpeer is G729? I know G711 passthrough is much better. Fax is on the PBX too.

Answer 1

Here is a rather old document (but still mostly valid) which says fax relay is the preferred method.
http://www.cisco.com/univercd/cc/td/doc/product/voice/c_access/fxmdmnt.htm
This is a good document that will help you understand the issues encountered with faxing over IP.
http://www.cisco.com/en/US/tech/tk652/tk777/technologies_tech_note09186a0080114565.shtml
The right answer will depend upon the specific requirements in your network. In my experience, faxes and modems are an area that can be challenging, and that may require trial and error to get it right.
As an example, we decided to use fax relay everwhere (some low speed WAN links don't have the bandwidth for upspeed), but ran into a very isolated problem with PSTN faxes between our Right Fax server and an internal fax board in a AS400 server at another company. All faxes everywhere else worked great, but this would always fail. Switching it to fax passthrough was the fix, so we now use fax relay for all faxing, except for RightFax to and from the PSTN, which is passthrough.
Please rate helpful posts.
Dave