1) SIP/SDP call establishment procedures for T.38 are specified in Annex D/T.38 (2005/09). This is normativ for T.38 implementations.
2) The term (G.711) pass-through mode is misleading, because there is a a) G.711 audio mode and b) G.711 VBD mode (see ITU-T V.152; G.711 used as VBD codec) SDP for VBD mode is specified in 7.1 & 7.1.3/V.152. SIP mechanisms for VBD, T.38 (& V.150.1) are specified in 7.1.2/V.152. Thus, SIP/SDP for Fax-over-V.152 (VBDoIP) and Fax-over-T.38 (FoIP) is specified in V.152 & T.38. Do agree that the extended SDP O/A model might be a more flexible tool for negotiating the finally selected transport mode in the IP domain. /Albrecht > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On > Behalf Of Jean-Francois Mule > Sent: Freitag, 19. September 2008 11:41 > To: Somesh S. Shanbhag; Rohit Aggarwal; Neranza Bundova; > [email protected] > Subject: Re: [Sip-implementors] Broadsoft FAX problem > > Hi, > > The best option is to contact Broadsoft. I do not know the > implementation of fax support in Broadsoft's products but > typically, you start a fax call using a vo-coder (G.711 in > your case) and then some implementations *may* switch to fax > relay using T.38. Some implementations do not support t.38 > and use G.711 pass-through mode which works fine for G3 fax > in a number of deployments. > > Unless the originating SIP UA is a fax-only device that is > always communicating with the same server (enterprise), you > cannot just offer one media description in SDP with just t.38 > (this will break most fax call negotiations). > > The SDP negotiation framework > (http://tools.ietf.org/html/draft-ietf-mmusic-sdp-capability-n > egotiation > -09) could be a way to indicate support for alternative > potential SDP configurations. But that is likely not supported yet. > > Jean-Francois. > > > -----Original Message----- > > From: [EMAIL PROTECTED] [mailto:sip- > > [EMAIL PROTECTED] On Behalf Of Somesh S. > > Shanbhag > > Sent: Friday, September 19, 2008 3:27 AM > > To: Rohit Aggarwal; Neranza Bundova; sip- > > [EMAIL PROTECTED] > > Subject: Re: [Sip-implementors] Broadsoft FAX problem > > > > Rohit, > > > > You may be right, may be driven by configuration or may be > because the > > client didn't indicate the T38 capability its switching > automatically > > to > > G711 Mode. > > > > Somesh S Shanbhag > > M G L Bangalore > > > > > > > > -----Original Message----- > > From: Rohit Aggarwal [mailto:[EMAIL PROTECTED] > > Sent: Fri 9/19/2008 2:51 PM > > To: Somesh S. Shanbhag; Neranza Bundova; sip- > > [EMAIL PROTECTED] > > Subject: RE: Broadsoft FAX problem > > > > Hi > > > > If I understand it correctly, Somesh is suggesting addition of T38 > > media stream in offer from the endpoint whereas Neranza's > query is how > > to make Broadsoft initiate T.38 fax instead of Pass-Through on tone > > detection? I think Neranza wants that Broadsoft should add > T38 stream > > in the Re-INVITE, probably some server configuration?? > > > > Please correct me if my interpretation of the original > query is wrong. > > > > Regards > > Rohit Aggarwal > > Aricent > > > > -----Original Message----- > > From: [EMAIL PROTECTED] [mailto:sip- > > [EMAIL PROTECTED] On Behalf Of Somesh S. > > Shanbhag > > Sent: Friday, September 19, 2008 2:42 PM > > To: Neranza Bundova; [email protected] > > Subject: Re: [Sip-implementors] Broadsoft FAX problem > > > > I think you will have to put something like this in SDP > > > > m=image 10000 udptl t38 > > a=T38FaxVersion:0 > > a=T38MaxBitRate:14400 > > a=T38FaxFillBitRemoval:0 > > a=T38FaxTranscodingMMR:0 > > a=T38FaxTranscodingJBIG:0 > > a=T38FaxRateManagement:transferredTCF > > a=T38FaxMaxBuffer:200 > > a=T38FaxMaxDatagram:300 > > a=T38FaxUdpEC:t38UDPRedundancy > > > > Somesh S Shanbhag > > M G L Bangalore > > > > > > > > -----Original Message----- > > From: [EMAIL PROTECTED] on behalf of > > Neranza Bundova > > Sent: Fri 9/19/2008 12:56 PM > > To: [email protected] > > Subject: [Sip-implementors] Broadsoft FAX problem > > > > Hello All, > > > > > > > > I have a problem with sending a T38 FAX over a Broadsoft server. > > > > I am sending to a PSTN FAX so the Broadsoft server is > terminating SIP > > point and it should send me REINVITE for T38 but it does not. It is > > just accepting the FAX transmission over G711. > > > > My question is there some specific advertisement(media attribute or > > media description) which I should add in my initial INVITE > request to > > the Broadsoft server to make it understand that I support T38? > > > > I saw also something called "Broadsoft FAX Messaging" but > did not find > > any description. > > > > > > > > Thanks > > > > > > > > _______________________________________________ > > Sip-implementors mailing list > > [email protected] > > https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors > > > > > > > > EMAIL DISCLAIMER : This email and any files transmitted with it are > > confidential and intended solely for the use of the individual or > > entity to whom they are addressed. Any unauthorised distribution or > > copying is strictly prohibited. If you receive this transmission in > > error, please notify the sender by reply email and then destroy the > > message. 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