[cisco-voip] T.38 Fax Issue
Nick Matthews
matthnick at gmail.com
Mon Jan 17 12:56:15 EST 2011
When you say SIP trunk, are you implying that this is going to a SIP
provider? Or is this just a SIP gateway and the fax is going out a TDM
interface?
If it's a SIP trunk you're sending the fax over, forget about anything using
NSEs - like Pete said they're Cisco proprietary.
You'll need to configure the other device for protocol based T.38 switchover
like you've got it configured on your end.
-nick
On Mon, Jan 17, 2011 at 10:21 AM, Antonio Soares <amsoares at netcabo.pt>wrote:
> We tried the "fax protocol t38 nse force" but it didn't work.
>
> Now with "fallback cisco" we have something different:
>
> --------------------------------------
> s=VoIP d=DSP payload 0x60 ssrc 0xFFD5D4C sequence 0x291 timestamp
> 0x19A50
> <<<Rcv> Pt:96 Evt:136 Pkt:01 40 50
> --------------------------------------
> s=DSP d=VoIP payload 0x61 ssrc 0xFFE2 sequence 0x0 timestamp 0x0
> Pt:97 Evt:0 Pkt:00 04 00 <Snd>>>
> --------------------------------------
> s=DSP d=VoIP payload 0x60 ssrc 0x0 sequence 0x0 timestamp 0x0
> Pt:96 Evt:0 Pkt:00 00 00 <Snd>>>
> --------------------------------------
> s=VoIP d=DSP payload 0x60 ssrc 0xFFD5D4C sequence 0x292 timestamp
> 0x19AA0
> <<<Rcv> Pt:96 Evt:136 Pkt:01 40 50
> --------------------------------------
> s=DSP d=VoIP payload 0x61 ssrc 0x60014 sequence 0x1 timestamp 0x1
> Pt:97 Evt:0 Pkt:01 00 00 <Snd>>>
> --------------------------------------
> s=VoIP d=DSP payload 0x60 ssrc 0xFFD5D4C sequence 0x293 timestamp
> 0x19AF0
> <<<Rcv> Pt:96 Evt:136 Pkt:01 40 50
> --------------------------------------
> s=DSP d=VoIP payload 0x61 ssrc 0x0 sequence 0x2 timestamp 0x2
> Pt:97 Evt:0 Pkt:01 00 00 <Snd>>>
> --------------------------------------
> s=VoIP d=DSP payload 0x60 ssrc 0xFFD5D4C sequence 0x294 timestamp
> 0x19B40
> <<<Rcv> Pt:96 Evt:136 Pkt:01 40 50
> --------------------------------------
> s=DSP d=VoIP payload 0x61 ssrc 0x0 sequence 0x3 timestamp 0x3
> Pt:97 Evt:0 Pkt:01 00 00 <Snd>>>
> --------------------------------------
> s=DSP d=VoIP payload 0x7A ssrc 0xFFFFFFFF sequence 0x9EBF
> timestamp 0x2FE4CED0
> Pt:122 Evt:0 Pkt:52 3A 00 <Snd>>>
> --------------------------------------
>
> Now we see:
>
> Pt:96 Evt:136 (Sent by a voice gateway to signal a switchover to Cisco
> fax relay)
> Pt:97 Evt:0 (Sent by a voice gateway to confirm a successful switchover
> to Cisco fax relay)
> Pt:122 Evt:0 (Indicates Cisco fax relay data)
>
> So I was expecting this would mean it was working but apparently it still
> doesn't work.
>
> I'm using this document as reference:
>
> Cisco RTP Payload Types
>
> https://supportforums.cisco.com/docs/DOC-1387
>
> Any other ideas ?
>
>
> Thanks.
>
> Regards,
>
> Antonio Soares, CCIE #18473 (R&S/SP)
> amsoares at netcabo.pt
>
>
> -----Original Message-----
> From: Peter Slow [mailto:peter.slow at gmail.com]
> Sent: segunda-feira, 17 de Janeiro de 2011 12:16
> To: Antonio Soares
> Cc: cisco-voip at puck.nether.net
> Subject: Re: [cisco-voip] T.38 Fax Issue
>
> No, "fallback cisco" is different. You need to try the "fax protocol
> t38 nse force" command.
>
> -pete
>
>
> On Mon, Jan 17, 2011 at 6:58 AM, Antonio Soares <amsoares at netcabo.pt>
> wrote:
> > It was working before so I assume the other end's configuration was
> changed.
> > This is a SIP trunk and we have this configuration for the T.38 fax:
> >
> > voice service voip
> > fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback pass-through
> > g711alaw
> >
> > We are now trying the following:
> >
> > voice service voip
> > fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback cisco
> >
> > This should match their PT=96 request, right ?
> >
> >
> > Thanks.
> >
> > Regards,
> >
> > Antonio Soares, CCIE #18473 (R&S/SP)
> > amsoares at netcabo.pt
> >
> >
> > -----Original Message-----
> > From: Peter Slow [mailto:peter.slow at gmail.com]
> > Sent: segunda-feira, 17 de Janeiro de 2011 11:50
> > To: Antonio Soares
> > Cc: cisco-voip at puck.nether.net
> > Subject: Re: [cisco-voip] T.38 Fax Issue
> >
> > Usually t.38 Fax relay operates by switching to t.38 based on an MGCP
> > MDCX, a new h245 TCS/OLC etc, or a SIP re-invite. this is referred to
> > as protocol based switchover, and is generally how people's gateways
> > are configured for t.38 when it is being used. it would appear that
> > the other GW you are talking to is set up for NSE based switchover,
> > which AFAIK is a cisco proprietary method. You may be configured for
> > protocol based switchover still, while it sounds like perhaps the
> > other side went and changed something and is now trying to do NSE
> > based switchover...
> >
> > Check out this link:
> >
>
> http://www.cisco.com/en/US/docs/ios/12_3/vvf_c/cisco_ios_fax_services_over_i
> > p_application_guide/t38.html#wp1156699
> >
> > It is tough to help you out beyond what I've said without knowing what
> > protocol (h.323, MGCP..) you are using for call control. More insight
> > there, plus perhaps some asn1 or mgcp packet debugs would help, but
> > try setting your side to use nse based switchover if it isnt set that
> > way already.
> >
> > -Peter
> >
> >
> >
> > On Mon, Jan 17, 2011 at 5:48 AM, Antonio Soares <amsoares at netcabo.pt>
> wrote:
> >> Hello group,
> >>
> >> A few days ago, fax stopped working on one gateway. The "debug voip rtp
> >> session nse" gives me this:
> >>
> >>
> >
>
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> >> ++++++++++++++
> >> s=VoIP d=DSP payload 0x60 ssrc 0x509B391F sequence 0x18E
> > timestamp
> >> 0xF8C0
> >> <<<Rcv> Pt:96 Evt:136 Pkt:02 80 50
> >> s=VoIP d=DSP payload 0x60 ssrc 0x509B391F sequence 0x18F
> > timestamp
> >> 0xF910
> >> <<<Rcv> Pt:96 Evt:136 Pkt:01 40 50
> >> s=VoIP d=DSP payload 0x60 ssrc 0x509B391F sequence 0x190
> > timestamp
> >> 0xF960
> >> <<<Rcv> Pt:96 Evt:136 Pkt:01 40 50
> >> s=VoIP d=DSP payload 0x60 ssrc 0x509B391F sequence 0x191
> > timestamp
> >> 0xF9B0
> >> <<<Rcv> Pt:96 Evt:136 Pkt:01 40 50
> >> s=VoIP d=DSP payload 0x60 ssrc 0x509B391F sequence 0x192
> > timestamp
> >> 0xFA00
> >> (...)
> >>
> >
>
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> >> ++++++++++++++
> >>
> >> Most likely, the problem is on the other end, a gateway that I do not
> >> control.
> >>
> >> I believe for this to work I need to receive PT=100 and EVT=200:
> >>
> >> Payload Type 100: Designates an NSE (Named Signaling Event packet). NSE
> >> packets can signal a variety of different messages so it is helpful to
> > know
> >> the NSE Event ID.
> >>
> >> Event 200: Triggered by the detection of a V.21 fax preamble when T.38
> is
> >> configured. This message initiates the switchover of the call from
> voice
> > to
> >> T.38. This message is sent by the terminating fax gateway to notify the
> >> originating fax gateway of the switch to T.38.
> >>
> >> And I'm receiving PT=96 and EVT=136. PT=96 means " Sent by a voice
> gateway
> >> to signal a switchover to Cisco fax relay". I wasn't able to find the
> >> meaning of EVT=136.
> >>
> >> With this information, can I assume that the problem is on the other end
> ?
> >> Can I do anything on my side to force the desired PT/EVT combination ?
> >>
> >>
> >> Thanks.
> >>
> >> Regards,
> >>
> >> Antonio Soares, CCIE #18473 (R&S/SP)
> >> amsoares at netcabo.pt
> >>
> >>
> >> _______________________________________________
> >> cisco-voip mailing list
> >> cisco-voip at puck.nether.net
> >> https://puck.nether.net/mailman/listinfo/cisco-voip
> >>
> >
> >
>
>
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