[cisco-voip] T.38 Fax Issue
Antonio Soares
amsoares at netcabo.pt
Mon Jan 17 13:22:46 EST 2011
It’ s a SIP trunk between a Cisco GW (the one I have control) and a ZTE
device
It was working with the config I have shown. Something was changed
on the other side. I was trying to make it work using the options available
at our side. Unfortunately I don’t have the debugs captured when this was
configured so I still have a doubt. What PT should be used in this T.38
negotiation ? PT=100 or PT=101 ?
PT=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.
PT=101: Designates an NTE (Named Telephony Event) as defined in RFC 2833.
Check this table:
https://supportforums.cisco.com/docs/DOC-1387
I was convinced that it was PT=100 (NSE) but as you said, they are Cisco
proprietary. So maybe it should be PT=101 (NTE) ?
Thanks.
Regards,
Antonio Soares, CCIE #18473 (R&S/SP)
<mailto:amsoares at netcabo.pt> amsoares at netcabo.pt
From: matthn at gmail.com [mailto:matthn at gmail.com] On Behalf Of Nick Matthews
Sent: segunda-feira, 17 de Janeiro de 2011 17:56
To: Antonio Soares
Cc: Peter Slow; cisco-voip at puck.nether.net
Subject: Re: [cisco-voip] T.38 Fax Issue
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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