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[frederic.ve at gmail.com]

Hello list,

We're currently facing some issues concerning T.38 gateway faxing.
This is a device used almost exclusively for receiving faxes. Calls
are incoming to asterisk on a SIP trunk (sangoma netborder) using
G711A. Gateway mode is activated in the asterisk dialplan towards a
Cisco SPA 112 running firmware 1.3.5. We are using asterisk 1.8.13.0
with the T.38 gateway patch applied (I know I know, we should move to
asterisk 11. I'm trying that tonight after business hours).

The issue we're seeing is that faxes incoming from some specific fax
machines consistenly fail. I have indentified 2 types of failures:
- Incoming call is sent to SPA112, reinvite to T.38 is initiated and
accepted. One T.38 packet is sent from the SPA112 to asterisk
(t30ind: no-signal, see pcap output below) followed by 20 seconds of
nothingness and then the call is hung up.
- Incoming call is sent to SPA112, reinvite to T.38 is initiated and
accepted. A number of T.38 packets is sent from the SPA112 to asterisk
(it repeats NSF,CSI,DIS signals 3 times) followed ba call hangup.

In none of the above 2 cases do I see T.38 packets flowing from
asterisk to the SPA112.

In the logs I see these things that indicate T.38 gateway being started:
[Oct 14 14:16:17] DEBUG[11426] res_fax.c: SIP/SDSD0005-0007cb05 is
attempting to negotiate T.38 but SIP/SOV20001-0007cb04 does not
support it
[Oct 14 14:16:17] DEBUG[11426] res_fax.c: starting T.38 gateway for
T.38 channel SIP/SDSD0005-0007cb05 and G.711 channel
SIP/SOV20001-0007cb04
[Oct 14 14:16:17] DEBUG[11426] res_fax.c: Requesting a new FAX session
from 'Spandsp FAX Driver'.
[Oct 14 14:16:17] DEBUG[11426] res_fax.c: channel
'SIP/SOV20001-0007cb04' using FAX session '660'
[Oct 14 14:16:17] DEBUG[11426] chan_sip.c: T38 state changed to 3 on
channel SIP/SDSD0005-0007cb05


PCAP text output of 1st case:
216.025063 192.168.196.3 -> 192.168.196.94 RTP PT=ITU-T G.711 PCMA,
SSRC=0x6118CC28, Seq=4877, Time=1179871936
216.042133 192.168.196.94 -> 192.168.196.3 RTP PT=ITU-T G.711 PCMA,
SSRC=0x205734A, Seq=8641, Time=2227760
216.045031 192.168.196.3 -> 192.168.196.94 RTP PT=ITU-T G.711 PCMA,
SSRC=0x6118CC28, Seq=4878, Time=1179872096
216.062169 192.168.196.94 -> 192.168.196.3 RTP PT=ITU-T G.711 PCMA,
SSRC=0x205734A, Seq=8642, Time=2227920
216.065031 192.168.196.3 -> 192.168.196.94 RTP PT=ITU-T G.711 PCMA,
SSRC=0x6118CC28, Seq=4879, Time=1179872256
216.082161 192.168.196.94 -> 192.168.196.3 RTP PT=ITU-T G.711 PCMA,
SSRC=0x205734A, Seq=8643, Time=2228080
216.085022 192.168.196.3 -> 192.168.196.94 RTP PT=ITU-T G.711 PCMA,
SSRC=0x6118CC28, Seq=4880, Time=1179872416
216.102145 192.168.196.94 -> 192.168.196.3 RTP PT=ITU-T G.711 PCMA,
SSRC=0x205734A, Seq=8644, Time=2228240
216.105045 192.168.196.3 -> 192.168.196.94 RTP PT=ITU-T G.711 PCMA,
SSRC=0x6118CC28, Seq=4881, Time=1179872576
216.122158 192.168.196.94 -> 192.168.196.3 RTP PT=ITU-T G.711 PCMA,
SSRC=0x205734A, Seq=8645, Time=2228400
216.125042 192.168.196.3 -> 192.168.196.94 RTP PT=ITU-T G.711 PCMA,
SSRC=0x6118CC28, Seq=4882, Time=1179872736
216.142145 192.168.196.94 -> 192.168.196.3 RTP PT=ITU-T G.711 PCMA,
SSRC=0x205734A, Seq=8646, Time=2228560
216.145043 192.168.196.3 -> 192.168.196.94 RTP PT=ITU-T G.711 PCMA,
SSRC=0x6118CC28, Seq=4883, Time=1179872896
216.146259 192.168.196.94 -> 192.168.196.3 SIP/SDP Request: INVITE
sip:0043767079@192.168.196.3:5060, with session description
216.147280 192.168.196.3 -> 192.168.196.94 SIP Status: 100 Trying
216.147993 192.168.196.3 -> 192.168.196.94 SIP/SDP Status: 200 OK,
with session description
216.162166 192.168.196.94 -> 192.168.196.3 RTP PT=ITU-T G.711 PCMA,
SSRC=0x205734A, Seq=8647, Time=2228720
216.182149 192.168.196.94 -> 192.168.196.3 RTP PT=ITU-T G.711 PCMA,
SSRC=0x205734A, Seq=8648, Time=2228880
216.187971 28:92:4a:34:19:72 -> ac:f2:c5:35:ed:66 ARP Who has
192.168.196.94? Tell 192.168.196.3
216.188251 ac:f2:c5:35:ed:66 -> 28:92:4a:34:19:72 ARP 192.168.196.94
is at ac:f2:c5:35:ed:66
216.203946 192.168.196.94 -> 192.168.196.3 RTP PT=ITU-T G.711 PCMA,
SSRC=0x205734A, Seq=8649, Time=2229040
216.229648 192.168.196.94 -> 192.168.196.3 SIP Request: ACK
sip:0043767079@192.168.196.3:5060
216.234987 192.168.196.94 -> 192.168.196.3 T.38 UDP: UDPTLPacket
Seq=00000 t30ind: no-signal
237.503971 192.168.196.94 -> 192.168.196.3 SIP Request: BYE
sip:0043767079@192.168.196.3:5060
237.505427 192.168.196.3 -> 192.168.196.94 SIP Status: 200 OK


PCAP text output of 2nd case:
116.087359 192.168.196.3 -> 192.168.196.94 RTP PT=ITU-T G.711 PCMA,
SSRC=0x62BD813F, Seq=59490, Time=2244459432
116.094618 192.168.196.94 -> 192.168.196.3 RTP PT=ITU-T G.711 PCMA,
SSRC=0x8EAA59B4, Seq=1641, Time=1264160
116.107393 192.168.196.3 -> 192.168.196.94 RTP PT=ITU-T G.711 PCMA,
SSRC=0x62BD813F, Seq=59491, Time=2244459592
116.113615 192.168.196.94 -> 192.168.196.3 RTP PT=ITU-T G.711 PCMA,
SSRC=0x8EAA59B4, Seq=1642, Time=1264320
116.127400 192.168.196.3 -> 192.168.196.94 RTP PT=ITU-T G.711 PCMA,
SSRC=0x62BD813F, Seq=59492, Time=2244459752
116.133640 192.168.196.94 -> 192.168.196.3 RTP PT=ITU-T G.711 PCMA,
SSRC=0x8EAA59B4, Seq=1643, Time=1264480
116.143569 192.168.196.94 -> 192.168.196.3 SIP/SDP Request: INVITE
sip:0042406282@192.168.196.3:5060, with session description
116.144319 192.168.196.3 -> 192.168.196.94 SIP Status: 100 Trying
116.144887 192.168.196.3 -> 192.168.196.94 SIP/SDP Status: 200 OK,
with session description
116.153850 192.168.196.94 -> 192.168.196.3 RTP PT=ITU-T G.711 PCMA,
SSRC=0x8EAA59B4, Seq=1644, Time=1264640
116.173646 192.168.196.94 -> 192.168.196.3 RTP PT=ITU-T G.711 PCMA,
SSRC=0x8EAA59B4, Seq=1645, Time=1264800
116.199127 192.168.196.94 -> 192.168.196.3 RTP PT=ITU-T G.711 PCMA,
SSRC=0x8EAA59B4, Seq=1646, Time=1264960
116.229940 192.168.196.94 -> 192.168.196.3 SIP Request: ACK
sip:0042406282@192.168.196.3:5060
116.237631 192.168.196.94 -> 192.168.196.3 T.38 UDP: UDPTLPacket
Seq=00000 t30ind: no-signal
116.747493 192.168.196.94 -> 192.168.196.3 T.38 UDP: UDPTLPacket
Seq=00001 t30ind: ced
116.757588 192.168.196.94 -> 192.168.196.3 T.38 UDP: UDPTLPacket
Seq=00002 t30ind: no-signal
117.387730 192.168.196.94 -> 192.168.196.3 T.38 UDP: UDPTLPacket
Seq=00003 t30ind: v21-preamble
117.397857 192.168.196.94 -> 192.168.196.3 T.38 UDP: UDPTLPacket
Seq=00003 t30ind: v21-preamble
117.407640 192.168.196.94 -> 192.168.196.3 T.38 UDP: UDPTLPacket
Seq=00003 t30ind: v21-preamble
117.435598 28:92:4a:34:19:72 -> ac:f2:c5:35:ed:66 ARP Who has
192.168.196.94? Tell 192.168.196.3
117.435899 ac:f2:c5:35:ed:66 -> 28:92:4a:34:19:72 ARP 192.168.196.94
is at ac:f2:c5:35:ed:66
118.677727 192.168.196.94 -> 192.168.196.3 T.38 UDP: UDPTLPacket
Seq=00004 data:v21: hdlc-data[FFC00400006AAA...] (HDLC fragment 0)
hdlc-fcs-OK (HDLC Reassembled: NSF - Non-Standard Facilities)
119.387802 192.168.196.94 -> 192.168.196.3 T.38 UDP: UDPTLPacket
Seq=00005 data:v21: hdlc-data[FFC002CCCC6C2C...] (HDLC fragment 0)
hdlc-fcs-OK (HDLC Reassembled: CSI - Called Subscriber Identification
- Number:042404633)
119.817794 192.168.196.94 -> 192.168.196.3 T.38 UDP: UDPTLPacket
Seq=00006 data:v21: hdlc-data[FFC80104771523...] (HDLC fragment 0)
hdlc-fcs-OK-sig-end (HDLC Reassembled: DIS - Digital Identification
Signal - DSR:ITU-T V.27 ter, V.29, and V.17)
119.877246 192.168.196.94 -> 192.168.196.3 T.38 UDP: UDPTLPacket
Seq=00007 t30ind: no-signal
119.887540 192.168.196.94 -> 192.168.196.3 T.38 UDP: UDPTLPacket
Seq=00008 t30ind: no-signal
123.167804 192.168.196.94 -> 192.168.196.3 T.38 UDP: UDPTLPacket
Seq=00009 t30ind: v21-preamble
123.177713 192.168.196.94 -> 192.168.196.3 T.38 UDP: UDPTLPacket
Seq=00009 t30ind: v21-preamble
123.187801 192.168.196.94 -> 192.168.196.3 T.38 UDP: UDPTLPacket
Seq=00009 t30ind: v21-preamble
124.427832 192.168.196.94 -> 192.168.196.3 T.38 UDP: UDPTLPacket
Seq=00010 data:v21: hdlc-data[FFC00400006AAA...] (HDLC fragment 0)
hdlc-fcs-OK (HDLC Reassembled: NSF - Non-Standard Facilities)
125.127833 192.168.196.94 -> 192.168.196.3 T.38 UDP: UDPTLPacket
Seq=00011 data:v21: hdlc-data[FFC002CCCC6C2C...] (HDLC fragment 0)
hdlc-fcs-OK (HDLC Reassembled: CSI - Called Subscriber Identification
- Number:042404633)
125.567949 192.168.196.94 -> 192.168.196.3 T.38 UDP: UDPTLPacket
Seq=00012 data:v21: hdlc-data[FFC80104771523...] (HDLC fragment 0)
hdlc-fcs-OK-sig-end (HDLC Reassembled: DIS - Digital Identification
Signal - DSR:ITU-T V.27 ter, V.29, and V.17)
125.627325 192.168.196.94 -> 192.168.196.3 T.38 UDP: UDPTLPacket
Seq=00013 t30ind: no-signal
125.637723 192.168.196.94 -> 192.168.196.3 T.38 UDP: UDPTLPacket
Seq=00014 t30ind: no-signal
128.917917 192.168.196.94 -> 192.168.196.3 T.38 UDP: UDPTLPacket
Seq=00015 t30ind: v21-preamble
128.927809 192.168.196.94 -> 192.168.196.3 T.38 UDP: UDPTLPacket
Seq=00015 t30ind: v21-preamble
128.937894 192.168.196.94 -> 192.168.196.3 T.38 UDP: UDPTLPacket
Seq=00015 t30ind: v21-preamble
130.177960 192.168.196.94 -> 192.168.196.3 T.38 UDP: UDPTLPacket
Seq=00016 data:v21: hdlc-data[FFC00400006AAA...] (HDLC fragment 0)
hdlc-fcs-OK (HDLC Reassembled: NSF - Non-Standard Facilities)
130.887932 192.168.196.94 -> 192.168.196.3 T.38 UDP: UDPTLPacket
Seq=00017 data:v21: hdlc-data[FFC002CCCC6C2C...] (HDLC fragment 0)
hdlc-fcs-OK (HDLC Reassembled: CSI - Called Subscriber Identification
- Number:042404633)
131.317940 192.168.196.94 -> 192.168.196.3 T.38 UDP: UDPTLPacket
Seq=00018 data:v21: hdlc-data[FFC80104771523...] (HDLC fragment 0)
hdlc-fcs-OK-sig-end (HDLC Reassembled: DIS - Digital Identification
Signal - DSR:ITU-T V.27 ter, V.29, and V.17)
131.377426 192.168.196.94 -> 192.168.196.3 T.38 UDP: UDPTLPacket
Seq=00019 t30ind: no-signal
131.387773 192.168.196.94 -> 192.168.196.3 T.38 UDP: UDPTLPacket
Seq=00020 t30ind: no-signal
133.914404 ac:f2:c5:35:ed:66 -> 28:92:4a:34:19:72 ARP Who has
192.168.196.3? Tell 192.168.196.94
133.914427 28:92:4a:34:19:72 -> ac:f2:c5:35:ed:66 ARP 192.168.196.3 is
at 28:92:4a:34:19:72
137.654538 ac:f2:c5:35:ed:66 -> ff:ff:ff:ff:ff:ff ARP Who has
192.168.196.1? Tell 192.168.196.94
157.053791 192.168.196.94 -> 192.168.196.3 SIP Request: BYE
sip:0042406282@192.168.196.3:5060
157.055245 192.168.196.3 -> 192.168.196.94 SIP Status: 200 OK


Is there anyone with expertise or recommendations on this list? Do let
me know if there is any information missing.

Thanks,

Frederic

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[lmoore at omninet.net.au]

It's been a while since I played with a Cisco SPA8800 with T.38 and with
incoming faxes. There were settings in the SIP configurations for the
SPA8800 to get it working with T.38 with asterisk, I don't know if the
same will apply for this device.

If memory serves me you don't need, or perhaps, shouldn't use the T.38
Gateway feature for the incoming call unless you are expecting your
endpoint to be running T.30, in your case the SPA-112.

A quick glance over the data sheet for this device suggests it supports
T.38 thus providing you have T.38 enabled on the SPA-211 I would advise
against attempting to use the gateway feature for the incoming call.

In my experience Cisco use UDP redundancy and the default value is 1,
you may want to experiment with this value and set it to 3. You may want
to adjust the values in asterisk's udptl.conf by setting udptlfecentries
& udptlfecspan to the same value, don't forget to restart asterisk after
the change, I can't remember if you can force an unload and reload of
the udptl module in asterisk.

You have not provided any information relating to the SPA-112's
configuration in sip.conf so here are some settings I have;

[9003]
; Cisco SPA8800 FXS Port 3
; Analogue FAX Modem attached
type=friend
call-limit=2
qualify=yes
canreinvite=no
;directmedia=no
host=dynamic
context=FAX-T38
faxdetect=no
;t38pt_udptl=yes,redundancy,maxdatagram=400

I can't recall if I tested receiving a fax using G711 and used the
faxgateway option when directing the call to the SPA8800

Larry.



On 14/10/2014 8:59 PM, Frederic Van Espen wrote:

[lmoore at omninet.net.au]

I don't know if this may help
https://www.escaux.com/docs/DRD_T38Support_AdminGuide.html assuming you
can enable T.38 on the Sangoma Netborder, then you can turn off the
faxgateway option.

Larry.

On 15/10/2014 3:19 PM, Larry Moore wrote: