FAX problem on CUBE

[j.smith@sepidarsystem.com]

Hi

We have recently implemented CUBE on CSR1000v and configured SIP Trunk line. Inbound and outbound calls work properly, but inbound fax does not work. Our fax server is Issabel and I configured SIP Trunk between CUBE and Issabel.  The PSTN supports fax protocol t.38.

PSTN==>CUBE (CSR1000v)==> Issabel

I configured CUBE as below:

voice service voip
dtmf-interworking standard
allow-connections h323 to h323
allow-connections h323 to sip
allow-connections sip to h323
allow-connections sip to sip
redirect ip2ip
signaling forward unconditional
fax protocol t38 version 0 ls-redundancy 0 hs-redundancy 0 fallback pass-through g711alaw
h323
trace
sip
min-se 90
error-passthru
registrar server
early-offer forced
midcall-signaling passthru

I configured Issabel Trunk as below:

host=172.20.253.6
context=from-trunk
type=friend
insecure=port,invite
qualify=yes&yes
dtmfmode=rfc2833
disallow=all
allow=ulaw,alaw

I attached the wireshark log.

Thank you for helping me solve the problem.

[Sadav Ansari]

Hi,

collect the below debug from cube and check.

debug bpm signal

debug VoIP vtsp all

Pls rate if its “Helpful”. If this answered your question pls “Accept as solutions”

[Nithin Eluvathingal · Accepted solution]

This is most probably due to Fax protocol negotiation. Is there a possibility of landing the call on Fax machine to test if it pass through the CUBE. If it goes through the CUBE, then we need to diagnose the issue from Issabel.

meanwhile try the below Config which i commonly use for Imagilce servers.

    voice service voip

        fax protocol t38 fallback pass-through g711alaw

Then a dial-peer must be added to route incoming faxes to Digital Fax. The session target points to the UC Suite server and the codec is G.711alaw.

   dial-peer voice 1 voip
   description INCOMING FAX FROM PSTN TO DIGITAL FAX
   destination-pattern 4..
   session target ipv4:10.10.10.1
   session protocol sipv2
   codec g711alaw
   no vad    

2.12.0.0

2.12.0.0

[j.smith@sepidarsystem.com]

Hi

Thank You for your reply.

I Implemented the scenario on Router 2911 ( PSTN (SIP Trunk) ==> Voice Gatway (Router 2911)  ==> Issabel ) and it worked properly. But it doesn't work through CSR1000v. I Think there is a negotiation problem between CSR1000v(CUBE) and Issabel.

I attached wireshark log. I think CUBE cannot wait to receive SDP response from Issabel and sends BYE to PSTN.

[j.smith@sepidarsystem.com]

Hi

I think that I found out the problem

While sending a fax both audio and image packets are being sent step by step. CUBE should receive image stream after audio stream, but it does not happen and it disconnects.

I searched and found a link as below:

https://www.cisco.com/c/en/us/support/docs/unified-communications/unified-border-element/118939-technote-cube-00.html

It seems that there is a bug. It says to try one of the theree ways to solve the problem.

• Use only one m-line for the voice-to-fax switch-over  ( I don't understand how to do that)
• Use protocol-based pass-through.  (It didn't work)
• Have the provider place the m=audio line above the m=image line. ( Provider won't do that)Thank you for helping me solve the problem.

[j.smith@sepidarsystem.com]

Thank you for your recommendation. It worked for me and I can receive fax through CUBE and Imagicle with no problem, but there is problem with outgoing faxes. While sending fax, the fax machine rings but cannot receive the file. How can I solve this problem?