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International Faxing

I have Fax Server (Brooktrout SR140) connected via SIP trunk to a CUCM.

CUCM is connected with a SIP trunk to a 2821 cube which has also a SIP trunk connectivity to PSTN.

Find attached a network diagram.

SR140 supports FoIP through T.38 fax relay only. My PSTN provider does not support the T.38 but only G711 passthrough.

To overcome this problem I install a 2 port ISDN BRI card on the Gateway and I create a ISDN loop (port1: user, port2:Network).

So when fax calls come in from SIP trunk from the provider are directed to ISDN network port and they come out of the user ISDN port and then are

directed to SR140.

Now we can send and receive faxes without any problems. The problem is that I cannot send faxes to international numbers even though I can receive faxes from international. Also I can send faxes in my country without any problems.

The error I receive from the fax server is handshaking failure. I debug the T.30 messages from the gateway (debug fax relay t30 all-level-1) and I found out that the call is established, the remote fax answers the call and send its capabilities information through DIS signal and then my fax server (SR140) send three times its capabilities information through DCS signal with no response and then  it disconnects the call. Find below a sample of the debug:

May 16 08:24:27.815: 0/0/0 (77408)  3961743997 fr-entered=10(ms)
    timestamp=3961753737 fr-msg-det CSI
    timestamp=3961754477 fr-msg-det DIS
    timestamp=3961756307 fr-msg-tx TSI
    timestamp=3961756927 fr-msg-tx DCS
    timestamp=3961762997 fr-msg-tx TSI
    timestamp=3961763607 fr-msg-tx DCS
    timestamp=3961769677 fr-msg-tx TSI
    timestamp=3961770277 fr-msg-tx DCS
    timestamp=3961776367 fr-msg-tx DCN

Also I notice when I run the command show call active voice brief that there are some values that indicate a delay or jitter. Note that the same values exist when you are sending fax locally in my country but the fax is transmitted without any problem. I tried to play with playout-delay to adjust the jitter but I didn't manage to solve the problem. Find below a sample of show call active voice brief:

Telephony call-legs: 1
SIP call-legs: 2
H323 call-legs: 0
Call agent controlled call-legs: 0
SCCP call-legs: 0
Multicast call-legs: 0
Total call-legs: 3
2FD1 : 78866 -253835006ms.1 +6700 pid:3904 Answer no_from_info connected
dur 00:00:08 tx:230/23556 rx:180/25876
IP 192.168.0.4:56070 SRTP: off rtt:0ms pl:1810/0ms lost:0/19/0 delay:65/65/145ms t38 TextRelay: off
media inactive detected:n media contrl rcvd:n/a timestamp:n/a
long duration call detected:n long duration call duration:n/a timestamp:n/a
13F0 : 78868 -253834966ms.1 +6640 pid:3901 Answer no_from_info active
dur 00:00:08 tx:448/75264 rx:447/71520
Tele 0/0/1 (78868) [0/0/1.1] tx:7050/7050/0ms g711alaw noise:-66 acom:6  i/0:-66/-66 dBm
13F0 : 78869 -253834956ms.1 +6620 pid:3905 Originate 003623343515 active
dur 00:00:08 tx:447/71520 rx:621/99360
IP 172.16.81.10:4510 SRTP: off rtt:3ms pl:4920/0ms lost:0/1/0 delay:55/55/75ms g711alaw TextRelay: off
media inactive detected:n media contrl rcvd:n/a timestamp:n/a
long duration call detected:n long duration call duration:n/a timestamp:n/a

I am attaching also the configuration of the gateway.

Note that there are a lot of dial-peers configured. The dial-peers used when sending an international fax are the 3900, 3901, 3904, 3905.

Any help will be appreciated.

Thanks,

3 REPLIES
Hall of Fame Super Gold

Re: International Faxing

Configure:

network-clock-select 1 bri 0/0/1

New Member

Re: International Faxing

Thanks very much for your reply.

I configure the command but the problem still exists.

Hall of Fame Super Gold

Re: International Faxing

I'm afraid that for reliable fax you will need a true PSTN BRI circuit.

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