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Community Member

fax over IP T38 using protocol between cisco and fax application software

We are trying to establish H.323 connection with the Cisco router(1751 with FXs port). The configurations on Cisco side shown below.

While calling (originating) from Cisco, H.323 connection is established successfully with the

codec G.711. Where as when our H.323 application calls the Cisco router, the H.323 negotiation is not established, Cisco sends call release, whenever H.323 application tries to negotiate.

please let us know if some more configurations have to be done at the Cisco side.

Router#show run

Building configuration...

Current configuration : 1057 bytes

!

version 12.2

!

hostname Router

!

voice service voip

fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback cisco

h323

!

!

no voice hpi capture buffer

no voice hpi capture destination

!

!

mta receive maximum-recipients 0

!

interface FastEthernet0/0

ip address 192.168.1.40 255.255.255.0

speed auto

!

ip classless

no ip http server

!

call rsvp-sync

!

voice-port 0/0

!

voice-port 0/1

!

!

dial-peer cor custom

!

dial-peer voice 222 voip

destination-pattern 222

session target ipv4:192.168.1.134

codec g723r53

fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback cisco

!

dial-peer voice 2000 voip

destination-pattern 2000

session target ipv4:192.168.1.177

fax rate 14400

fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback cisco

!

!

line con 0

3 REPLIES
Silver

Re: fax over IP T38 using protocol between cisco and fax applica

You will need POTS dial peers to make outside calls. Assuming the above config is an edited one, paste the following config in to the router :

voice class codec 1

codec preference 1 g723r53

codec preference 2 g729r8

codec preference 3 g711ulaw

!

no dial-peer voice 222 voip

!

no dial-peer voice 2000 voip

!

dial-peer voice 9999 voip

description - dummy dial peer to allow codec negotiation

incoming called-number .

voice-class codec 1

fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback cisco

fax-rate 14400

!

dial-peer voice 222 voip

destination-pattern 222

session target ipv4:192.168.1.134

codec g723r53

fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback cisco

!

dial-peer voice 2000 voip

destination-pattern 2000

session target ipv4:192.168.1.177

fax rate 14400

fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback cisco

!

Community Member

Re: fax over IP T38 using protocol between cisco and fax applica

Below are the detailed results of tests conducted configuring the CISCO gateway as the fax transmitter with the above suggested configurations.

1.When CISCO gateway originated the call:

With fast_start alone enabled on our H.323Stack also, the voice call is established during the H.225 "CONNECT" message. In our H.245 "TERMINALCAPABILITYSET", one of the codecs we support is T.38 fax for UDP protocol with a maxbitrate of 144. Yet, after the TERMINALCAPABILITYSET (TCS), MASTERSLAVEDETERMINATION (MSD), TERMINALCAPABILITYSETACK (TCSACK), and MASTERSLAVEDETERMINATIONACK (MSDACK) messages exchange between both the endpoints, no other messages are either sent to or received from either ends while, CISCO gateway is supposed to send a H.245 REQUESTMODE message after detecting the faxtone hence, allowing us to switch from voice to fax mode. After sometime, CISCO gateway sends a RELEASECOMPLETE message without specifying any reason in the ReleaseCompleteReason field.

With Fast_Start and Tunneling enabled, the voice call is established during the H.225 "CONNECT" message. Then, the TCS, MSD, TCSACK and MSDACK messages are also exchanged in the H.225 "FACILITY" massage as per tunnelling requirements. In our TCS, we send T38FAX supporting UDP protocol with a maxbitrate of 144 as one of our capabilities. But still, the REQUESTMODE message is not sent from the CISCO gateway in order to switch from voice to fax mode. Similar to the above case, a RELEASECOMPLETE mesage is sent and the call ends abruptly.

2.When ENCORE H.323 STACK originates the call:

When we send a normal H.225 SET_UP message with all the mandatory fields set, we receive a RELEASECOMPLETE message from the CISCO gateway without the reason field set. When we send a H.225 SET_UP message with fast_start enabled and the one of the FASTSTART elements' OPENLOGICALCHANNEL codec's being T.38FAX supporting UDP protocol with a maxbitrate of 144, the CISCO gateway sends a RELEASECOMPLETE message without specifying the reason.

When a tunnelling enabled H.225 SET_UP message is sent from H.323 stack, similar to the above cases, a RELEASECOMPLETE message is sent from the CISCO gateway.

regds.

Naveed

Silver

Re: fax over IP T38 using protocol between cisco and fax applica

Could be related to the following :

http://www.cisco.com/warp/public/788/voip/call_fail.html

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