Fax t.38 protocol based between H.323 and MGCP gateway

[c.hennrich]

Hi,

I'm trying to find a generic configuration to support T.38 protocol based on VG224s with H323 cisco GW and h323 VoIP service provider. This H.323 VoIP Provider, is not running cisco gateways, so I need to use T.38 protocol base instead of NSE based.

I changed the call control protocol on the vg224 from SCCP to MGCP to have support for protcol based t.38. I have configure the gateway CA controlled so that it can use use protocol based t.38.

Now I have my PSTN gateway running as H323 gateways.Then I found this statement in the fax documentation:

http://www.cisco.com/en/US/partner/docs/ios/voice/fax/configuration/guide/vf_cfg_t38_fxrly_ps6441_TSD_Products_Configuration_Guide_Chapter.html#wp1156645

H.323 or SIP T.38 Fax Relay Interworking with Cisco MGCP Gateways

Specify that gateways must use T.38 fax relay and NSEs even though those gateways may be unable to negotiate those attributes by themselves at the time of call setup. This may happen during negotiations for fax attributes between H.323 or SIP gateways and MGCP gateways.

Both gateways must be configured to use T.38 fax relay and NSEs. On an H.323 or SIP gateway, use the fax protocol t38 nse force command. On an MGCP gateway, use the mgcp fax t38 gateway force command.

so I read this, that I cannot use t.38 protocol based between the gateways, do I miss anything here?

Or is it just that I force NSE based and if that fails, protocol based t.38 will be used. In the case I want to send a fax via H323 Voip provider instead of my Cisco H323 gateway?

So do I need to change my PSTN gateways from H323 to MGCP, if I want use everywhere t.38 protocol based?

Running the VG224 with h323 or SIP is not is not desired, because the operations team would need to configure the GW via IOS. And all endpoint configuration should be done via CUCM webinterface.

Any help is very much appreaciated.

With Best Regards

Christian

[William Bell]

Christian,

I am not sure how to interpret the section you quoted. I do know that I have tested T.38 fax relay between VG224(mgcp) --> CUCM --> 28xx(h323) successfully. It could be that your quote is referring to a scenario where the H323 device doesn't traverse a call control agent (like the CUCM)? Though, I don't see how one would put themselves in that spot.

I can't speak to the h323 trunk to your service provider. I can say that you should be able to run MGCP and H.323 gateways in the same CUCM environment AND supporting T.38 fax relay.

Note that my testing was on the CUCM 7.1 release.

HTH.

Regards,
Bill

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[c.hennrich]

Thank you for your answer!

have you configured your VG224 CA controlled, wchich should be protocol based?

In my understanding the quote says, that MGCP works, but only if we use NSE based t.38.

I think I need to test and then come back, if it works or not.

Regards

[Felipe Garrido · Accepted solution]

Protocol based switchover will work between MGCP and H.323 gateways in CUCM.

-Felipe

[c.hennrich]

thank you! that helps

[William Bell · Accepted solution]

CA controlled? Yes, in my test scenarios I have had a VG-224 running MGCP (using CUCM as backhaul) with protocol-based T.38 fax-relay interacting with a 2821 ISR running MGCP and a 2811 ISR running H.323. In all cases I was running T.38 fax relay (protocol based) with a CUCM 7.1(3b)SU2 cluster.

HTH.

Regards,
Bill