i'm experiencing some fax quality issues after connecting 3845 gateways to ISDN PRI (with CUCM 7.1.3). I explain the steps of my Voip migration:
7 days ago i had this situation:
- Nortel Meridian PBX connected to 10 E1 PRI lines
- fax server running on Nortel Meridian receiving faxes
- all Nortel phones
- CUCM and Voice Gateway configured and ready to get connected to PSTN
Now i started migration to CUCM 7.1.3 doing these steps:
- disconnected PRI lines from Nortel Meridian
- connected 5 3845 Voice Gateways to PSTN (10 E1 PRI lines)
- connected 15 QSIG from 3845 to Nortel Meridian
- no Cisco IP phones in production (want to test complete infrastructure before deploying Cisco phones)
- all phones and faxes are still Nortel: they go through Meridian PBX and the QSIG lines to reach gateway and PSTN
All was working fine (calls are perfect and everything seemed good) but today i noticed this problem: faxes received by Nortel Fax server are not good quality. I mean that fax connections are fully estabilished and completed but if receive, for example a 6 pages fax, one of these pages is completely black or not correctly received. This problem was NOT present before putting Voice Gateway between PSTN and Nortel (so before migration)
I tried to configure many options especially on gateways. For example:
- T38 Fax Relay enabled (default: disabled)
- Cisco Fax Relay enabled (default: disabled)
I had no success. Is there any other configuration or workaround to troubleshoot fax quality ? My problem is not about connection (fax send and receive is good) but i think is more difficult because issue is inside 1 or 2 pages of a fax that is generally well transmitted.
maybe the issue could be because i have 2 E1 controllers connected to PRI for each router. I tried to set (as the documentation said) only one as primary clock. The problem is that i reloaded the router and the command "clock source line primary" is disappeared: maybe because MGCP ovveride my manual command. So i checked in CUCM web interface but there is no place to set a controller as a primary clock source.
* Faxes failing to swtichover to a fax protocol (g711, modempass, or T38).
* Controllers slipping
* Packet loss on RTP traffic.
Please collect the following from the PSTN gateway, as well as from the PBX gateway (if a different device):
sh controller t1
sh controller e1
sh call history voice br
If any of your controls report slips, also respond with a description of where each controller is connected to, and who is set to send clocking, since there may be a clocking design issue which needs to be addressed.
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