Fax fails from Outside caller after several pages

[MitelAvayaNortel]

I'm trying to trace a strange issue.  I can fax multiple page faxes between two sites over the IP link (even to the external number of the fax machines) but when a call comes in to the fax at site B from an ISDN connection at site A the fax will fail after several pages.  Does anyone have any suggestions please?

Thanks

[lundah]

Are you using T.38 or the G.711 codec?

[MitelAvayaNortel]

It is using T38.

[LoopyLou]

Would verify it is using T.38. Would see if slowing down the fax speed helps.

[MitelAvayaNortel]

Hi,

I have slowed the faxes down to 14000 bps and still have the same issue (I also turned off ECM on the fax at the same time to see if that helped.)

How can I verify that the T38 is being used?

Thanks.

[wiseguy]

Would be usefull to know the software version. The question I have is how is this setup as a fax call is coming in through ISDN (does it ??) and goes via IP trunk to the next node. Is the fax machine connected via an ATA? If your running version 6.0 then use the SIP TCPdump command to capture the SIP messages to see if it's using T38 on the Fax node.

[MitelAvayaNortel]

Thanks for your help, we located the issue being that the COS for the ISDN trunks did not enable Busy Override Security.  With this set faxes seem to work OK.