After migrating two sites' PSTN connections over from T-1 PRI and T-1 CAS to SIP, problems have been reported of intermittent/inconsistent faxing success. Initially, these reports came out of our "Trouble Site" which has all fax machines hung off a PBX, and we just swung their PSTN connection(s) from the PBX over to CUBEs using T-1 integrations. However, my "test site" (where I'm at), which has been VoIP for 15 years with fax machines connected via VG224 MGCP gateway, but recently converted from T-1 ISDN PRI to SIP is also experiencing fax issues. In fact, at my test site, I can do 5-digit dial from two fax machines (on-net, within campus) and it works, however, when I dial off-net (10-digit) between the two fax machines, I have intermittent success (this is just going out to Lumen's peer and back in). Therefore, I'm now looking at my test site's MGCP gateway config. (Please see my config excerpts below).
My comprehension of T38 vs. T30 vs. pass-thru is tenuous at best and was hoping someone could answer some basic questions to help me grasp my situation further. (Please see the attached diagram for reference). Both carriers claim to support T38, and all our CUBES are configured on VoIP dial-peers for T38.
When a fax goes from a machine in "Test Site" to a fax machine in "Trouble Site", Point "A" would be analog T30, Point "B" would be VoIP RTP...My CUBE at "Test Site" would not know to switch over to T38- correct? (Now as I look at my Test Site MGCP config, I'm thinking that there's issues, though we haven't had complaints of faxing for the 15 years prior when this site was T-1 ISDN PRI connected to the PSTN).
Assume my Site SITE CUBE knows to convert to T38 to Trouble Site, and Trouble Site speaks T38, do my two CUBEs at Trouble Site and Test Site end up "peering" T38 to each other for capabilities exchanges, etc., or does each CUBE "Peer"/talk T38 to the local carrier's IPBE? (Is there T38 conversations between local CUBE and local IPBE and between the carriers' peering IPBEs?)
Thank you for any clarity you can provide.
Mike
Analog VGW at "Test Site" (All VoIP)
!
ccm-manager fallback-mgcp
ccm-manager redundant-host 10.10.52.66 10.10.52.65
ccm-manager mgcp
no ccm-manager fax protocol cisco
ccm-manager music-on-hold
ccm-manager config server 10.10.52.66
ccm-manager config
!
mgcp
mgcp call-agent 10.10.52.2 2427 service-type mgcp version 0.1
mgcp dtmf-relay voip codec all mode out-of-band
mgcp rtp unreachable timeout 1000 action notify
mgcp modem passthrough voip mode nse
mgcp modem passthrough voip codec g711alaw
mgcp ip qos dscp cs3 signaling
mgcp package-capability rtp-package
mgcp package-capability sst-package
no mgcp package-capability res-package
no mgcp package-capability fxr-package
no mgcp timer receive-rtcp
mgcp sdp simple
mgcp fax t38 inhibit
no mgcp explicit hookstate
mgcp rtp payload-type g726r16 static
mgcp bind control source-interface FastEthernet0/0
mgcp bind media source-interface FastEthernet0/0
!
CUBEs at Test Site and Trouble Site::
Voice service voip
fax protocol t38 version 0 ls-redundancy 0 hs-redundancy 0 fallback none
VoIP Dial-peers have the following:
fax-relay ecm disable
fax-relay sg3-to-g3
fax rate 14400
fax nsf 000000
Trouble Site POTS Dial-Peer(s) and Controller T1 (Fax machines are off of PBX- which is connected via T-1 CAS):
!
controller T1 0/1/1
framing esf
clock source line secondary
linecode b8zs
cablelength long 0db
ds0-group 1 timeslots 1-24 type e&m-wink-start
description
!
!
voice-port 0/1/1:1
!
dial-peer voice 20001 pots
description VoIP call to PBX (Outbound leg)
preference 1
destination-pattern [26]....
port 0/1/1:1
forward-digits all
