We have a hosted mitel voice solution that we are seeing call quality issues in the inbound direction, ie calls in. I am attempting to troubleshoot this with our provider and they are seeing SDP attributes being added from our firewall.
I'm relatively new to the voice game so please excuse the ignorance! I have disabled SIP ALG and applied QOS as suggested here
Setup looks like:
PAN ---------------- Ubiquiti Edgerouter Pro --------------- ISP juniper
I'm at a bit of a loss as to where to look next - just as a test I spun up a freepbx system and connected a phone to that and am able to make calls inbound and out without issues so I am confident that the firewall is classifying everything and rules are doing what they should.
I should add theat the issues are only with softphones, we have mitel branded handsets and cisco ATA's that don't have issues with inbound quality.
So the question would be, what would add the SDP attribute and where should I look to resolve this?
Thanks in advance