480 temporarily unavailable on Mitel sip phone ( in wireshark trace )

[abmitel]

Mitel 6863i phone registered with Mxone . the phone display is normal , but any incoming call
Summary:   Mitel 6863i phones is idle when user is dialing any extension number user gets blank tone.
Details:   All sip phones Mitel and third party sip phones are responding intermediately with extension not been able to dial any other extension.

While dialing it give a blank tone, It will start working randomly once received a call from another extension.

Analog phones in the same system works fine.

Also we have take a capture of 6863i phone (Pcap file) call scenario tested while capture are mentioned below: and in wireshark trace it shows "

[bojo387]

If you check in MX-ONE, what is the status of the extensions/terminals when the problem is there?
Registered? Marooned?

What about the System Information>SIP Status on the phone's web UI?

[abmitel]

Hi
the extension status is registered in Mxone and phone UI

only when we make a call the display says "call failed" .

[abmitel]

Hi
addon info on this issue

the phone detach status show marooned in this state , if we make an incoming call to such affected sip phone users the incoming call is successfull . now we can make outgoing calls from this phones . if these phones are kept idle for a very long time then it gives similar symptom and detach status shows marroned

anything can be done from network side 

[bojo387]

https://mitel.custhelp.com/app/answers/answer_view/a_id/1014773/loc/en_US

There are many things to be checked on the network side but starting with the basics would be good. Using a separate VLAN, try and simulate the issue in different setups, adjust the keep-alive timer in the terminals. Maybe there are too many hops, not good latency, etc. It's best to consult a network engineer.

[abmitel]

Hi
we have configured Vlan but same result . this symptom is not static .
we are debugging this issue jointly with customer network team , we will keep updated

Regards