Problem Description
An IVR has encountered an issue where in certain Announcement is not being played. The signaling path is from SipServer where the incoming call is receive and communicates to an IVR application for some announcement to be played. The customer has integrated F5 in between SipServer and to the IVR possibly for load balancing. It was expected that once F5 receives the Sip Messages it will just forward it to the destination IP.
It was observe that previous INVITE messages to the IVR for the same call was successful and was only failing for some. We have compared the two example and observe that successful INVTES were not fragmented compared to the failed ones. We conducted packet traces on the SipServer and F5 and confirmed the following:
1. Verified from Sip Server that Invite is sent to the IVR for the announcement however the Sip packet has been fragmented due to custom sip headers required by the IVR application to play the correct announcement audio.
2. Using wireshark/packet trace it was confirmed that F5 device was able to receive the complete fragmented packets however it was not able to forward the Invite request to the IVR.
Issue was identified with the F5 device in regards to processing fragmented sip packets. Configuration changes was made on the F5 device.
