[Serusers] About "Expire" header in INVITE method

hello, As a basic call flow like below. UAC (SER) | | | INVITE F1 | |----------------------->| | 100 Trying F2 | |<-----------------------| | | | 200 OK F3 | |<-----------------------| | ACK F4 | |----------------------->| if the UAC request INVITE method contain a "Expire" field with the value of 120. and after 120 second the final response ACK reach the SER. in this scenarios, Would SER think this ACK is valid respone from UAC? and would SER correctly proxy this message to corresponding UAS? Regards Disclaimer: The contents of this e-mail, and its attachments, if any, are confidential and may be protected by law against any unauthorized use. If you have received this e-mail by mistake or have reason to believe that you are not the intended recipient, please notify the sender by reply e-mail as soon as possible and delete it from your computer system immediately thereafter. If you are not the intended recipient, you must not copy this e-mail or attachment or disclose the contents to any other person. While we have made every effort to keep our network virus free, we take no responsibility for any computer virus which might be transferred by way of this e-mail.