No.     Time        Source                Destination           Protocol Info
    760 19.653986   192.168.1.10          192.168.1.15          SIP      Request: ACK sip:+41215509999@192.168.1.11

Frame 760 (566 bytes on wire, 566 bytes captured)
Linux cooked capture
Internet Protocol, Src: 192.168.1.10 (192.168.1.10), Dst: 192.168.1.15 (192.168.1.15)
User Datagram Protocol, Src Port: sip (5060), Dst Port: sip (5060)
Session Initiation Protocol
    Request-Line: ACK sip:+41215509999@192.168.1.11 SIP/2.0
    Message Header
        Via: SIP/2.0/UDP 192.168.1.10;branch=z9hG4bK808da23a9d1db5f9
        Route: <sip:192.168.1.15;lr=on;ftag=b03fbb977e692e28>
        From: <sip:+41215501111@192.168.1.15>;tag=b03fbb977e692e28
        To: <sip:+41215509999@192.168.1.15>;tag=2d39d82d4efb221d
        Contact: <sip:+41215501111@192.168.1.10>
        Call-ID: 3f6b72ef41379493@192.168.1.10
        CSeq: 43883 ACK
        User-Agent: Grandstream BT110 1.0.8.33
        Max-Forwards: 70
        Allow: INVITE,ACK,CANCEL,BYE,NOTIFY,REFER,OPTIONS,INFO,SUBSCRIBE
        Content-Length: 0