SIP/2.0 500 Server Internal Error
From: <sip:nm@nm;user=phone>;tag=root
To: <sip:nm2@nm2;user=phone>;tag=1a408c8-68354957-55a02832-7769fa4a-68619f61-EA6C70
Call-ID: 50000
CSeq: 42 OPTIONS
Via: SIP/2.0/UDP nm;received=224.56.170.160;rport=26810;branch=foo
Supported: replaces,timer
Allow: INVITE, ACK, BYE, REFER, NOTIFY, CANCEL, OPTIONS, INFO, UPDATE
User-Agent: Technicolor / VANT-6 / AGTOT_2.2.3 / AGTOT_2.2.3
X-Serialnumber: CP1821TA7AP
Accept: application/dtmf-relay, x-application/dtmf-relay, application/sdp
Accept-Contact: *;audio;+g.3gpp.icsi-ref="urn%3Aurn-7%3A3gpp-service.ims.icsi.mmtel"
Content-Length: 0