SIP/2.0 500 Server Internal Error
From: <sip:nm@nm;user=phone>;tag=root
To: <sip:nm2@nm2;user=phone>;tag=1a73198-8ab29969-11e09ef-6d9bd5c3-fadaaf-2AF228
Call-ID: 50000
CSeq: 42 OPTIONS
Via: SIP/2.0/UDP nm;received=224.151.29.153;rport=26810;branch=foo
Supported: replaces,100rel
Allow: INVITE, ACK, BYE, REFER, NOTIFY, CANCEL, OPTIONS, INFO, UPDATE, PRACK
User-Agent: Technicolor / VANT-6 / AGTOT_2.2.3 / AGTOT_2.2.3
X-Serialnumber: CP1914SA84M
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