SIP/2.0 401 Unauthorized
Via: SIP/2.0/UDP nm;rport=26810;received=224.27.72.124;branch=foo
Call-ID: 50000
From: <sip:nm@nm>;tag=root
To: <sip:nm2@nm2>;tag=foo
CSeq: 42 OPTIONS
WWW-Authenticate: Digest realm="asterisk",nonce="1790432517/13b2bad772c86e766e5a3d3dfbc77ce0",opaque="4cd0a56b5e631b34",algorithm=MD5,qop="auth"
Server: Asterisk PBX 20.6.0~dfsg+~cs6.13.40431414-2build5
Content-Length: 0