SIP/2.0 401 Unauthorized
Via: SIP/2.0/UDP srlab.sr.ntc.nokia.com:5060;maddr=192.168.102.5
Via: SIP/2.0/UDP 172.21.9.155
Record-Route: <sip:garage.sr.ntc.nokia.com:5060;maddr=srlab.sr.ntc.nokia.com>
From: sip:digest@garage.sr.ntc.nokia.com
To: sip:digest@garage.sr.ntc.nokia.com
Call-ID: 982773899-reg@172.21.9.155
CSeq: 1 REGISTER
WWW-Authenticate: Digest realm="garage.sr.ntc.nokia.com", 
  nonce="MjAwMS0wMS0yMSAxNTowODo1OA==", algorithm=MD5, qop="auth"
Content-Length: 0