Version 6.4 353 March 2012
SIP User's Manual 18. GW and IP to IP
User agents, Redirect or Registrar servers typically use 401 Unauthorized response to
challenge authentication containing a WWW-Authenticate header, and expect the re-
INVITE to contain an Authorization header.
The following example describes the Digest Authentication procedure, including
computation of user agent credentials:
1. The REGISTER request is sent to a Registrar/Proxy server for registration:
REGISTER sip:10.2.2.222 SIP/2.0
Via: SIP/2.0/UDP 10.1.1.200
From: <sip: 122@10.1.1.200>;tag=1c17940
To: <sip: 122@10.1.1.200>
Call-ID: 634293194@10.1.1.200
User-Agent: Audiocodes-Sip-Gateway/Mediant 1000/v.6.40.010.006
CSeq: 1 REGISTER
Contact: sip:122@10.1.1.200:
2. Upon receipt of this request, the Registrar/Proxy returns a 401 Unauthorized
response:
SIP/2.0 401 Unauthorized
Via: SIP/2.0/UDP 10.2.1.200
From: <sip:122@10.2.2.222 >;tag=1c17940
To: <sip:122@10.2.2.222 >
Call-ID: 634293194@10.1.1.200
Cseq: 1 REGISTER
Date: Mon, 30 Jul 2001 15:33:54 GMT
Server: Columbia-SIP-Server/1.17
Content-Length: 0
WWW-Authenticate: Digest realm="audiocodes.com",
nonce="11432d6bce58ddf02e3b5e1c77c010d2",
stale=FALSE,
3. According to the sub-header present in the WWW-Authenticate header, the correct
REGISTER request is created.
4. Since the algorithm is MD5:
• The username is equal to the endpoint phone number 122.
• The realm return by the proxy is audiocodes.com.
• The password from the ini file is AudioCodes.
• The equation to be evaluated is (according to RFC this part is called A1)
‘122:audiocodes.com:AudioCodes’.
• The MD5 algorithm is run on this equation and stored for future usage.
• The result is ‘a8f17d4b41ab8dab6c95d3c14e34a9e1’.
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