3Com V7111 - VCX 4 Channels Analog FXO Media Gateway User Manual page 60

Since the algorithm used is MD5, take:
The username is equal to the endpoint phone number: 122.
The realm return by the proxy: 3com.com.
The password from the INI file: 3Com.
The equation to be evaluated: (according to RFC this part is called A1).
122:3com.com:3Com.
The MD5 algorithm is run on this equation and stored for future usage.
The result is: a8f17d4b41ab8dab6c95d3c14e34a9e1.
Next we need to evaluate the par called A2. We take:
The method type REGISTER
Using SIP protocol sip
Proxy IP from INI file 10.2.2.222
The equation to be evaluated:
REGISTER:sip:10.2.2.222.
The MD5 algorithm is run on this equation and stored for future usage. The result is:
a9a031cfddcb10d91c8e7b4926086f7e.
The final stage:
The A1 result
The nonce from the proxy response: 11432d6bce58ddf02e3b5e1c77c010d2
The A2 result
The equation to be evaluated:
"A1:11432d6bce58ddf02e3b5e1c77c010d2:A2".
The MD5 algorithm is run on this equation. The outcome of the calculation is the response
needed by the Gateway to be able top register with the proxy. The response is:
b9c45d0234a5abf5ddf5c704029b38cf.
At this time a new REGISTER request is issued with the response:
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=1c23940
To: <sip: 122@10.1.1.200>
Call-ID: 654982194@10.1.1.200
CSeq: 1 REGISTER
Contact: sip:122@10.1.1.200:
Expires:3600
Authorization: Digest, username: 122,
60 3Com VCX V7111 VoIP SIP Gateways User Manual