User's Manual

108 Appendix A: Basic call flows
NN10029-111 Standard MCP 1.1 FP1 (02.02) April 2003 Copyright © 2003, Nortel Networks
Nortel Networks Confidential
Figure 7 Authentication call flow
The following steps provide more detail about the call flow:
1. Client A sends a Register (SIP) message to the SIP Application
Module.
Initial requests never contain the user's credentials (basically, the
initial request just contains a password). Client A makes the
request, the SIP Application Server rejects it and gives them a
piece of information called a nonce in the 401 Unauthorized
message. The client takes that nonce and uses it to encrypt their
password information and sends this back in the second request.
2. The SIP Application Module returns a 100 Trying message to Client
A, then
3. The SIP Application Module attempts to retrieve the FROM party's
subscriber information to see if they've been marked as INACTIVE
in the system. This also causes the information to be cached at the
SIP Application Server, so the same dip is not made to the
database on the subsequent registration attempt. This profile
information allows the system to determine what their password is
in order to authenticate them.
4. In this case, the Database Module has returned a 401
Unauthorized message to the SIP Application Module, which sends
the information on to Client A.
Database
SIP
Module
Application
Client A
1. Register
2. 100 Trying
4. 401 Unauthorized
5. Register
6. 100 Trying
9. 200 Registration successful
7. Add user
8. User registered
3. Retrieve user profile
4. 401 Unauthorized