What is the initial REGISTER request from a SIP endpoint rejected by Avaya Aura® Session Manager (SM)?

Question

Options

• AThe initial REGISTER request does not contain authentication details.
• BThe initial REGISTER request is rejected only if the user provided the wrong security
• CIt must confirm the reliable delivery of this initial REGISTER request
• DSystem manager needs time to look-up the Communication Address in its database.

• A
  92% (22)
• B
  4% (1)
• C
  4% (1)

Explanation

In SIP digest authentication (RFC 3261), the initial REGISTER request is intentionally sent without credentials as the first step of a two-step challenge-response handshake. Session Manager responds with a 401 Unauthorized containing a server-generated nonce (challenge), and only then does the endpoint re-submit the REGISTER with hashed credentials. This is by design - the server must first issue a challenge before the client can prove identity.

Why the distractors are wrong:

• B is wrong because the rejection happens regardless of credential correctness - the first REGISTER carries no credentials at all, so wrong vs. right is irrelevant at this stage.
• C is wrong because reliable delivery (e.g., PRACK for provisional responses) is a separate SIP mechanism unrelated to the reason for rejecting the initial REGISTER.
• D is wrong because the 401 rejection is a standard protocol step, not a timing workaround for database lookups.

Memory tip: Think of it as a two-knock rule - the first knock (initial REGISTER) always gets a "who are you?" back (401 challenge), and only your second knock with ID (re-REGISTER with credentials) gets you in. The door never opens on the first knock, by design.

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