SSCA Registration Process 3

Question 1

When a registrar challenges a REGISTER request for credentials, which response code does it return?

Accepted Answer

401 Unauthorized

Answer

A registrar (not a proxy) challenges REGISTER with 401 Unauthorized, which includes a WWW-Authenticate header.

Question 2

Which authentication scheme does SIP define for protecting the REGISTER method?

Accepted Answer

Digest Authentication

Answer

RFC 3261 mandates Digest Authentication for SIP, which avoids sending passwords in cleartext by using MD5 hashing.

Question 3

After receiving a 401 challenge, what header does the UA include in its re-submitted REGISTER request?

Accepted Answer

Authorization

Answer

The UA places its computed credentials in the Authorization header when responding to a 401 Unauthorized challenge from a registrar.

Question 4

What is the 'nonce' value used for in SIP Digest Authentication during registration?

Accepted Answer

It is a server-generated random value used to prevent replay attacks

Answer

The nonce is a random, server-generated string included in the challenge; including it in the hashed response prevents replaying captured credentials.

Question 5

When a SIP proxy (not the registrar) requires authentication during registration, which response code is sent?

Accepted Answer

407 Proxy Authentication Required

Answer

407 Proxy Authentication Required is sent by an intermediate proxy that requires credentials, accompanied by a Proxy-Authenticate header.

(SSCA) Sip School Certified Associate Practice Test

(SSCA) Sip School Certified Associate Practice Test

SSCA Registration Process 3