Practice Test Geeks(SSCA) Sip School Certified Associate Practice Test
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Proxy Servers Flashcards

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  1. What is the primary difference between a stateful SIP proxy and a stateless SIP proxy?

    Answer: A stateful proxy retains transaction state while a stateless proxy forwards each message independently

    A stateful proxy maintains transaction state and can make routing decisions based on prior messages, while a stateless proxy treats each message independently.

  2. When a SIP proxy adds a Record-Route header to an INVITE request, what is its primary purpose?

    Answer: To ensure subsequent in-dialog requests route through the proxy

    A proxy inserts a Record-Route header so that it remains in the signaling path for all subsequent in-dialog requests (e.g., re-INVITE, BYE).

  3. Which SIP header is decremented by each proxy that forwards a request, and causes the request to be rejected with a 483 response when it reaches zero?

    Answer: Max-Forwards

    Each proxy decrements the Max-Forwards header by 1, and when it reaches 0 the proxy returns a 483 Too Many Hops response.

  4. In SIP loose routing, what distinguishes a loose-route URI from a strict-route URI?

    Answer: Loose-route URIs contain the 'lr' parameter in the Route header

    A URI with the 'lr' parameter in the Route header indicates loose routing, where the proxy forwards based on the Request-URI without requiring it to be the proxy's own address.

  5. What type of SIP proxy forking sends an INVITE simultaneously to multiple potential destinations?

    Answer: Parallel forking

    Parallel forking sends the INVITE to multiple destinations at the same time, while sequential forking tries each destination one at a time.

  6. When a SIP proxy challenges a UAC for credentials, which response code does it use?

    Answer: 407 Proxy Authentication Required

    A proxy uses 407 Proxy Authentication Required to challenge the client, while 401 Unauthorized is used by UAS/registrars.

  7. Which header does a UAC include in a re-submitted request after receiving a 407 challenge from a proxy?

    Answer: Proxy-Authorization

    After receiving a 407, the UAC re-sends the request with a Proxy-Authorization header containing the credentials.

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