SSCA Proxy Servers 2

Question 1

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

Accepted Answer

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

Answer

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

Question 2

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

Accepted Answer

To ensure subsequent in-dialog requests route through the proxy

Answer

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).

Question 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?

Accepted Answer

Max-Forwards

Answer

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

Question 4

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

Accepted Answer

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

Answer

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.

Question 5

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

Accepted Answer

Parallel forking

Answer

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

(SSCA) Sip School Certified Associate Practice Test

(SSCA) Sip School Certified Associate Practice Test

SSCA Proxy Servers 2