Which device is similar to a packet filter, but also provides network address translation?

A.
A circuit-level gateway

B.
An application-level gateway

C.
A proxy server

D.
A choke router

Explanation:
A circuit-level gateway operates at the session layer, and NAT is a primary advantage.
Incorrect Answers:
B: An application-level gateway operates at all levels of the OSI model. It is too high in the level to provide NAT, NAT has to be provided at a lower layer through a different service.
C: A proxy server can provide packet filtering, such as provided in Microsoft’s Proxy Server and ISA server. However, the main functionality of the proxy server is to act in behalf of the clients it services. It is not similar to a packet filter when it is proxying, no to be confused in that it can also provide the packet filter feature.
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D: A choke router is a router in which all traffic has to pass through it. Like a funnel. Usually a choke is used in a firewall, where all traffic entering and leaving a network has that one point of entry/exit. It does not provide network address translation (NAT).