Which system provides relay services between two devices?

A.
Proxy server

B.
Gateway

C.
VPN

D.
Screening router

Explanation:
By definition a gateway is a device that relays services between two systems. One example is a gateway that connects two (or more) network segments. This gateway is used when the two networks have different protocols and the gateway has to do a protocol conversion. The gateway then provides relay services between devices in the different segments.
Incorrect Answers:
A: A Proxy Server also connects two (or more) networks segments, and acts as a single control point to perform requests on behalf of the requesting client
C: A VPN (Virtual Private Network) provides secure remote point-to-point communication. It doesn’t provide relay services.
D: A screen routing connects two (or more) network segments. It is a type of firewall, it only uses packet filters.
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