Which device is needed to connect two computer systems, if the systems use different protocols ?

Question

Accepted Answer

The correct option is (2):
A **Gateway** is the only network device listed whose primary function is to connect two computer systems or networks that operate using fundamentally **different communication protocols**. A Gateway operates at the **Application Layer (Layer 7)** of the OSI model, and often encompasses all seven layers, acting as a complete protocol translator. When data moves from one network to the other, the Gateway strips the data down to the application-level information and re-encapsulates it using the entirely new protocol stack of the destination network. This deep level of inspection and translation—from one architecture, format, and set of rules to another—is essential for seamless communication between truly disparate systems.

The incorrect option is (1):
A **Repeater** operates exclusively at the **Physical Layer (Layer 1)** of the OSI model. Its function is extremely simple and low-level: to receive a weakened electrical, optical, or radio signal, regenerate it to its original strength, and retransmit it. Because it deals only with raw bits (1s and 0s), a Repeater is completely unaware of network addresses, data packets, or any communication protocols. It cannot inspect the data structure or perform the necessary protocol conversion to link systems using different protocols.

The incorrect option is (3):
A **Bridge** operates at the **Data Link Layer (Layer 2)** of the OSI model. Its function is to filter traffic based on MAC addresses and connect two or more separate network segments. While a Bridge can connect different physical media (like wired and wireless), it requires both segments to be running the *same* underlying network layer protocol (e.g., both must use the same type of Ethernet). It can separate a local collision domain but does not have the intelligence to perform the high-level protocol translation needed for systems with disparate protocol stacks.

The incorrect option is (4):
A **Hub** is a very simple, non-intelligent device that also operates at the **Physical Layer (Layer 1)**, essentially acting as a multi-port Repeater. Its operation involves receiving a signal on one port and broadcasting it blindly to every other connected port. Like a Repeater, a Hub does not examine data frames, MAC addresses, or protocols. It merely extends the physical network segment, makes no logical decisions, and is incapable of translating or converting different communication protocols.