Which layer is described as ensuring hardware and software made by different vendors work together?

• A. Physical layer
• B. Data Link layer
• C. Network layer
• D. Session layer

Answer: (C)

The key idea is interoperability through standardized addressing and routing across networks. The layer that makes devices from different vendors work together is the one that provides end-to-end delivery across multiple networks by using logical addressing and routing. It defines how packets are forwarded from one network to another and selects paths using standardized protocols like IP. This abstraction lets routers and other network devices from various vendors interoperate because they all follow the same addressing and routing rules, regardless of hardware specifics. The lower layers handle the physical transmission and local link details, while higher layers handle sessions and applications.