What technology allows transmissions to be sent even if several sites are not operational?

Packet switching is the technology that enables transmissions to continue even if several sites are not operational. This method of data transmission breaks messages into packets, which are then sent independently across the network. Each packet can take different paths to reach the destination, where they are reassembled in the correct order. This inherent flexibility and redundancy allow for robust connections because if one route is unavailable or a site is down, other available routes can be utilized to ensure the data still reaches its destination.

In contrast, virtual switching and grid computing do not inherently possess the same degree of resilience in handling network failures. Virtual switching is more focused on managing communication within virtualized environments, while grid computing emphasizes resource sharing across distributed systems rather than maintaining communication in the face of outages. Distributed computing, while also designed to work across multiple nodes, does not specifically address the resilience of data transmission like packet switching does.