What is a unique characteristic of the Gnutella protocol?

The characteristic that highlights the Gnutella protocol is its support for multiple software clients to connect. Gnutella is a decentralized peer-to-peer (P2P) network protocol, which means that it allows numerous users (or clients) to connect directly to one another without the need for a central server. This facilitates file sharing among a large number of users, as each client can both upload and download files from other peers in the network. This characteristic enhances the resilience and scalability of file sharing since the network does not rely on a single point of failure.

The other options do not align with the fundamental design and operation of the Gnutella protocol; for instance, it does not require centralized servers, it is not limited to localized network file sharing, and it is certainly capable of sharing not just large files but also smaller files as well.