Which option is connection-oriented and guarantees delivery while upgrading switch firmware remotely over the LAN?

The correct answer is FTP, which stands for File Transfer Protocol. FTP is a connection-oriented protocol, meaning that it establishes a dedicated connection between the client and server before any data is transferred. This characteristic is crucial for tasks such as upgrading switch firmware over a LAN, as it allows for reliable data transmission.

One of FTP's key features is its ability to guarantee delivery of the files being transferred. If any packets of data are lost during the transfer process, FTP can detect this and retransmit the necessary data, ensuring that the complete firmware file arrives intact. This reliability is essential when dealing with firmware upgrades, as any corruption in these files could lead to device failure or misconfiguration.

In contrast, protocols like HTTP, Telnet, and SNMP do not offer the same level of connection-oriented features suited for file transfers. HTTP is primarily designed for web traffic and does not guarantee reliable delivery in the way that FTP does. Telnet is a text-based protocol primarily used for remote terminal access rather than file transfer, and while it provides a connection, it does not inherently guarantee data integrity. SNMP, which is used for network management and monitoring, operates over UDP instead of TCP, making it connectionless and unsuitable for guaranteed delivery of firmware files.