What protocol or technology allows data to transmit over redundant switch links?

The protocol or technology that allows data to transmit over redundant switch links without causing a loop is EtherChannel. EtherChannel bundles individual Ethernet links into a single logical link, providing increased bandwidth and redundancy. If one of the physical links in the EtherChannel fails, traffic previously carried over the failed link is carried over the remaining links within the EtherChannel.

STP (Spanning Tree Protocol) is designed to prevent loops rather than to allow data transmission over redundant links. VTP (VLAN Trunking Protocol) is used to manage VLANs across a switched network and does not relate to link redundancy. DTP (Dynamic Trunking Protocol) is used to negotiate forming trunks between switches but does not provide redundancy or load balancing itself.