Which standard identifies a hop-by-hop technique for data path virtualization?

The correct choice is based on the fact that IEEE 802.1Q is the standard that specifies VLAN (Virtual Local Area Network) tagging for Ethernet frames, thereby providing a method for data path virtualization. This standard enables the creation of virtual networks over a single physical network infrastructure. The "hop-by-hop" technique refers to the process where data packets are tagged at each switch (hop) they traverse, ensuring that they remain associated with the correct VLAN throughout their journey across the network.

By implementing 802.1Q, a network can efficiently separate different types of traffic and improve overall network management through virtualization. This is crucial for maintaining data integrity and network performance in environments that require multiple, isolated networks sharing the same physical resources.

The other standards listed do not pertain specifically to the hop-by-hop technique for data path virtualization. For instance, 802.1X is focused on network access control and authentication, while 802.1P deals with traffic prioritization through QoS (Quality of Service). On the other hand, 802.1S addresses Multiple Spanning Tree Protocol (MSTP), which optimizes the spanning tree operation across multiple VLANs but does not directly relate to hop-by-hop data path virtualization.