This counter tracks requests for payload encapsulation that this protocol sent to the accelerators, counted since the last reboot. Encapsulation is the step of wrapping a packet in a new header for tunneling, like adding an ESP or GRE-over-IPsec header, so this counter's rate reflects outbound tunneled traffic volume for that specific protocol, independent of the encryption step itself. On a router running both GRE-over-IPsec and plain IPsec tunnels, comparing this counter between the two protocol rows would show an admin which tunneling method is carrying more outbound traffic.