How is the connection established with PB-GATT in regards to BLE Mesh?

Answer

An unprovisioned device will advertise a beacon, per the BT spec it shall be advertised with non-connectable and non-scannable undirected advertising events.The provisioning protocol can use PB-ADV or PB-GATT. PB-GATT involves making a connection with the mesh profile stating that the connection interval is recommended to be between 250 and 1000 milliseconds. PB-GATT uses Proxy protocol (GATT bearer) so a BLE connection needs to be established. The unprovisioned device needs to send normal connectable advertising packets and the provisioner should establish the connection like a normal BLE connection after which they can start provisioning via PB-GATT. There will need to be additional adverts that the unprovisioned device will send to invite connections if it wants to be provisioned by both options. If the beacon is PB-ADV it has to be nonconnectable non-scannable as stated in the spec.