The Timestamp (attribute AT-T056) is always set by the Requesting PSP. In case the Requesting PSP uses an RVM, the PSP needs to send it to the RVM together with the VOP request, regardless of the protocol and interface used between the Requesting PSP and its RVM. The RVM should then insert it in the outgoing VOP Request to the Responding PSP.
It is also the Requesting PSP who will determine if there is a time-out, not the RVM.