This object contains the optional service allowed for this
Virtual configuration.
- 'none', there is no optional service provided.
- `ftp', indicates that the Virtual configuration service type
is FTP. The service type can only be set to 'ftp' if the
etsysLsnatVserverVirtualProtocol type is set to 'tcp'.
- `tftp', indicates that the Virtual configuration service type
is TFTP. The service type can only be set to 'tftp' if the
etsysLsnatVserverVirtualProtocol type is set to 'udp'.