This TS defines the Radio Network Layer user plane protocol being used over the Iu interface.
The Iu UP protocol is located in the User plane of the Radio Network layer over the Iu interface: the Iu UP protocol layer.
The Iu UP protocol is used to convey user data associated to Radio Access Bearers.
One Iu UP protocol instance is associated to one RAB and one RAB only. If several RABs are established towards one
given UE, then these RABs make use of several Iu UP protocol instances.