The invention provides a method, to be used by a network node, for assisting a handover of a data session from a first routing path, associated with a first access network, to an alternative routing path, associated with an alternative access network, wherein data is routed over said first access network to a UT by binding a session identifier to a first routing identifier, wherein said session identifier and said first routing identifier are defined in accordance with a standard protocol routing scheme of said first access network, the method comprising the following steps: receiving a capability message uniquely identifying said UT according to a standard protocol routing scheme of said first access network and according to an alternative standard protocol routing scheme of said alternative access network, creating an alternative routing identifier for said session complying with the standard protocol routing scheme of said alternative access network and associating said alternative routing identifier with said UT, and, associating said session identifier with said alternative routing identifier. The invention also provides a network node, a UT, software and software media for realising the invention.