| CPC H04W 76/12 (2018.02) [H04L 12/4633 (2013.01)] | 20 Claims |

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1. A method comprising:
receiving, by a user plane function (UPF) from a control plane function (CPF), a request to establish a layer 2 tunneling protocol (L2TP) tunnel between the UPF and an L2TP network server (LNS) for a first protocol data unit (PDU) session of a wireless device, wherein the UPF supports an L2TP service;
determining, by the UPF, a failure of the L2TP tunnel establishment; and
sending, by the UPF to the CPF and based on the determining, a message comprising a tunnel failure cause for the L2TP tunnel indicating:
an L2TP tunnel failure of the L2TP tunnel; and
that an L2TP access concentrator (LAC) and LNS pair connection between the UPF and the LNS does not exist;
wherein the UPF comprises the LAC.
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