Systems, methods, and instrumentalities are disclosed herein for establishing a connection between a network node and a wireless transmit/receive unit (WTRU). A network node (e.g., a user plane function (UPF)) may receive a connection request message from another network node (e.g., a session management function). The connection request may indicate a request to establish a connection between the network node (e.g., the UPF) and a WTRU. The connection request message may indicate a header compression configuration (HCC) supported by a proxy. The network node may receive a request message from the WTRU indicating an HCC supported by the WTRU. The network node may determine a supported HCC using the HCC supported by the proxy and the HCC supported by the WTRU. The network node may configure the proxy to use the supported HCC. The network node may establish a connection with the WTRU.