A
residential gateway (RG), e.g., a 5G-RG, indicates its support for ECN marking for L4S in uplink and / or downlink via a PDU Session Request message, e.g., a PDU Session Establishment Request message, communicated from the RG via a
wireline access gateway function (W-AGF) to a
core network, e.g., a 5GC. The indication, in some embodiments, is provided in either: a
Session Management (SM) capability field, e.g., a 5
GSM capability field, or as a new indication, which is included as part of a N1 SM container. A RG may, and sometimes does, determine congestion in its buffers / queues and perform ECN marking and report if
traffic congestion is being experienced within its own buffers / queues for uplink and / or downlink traffic. In some such embodiments, both an RG and a W-AGF can, and sometimes do, perform ECN marking for L4S simultaneously in both directions (i.e. uplink and downlink).