In MPTN architecture, with respect to a particular transport user, a transport network that provides the address type and transport characteristics assumed in the design of the transport user. No MPTN address mapping or compensation protocols are used for data transfer.
In some cases, an untagged frame will arrive on a tagged port. To handle this, tagged ports have a special VLAN configured on them called the untagged VLAN. This is also known as the ‘native VLAN’.
Example of usage – “The switch assigns any untagged frame that arrives on a tagged port to the native VLAN. If a frame on the native VLAN leaves a trunk (tagged) port, the switch strips the VLAN tag out. In short, the native VLAN is a way of carrying untagged traffic across one or more switches.”