An IPv6 address of the MAP-T node is constructed according to RFC 7597, §5.2 and RFC 7599, §6. Figure: IPv6 address construction shows the IPv6 address of the MAP-T node.
The subnet ID for a MAP node (CE) is set to 0. Figure: Node interface shows the node interface (PSID is left-padded with zeros to create a 16-bit field and the IPv4 address is the public IPv4 address assigned to the CE).
This constructed IPv6 address represents the source IPv6 address of traffic sent from the CE to BR (upstream direction), and the destination IPv6 address in the opposite direction (downstream traffic sent from the BR to the CE).
The source IPv6 address in the downstream direction is a combination of the BR IPv6 prefix and the source IPv4 address (per RFC 7599, §5.1) received in the original packet.
The destination IPv6 address in the upstream direction is a combination of the BR IPv6 prefix and the IPv4 destination address (RFC 7599, §5.1) in the original packet.