Softwire (protocol)
In computer networking, a softwire protocol is a category of network-layer tunneling protocols that enable the transparent encapsulation of one Internet protocol (usually IPv4 or IPv6) within another, allowing original packets to traverse network domains that natively support only the carrier protocol. Softwire protocols provide a virtual point-to-point or point-to-multipoint connection, emulating the behavior of a dedicated physical wire entirely in software.