The Internet Protocol (IP) will be moving to the new IP version 6 (IPv6) from the current IP version 4 (IPv4). IPv6 addresses IPv4 limitations, such as a quickly evaporating address space and a lack of quality-of-service (QoS) support. But IPv4 is used throughout the Internet, and current TCP/IP stacks won't support IPv6.
IPv4 and IPv6 can coexist on the same network because the Version field in a packet header identifies the type of packet. A device can support both protocols, but it must have both IPv6 and IPv4 protocol stacks.
IPv4 and IPv6 can be mixed on the same network by using a router that supports network address translation (NAT). IPv6 will first find use on the Internet backbone, with NAT router support letting IPv4 nodes operate unchanged. IPv6 will be exposed as subnets. Internet service providers support IPv6.