When an IPv6-only application needs to communicate with an IPv4-only host or application, some form of IPv6-to-IPv4 translation or application-layer gateway must occur. If needed, an outboard protocol translator or application-layer gateway component must be used, as z/OS® Communications Server TCP/IP does not include such support. There are various technologies which can be used, such as NAT-PT or SOCKS64. See Application layer gateways and protocol translation for more information.