DSTM (Dual Stack Transition Mechanism) is a tunnelling solution for IPv6-only networks, where IPv4 applications are still needed on dual-stack hosts within an IPv6-only infrastructure. IPv4 traffic is tunnelled over the IPv6-only domain until it reaches an IPv6/IPv4 gateway, which is in charge of packet encapsulation/decapsulation and forwarding between the IPv6-only and IPv4-only domains. The solution proposed by DSTM is transparent to any type of IPv4 application and allows the use of layer 3 security.