stateless transport tunneling (overlay) (STT)

Stateless Transport Tunneling(STT) is a tunneling method for virtual networks and virtual data centers, functionally comparable to Virtual Extensible LAN (VXLAN) and Network Virtualization Using GRE( NVGRE). The STT method works with encapsulation and is used in VMware, usually for communication between servers and virtual switches, the vSwitches.

Unlike the other tunneling techniques, STT tunneling is designed to transfer large data packets, up to 64 KB. In general, physical networks can only handle a limited packet size. According to the Ethernet standard, the maximum packet size, the Maximum Transmission Unit( MTU), is only 1,500 bytes. However, there are Ethernet components that can handle much larger data packets. To enable large data packets to be transmitted, they are fragmented as in the TCP protocol. Fragmentation can be moved to the Network Interface Controller( NIC) and implemented hardware-wise, which results in a higher speed than a software-wise solution.

Thanks to this technique - hardware fragmentation on the NIC and encapsulation in the TCP/ IP protocol - Stateless Transport Tunneling allows data packets of 64 KB to be transmitted from a server virtual machine( VM) to the end station via a tunnel. The fragmented data packets are reassembled on the receiving side.