> For the complete documentation index, see [llms.txt](https://docs.cybersim.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.cybersim.io/flows/layer-4-protocol-l4-proto.md).

# Layer-4 Protocol (L4 Proto)

The layer-4 protocol is the one used at the transport level. Most common transport protocol are the reliable Transmission Control Protocol (TCP) and the best-effort User Datagram Protocol (UDP).