digraph G {
    node [ shape=box ]

    upstreamrouter1 [ label="Upstream Router 1\nStateless routing" ];
    upstreamrouter2 [ label="Upstream Router 2\nStateless routing" ];

    router1 [ label="Internal Router 1\nStateful routing" ];
    router2 [ label="Internal Router 2\nStateful routing" ];

    servers [ label="Servers" ]
    internet [ label="Internet" shape=oval ]

    servers->router1 [ label="Use as default router" ]
    router1->{upstreamrouter1,upstreamrouter2} [ label="Forward packet" ]
    {upstreamrouter1,upstreamrouter2}->internet [ label="Forward packet" ]
    internet->{upstreamrouter1,upstreamrouter2} [ label="Send answers" ]
    {upstreamrouter1,upstreamrouter2}->router2 [ label="Return anwers from the Internet" ]
    router2->servers [ label="Drop the answer, no state entry" ]

}