graph { flow: up; }

[ Client ] { offset: 0,2; origin: Proxy; }
[ Client1 ] { offset: 0,-2; origin: Proxy; }
[ Client2 ] { offset: 2,0; origin: Proxy; }
[ Client3 ] { offset: -2,0; origin: Proxy; }
[ Proxy ] { size: 3,2; }

[ Client ] <--> [ Proxy ]
[ Client1 ] <--> [ Proxy ]
[ Client2 ] <--> [ Proxy ]
[ Client3 ] <--> [ Proxy ]
