unitsize(1cm);

real marge=1mm;
pair z1=(0,0), z2=(4,0), z3=(4,-3), z4=(0,-3);
transform r=scale(.8);

object etat_1=draw("1",ellipse,z1,marge),
       etat_2=draw("2",ellipse,z2,marge),
       etat_3=draw("3",ellipse,z3,marge),
       etat_4=draw("4",ellipse,z4,marge);

add(new void(picture pic, transform t) {
   draw(pic,r*Label("3/5"),point(etat_1,N,t){N}..{E}point(etat_1,W,t),Arrow);
   draw(pic,r*Label("2/5"),point(etat_2,E,t){E}..{S}point(etat_2,N,t),Arrow);
   draw(pic,r*Label("1/5"),point(etat_3,S,t){S}..{W}point(etat_3,E,t),Arrow);
   draw(pic,r*Label("1"),point(etat_4,W,t){W}..{N}point(etat_4,S,t),Arrow);
   
   draw(pic,r*Label("3/10"),point(etat_1,E,t){NE}..point(etat_2,W,t),Arrow);
   draw(pic,r*Label("1/10"),point(etat_2,W,t){SW}..point(etat_1,E,t),Arrow);
   draw(pic,r*Label("1/2"),point(etat_2,S,t){S}..point(etat_3,N,t),Arrow);
   draw(pic,r*Label("1/20"),point(etat_3,W,t){W}..point(etat_4,E,t),Arrow);
   draw(pic,r*Label("1/10"),point(etat_1,S,t){S}..point(etat_4,N,t),Arrow);
   draw(pic,r*Label("3/4"),point(etat_3,NW,t){NW}..point(etat_1,SE,t),Arrow);
});