.PS
C1: box wid 1.5 "lpr -Pmain";

B1: box wid 1.5 "main" with .w at C1.e+(.5,0);

P1: box wid 1.5 with .w at B1.e+(.5,0) "s1:";
P2: box wid 1.5 with .n at P1.s+(0,-.5) "s2:";
P3: box wid 1.5 with .n at P2.s+(0,-.5) "s2:";

arrow from C1.e to B1.w;
arrow dashed from B1.e to P1.w;
arrow dashed from B1.e to P2.w;
arrow dashed from B1.e to P3.w;

"main:" ljust at C1.sw+(0,-.5);
"  :chooser=/.../chooser" ljust at C1.sw+(.125,-.5-.2);
"  :destinations=s1@host1,s2@host2,s3@host3" ljust at C1.sw+(.125,-.5-.4);
"Queues can be on different servers" ljust at C1.sw+(0,-1.25);
.PE
