.PS
.ps 20
## figure 3
boxwid  =       3*boxwid
define boxit @
        box "$1" with .n at ($2.s.x, $2.s.y-lineht/2)
        line from $2.s to last box.n
@
define peer @
        box "$1" with .n at ($3.s.x, $3.s.y-lineht/2)
        line    from $3.s to last box.n
        line $4 from $2.e to last box.w
@
##
B1:     box "APPLICATION"
B2:     boxit(PRESENTATION,B1)
B3:     boxit(SESSION,B2)
B4:     boxit(TRANSPORT,B3)
B5:     boxit(NETWORK,B4)
B6:     boxit(DATA LINK,B5)
B7:     boxit(PHYSICAL,B6)
##
L1:	line dashed from (B3.sw.x-boxwid/2,B3.sw.y-(B3.sw.y-B4.nw.y)/2) \
		      to (B3.se.x+boxwid/2,B3.sw.y-(B3.sw.y-B4.nw.y)/2)
##
.PE