[ns] blue.cc for ns-1.1

i m doing some simulations on buffer managemente schemes. For blue techinque i have downloaded ns-1.1 from wood's homepage....
now when i try to comile it , it gives me following error :

c++ -static -o ns -I. -mv8 -msupersparc -DSIGRET=void -DNO_TK -O2 version.o ns
_tcl.o scheduler.o link.o lossy.o ns_tclsh.o Tcl.o Tcl2.o object.o packet.o node
.o agent.o cbr.o misc.o route.o flow.o tcp.o tcp-reno.o tcp-sink.o loss-monitor.
o ivs.o data-source.o red.o blue.o fairblue.o drop-tail.o cbq.o trace.o random.o
tcp-newreno.o scoreboard.o tcp-sack1.o loss-policy.o tcp-fack.o message.o tcpli
b-telnet.o -L/user/ubt4139/ns-1.1/../tcl7.5/unix -ltcl7.5 -lsocket -lnsl -lintl
-lm -lc -ldl
ld: fatal: library -ldl: not found
ld: fatal: File processing errors. No output written to ns
collect2: ld returned 1 exit status
make: *** [ns] Error 1 &! nbsp;