ICMP traffic archives/writing ICMP traffic in a file
 

hi
Im working on an developing IDS against "smurf" attack for which i need ICMP traffic. TCP and UDP trffic archives are easily available But i didnt find ICMP traffic. can any one send me some links from where i can download ICMP traffic archives.
ALSO can anyone tell how i can write ICMP traffic into file through TCPDUMP or ETHEREAL. what i know that

tcpdump[-w file]
tcpdump[-p file] //for specific protocol/port
are used. but i need complete procedure how can i write ICMP traffic into afile?
thanks in advance
bye