Wireshark-users: [Wireshark-users] packet id 0 ???

From: "Fabiana moreno" <fvmoreno@xxxxxxxxx>
Date: Fri, 11 Apr 2008 12:35:30 +0100
Hello there,

i have the following capture made by tcpdump and it looks weird to me as the packets id are always 0, has this happened to anyone? what does this mean?

1207912741.803450 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto UDP (17), length 85) 192.168.123.100.6970 > 192.168.123.103.6970: UDP, length 57
1207912741.803515 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto UDP (17), length 1500) 192.168.123.100.6970 > 192.168.123.103.6970: UDP, length 1472
1207912741.803591 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto UDP (17), length 1500) 192.168.123.100.6970 > 192.168.123.103.6970: UDP, length 1472
1207912741.803666 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto UDP (17), length 1500) 192.168.123.100.6970 > 192.168.123.103.6970: UDP, length 1472