FRC 1149 CPIP is the protocol name http://www.blug.linux.no/rfc1149/
CPIP stands for Carrier Pigeon Internet Protocol.
and althought the first useage of CPIP was on april fools day, i assure you that this is no joke !
(maybe origonally intended as a joke.. but it was actually done !!!!)
Here is how CPIP works....
A normal outgoing Ethernet packet is printed out onto a small piece of paper, which isthen attacjed to a homing pigion and sent of the the destination address.
On arival, the message is scanned into the computer, and converted back to an IP datagram packet.
And the crazy thing is,.... it works !!!
They tested it with 2 com[uters on either side of a small mountain in Bergen !
here is the output of the Ping command !!!
(note the HUGE ping times)
CODE
vegard@gyversalen:~$ /sbin/ifconfig tun0
tun0 Link encap:Point-to-Point Protocol
inet addr:10.0.3.2 P-t-P:10.0.3.1 Mask:255.255.255.255
UP POINTOPOINT RUNNING NOARP MULTICAST MTU:150 Metric:1
RX packets:1 errors:0 dropped:0 overruns:0 frame:0
TX packets:2 errors:0 dropped:0 overruns:0 carrier:0
collisions:0
RX bytes:88 (88.0 B) TX bytes:168 (168.0 B)
vegard@gyversalen:~$ ping -i 450 10.0.3.1
PING 10.0.3.1 (10.0.3.1): 56 data bytes
64 bytes from 10.0.3.1: icmp_seq=0 ttl=255 time=6165731.1 ms
64 bytes from 10.0.3.1: icmp_seq=4 ttl=255 time=3211900.8 ms
64 bytes from 10.0.3.1: icmp_seq=2 ttl=255 time=5124922.8 ms
64 bytes from 10.0.3.1: icmp_seq=1 ttl=255 time=6388671.9 ms
— 10.0.3.1 ping statistics —
9 packets transmitted, 4 packets received, 55% packet loss
round-trip min/avg/max = 3211900.8/5222806.6/6388671.9 ms
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I think its just abuse of animals though... Whats more is that you have to TRAIN those pigeons before you can let them fly, and especially if the package contains something confidential and the pigeon somehow got off course and the package was intercepted by some other person... That would be something to ponder upon! 
