udp packet loss

Question

I have a program which sends data from one pc to another using UDP (size of data 150 bytes). That program is writen in delphi 7 (TldUDPClient and TldUDPServer components using to send and recive data). I need to test this program on 30% packet loss.

I use ipfw for windows (downloaded from sourceforge) :

ipfw -f flush
ipfw add pipe 1 ip from any to any out
ipfw pipe 1 config plr 0.3

When I use ping I see that 30% of data loss.

When I launch my delphi program, after some time of working it returns an error: socket error 10004. The description of the error was: Interrupted function call. A blocking operation was interrupted by a call to WSACancelBlockingCall.

Is that problem of capability between my network component and packet loss emulation? Or will I see that in real situations too, when suffering packet loss? Which another firewall or another software i can use for emulation of packet loss?

Answer 1

Sounds more like a packet loss emulation issue. The ipfw tool seems to interrupt the connection - from this site - is it your version? - the source code does not implement this option - but it's 4 years old. With the ping command, you just know that you did not receive any answer within the expected time - there is no "connection" in the ARP protocol AFAIR.

From the UDP standard, packet loss is painless: there is no acknowledge nor error message retrieved to the socket layer.

On a real network connection, UDP packets are lost silently.

And painfully... perhaps ;)