[p2p-hackers] How reliable is UDP?

Stephen Samuel (leave the email alone) samnospam at bcgreen.com
Fri Dec 24 20:32:02 UTC 2004


ping (or mtr) can generally give you a good estimation of
packet loss in a connection.

1% packet loss is generally considered bad.  More than that will cause
severe performance penalties for things like NFS and also slow down
TCP transmissions noticably.

Local connections should generally have 0% packet loss (It's not
unusuall for me to leave ping sessions running for days to a local
box and get things like 80000 packets transmitted with 0 or 1 packet
lost).

 From a quick test with 10 packets/second:(about a 2500 mile round trip).

1626 packets transmitted, 1626 received, 0% packet loss, time 164186ms
rtt min/avg/max/mdev = 28.195/29.424/52.322/1.056 ms, pipe 2, ipg/ewma 101.037/29.204 ms


I get similar results for a ping session transcontinental * transatlantic.
472 packets transmitted, 470 received, 0% packet loss, time 54703ms
rtt min/avg/max/mdev = 200.554/202.114/230.265/2.298 ms, pipe 4, ipg/ewma 116.143/201.708 ms


and pinging a chinese SPAM site:

[samuel at me samuel]% ping -f -i.1 202.102.230.36
PING 202.102.230.36 (202.102.230.36) 56(84) bytes of data.
....................................................................
--- 202.102.230.36 ping statistics ---
1762 packets transmitted, 1694 received, 3% packet loss, time 178508ms
rtt min/avg/max/mdev = 466.896/479.661/621.438/6.357 ms, pipe 8, ipg/ewma 101.367/479.347 ms
[root at me samuel]#



David E. Meier wrote:
> Hi p2p-hackers,
> 
> I know that UDP traffic is not reliable by design. However, I wonder how
> reliable UDP packets reach their destination. Does someone on the list
> have experience with UDP packet loss? Is this usually in the range of a
> percent or more or less? Or is it even a common case that all packets
> arrive? Dave.

-- 
Stephen Samuel +1(604)876-0426             samnospam at bcgreen.com
		   http://www.bcgreen.com/
    Powerful committed communication. Transformation touching
      the jewel within each person and bringing it to light.



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