I was thinking about the mean ping times that are used for handling node
load as I understood it, and had the idea to use a median instead.
Using an average means one single node can artificially push the avg
ping very high, unless you have more than 13 other active peers (the
influence from a 30s ping (is this the max, btw?) with 13 peers is
2000ms, so even with ping=0 for the other 13 peers, the mean ping will
be 2000ms. This could be a very easy way to DoS the network, no? Just
create a very popular node (read: SkarX) and then answer pings/packets
very slowly.
A median suppresses outliers, and outliers in a latency calculation will
mostly be, I suspect, those with high latency due to DoS:ing or just
having very bad connections (or absurd overutilization). Another form of
latency outliers is having local nodes, which could have very low
latency not affected by internet connection load.
Anyway, attached is a patch to print the median aswell. I had guessed
that a few nodes would have "insanely" high ping and be one reason for
overloads, and that seems to be the case atleast on my darknet node,
which has more active connections. The difference isnt major or anythng
though: mean is 353ms, and median is 311ms, caused mainly by one node
with a latency of about 3000ms. I will try to graph these two aswell for
some extended period of time for my node.
---
John Bäckstrand
Index: src/freenet/node/NodePinger.java
===================================================================
--- src/freenet/node/NodePinger.java (revision 8505)
+++ src/freenet/node/NodePinger.java (working copy)
@@ -1,5 +1,9 @@
package freenet.node;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.lang.Double;
+
import freenet.support.Logger;
public class NodePinger implements Runnable {
@@ -30,20 +34,32 @@
void recalculateMean(PeerNode[] peers) {
int peerCount = 0;
double total = 1.0;
+ ArrayList pingTimes = new ArrayList();
for(int i=0;i<peers.length;i++) {
PeerNode peer = peers[i];
if(!peer.isConnected()) continue;
peerCount++;
double avgPingTime = peer.averagePingTime();
+ pingTimes.add(new Double(avgPingTime));
double avgThrottledPacketSendTime =
peer.throttledPacketSendAverage.currentValue();
double value = Math.max(avgPingTime,
avgThrottledPacketSendTime);
Logger.minor(this, "Peer: "+peer.getPeer()+",
avgPingTime: "+avgPingTime+", avg throttled send time:
"+avgThrottledPacketSendTime);
total *= value;
}
+
+ Collections.sort(pingTimes);
+
+ for(int i=0; i<pingTimes.size(); i++){
+ Logger.minor(this, "at " + i + " " + pingTimes.get(i));
+ }
+
if(peerCount > 0) {
total = Math.pow(total, 1.0 / peerCount);
meanPing = total;
- Logger.minor(this, "Mean ping: "+meanPing+"ms");
+
+ double median = ((Double)
pingTimes.get((pingTimes.size()-1)/2)).doubleValue();
+
+ Logger.minor(this, "Mean ping: "+meanPing+"ms, median:
" + median + "ms");
}
}
_______________________________________________
Devl mailing list
[email protected]
http://emu.freenetproject.org/cgi-bin/mailman/listinfo/devl
