It's still a hack (as far as I can tell) because we are patching the rates tables, and hence I think it is only loosly coupled with the actual calculation of bytes in each bucket.
However, it works very nicely for me! I have only been lightly testing with downloading stuff (hence packet dropping to slow rates), and I can set the max download rate to within a few kbyte/sec of the maximum and still keep near min ping times. I assume that the remaining sliver of bandwidth is taken up passing packets which arrive in a slight cluster, and for packets which I later need to drop (since I'm testing on an incoming interface and dropped packets don't count for bandwidth used calcs). However, I seem to be able to get *extremely* close to the max with this patch
Obviously all the numbers are hard coded, but they should be suitable for all ATM users. PPoE users will need to do something different (if someone can supply the details then I will see what we can do to make a more generic patch and use module params.
Note: That this code will probably affect the policer and CBQ modules in the same way as HTB, however, I don't have such a setup, so I can't test effectiveness (or detriment...). Feedback appreciated
Note also that rates in your scripts will now be expressed in terms of the ATM bandwidth, ie you put in something like the bandwidth you paid for, but (of course) you get roughly (bw * 48/53) passing through (this is normal, it's the overhead of running ATM).
--- iproute2-2.4.7.20020116/tc/tc_core.c 2000-04-16 18:42:55.000000000 +0100
+++ iproute2/tc/tc_core.c 2004-06-18 12:20:39.912974518 +0100
@@ -59,10 +59,19 @@
while ((mtu>>cell_log) > 255)
cell_log++;
}
+
+ // HACK - UK ATM Params
+ int encaps_cell_sz = 53;
+ int encaps_cell_overhead = 5;
+ int encaps_data_sz = encaps_cell_sz - encaps_cell_overhead;
+ int proto_overhead = 10; // PPP Overhead
+
for (i=0; i<256; i++) {
- unsigned sz = (i<<cell_log);
- if (sz < mpu)
- sz = mpu;
+ unsigned sz = ((i+1)<<cell_log)-1;
+ sz = sz + proto_overhead;
+ sz = ( (int)((sz-1)/encaps_data_sz) + 1) * encaps_cell_sz;
+// if (sz < mpu)
+// sz = mpu;
rtab[i] = tc_core_usec2tick(1000000*((double)sz/bps));
}
return cell_log;
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