updated IP->ID formula for DHT

docs/ips.py

@@ -0,0 +1,50 @@
+#/bin/python
+
+import os
+import sys
+
+def num_ids(bits, total_bits):
+
+	ret = 8;
+	modulus = 0x100
+	mod_shift = 6 * 32 / total_bits
+	while bits >= 0:
+		ret *= min(1 << bits, 256)
+		ret = min(ret, modulus)
+		bits -= 8
+		modulus <<= mod_shift
+	return ret
+
+f = open('ip_id_v4.dat', 'w+')
+for i in range(0, 33):
+	print >>f, '%d\t%d\t%d' % (i, num_ids(i, 32), 1 << i)
+f.close()
+
+f = open('ip_id_v6.dat', 'w+')
+for i in range(0, 65):
+	print >>f, '%d\t%d\t%d' % (i, num_ids(i, 64), 1 << i)
+f.close()
+
+f = open('ip_id.gnuplot', 'w+')
+
+f.write('''
+set term png size 600,300
+set output "ip_id_v4.png"
+set logscale y
+set title "Number of possible node IDs"
+set ylabel "possible node IDs"
+set xlabel "bits controlled in IPv4"
+set xtics 4
+set grid
+plot "ip_id_v4.dat" using 1:2 title "octet-wise modulus" with lines, \
+	"ip_id_v4.dat" using 1:3 title "hash of IP" with lines
+
+set output "ip_id_v6.png"
+set title "Number of possible node IDs"
+set xlabel "bits controlled in IPv6"
+plot "ip_id_v6.dat" using 1:2 title "octet-wise modulus" with lines, \
+	"ip_id_v6.dat" using 1:3 title "hash of IP" with lines
+''')
+f.close()
+os.system('gnuplot ip_id.gnuplot')
+