Finished Network Design documentation part in README.rdoc

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@@ -376,6 +376,100 @@ We can go even further and divide into 11 subnets:
 As you can see, most of the networks are /28, with a few /27 and one
 /26 to fill up the remaning space.
 
+=== Summarization
+
+Summarization (or aggregation) is the process when two or more
+networks are taken together to check if a supernet, including
+all and only these networks, exists. If it exists then this supernet 
+is called the summarized (or aggregated) network.
+It is very important to understand that summarization can only
+occur if there are no holes in the aggregated network, or, in
+other words, if the given networks fill completely the address space
+of the supernet. So the two rules are:
+
+  1) The aggregate network must contain +all+ the IP addresses of the
+  original networks;  
+  2) The aggregate network must contain +only+ the IP addresses of the
+  original networks; 
+
+A few examples will help clarify the above. Let's consider for
+instance the following two networks:
+
+  ip1 = IPAddress("172.16.10.0/24")
+  ip2 = IPAddress("172.16.11.0/24")
+
+These two networks can be expressed using only one IP address
+network if we change the prefix. Let Ruby do the work:
+
+  IPAddress::IPv4::summarize(ip1,ip2).to_s
+    #=> "172.16.10.0/23"
+
+We note how the network "172.16.10.0/23" includes all the
+addresses specified in the above networks, and (more important) includes
+ONLY those addresses.
+
+If we summarized +ip1+ and +ip2+ with the following network:
+
+  "172.16.0.0/16"
+
+we would have satisfied rule #1 above, but not rule #2. So
+
+  "172.16.0.0/16"
+
+is not an aggregate network for +ip1+ and +ip2+.
+
+If it's not possible to compute a single aggregated network for
+all the original networks, the method returns an array with all the
+aggregate networks found. For example, the following four networks can be
+aggregated in a single /22:
+
+  ip1 = IPAddress("10.0.0.1/24")
+  ip2 = IPAddress("10.0.1.1/24")
+  ip3 = IPAddress("10.0.2.1/24")
+  ip4 = IPAddress("10.0.3.1/24")
+
+  IPAddress::IPv4::summarize(ip1,ip2,ip3,ip4).to_s
+    #=> "10.0.0.0/22",
+
+But the following networks can't be summarized in a single
+network:
+
+  ip1 = IPAddress("10.0.1.1/24")
+  ip2 = IPAddress("10.0.2.1/24")
+  ip3 = IPAddress("10.0.3.1/24")
+  ip4 = IPAddress("10.0.4.1/24")
+  IPAddress::IPv4::summarize(ip1,ip2,ip3,ip4).map{|i| i.to_s}
+    #=> ["10.0.1.0/24","10.0.2.0/23","10.0.4.0/24"]
+
+In this case, the two summarizables networks have been aggregated into
+a single /23, while the other two networks have been left untouched.
+
+=== Supernetting
+
+Supernetting is a different operation than aggregation, as it only
+works on a single network and returns a new single IPv4 object,
+representing the supernet.
+
+Supernetting is similar to subnetting, except that you getting as a
+result a network with a smaller prefix (bigger host space). For
+example, given the network
+
+  ip = IPAddress("172.16.10.0/24")
+
+you can supernet it with a new /23 prefix
+
+  ip.supernet(23).to_s
+    #=> "172.16.10.0/23"
+
+However if you supernet it with a /22 prefix, the network address will
+change: 
+
+  ip.supernet(22).to_s
+    #=> "172.16.8.0/22"
+
+This is because "172.16.10.0/22" is not a network anymore, but an host
+address.
+
 =IPv6
 
 Coming soon