on IPv4 address scarcity

Author: vladak

network.tex

@@ -408,9 +408,10 @@
 \item Wildcard sockets are primarily used for servers.  If you need to
 distinguish between interfaces, you need a socket per an IP address.  This used
 to be used for web servers that distinguished virtual servers based on the IP
-address.  However, that is remote past.  To distinguish between virtual servers
-running on the same host, a HTTP header \uv{\texttt{Host:}} is used.  Similarly,
-the TLS protocol uses the \texttt{ServerName} extension.
+address.  However, that is remote past. These days, with the scarcity of public
+IPv4 addresses that would not be practical. To distinguish between virtual servers
+running on the same host, the \uv{\texttt{Host:}} HTTP header is used.
+Similarly, the TLS protocol uses the \texttt{ServerName} extension.
 \item The fact that the system starts listening on a port means that a TCP
 handshake is performed and data is being accepted.  The data is stored
 in a fixed length buffer and after it is filled out, the connection is still