rnet server, the network translation address (NAT) is used [21]. The LAN communicates to the Internet through a gateway that has a globally unique IPv4 address. Outgoing IP datagrams are coded by the gateway to be correctly routed by the Internet while incoming datagrams are routed by the gateway to reach the suitable LAN destination. An IPv4 address (dotted decimal notation) 10101100 00010000 11111110 00000001 1 byte = 8 bits FIGURE 3.25 IPv4 address in dotted decimal notation and 32 bits (4*8), or 4 bytes in binary notation. Telecommunication Networks The rapid exhaustion of IPv4 address space, despite conservation techniques, prompted IETF to explore new technologies to expand the Internet's addressing capability. The per- manent solution was a redesign of the IP itself. This next generation of the IP was named IP Version 6 (IPv6) in 1995 [26]. The address size was increased from 32 to 128 bits or 16 octets, which, even with a generous assignment of network blocks, is deemed sufficient for the foreseeable future. Mathematically, the new address space provides the potential for a maximum of about 3.4x1038 unique addresses. The new design is not only based on the goal to provide a sufficient quantity of addresses, but also targets the efficient aggregation of subnet routing prefixes to occur at routing nodes. As a result, routing tables are smaller, which is an important result for faster work- ing of routers. The new design also provides the opportunity to separate the whole Internet into subnetworks with an independent local administration. As a matter of fact, the IPv6 address can be divided into a prefix indicating the address of the subnetwork within the whole Internet and a suffix that indicates the position of individual machines inside the subnetwork. If the global routing policy changes, IPv6 has facilities that automatically change the routing prefix of entire networks without requiring renumbering of the subnetwork suffix. The partition of the Internet in subnetworks managed by gateways also transform