ecified in RFC 5771 [14]. Reserved for Future Use The block 240.0.0.0/4 is marked as reserved for future use. There has been much controversy about the usage of this address block. It seems that some routers think it is an error if they see a packet from this address space. Therefore, the use of the address space is relatively difficult - at least at the level of the Internet. It is clear that there has been a lot of pressure and interest in doing something with this block as it is about 6 per cent of the overall address space. However, at the time of writing, there has been no use found for it. Limited Broadcast Address The address 255.255.255.255/32 is a special address for link-local broadcast. Packets with this destination address are not forwarded on the IP layer, but all the nodes within the link-scope get the packet. Some applications use this address as their destination for initial boot strapping. 1.4.2 IPv6 Addresses The IPv6 address field is 128 bits long, and hence gives much bigger address space than IPv4. The theoretical maximum of the IPv6 address space is 2128 = 3.4 X 1038. A number this big is rather difficult to understand, and people have tried to explain the number in various ways. One of the examples is that there are 6.5 X 1023 addresses per every square meter of the earth. It is not clear why anybody would want to allocate addresses per square meter, but the message is clear: the IPv6 address space is very, very big. To distinguish IPv6 addresses from IPv4 addresses, and to have an address format that is at least vaguely readable, IPv6 has its own textual format. The textual format has been defined in RFC 4291 [15] and RFC 5952 [16]. The textual Deploying IPv6 in 3GPP Networks representation of an IPv6 address consists of eight 16-bit hexadecimal fields separated by colons As the IPv6 address format is quite long, and rather complex, SO are the rules on how to represent the addresses. Below are examples of legitimate address representations: 2001:41d0:1:7827::1 2001 db8::a:0:0 2001 db8 a Th