| Internet Protocol version 6 (IPv6) is an evolutionary step from the current version of IP, version 4. It previously was known as IPng, meaning "IP next generation." IPv6 has been designed to work alongside IPv4 so that the transition can be carried out in a piecemeal fashion, reducing the impact on the Internet community. What Happened to IPv5? IPv5 could not be designated for the next generation of IP because it had already been used for an experimental protocol called the Internet Stream Protocol Version 2 (ST2). It was never widely used, but because version 5 had already been allocated, the new version of IP had to be given its own unique identifying number ”hence, version 6. ST2 is described in RFC 1819.
The actual IP addressing structure is discussed in the next section, "IPv6 Addressing." The remainder of this section looks at the features that the migration to IPv6 will provide: -
Increased address space ”The current number of IP addresses available with IPv4 is about 4 x 10 9 , or 4 billion, whereas IPv6 allows nearly 10 39 ”and that is without subnetting to create additional addresses. The number of addresses that can be allocated permits hundreds of computers per square meter of the Earth's surface, so it is intended to satisfy requirements for the foreseeable future. -
Classless addresses ”Unlike IPv4, in which IP addresses are identified by their network class (A, B, or C), IPv6 addresses will not contain address classes. Obviously some addresses will be reserved for specific use, but the general concept of IP address classes will cease . -
Better routing ”IPv6 will use classless Internet domain routing (CIDR) algorithms, which are more efficient in handling routes for large network environments. The longer IP address improves router efficiency by allowing grouping of addresses into hierarchies of network based on geographical location, (such as service provider or corporation, for example), something that IPv4 can not accommodate. -
Increased security ”IPv6 will be capable of providing authentication, a method of ensuring that a received packet has actually come from the origin provided in the packet's source address, and, more important, that it has not been altered (spoofed) during transmission. IPv6 also allows the data to be encrypted, something that IPv4 cannot do. Additionally, groups of managers can agree to use certain procedures, such as encryption keys, and then create what has been termed "security associations" for the secure exchange of data. -
Accommodation of non-IP address formats ”The longer IP address structure will provide sufficient space to allow translations of non-IP address formats, such as IPX or Ethernet, into IPv6 addresses. For example, an Ethernet address that is 48 bits long is too long to map directly into an IPv4 address, which is 32 bits long. With IPv6 being 128 bits long, direct mapping is now possible. -
More efficient broadcasting ”IPv6 introduces limited broadcasting to only those hosts that request to receive the data. This differs from the current IP broadcast method, whereby the packet is sent to every host on the network. This is especially important in the use of multimedia, for example, in which video or real-time data (which can be very large) can be transmitted efficiently using guaranteed bandwidth. -
Address discovery ”With the current IPv4 protocol, every host must be manually configured with its own address information or must rely on a DHCP server. IPv6 allows automatic address discovery using the IPv6 Stateless Address Autoconfiguration Protocol, by which a computer can "discover" its own IPv6 address. The protocol uses the unique Media Access Control (MAC) 48-bit address to form an interface identifier. For example, if a system has an Ethernet interface, then the 48-bit address is formed into a 64-bit interface ID. The Neighbor Discovery (ND) protocol then checks that there is not a duplicate on the subnet ”there shouldn't be because Ethernet addresses should be unique. Having obtained a unique address, a message is sent out to see if there is a local router capable of supporting IPv6. This allows two or more hosts on a network to operate with no router present; it allows automatic configuration of their IPv6 addresses and does not rely on any other server, such as a DHCP server. This list highlights the major differences between IPv4 and IPv6. See the Appendix for links to a more detailed technical specification of the protocol and a more comprehensive list of the features. The next section outlines the new format of the IPv6 address, as well as the changes that have been made to the address notation. |
