Internet Protocol version 6 (IPv6)
The most widespread implementation of IP currently is IPv4, which utilizes a 32-bit address. Mathematically, a 32-bit address can provide roughly 4 billion unique IP addresses (232 = 4,294,967,296). Practically, the number of usable IPv4 addresses is much lower, as many addresses are reserved for diagnostic, experimental, or multicast purposes.
The explosive growth of the Internet and corporate networks quickly led to an IPv4 address shortage. Various solutions were developed to alleviate this shortage, including CIDR, NAT, and Private Addressing. However, these solutions could only serve as temporary fixes.
In response to the address shortage, IPv6 was developed. IPv6 increases the address size to 128 bits, providing a nearly unlimited supply of addresses (340,282,366,920,938,463,463,374,607,431,768,211,456 to be exact). This provides roughly 50 octillion addresses per person alive on Earth today, or roughly 3.7 x 1021 addresses per square inch of the Earth’s surface.
Hexadecimal Number –
Hexadecimal is a positional number system that uses radix (base) of 16. To represent the values in readable format, this system uses 0-9 symbols to represent values from zero to nine and A-F to represent values from ten to fifteen. Every digit in Hexadecimal can represent values from 0 to 15.
An IPv6 address is made of 128 bits divided into eight 16-bits blocks. Each block is then converted into 4-digit Hexadecimal numbers separated by colon symbols.
Example - 2001:0000:3238:DFE1:0063:0000:0000:FEFB
Even after converting into Hexadecimal format, IPv6 address remains long. IPv6 provides some rules to shorten the address. The rules are as follows:
Rule.1: Discard leading Zero(es):
For Example - In Block 5, 0063, the leading two 0s can be omitted such as (5th block): 2001:0000:3238:DFE1:63:0000:0000:FEFB
Rule.2: If two of more blocks contain consecutive zeroes, omit them all and replace with double colon sign ::
For Example Such as (6th and 7th block):2001:0000:3238:DFE1:63::FEFB
Rule.3:Consecutive blocks of zeroes can be replaced only once by :: so if there are still blocks of zeroes in the address, they can be shrunk down to a single zero
For Example such as (2nd block): 2001:0:3238:DFE1:63::FEFB
Network And Node Addresses
IPv4 an address is split into two components a network component and a node component.This was done initially using Address classes and later using subnet masking.
In IPv6 we do the same. The first step is to split the address into two parts.
The address is split into 2 ,64 bit segments the top 64 bits is the network part and the lower 64 bits the node part:
The upper 64 bits are used for routing.
The lower 64 bits identify the address of the interface or node, and is derived from the actual physical or MAC address using IEEE’s Extended Unique Identifier (EUI-64) format.
If we look at the upper 64 bits in more detail we can see that it is split into 2 blocks of 48 and 16 bits respectively the lower 16 bits are used for subnets on an internal networks, and are controlled by a network administrator.
The upper 48 bits are used for the global network addresses and are for routing over the internet.
The MAC address of a system is composed of 48-bits and represented in Hexadecimal. MAC addresses are considered to be uniquely assigned worldwide. Interface ID takes advantage of this uniqueness of MAC addresses. A host can auto-configure its Interface ID by using IEEE’s Extended Unique Identifier (EUI-64) format. First, a host divides its own MAC address into two 24-bits halves. Then 16-bit Hex value 0xFFFE is sandwiched into those two halves of MAC address, resulting in EUI-64 Interface ID.
Conversion of EUI-64 ID into IPv6 Interface Identifier
To convert EUI-64 ID into IPv6 Interface Identifier, the most significant 7th bit of EUI-64 ID is complemented. For example:
IPv6 Address Type-
The three types of IPv6 addresses are:
1) Unicast Address-Unicast addresses identify a single interface.
2) Anycast Address-Anycast addresses identify a set of interfaces in such a way that a packet sent to an anycast address is delivered to a member of the set.
3) Multicast Address-Multicast addresses identify a group of interfaces in such a way that a packet sent to a multicast address is delivered to all of the interfaces in the group.
Note :- IPv6 has no broadcast addresses: multicast addresses took over.
Global Unicast Address–
This address type is equivalent to IPv4’s public address.Global Unicast addresses in IPv6 are globally identifiable and uniquely addressable. These addresses are assigned by the IANA and used on public networks. They have a prefix of 2000::/3, (all the addresses that begin with binary 001).
Unique Local –
Similar to IPv4 private addresses. They are used in private networks and aren’t routable on the Internet. These addresses have a prefix of FD00::/8.This type of IPv6 address is globally unique, but it should be used in local communication. The second half of this address contain Interface ID and the first half is divided among Prefix, Local Bit, Global ID and Subnet ID.
Link Local –
these addresses are used for sending packets over the local subnet. Routers do not forward packets with this addresses to other subnets. IPv6 requires a link-local address to be assigned to every network interface on which the IPv6 protocol is enabled. These addresses have a prefix of FE80::/10. Auto-configured IPv6 address is known as Link-Local address. This address always starts with FE80. The first 16 bits of link-local address is always set to 1111 1110 1000 0000 (FE80). The next 48-bits are set to 0, thus:
Link-local addresses are used for communication among IPv6 hosts on a link (broadcast segment) only. These addresses are not routable, so a Router never forwards these addresses outside the link.
Scope of IPv6 Unicast Addresses:
The scope of Link-local address is limited to the segment. Unique Local Address are locally global, but are not routed over the Internet, limiting their scope to an organization’s boundary. Global Unicast addresses are globally unique and recognizable. They shall make the essence of Internet v2 addressing.
