Lec36-IPv6 Addressing |Computer Networks

Key Concepts

IPv6 addressing, 128 bits, binary notation, colon hexadecimal notation, compression, expansion, mixed notation, CIDR notation, prefix, suffix, address space allocation, special addresses, global unicast, unique local unicast, link local addresses, multicast addresses, address blocks.

IPv6 Addressing Overview

IPv6 addressing utilizes 128 bits, a significant increase from IPv4's 32 bits. This allows for 2¹²⁸ possible addresses, which is 2⁹⁶ times more than IPv4.

Notations for IPv6 Addresses

• Binary Notation: Represents the address as a string of 128 ones and zeros. Primarily used by computers.
• Colon Hexadecimal Notation: Divides the 128 bits into eight sections, each containing 16 bits (2 bytes). Each section is represented by a hexadecimal number and separated by colons. Example: 2001:0db8:85a3:0000:0000:8a2e:0370:7334.
• Compression: Colon hexadecimal notation can be compressed for easier readability.
  • Leading zeros in a section can be omitted (e.g., 0000 becomes 0).
  • A single zero can represent a section of all zeros.
  • Consecutive sections of all zeros can be replaced with a double colon (::). Only one double colon is allowed per address.
  • Example: fdec:0000:0000:0000:0000:000f:bbff:ffff can be compressed to fdec::f:bbff:ffff.
• Expansion: The reverse process of compression, where the double colon is expanded to the appropriate number of zero-filled sections to ensure a total of eight sections.
• Mixed Notation: Combines hexadecimal notation with dotted decimal notation (IPv4). The last 32 bits of the IPv6 address are represented in IPv4 format. Example: ::192.168.2.13. This is valid when transitioning from IPv4 to IPv6.
• CIDR Notation: Uses a slash followed by a prefix number to indicate the network prefix length. Example: fac2:0:0:0:0:0:0:8/8.

Rationale for IPv6

IPv4 address exhaustion is the primary driver for IPv6 adoption. The proliferation of IoT devices and the increasing number of devices per user necessitate a larger address space.

IPv6 Address Space Allocation (Address Blocks)

The IPv6 address space is divided into five blocks:

1. Special Addresses: Starts with eight zeros (0000:0000:0000:0000::/8).
2. Global Unicast: Starts with 001 (three bits). Represents 1/8th of the IPv6 address space.
3. Unique Local Unicast: Starts with 1111 110.
4. Link Local Addresses: Starts with 1111 1110 10.
5. Multicast Addresses: Starts with 1111 1111.

| Block | Prefix (Binary) | CIDR Notation | | ---------------------- | --------------- | ------------- | | Special Addresses | 00000000 | /8 | | Global Unicast | 001 | | | Unique Local Unicast | 1111110 | | | Link-Local | 1111111010 | | | Multicast | 11111111 | /8 |

Prefix and Suffix

Similar to IPv4, IPv6 addresses are divided into a prefix and a suffix. The prefix identifies the network, and the suffix identifies the host within that network. The CIDR notation specifies the length of the prefix.

Conclusion

IPv6 addressing is essential for the future of the internet due to the limitations of IPv4. Understanding the different notations, compression techniques, and address space allocation is crucial for network administrators and developers. The global unicast address block is the most commonly used and will be discussed in detail in the next video.