In IPv6, what is the size of an address?

An IPv6 address is precisely 128 bits in size, which allows for a vast number of unique addresses. This increase in size is a significant advancement over IPv4, which utilizes only 32 bits.

The rationale behind the 128-bit address length is to accommodate the growing number of devices connected to the internet, ensuring that every device can have a unique address without the limitations imposed by IPv4's smaller address space. The 128-bit structure enables the representation of an enormous number of unique addresses, specifically 2^128 addresses, which translates to approximately 340 undecillion options. This immense capacity addresses the limitations of IPv4 and supports the expansion of the internet, especially in scenarios where the Internet of Things (IoT) is becoming prevalent.

In summary, the choice of 128 bits for IPv6 addresses is a critical aspect of its design, reflecting the need for sustainable growth in network addressing.