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An IP address (Internet Protocol) is a numerical identifier assigned to every device connected to a network that uses the Internet Protocol. Its primary function is twofold:
- To uniquely identify a device (computer, smartphone, server, printer, etc.)
- To allow communication between devices, indicating where data starts from and where it must arrive
We can compare an IP address to a postal address: without it, data packets wouldn't know which destination to reach.
Over time, to respond to the exponential growth of the Internet, two main versions of the IP protocol were developed:
- IPv4 (Internet Protocol version 4)
- IPv6 (Internet Protocol version 6)
The goal of this article is to clearly explain how IPv4 and IPv6 work, what their characteristics are, and why they coexist today.
IPv4: Internet Protocol version 4
What is IPv4
IPv4 is the first widely used version of the IP protocol and is still very common today. It was standardized in the 1980s and served as the foundation for the development of the Internet for decades.
Structure of an IPv4 address
An IPv4 address consists of:
- 32 bits in total
- Divided into 4 octets (8-bit blocks)
- Represented in dotted decimal notation
Example:
192.168.1.1Each number can take a value between 0 and 255.
Number of available addresses
With 32 bits, IPv4 can theoretically provide:
- 2³² ≈ 4.3 billion addresses
At first, this number seemed enormous, but with the spread of:
- Computers
- Smartphones
- IoT devices
- Servers and cloud services
the IPv4 address space has progressively run out.
Classes and subnets (overview)
Historically, IPv4 used a class system (A, B, C, D, E), which is now largely replaced by CIDR (Classless Inter-Domain Routing), allowing for a more efficient use of addresses.
Main limitations of IPv4
- Limited address space
- Need for techniques like NAT (Network Address Translation)
- Security configurations not natively integrated
These limits led to the development of a new version of the protocol.
IPv6: Internet Protocol version 6
What is IPv6
IPv6 was designed to replace IPv4 and solve its limitations, specifically the address shortage. Its design began in the 1990s.
Structure of an IPv6 address
An IPv6 address consists of:
- 128 bits in total
- Divided into 8 groups of 16 bits
- Represented in hexadecimal notation, separated by colons
Example:
2001:0db8:85a3:0000:0000:8a2e:0370:7334Leading zeros can be omitted and consecutive sequences of zeros can be abbreviated, making the address more readable.
Number of available addresses
With 128 bits, IPv6 offers:
- 2¹²⁸ addresses
An extremely large number, sufficient to assign billions of addresses to every human being on Earth.
Key features of IPv6
- Virtually unlimited address space
- No NAT: every device can have a public address
- Address autoconfiguration
- Integrated security (IPsec)
- More efficient routing
The intrinsic security of IPv6 stems from the fact that it was designed with the needs of a modern global network in mind, where data protection is a fundamental requirement rather than an optional add-on. Unlike IPv4, IPv6 natively integrates IPsec (Internet Protocol Security) as part of the protocol standard.
IPsec provides authentication, integrity, and encryption of IP packets. This means that data can be verified to ensure it comes from a trusted source, hasn't been altered during transit, and, if necessary, is encrypted to prevent reading by unauthorized parties. In IPv4, IPsec is optional and often not implemented; in IPv6, however, support is mandatory at the protocol level.
Another key aspect is the absence of NAT. In IPv4, NAT is often considered a form of "security," but in reality, it introduces complexity and can hinder end-to-end security mechanisms. IPv6 restores direct communication between devices, allowing for the consistent application of security policies and encryption from one end of the communication to the other.
Finally, IPv6 improves traffic management and reduces certain types of attacks related to packet fragmentation, making networks more transparent, controllable, and secure when properly configured.
Adoption of IPv6
Despite the advantages, IPv6 did not immediately replace IPv4. Today, the two protocols coexist, thanks to transition mechanisms such as:
- Dual Stack
- Tunneling
- IPv4/IPv6 translation
Comparison between IPv4 and IPv6
Comparative table
| Feature | IPv4 | IPv6 |
|---|---|---|
| Address length | 32 bits | 128 bits |
| Number of addresses | ~4.3 billion | 2¹²⁸ |
| Notation | Dotted decimal | Hexadecimal with colons |
| NAT | Necessary | Not necessary |
| Security | Optional | Integrated |
| Autoconfiguration | Limited | Advanced |
| Current status | Widely used | Growing |
Not a simple version update...
IPv4 played a fundamental role in the development of the Internet, but it is now technically limited. The use of NAT has allowed its life to be extended, but at the cost of increased network complexity.
IPv6 represents the future of connectivity, thanks to an enormous address space, better traffic management, and modern integrated features. However, the transition requires time, investment, and compatibility with existing systems.
Migrating from IPv4 to IPv6 presents several technical and operational difficulties. First, IPv6 is not backward compatible with IPv4, making it necessary to use transition mechanisms like dual stack, tunneling, or translation, which increase network complexity. Many legacy devices, software, and network equipment do not fully support IPv6 or require updates. Furthermore, security management and monitoring change, requiring new skills for IT staff. Finally, the costs of updating and the need to maintain both protocols slow down the full adoption of IPv6.
For this reason, today the Internet operates in a phase of coexistence between IPv4 and IPv6, which is destined to last for several more years.
Conclusion
Understanding the differences between IPv4 and IPv6 is essential for anyone studying networking, computer science, or working with digital infrastructure. IPv4 made the Internet as we know it possible, while IPv6 ensures its future scalability and sustainability.
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