IPv4 vs. IPv6: What’s the difference between the two protocols?

  • IPv4 utilises a 32-bit address format, accommodating approximately 4.3 billion unique addresses.
  • In contrast, IPv6 employs a 128-bit address format, offering an immense pool of addresses—approximately 340 undecillion.
  • IPv6, as the successor to IPv4, addresses the limitations of its predecessor while facilitating future internet expansion.

At the core of internet communication lies the Internet Protocol (IP), a fundamental set of rules governing the transmission of data across interconnected networks. Over time, the proliferation of internet-connected devices and the exhaustion of available addresses within the IPv4 system have catalysed the development of IPv6, a more robust and scalable successor.

What is the Internet Protocol (IP)?

The Internet Protocol (IP) serves as the foundation of internet communication, enabling devices to exchange data packets across networks. It assigns unique numerical addresses to each device, facilitating seamless transmission and routing of information within the vast expanse of the internet.

Also read: What is a public IP address?

What are IPv4 and IPv6?

IPv4, or Internet Protocol version 4, represents the longstanding standard for IP addressing. It employs a 32-bit address format, allowing for approximately 4.3 billion unique addresses. While revolutionary in its time, the finite nature of the IPv4 address space has become a bottleneck in the face of surging global connectivity demands.

IPv6, the successor to IPv4, was devised to address the limitations of its predecessor while laying the groundwork for future internet expansion. With a 128-bit address space, IPv6 offers an incomprehensibly vast pool of addresses—enough to assign a unique address to every grain of sand on Earth multiple times over. This expanded address space ensures the longevity and scalability of internet connectivity in the face of exponential growth.

Also read: Professor Li Xing: The challenges of IPv4 and IPv6 in China

What are the differences between IPv4 and IPv6?

1. Address space

IPv4: The defining characteristic of IPv4 is its utilisation of a 32-bit address space, capable of accommodating approximately 4.3 billion unique addresses. However, the rapid proliferation of internet-connected devices, fueled by the advent of smartphones, IoT devices, and other technologies, has precipitated the depletion of available IPv4 addresses. This scarcity poses a significant impediment to the seamless expansion of internet connectivity.

IPv6: In response to the limitations of IPv4, IPv6 was developed with a vastly expanded 128-bit address space. This exponential increase in address capacity—approximately 340 undecillion (3.4 × 10^38) addresses—ensures an ample supply of unique identifiers to accommodate the burgeoning array of internet-enabled devices. IPv6’s expansive address space not only mitigates the risk of address exhaustion but also facilitates the proliferation of innovative applications and services in the digital ecosystem.

2. Address format

IPv4: IPv4 addresses are expressed in a dotted-decimal notation, comprising four octets separated by periods. Each octet represents eight bits, resulting in a total of 32 bits in the address. For example, an IPv4 address may appear as “,” where each octet can range from 0 to 255.

IPv6: In contrast, IPv6 addresses are represented in hexadecimal format, consisting of eight groups of four hexadecimal digits separated by colons. This format accommodates the significantly larger address space of IPv6 while enhancing human readability. Additionally, IPv6 allows for the omission of leading zeros within each group, further simplifying address presentation. For instance, an IPv6 address might be depicted as “2001:0db8:85a3:0000:0000:8a2e:0370:7334,” with each group representing 16 bits of the address.

Also read: What to understand about APNIC IPv6 addresses?

3. Header length and efficiency

IPv4: IPv4 packets feature a fixed header length of 20 bytes, which includes essential information such as source and destination addresses, packet length, and protocol type. While this standardised header facilitates interoperability, it can lead to inefficiencies, particularly for smaller packets. Additionally, IPv4 headers may include various fields for optional services and fragmentation, contributing to packet overhead.

IPv6: IPv6 addresses the inefficiencies of IPv4 headers by standardising packet headers to a fixed length of 40 bytes. This streamlined header structure reduces overhead and enhances efficiency, especially for smaller packets. Furthermore, IPv6 eliminates certain fields present in IPv4 headers, such as the checksum field, which is recalculated at each intermediate router in IPv6, streamlining packet processing and improving network performance.

4. Autoconfiguration

IPv4: Typically relies on manual configuration or Dynamic Host Configuration Protocol (DHCP) servers to assign IP addresses to devices on a network. Manual configuration can be cumbersome and prone to errors, while DHCP introduces additional complexity and overhead.

IPv6: Introduces stateless address autoconfiguration (SLAAC), allowing devices to automatically generate IPv6 addresses based on network prefixes and their own unique identifiers. SLAAC simplifies network administration and eliminates the need for DHCP in many scenarios, streamlining the process of connecting devices to IPv6 networks.

Also read: How to get an APNIC IPv6 address?

5. Security features

IPv4: Lacks built-in security features, leading to vulnerabilities such as IP address spoofing, packet sniffing, and man-in-the-middle attacks. Security measures must be implemented at higher network layers or through additional protocols (e.g., IPsec) to mitigate these risks.

IPv6: Incorporates IPsec (Internet Protocol Security) as an integral part of the protocol suite, providing end-to-end encryption, authentication, and data integrity protection for IPv6 traffic by default. IPsec enhances network security and privacy without the need for supplementary protocols, addressing longstanding concerns associated with IPv4.

6. Multicasting and anycasting

IPv4: Supports multicasting, allowing a single packet to be sent to multiple recipients simultaneously. However, IPv4 multicast addresses are limited in number and scope, constraining the scalability and efficiency of multicast applications.

IPv6: Enhances multicasting capabilities with a significantly expanded range of multicast addresses, facilitating the deployment of multicast applications such as multimedia streaming, online gaming, and content delivery networks. Additionally, IPv6 introduces anycasting, enabling a packet to be sent to the nearest of several destinations, improving network efficiency and fault tolerance.


Lydia Luo

Lydia Luo, an intern reporter at BTW media dedicated in IT infrastructure. She graduated from Shanghai University of International Business and Economics. Send tips to j.y.luo@btw.media.

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