IPv6 protocol: the ultimate evolution of IPv4, the concepts, addresses and messages you need to know

Hello everyone, I am Bernie, an IT pre-sales engineer.

IPv4 has been popular since September 1981. As the fourth version of the Internet communication protocol, IPv4 has been the core of the network layer for more than 30 years.

It is a connectionless protocol, that is, the two communicating devices do not need to establish a stable connection channel in advance, the system only needs to select a route for transmission.

IPv4 is useful, but with the rapid development of the Internet, the number of connections has increased exponentially. The 32-bit IPv4 can only provide about 4.3 billion addresses (2 to the power of 32, 4294967296). In September 2011, 4.3 billion IPv4 addresses were used up!

Thus, IPv6 came to the fore. IPv6 is said to be able to "address every grain of sand on the earth", which sounds a bit exaggerated, but it actually makes sense. Because it is 128 bits long, the number of addresses it can provide is 2 to the 128th power (3.4028237e+38, 256 trillion trillion trillion trillion).

IPv6 Development Timeline

• In 1992, IETF (Internet Engineering Task Force) put forward recommendations on the development of the next generation of IP addresses and formed a white paper.
• In 1994, the RFC (Request For Comments) used to define IPv6 was published and established guidelines for the parallel use of IPv4 and IPv6.
• In 2003, IETF released the IPv6 test network (6bone network) to verify the feasibility of the IPv4 to IPv6 migration plan.
• In 2009, the 6bone network architecture used to verify the IPv6 protocol began to be implemented in 260 organizations in 39 countries around the world.
• In 2011, most servers and computer operating systems support IPv6.
• In 2012, the Internet Society held the IPv6 Anniversary Day and the global IPv6 network was officially launched.
• In 2017, my country issued the "Action Plan for Promoting Large-Scale Deployment of Internet Protocol Version 6 (IPv6)", and major companies have joined the vigorous upgrade plan.

Address indication

Unlike IPv4, which uses dotted decimal notation, IPv6 uses dotted hexadecimal notation. The entire address includes two aspects: the network prefix and the interface identifier. The network prefix is ​​the network ID, and the interface identifier is the host ID. IPv6 has three representation methods.

① Hexadecimal system

Format: x:x:x:x:x:x:x:x, where each X represents 16 bits in the address, expressed in hexadecimal.

Example:
5BCD:E901:23C5:6789:AEC7:E

② 0 bit compression

If an IPv6 address contains a continuous segment of 0s, the continuous segment of 0s can be compressed into “::”.

Example: AB00:0:0:0:0:0:0:1101 → AB00::1101

③ Embedded IPv4

An IPv6 address can be embedded in an IPv4 segment: the first 96 bits are the v6 address, and the last 32 bits are the v4 address x:x:x:x:dddd

Example: ::192.168.10.1 ::FF:169.167.3.1

Address Type

There are three types of IPv6 addresses: unicast address, multicast address, and anycast address.

It should be noted that the broadcast address of the IPv4 address is cancelled in IPv6 and replaced by multicast.

Unicast Address

Just like the unicast address in IPv4 address, it is used to uniquely identify a port. Data packets sent to the unicast address will be sent to a port identified by this address.

For example, by using unicast address communication, PC1 can uniquely find PC2 in the port under the same switch for communication.

Multicast Address

Used to identify a group of ports. Data packets sent to the multicast address are transmitted to all interfaces identified by this address.

For example, using the multicast address method, PC1 can communicate with PC2/3/4 at the same time.

Anycast Address

A datagram sent to an anycast address is delivered to the port closest to the source node among a group of ports identified by the address.

Note: The distance mentioned here is calculated based on the routing protocol, not the physical length of the address.

IPv6 Header

The overall structure of an IPv6 message includes a header, an extension header, and upper-layer protocol data. The header includes the following contents as shown in the figure.

• Version: 4-digit version number, IPv6 corresponds to 6
• Traffic Class: Traffic class, mainly QoS class
• Flow label: identifies the content of packets in the same flow
• Data length: The number of bytes following the current IPv6 packet header, including the extension header
• Next header: The header type of the message following the current header
• Hop limit: decrement after each forwarding, similar to TTL of IPv4

1.6. Comparison between IPv6 and IPv4

Compared with IPv4, IPv6 is more than just a large number. It has many advantages, such as supporting QoS network quality level, and being able to do route aggregation to improve route forwarding efficiency. A small part of the differences is listed below.

Summary

The above is a brief introduction to IPv6, but it does not cover many technical details, such as IPv6 addressing technology and the important basic protocol ICMPv6.

In 2023, Internet technology and IoT technology have developed rapidly. The number of global mobile connections has exceeded 5.5 billion, and the number of IP addresses has exceeded 4.29 billion. Both numbers have exceeded the total number of IPv4 addresses, but for IPv6, this number is not enough. With IPv6, we no longer have to worry about too many connections.

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