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Today is World IPv6 Day

Today is World IPv6 Day, the day where some of the major internet companies around the globe switch to IPv6 to test out the new protocol and to see how their network configurations fare. The internet is set to fully run out of IPv4 addresses very, very shortly, so World IPv6 Day is an easy way to test IPv6 connections with a huge test user base (the entire internet population) and evaluate the effects of the switch.

Popular internet sources such as Google, Facebook, Bing, YouTube, Yahoo and more have switched to using IPv6 before IPv4 to connect its users today, meaning both protocols will be in use. Despite this fact, around 0.05% of internet users will have problems connecting to websites on World IPv6 Day due to misconfigured home networks, according to Sierra Madre Patch. They mention that despite the low sounding figure, it actually equates to around 150,000 North Americans and more than a million people worldwide.

IPv6 has actually been around for more than a decade as engineers realized that IPv4 addresses will eventually come to a close, however companies have been slow to deploy proper IPv6 solutions as the situation hasnít been particularly grave. Unlike IPv4, which only allows for around 4.3 billion addresses (232 to be specific), IPv6 supports 340 undecillion addresses (2128) for extreme flexibility Ė or around 50 octillion addresses per person. To accommodate this huge increase, IPv6 addresses are longer compared to IPv4 addresses and use hexadecimal characters; an example would be 2001:db8:1f70:999:de8:7648:6e8.

You will most likely find your favourite internet sources participating in World IPv6 Day fully functional today, however if you are not, the day will end at 23:59 UTC where the sites will switch back to the standard IPv4 configuration.

Are you already on IPv6? Let us know in the comments.


Are there any differences between v4 and v6 or the only one is the length of the address?

Are there any differences between v4 and v6 or the only one is the length of the address?

There are protocol changes also.

IPv6 specifies a new packet format, designed to minimize packet header processing by routers. Because the headers of IPv4 packets and IPv6 packets are significantly different, the two protocols are not interoperable. However, in most respects, IPv6 is a conservative extension of IPv4. Most transport and application-layer protocols need little or no change to operate over IPv6; exceptions are application protocols that embed internet-layer addresses, such as FTP and NTPv3.

Simplified processing by routers

In IPv6, the packet header and the process of packet forwarding have been simplified. Although IPv6 packet headers are at least twice the size of IPv4 packet headers, packet processing by routers is generally more efficient, thereby extending the end-to-end principle of Internet design. Specifically:

  • The packet header in IPv6 is simpler than that used in IPv4, with many rarely used fields moved to separate optional header extensions.
  • IPv6 routers do not perform fragmentation. IPv6 hosts are required to either perform path MTU discovery, perform end-to-end fragmentation, or to send packets no larger than the IPv6 default minimum MTU size of 1280 octets.
  • The IPv6 header is not protected by a checksum; integrity protection is assumed to be assured by both link layer and higher layer (TCP, UDP, etc.) error detection. Therefore, IPv6 routers do not need to recompute a checksum when header fields (such as the time to live (TTL) or hop count) change.
  • The TTL field of IPv4 has been renamed to Hop Limit, reflecting the fact that routers are no longer expected to compute the time a packet has spent in a queue.

Unlike mobile IPv4, mobile IPv6 avoids triangular routing and is therefore as efficient as native IPv6. IPv6 routers may also support network mobility which allows entire subnets to move to a new router connection point without renumbering.

IPv4 limits packets to 65535 (216 - 1) octets of payload. IPv6 has optional support for packets over this limit, referred to as jumbograms, which can be as large as 4294967295 (232 - 1) octets. The use of jumbograms may improve performance over high-MTU links. The use of jumbograms is indicated by the Jumbo Payload Option header.

Options extensibility
The IPv6 protocol header has a fixed size (40 octets). Options are implemented as additional extension headers after the IPv6 header, which limits their size only by the size of an entire packet. The extension header mechanism provides extensibility to support future services for quality of service, security, mobility, and others, without redesign of the basic protocol

Packet format
The IPv6 packet is composed of two parts: the packet header and the payload. The header consists of a fixed portion with minimal functionality required for all packets and may contain optional extension to implement special features.

The fixed header occupies the first 40 octets (320 bits) of the IPv6 packet. It contains the source and destination addresses, traffic classification options, a hop counter, and a pointer for extension headers if any. The Next Header field, present in each extension as well, points to the next element in the chain of extensions. The last field points to the upper-layer protocol that is carried in the packet's payload.

Extension headers carry options that are used for special treatment of a packet in the network, e.g., for routing, fragmentation, and for security using the IPsec framework.

The payload can have a size of up to 64KB without special options, or larger with a jumbo payload option in a Hop-By-Hop Options extension header.

Unlike in IPv4, fragmentation is handled only in the end points of a communication session; routers never fragment a packet, and hosts are expected to use Path MTU Discovery to select a packet size that can traverse the entire communications path.

This are the few which I know.