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Internet Protocol
Internet Protocol
version 6 (IPv6) is the most recent version of the Internet Protocol
Internet Protocol
(IP), the communications protocol that provides an identification and location system for computers on networks and routes traffic across the Internet. IPv6
IPv6
was developed by the Internet Engineering Task Force (IETF) to deal with the long-anticipated problem of IPv4
IPv4
address exhaustion. IPv6
IPv6
is intended to replace IPv4.[1] IPv6
IPv6
became a Draft Standard in December 1998, but did not formally become an Internet
Internet
Standard until 14 July 2017.[2] Every device on the Internet
Internet
is assigned a unique IP address
IP address
for identification and location definition. With the rapid growth of the Internet
Internet
after commercialization in the 1990s, it became evident that far more addresses would be needed to connect devices than the IPv4 address space had available. By 1998, the Internet
Internet
Engineering Task Force (IETF) had formalized the successor protocol. IPv6
IPv6
uses a 128-bit address, theoretically allowing 2128, or approximately 7038340000000000000♠3.4×1038 addresses. The actual number is slightly smaller, as multiple ranges are reserved for special use or completely excluded from use. The total number of possible IPv6 addresses is more than 7028790000000000000♠7.9×1028 times as many as IPv4, which uses 32-bit addresses and provides approximately 4.3 billion addresses. The two protocols are not designed to be interoperable, complicating the transition to IPv6. However, several IPv6 transition mechanisms
IPv6 transition mechanisms
have been devised to permit communication between IPv4
IPv4
and IPv6
IPv6
hosts. IPv6
IPv6
provides other technical benefits in addition to a larger addressing space. In particular, it permits hierarchical address allocation methods that facilitate route aggregation across the Internet, and thus limit the expansion of routing tables. The use of multicast addressing is expanded and simplified, and provides additional optimization for the delivery of services. Device mobility, security, and configuration aspects have been considered in the design of the protocol. IPv6
IPv6
addresses are represented as eight groups of four hexadecimal digits with the groups being separated by colons, for example 2001:0db8:0000:0042:0000:8a2e:0370:7334, but methods to abbreviate this full notation exist.

Contents

1 Main features 2 Motivation and origin

2.1 IPv4 2.2 Working-group proposals

3 Comparison with IPv4

3.1 Larger address space 3.2 Multicasting 3.3 Stateless address autoconfiguration (SLAAC) 3.4 Network-layer security 3.5 Simplified processing by routers 3.6 Mobility 3.7 Options extensibility 3.8 Jumbograms 3.9 Privacy

4 Packet format 5 Addressing

5.1 Address representation 5.2 Address uniqueness 5.3 Link-local address 5.4 Global addressing

6 IPv6
IPv6
in the Domain Name System 7 Transition mechanisms

7.1 Dual-stack IP implementation 7.2 Tunneling

7.2.1 Automatic tunneling 7.2.2 Configured and automated tunneling (6in4)

7.3 Proxying and translation for IPv6-only hosts

8 IPv6
IPv6
readiness

8.1 Software

8.1.1 IPv4-mapped IPv6
IPv6
addresses

8.2 Hardware and embedded systems 8.3 Shadow networks

9 Security 10 Deployment 11 See also 12 References 13 External links

Main features[edit]

Decomposition of the IPv6 address
IPv6 address
representation into its binary form

IPv6
IPv6
is an Internet
Internet
Layer protocol for packet-switched internetworking and provides end-to-end datagram transmission across multiple IP networks, closely adhering to the design principles developed in the previous version of the protocol, Internet Protocol
Internet Protocol
Version 4 (IPv4). IPv6
IPv6
was first formally described in Internet
Internet
standard document RFC 1883, published in December 1995.[3] That RFC was obsoleted and replaced by RFC 2460, published in December 1998.[4] In July 2017 this specification was obsoleted and replaced by RFC 8200.[5] In addition to offering more addresses, IPv6
IPv6
also implements features not present in IPv4. It simplifies aspects of address assignment (stateless address autoconfiguration), network renumbering, and router announcements when changing network connectivity providers. It simplifies processing of packets in routers by placing the responsibility for packet fragmentation into the end points. The IPv6 subnet size is standardized by fixing the size of the host identifier portion of an address to 64 bits to facilitate an automatic mechanism for forming the host identifier from link layer addressing information (MAC address). Network security was a design requirement of the IPv6 architecture, and included the original specification of IPsec. IPv6
IPv6
does not specify interoperability features with IPv4, but essentially creates a parallel, independent network. Exchanging traffic between the two networks requires translator gateways employing one of several transition mechanisms, such as NAT64, or a tunneling protocol like 6to4, 6in4, or Teredo. Motivation and origin[edit] IPv4[edit]

Decomposition of the quad-dotted IPv4
IPv4
address representation to its binary value

Internet Protocol
Internet Protocol
Version 4 (IPv4) was the first publicly used version of the Internet
Internet
Protocol. IPv4
IPv4
was developed as a research project by the Defense Advanced Research Projects Agency (DARPA), a United States Department of Defense agency, before becoming the foundation for the Internet
Internet
and the World Wide Web. It is currently described by IETF publication RFC 791 (September 1981), which replaced an earlier definition (RFC 760, January 1980). IPv4
IPv4
included an addressing system that used numerical identifiers consisting of 32 bits. These addresses are typically displayed in quad-dotted notation as decimal values of four octets, each in the range 0 to 255, or 8 bits per number. Thus, IPv4
IPv4
provides an addressing capability of 232 or approximately 4.3 billion addresses. Address exhaustion was not initially a concern in IPv4
IPv4
as this version was originally presumed to be a test of DARPA's networking concepts.[6] During the first decade of operation of the Internet, it became apparent that methods had to be developed to conserve address space. In the early 1990s, even after the redesign of the addressing system using a classless network model, it became clear that this would not suffice to prevent IPv4
IPv4
address exhaustion, and that further changes to the Internet
Internet
infrastructure were needed.[7] The last unassigned top-level address blocks of 16 million IPv4 addresses were allocated in February 2011 by the Internet
Internet
Assigned Numbers Authority (IANA) to the five regional Internet
Internet
registries (RIRs). However, each RIR still has available address pools and is expected to continue with standard address allocation policies until one /8 Classless Inter-Domain Routing
Classless Inter-Domain Routing
(CIDR) block remains. After that, only blocks of 1024 addresses (/22) will be provided from the RIRs to a local Internet
Internet
registry (LIR). As of September 2015, all of Asia-Pacific Network Information Centre
Asia-Pacific Network Information Centre
(APNIC), the Réseaux IP Européens Network Coordination Centre (RIPE_NCC), Latin America and Caribbean Network Information Centre (LACNIC), and American Registry for Internet
Internet
Numbers (ARIN) have reached this stage.[8][9][10] This leaves African Network Information Center (AFRINIC) as the sole regional internet registry that is still using the normal protocol for distributing IPv4
IPv4
addresses. Working-group proposals[edit] By the beginning of 1992, several proposals appeared for an expanded Internet
Internet
addressing system and by the end of 1992 the IETF
IETF
announced a call for white papers.[11] In September 1993, the IETF
IETF
created a temporary, ad-hoc IP Next Generation (IPng) area to deal specifically with such issues. The new area was led by Allison Mankin and Scott Bradner, and had a directorate with 15 engineers from diverse backgrounds for direction-setting and preliminary document review:[7][12] The working-group members were J. Allard
J. Allard
(Microsoft), Steve Bellovin (AT&T), Jim Bound (Digital Equipment Corporation), Ross Callon (Wellfleet), Brian Carpenter (CERN), Dave Clark (MIT), John Curran (NEARNET), Steve Deering (Xerox), Dino Farinacci (Cisco), Paul Francis (NTT), Eric Fleischmann (Boeing), Mark Knopper (Ameritech), Greg Minshall (Novell), Rob Ullmann (Lotus), and Lixia Zhang (Xerox).[13] The Internet
Internet
Engineering Task Force adopted the IPng model on 25 July 1994, with the formation of several IPng working groups.[7] By 1996, a series of RFCs was released defining Internet Protocol
Internet Protocol
version 6 (IPv6), starting with RFC 1883. (Version 5 was used by the experimental Internet
Internet
Stream Protocol.) It is widely expected that the Internet
Internet
will use IPv4
IPv4
alongside IPv6 for the foreseeable future. Direct communication between the IPv4
IPv4
and IPv6
IPv6
network protocols is not possible; therefore, intermediary trans-protocol systems are needed as a communication conduit between IPv4
IPv4
and IPv6
IPv6
whether on a single device or among network nodes. Comparison with IPv4[edit] On the Internet, data is transmitted in the form of network packets. IPv6
IPv6
specifies a new packet format, designed to minimize packet header processing by routers.[4][14] Because the headers of IPv4
IPv4
packets and IPv6
IPv6
packets are significantly different, the two protocols are not interoperable. However, in most respects, IPv6
IPv6
is an 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 File Transfer Protocol
File Transfer Protocol
(FTP) and Network Time Protocol
Network Time Protocol
(NTP), where the new address format may cause conflicts with existing protocol syntax. Larger address space[edit] The main advantage of IPv6
IPv6
over IPv4
IPv4
is its larger address space. The length of an IPv6 address
IPv6 address
is 128 bits, compared with 32 bits in IPv4.[4] The address space therefore has 2128 or approximately 7038340000000000000♠3.4×1038 addresses. In addition, the IPv4
IPv4
address space is poorly allocated; in 2011, approximately 14% of all available addresses were utilized.[15] While these numbers are large, it was not the intent of the designers of the IPv6 address
IPv6 address
space to assure geographical saturation[clarification needed] with usable addresses. Rather, the longer addresses simplify allocation of addresses, enable efficient route aggregation, and allow implementation of special addressing features. In IPv4, complex Classless Inter-Domain Routing
Classless Inter-Domain Routing
(CIDR) methods were developed to make the best use of the small address space. The standard size of a subnet in IPv6
IPv6
is 264 addresses, the square of the size of the entire IPv4 address space. Thus, actual address space utilization rates will be small in IPv6, but network management and routing efficiency are improved by the large subnet space and hierarchical route aggregation. Renumbering an existing network for a new connectivity provider with different routing prefixes is a major effort with IPv4.[16][17] With IPv6, however, changing the prefix announced by a few routers can in principle renumber an entire network, since the host identifiers (the least-significant 64 bits of an address) can be independently self-configured by a host.[18] Multicasting[edit] Multicasting, the transmission of a packet to multiple destinations in a single send operation, is part of the base specification in IPv6. In IPv4
IPv4
this is an optional although commonly implemented feature.[19] IPv6
IPv6
multicast addressing shares common features and protocols with IPv4
IPv4
multicast, but also provides changes and improvements by eliminating the need for certain protocols. IPv6
IPv6
does not implement traditional IP broadcast, i.e. the transmission of a packet to all hosts on the attached link using a special broadcast address, and therefore does not define broadcast addresses. In IPv6, the same result can be achieved by sending a packet to the link-local all nodes multicast group at address ff02::1, which is analogous to IPv4 multicasting to address 224.0.0.1. IPv6
IPv6
also provides for new multicast implementations, including embedding rendezvous point addresses in an IPv6
IPv6
multicast group address, which simplifies the deployment of inter-domain solutions.[20] In IPv4
IPv4
it is very difficult for an organization to get even one globally routable multicast group assignment, and the implementation of inter-domain solutions is arcane.[21] Unicast
Unicast
address assignments by a local Internet
Internet
registry for IPv6
IPv6
have at least a 64-bit routing prefix, yielding the smallest subnet size available in IPv6
IPv6
(also 64 bits). With such an assignment it is possible to embed the unicast address prefix into the IPv6
IPv6
multicast address format, while still providing a 32-bit block, the least significant bits of the address, or approximately 4.2 billion multicast group identifiers. Thus each user of an IPv6
IPv6
subnet automatically has available a set of globally routable source-specific multicast groups for multicast applications.[22] Stateless address autoconfiguration (SLAAC)[edit] See also: IPv6 address
IPv6 address
§ Stateless address autoconfiguration IPv6
IPv6
hosts can configure themselves automatically when connected to an IPv6
IPv6
network using the Neighbor Discovery Protocol via Internet Control Message Protocol version 6 (ICMPv6) router discovery messages. When first connected to a network, a host sends a link-local router solicitation multicast request for its configuration parameters; routers respond to such a request with a router advertisement packet that contains Internet
Internet
Layer configuration parameters.[18] If IPv6
IPv6
stateless address auto-configuration is unsuitable for an application, a network may use stateful configuration with the Dynamic Host Configuration Protocol version 6 (DHCPv6) or hosts may be configured manually using static methods. Routers present a special case of requirements for address configuration, as they often are sources of autoconfiguration information, such as router and prefix advertisements. Stateless configuration of routers can be achieved with a special router renumbering protocol.[23] Network-layer security[edit] Internet Protocol
Internet Protocol
Security (IPsec) was originally developed for IPv6, but found widespread deployment first in IPv4, for which it was re-engineered. IPsec was a mandatory specification of the base IPv6 protocol suite,[4][24] but has since been made optional.[25] Simplified processing by routers[edit] 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
IPv4
packet headers, packet processing by routers is generally more efficient, because less processing is required in routers due to the headers being aligned to match common word sizes[4][14]. Moreover, IPv6
IPv6
doesn't implement a header checksum, in contrast to IPv4. This furthers the end-to-end principle of Internet
Internet
design, which envisioned that most processing in the network occurs in the leaf nodes. The packet header in IPv6
IPv6
is simpler than the IPv4
IPv4
header. Many rarely used fields have been moved to optional header extensions. IPv6
IPv6
routers do not perform IP fragmentation. IPv6
IPv6
hosts are required to either perform path MTU discovery, perform end-to-end fragmentation, or to send packets no larger than the default Maximum transmission unit (MTU), which is 1280 octets. The IPv6
IPv6
header is not protected by a checksum. Integrity protection is assumed to be assured by both the link layer or error detection and correction methods in higher-layer protocols, such as TCP and UDP. In IPv4, UDP may actually have a checksum of 0, indicating no checksum; IPv6
IPv6
requires a checksum in UDP. Therefore, IPv6
IPv6
routers do not need to recompute a checksum when header fields change, such as the time to live (TTL) or hop count. The TTL field of IPv4
IPv4
has been renamed to Hop Limit in IPv6, reflecting the fact that routers are no longer expected to compute the time a packet has spent in a queue. Mobility[edit] Unlike mobile IPv4, mobile IPv6
IPv6
avoids triangular routing and is therefore as efficient as native IPv6. IPv6
IPv6
routers may also allow entire subnets to move to a new router connection point without renumbering.[26] Options extensibility[edit] The IPv6 packet header has a minimum size of 40 octets. Options are implemented as extensions. This provides the opportunity to extend the protocol in the future without affecting the core packet structure.[4] However, a study in 2015 indicated that there was still widespread dropping of IPv6
IPv6
packets containing extension headers.[27] Jumbograms[edit] IPv4
IPv4
limits packets to 65,535 (216−1) octets of payload. An IPv6 node can optionally handle packets over this limit, referred to as jumbograms, which can be as large as 4,294,967,295 (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.[28] Privacy[edit] Like IPv4, IPv6
IPv6
supports globally unique IP addresses by which the network activity of each device can potentially be tracked. The design of IPv6
IPv6
intended to re-emphasize the end-to-end principle of network design that was originally conceived during the establishment of the early Internet. In this approach each device on the network has a unique address globally reachable directly from any other location on the Internet. Network prefix tracking is less of a concern if the user's ISP assigns a dynamic network prefix via DHCP.[29][30] Privacy extensions do little to protect the user from tracking if the ISP assigns a static network prefix. In this scenario, the network prefix is the unique identifier for tracking and the interface identifier is secondary. In IPv4
IPv4
the effort to conserve address space with network address translation (NAT) obfuscates network address spaces, hosts, and topologies. In IPv6
IPv6
when using address auto-configuration, the Interface Identifier (MAC address) of an interface port is used to make its public IP address
IP address
unique, exposing the type of hardware used and providing a unique handle for a user's online activity. It is not a requirement for IPv6
IPv6
hosts to use address auto-configuration, however. Yet, even when an address is not based on the MAC address, the interface's address is globally unique, in contrast to NAT-masqueraded private networks. Privacy extensions for IPv6
IPv6
have been defined to address these privacy concerns,[31] although Silvia Hagen describes these as being largely due to "misunderstanding".[32] When privacy extensions are enabled, the operating system generates random host identifiers to combine with the assigned network prefix. These ephemeral addresses are used to communicate with remote hosts making it more difficult to track a single device.[33] Privacy extensions are enabled by default in Windows (since XP SP1), OS X (since 10.7), and iOS (since version 4.3).[34][35] Some Linux distributions have enabled privacy extensions as well.[36] In addition to the temporary address assignments, interfaces also receive a stable address.[37] Interface Identifiers are generated such that they are stable for each subnet, but change as a host moves from one network to another. In this way it is difficult to track a host as it moves from network to network, but within a particular network it will always have the same address (unless the state used in generating the address is reset and the algorithm is run again) so that network access controls and auditing can potentially be configured. The traditional method of generating interface identifiers in use for unique address assignments was based on MAC addressing. In favor of better privacy protection, this method has been deprecated in some operating systems with newly established methods of RFC 7217.[38] Privacy extensions do not protect the user from other forms of tracking at other layers, e.g. Application Layer: tracking cookies or browser fingerprinting and Link Layer: IMSI-catcher or iBeacon Packet format[edit] Main article: IPv6
IPv6
packet

IPv6 packet header

An IPv6 packet has two parts: a header and payload. The header consists of a fixed portion with minimal functionality required for all packets and may be followed by optional extensions to implement special features. The fixed header occupies the first 40 octets (320 bits) of the IPv6
IPv6
packet. It contains the source and destination addresses, traffic classification options, a hop counter, and the type of the optional extension or payload which follows the header. This Next Header field tells the receiver how to interpret the data which follows the header. If the packet contains options, this field contains the option type of the next option. The "Next Header" field of the last option, 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. Without special options, a payload must be less than 64KB. With a Jumbo Payload option (in a Hop-By-Hop Options extension header), the payload must be less than 4 GB. Unlike with IPv4, routers never fragment a packet. Hosts are expected to use Path MTU Discovery to make their packets small enough to reach the destination without needing to be fragmented. See IPv6
IPv6
packet fragmentation. Addressing[edit] Main article: IPv6
IPv6
address IPv6
IPv6
addresses have 128 bits. The design of the IPv6 address
IPv6 address
space implements a very different design philosophy than in IPv4, in which subnetting was used to improve the efficiency of utilization of the small address space. In IPv6, the address space is deemed large enough for the foreseeable future, and a local area subnet always uses 64 bits for the host portion of the address, designated as the interface identifier, while the most-significant 64 bits are used as the routing prefix.[39] The identifier is only unique within the subnet to which a host is connected. IPv6
IPv6
has a mechanism for automatic address detection,[40] so that address autoconfiguration always produces unique assignments. Address representation[edit] The 128 bits of an IPv6 address
IPv6 address
are represented in 8 groups of 16 bits each. Each group is written as four hexadecimal digits (sometimes called hextets[41][42]) and the groups are separated by colons (:). An example of this representation is 2001:0db8:0000:0000:0000:ff00:0042:8329. For convenience, an IPv6 address
IPv6 address
may be abbreviated to shorter notations by application of the following rules.

One or more leading zeroes from any groups of hexadecimal digits are removed; this is usually done to either all or none of the leading zeroes. For example, the group 0042 is converted to 42. Consecutive sections of zeroes are replaced with a double colon (::). The double colon may only be used once in an address, as multiple use would render the address indeterminate. RFC 5952 recommends that a double colon not be used to denote an omitted single section of zeroes.[43]

An example of application of these rules:

Initial address: 2001:0db8:0000:0000:0000:ff00:0042:8329 After removing all leading zeroes in each group: 2001:db8:0:0:0:ff00:42:8329 After omitting consecutive sections of zeroes: 2001:db8::ff00:42:8329

The loopback address, 0000:0000:0000:0000:0000:0000:0000:0001, may be abbreviated to ::1 by using both rules. As an IPv6 address
IPv6 address
may have more than one representation, the IETF
IETF
has issued a proposed standard for representing them in text.[44] Address uniqueness[edit] Hosts verify the uniqueness of addresses assigned by sending a neighbor solicitation message asking for the Link Layer address of the IP address. If any other host is using that address, it responds. However, MAC addresses are designed to be unique on each network card which minimizes chances of duplication.[45] The host first determines if the network is connected to any routers at all, because if not, then all nodes are reachable using the link-local address that already is assigned to the host. The host will send out a Router Solicitation message to the all-routers[46][47] multicast group with its link-local address as source. If there is no answer after a predetermined number of attempts, the host concludes that no routers are connected. If it does get a response from a router, there will be network information inside that is needed to create a globally unique address. There are also two flag bits that tell the host whether it should use DHCP to get further information and addresses:

The Manage bit, that indicates whether or not the host should use DHCP to obtain additional addresses The Other bit, that indicates whether or not the host should obtain other information through DHCP. The other information consists of one or more prefix information options for the subnets that the host is attached to, a lifetime for the prefix, and two flags:[45]

On-link: If this flag is set, the host will treat all addresses on the specific subnet as being on-link, and send packets directly to them instead of sending them to a router for the duration of the given lifetime. Address: This is the flag that tells the host to actually create a global address.

Link-local address[edit] All interfaces of IPv6
IPv6
hosts require a link-local address. A link-local address is derived from the MAC address
MAC address
of the interface and the prefix fe80::/10. The process involves filling the address space with prefix bits left-justified to the most-significant bit, and filling the MAC address
MAC address
in EUI-64 format into the least-significant bits. If any bits remain to be filled between the two parts, those are set to zero.[40] The uniqueness of the address on the subnet is tested with the Duplicate Address Detection (DAD) method.[48] Global addressing[edit] The assignment procedure for global addresses is similar to local address construction. The prefix is supplied from router advertisements on the network. Multiple prefix announcements cause multiple addresses to be configured.[45] Stateless address autoconfiguration (SLAAC) requires a /64 address block, as defined in RFC 4291. Local Internet
Internet
registries are assigned at least /32 blocks, which they divide among subordinate networks.[49] The initial recommendation stated assignment of a /48 subnet to end-consumer sites (RFC 3177). This was replaced by RFC 6177, which "recommends giving home sites significantly more than a single /64, but does not recommend that every home site be given a /48 either". /56s are specifically considered. It remains to be seen if ISPs will honor this recommendation. For example, during initial trials, Comcast
Comcast
customers were given a single /64 network.[50] IPv6
IPv6
addresses are classified by three types of networking methodologies: unicast addresses identify each network interface, anycast addresses identify a group of interfaces, usually at different locations of which the nearest one is automatically selected, and multicast addresses are used to deliver one packet to many interfaces. The broadcast method is not implemented in IPv6. Each IPv6 address
IPv6 address
has a scope, which specifies in which part of the network it is valid and unique. Some addresses are unique only on the local (sub-)network. Others are globally unique. Some IPv6
IPv6
addresses are reserved for special purposes, such as loopback, 6to4
6to4
tunneling, and Teredo tunneling, as outlined in RFC 5156. Also, some address ranges are considered special, such as link-local addresses for use on the local link only, Unique local addresses (ULA), as described in RFC 4193, and solicited-node multicast addresses used in the Neighbor Discovery Protocol. IPv6
IPv6
in the Domain Name System[edit] In the Domain Name System, hostnames are mapped to IPv6
IPv6
addresses by AAAA resource records, so-called quad-A records. For reverse resolution, the IETF
IETF
reserved the domain ip6.arpa, where the name space is hierarchically divided by the 1-digit hexadecimal representation of nibble units (4 bits) of the IPv6
IPv6
address. This scheme is defined in RFC 3596. At the design stage of the IPv6
IPv6
DNS architecture, the AAAA scheme faced a rival proposal. This alternate approach, designed to facilitate network renumbering, uses A6 records for the forward lookup and a number of other innovations such as bit-string labels and DNAME records. It is defined in RFC 2874 and its references (with further discussion of the pros and cons of both schemes in RFC 3364), but has been deprecated to experimental status (RFC 3363). Transition mechanisms[edit] Main article: IPv6
IPv6
transition mechanism IPv6
IPv6
is not foreseen to supplant IPv4
IPv4
instantaneously. Both protocols will continue to operate simultaneously for some time. Therefore, some IPv6 transition mechanisms
IPv6 transition mechanisms
are needed to enable IPv6
IPv6
hosts to reach IPv4
IPv4
services and to allow isolated IPv6
IPv6
hosts and networks to reach each other over IPv4
IPv4
infrastructure.[51] Many of these transition mechanisms use tunneling to encapsulate IPv6 traffic within IPv4
IPv4
networks. This is an imperfect solution, which reduces the maximum transmission unit (MTU) of a link and therefore complicates Path MTU Discovery, and may increase latency.[52] Tunneling protocols are a temporary solution for networks that do not support native dual-stack, where both IPv6
IPv6
and IPv4
IPv4
run independently. Dual-stack IP implementation[edit] Dual-stack IP implementations provide complete IPv4
IPv4
and IPv6
IPv6
protocol stacks in the same network node on top of common physical layer implementation, such as Ethernet. This permits dual-stack hosts to participate in IPv6
IPv6
and IPv4
IPv4
networks simultaneously. The method is defined in RFC 4213[53]. Dual-stack configuration is the most desirable IPv6
IPv6
implementation during the transition from IPv4
IPv4
to IPv6, as it avoids the complexities of tunneling and security considerations, increased latency, management overhead, and a reduced path MTU.[54] However, it is not always possible when outdated network equipment may not support IPv6. Dual-stack configurations, however, might introduce additional security issues as hosts could be subject to attacks from both IPv4 and IPv6
IPv6
networks. It has been argued that the dual-stack architecture could ultimately overburden the global networking infrastructure by requiring routers to support IPv4
IPv4
and IPv6
IPv6
routing simultaneously.[55] Dual-stack implementation still requires an IPv4
IPv4
address on every node, which is limited by IPv4
IPv4
address exhaustion, one of the main motivations for IPv6. To address this, Dual-stack Lite (DS-Lite) was introduced, which uses network address translation and tunneling to encapsulate IPv4
IPv4
packets in IPv6
IPv6
transport, then deliver them to their final destination.[56] Tunneling[edit] Many current Internet
Internet
users do not have IPv6
IPv6
dual-stack support, and thus cannot reach IPv6
IPv6
sites directly. Instead, they must use IPv4 infrastructure to carry IPv6
IPv6
packets. This is done using a technique known as tunneling, which encapsulates IPv6
IPv6
packets within IPv4, in effect using IPv4
IPv4
as a link layer for IPv6. IP protocol 41 indicates IPv4
IPv4
packets which encapsulate IPv6 datagrams. Some routers or network address translation devices may block protocol 41. To pass through these devices, UDP packets may be used to encapsulate IPv6
IPv6
datagrams. Other encapsulation schemes, such as AYIYA or Generic Routing Encapsulation, are also popular. Conversely, on IPv6-only Internet
Internet
links, when access to IPv4
IPv4
network facilities is needed, tunneling of IPv4
IPv4
over IPv6
IPv6
protocol occurs, using the IPv6
IPv6
as a link layer for IPv4. Automatic tunneling[edit] Automatic tunneling refers to a technique by which the routing infrastructure automatically determines the tunnel endpoints. Some automatic tunneling techniques are below. 6to4
6to4
is recommended by RFC 3056. It uses protocol 41 encapsulation.[57] Tunnel endpoints are determined by using a well-known IPv4
IPv4
anycast address on the remote side, and embedding IPv4 address information within IPv6
IPv6
addresses on the local side. 6to4
6to4
is the most common tunnel protocol currently deployed. Teredo is an automatic tunneling technique that uses UDP encapsulation and can allegedly cross multiple NAT nodes.[58] IPv6, including 6to4 and Teredo tunneling, are enabled by default in Windows Vista[59] and Windows 7. Most Unix systems implement only 6to4, but Teredo can be provided by third-party software such as Miredo. ISATAP (Intra-Site Automatic Tunnel Addressing Protocol)[60] uses the IPv4
IPv4
network as a virtual IPv6
IPv6
local link, with mappings from each IPv4
IPv4
address to a link-local IPv6
IPv6
address. Unlike 6to4
6to4
and Teredo, which are inter-site tunneling mechanisms, ISATAP is an intra-site mechanism, meaning that it is designed to provide IPv6
IPv6
connectivity between nodes within a single organization. Configured and automated tunneling (6in4)[edit] 6in4 tunneling requires the tunnel endpoints to be explicitly configured, either by an administrator manually or the operating system's configuration mechanisms, or by an automatic service known as a tunnel broker;[61] this is also referred to as automated tunneling. Configured tunneling is usually more deterministic and easier to debug than automatic tunneling, and is therefore recommended for large, well-administered networks. Automated tunneling provides a compromise between the ease of use of automatic tunneling and the deterministic behavior of configured tunneling. Raw encapsulation of IPv6
IPv6
packets using IPv4
IPv4
protocol number 41 is recommended for configured tunneling; this is sometimes known as 6in4 tunneling. As with automatic tunneling, encapsulation within UDP may be used in order to cross NAT boxes and firewalls. Proxying and translation for IPv6-only hosts[edit] After the regional Internet
Internet
registries have exhausted their pools of available IPv4
IPv4
addresses, it is likely that hosts newly added to the Internet
Internet
might only have IPv6
IPv6
connectivity. For these clients to have backward-compatible connectivity to existing IPv4-only resources, suitable IPv6 transition mechanisms
IPv6 transition mechanisms
must be deployed. One form of address translation is the use of a dual-stack application-layer proxy server, for example a web proxy. NAT-like techniques for application-agnostic translation at the lower layers in routers and gateways have been proposed. The NAT-PT standard was dropped because of criticisms;[62] however, more recently, the continued low adoption of IPv6
IPv6
has prompted a new standardization effort of a technology called NAT64. IPv6
IPv6
readiness[edit] Compatibility with IPv6
IPv6
networking is mainly a software or firmware issue. However, much of the older hardware that could in principle be upgraded is likely to be replaced instead. In 2010, the American Registry for Internet
Internet
Numbers (ARIN) suggested that all Internet servers be prepared to serve IPv6-only clients by January 2012.[63] Software[edit] Host software may have only IPv4
IPv4
or only IPv6
IPv6
networking software, or it may support dual-stack, or hybrid dual-stack operation. The majority of personal computers running recent operating system versions support IPv6. Many popular applications with networking capabilities are compliant. Some software transitioning mechanisms are outlined in RFC 4038, RFC 3493, and RFC 3542. IPv4-mapped IPv6
IPv6
addresses[edit] Hybrid dual-stack IPv6/ IPv4
IPv4
implementations recognize a special class of addresses, the IPv4-mapped IPv6
IPv6
addresses. These addresses consist of an 80-bit prefix of zeros, the next 16 bits are ones, and the remaining, least-significant 32 bits contain the IPv4
IPv4
address. These addresses are typically written with a 96-bit prefix in the standard IPv6
IPv6
format, and the remaining 32 bits written in the customary dot-decimal notation of IPv4. For example, ::ffff:192.0.2.128 represents the IPv4
IPv4
address 192.0.2.128. A deprecated format for IPv4-compatible IPv6
IPv6
addresses is ::192.0.2.128.[64] Because of the significant internal differences between IPv4
IPv4
and IPv6, some of the lower-level functionality available to programmers in the IPv6
IPv6
stack does not work the same when used with IPv4-mapped addresses. Some common IPv6
IPv6
stacks do not implement the IPv4-mapped address feature, either because the IPv6
IPv6
and IPv4
IPv4
stacks are separate implementations (e.g., Microsoft Windows
Microsoft Windows
2000, XP, and Server 2003), or because of security concerns (OpenBSD).[65] On these operating systems, a program must open a separate socket for each IP protocol it uses. On some systems, e.g., the Linux kernel, NetBSD, and FreeBSD, this feature is controlled by the socket option IPV6_V6ONLY, as specified in RFC 3493.[66] Hardware and embedded systems[edit] The CableLabs
CableLabs
consortium published the 160 Mbit/s DOCSIS 3.0 IPv6-ready specification for cable modems in August 2006. DOCSIS 2.0 was updated as DOCSIS 2.0 + IPv6
IPv6
to provide IPv6
IPv6
support, which may be available with a firmware upgrade.[67][68] Shadow networks[edit] The addition of nodes having IPv6
IPv6
enabled by default by the software manufacturer, may result in the inadvertent creation of shadow networks, causing IPv6
IPv6
traffic flowing into networks having only IPv4 security management in place. This may also occur with operating system upgrades, when the newer operating system enables IPv6
IPv6
by default, while the older one did not. Failing to update the security infrastructure to accommodate IPv6
IPv6
can lead to IPv6
IPv6
traffic bypassing it.[69] Shadow networks have occurred on business networks in which enterprises are replacing Windows XP
Windows XP
systems that do not have an IPv6 stack enabled by default, with Windows 7
Windows 7
systems, that do.[70] Some IPv6
IPv6
stack implementors have therefore recommended disabling IPv4 mapped addresses and instead using a dual-stack network where supporting both IPv4
IPv4
and IPv6
IPv6
is necessary.[71] Security[edit] Research has shown that the use of fragmentation can be leveraged to evade network security controls. As a result, RFC 7112 requires that the first fragment of an IPv6 packet contains the entire IPv6 header chain, such that some very pathological fragmentation cases are forbidden. Additionally, as a result of research on the evasion of RA-Guard in RFC 7113, RFC 6980 has deprecated the use of fragmentation with Neighbor Discovery, and discouraged the use of fragmentation with Secure Neighbor Discovery (SEND). Deployment[edit] Main article: IPv6
IPv6
deployment The 1993 introduction of Classless Inter-Domain Routing
Classless Inter-Domain Routing
(CIDR) in the routing and IP address
IP address
allocation for the Internet, and the extensive use of network address translation (NAT), delayed IPv4
IPv4
address exhaustion. The final phase of exhaustion started on 3 February 2011.[72] However, despite a decade long development and implementation history as a Standards Track protocol, general worldwide deployment of IPv6
IPv6
is increasing slowly. As of September 2013[update], about 4% of domain names and 16.2% of the networks on the Internet
Internet
had IPv6
IPv6
protocol support.[73] IPv6
IPv6
has been implemented on all major operating systems in use in commercial, business, and home consumer environments. Since 2008, the domain name system can be used in IPv6. IPv6
IPv6
was first used in a major world event during the 2008 Summer Olympic Games,[74] the largest showcase of IPv6
IPv6
technology since the inception of IPv6.[75] Some governments including the Federal government of the United States
Federal government of the United States
and China
China
have issued guidelines and requirements for IPv6
IPv6
capability. In 2009, Verizon mandated IPv6
IPv6
operation, and reduced IPv4
IPv4
to an optional capability, for LTE cellular hardware.[76] As of June 2012[update], T-Mobile USA also supports external IPv6
IPv6
access.[77] As of 2014, IPv4
IPv4
still carried more than 99% of worldwide Internet traffic.[78][79] The Internet
Internet
exchange in Amsterdam and Seattle are the only large exchanges that publicly show IPv6
IPv6
traffic statistics, which as of December 2017 are tracking at about 2.1% and 8.8%, growing at about 0.9% and 4.0% per year, respectively.[80][81] As of 31 December 2017[update], the percentage of users reaching Google
Google
services with IPv6
IPv6
reached 22.6% for the first time in regular measurements, growing at about 5.8% per year, although varying widely by region.[82] As of December 2017[update] about 33% of Alexa Top 500 web servers support IPv6.[83] See also[edit]

Internet
Internet
portal

DHCPv6 China
China
Next Generation Internet Comparison of IPv6
IPv6
support in operating systems Comparison of IPv6
IPv6
support in common applications DoD IPv6
IPv6
product certification Happy Eyeballs List of IPv6
IPv6
tunnel brokers University of New Hampshire InterOperability Laboratory

References[edit]

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IPv6
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IPv6
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Internet
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Internet
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Internet
Engineering Task Force (IETF), RFC 2460   Obsoletes RFC 1883. ^ S. Deering; R. Hinden (July 2017), Internet
Internet
Protocol, Version 6 (IPv6) Specification, Internet
Internet
Engineering Task Force (IETF), ISSN 2070-1721, RFC 8200   Obsoletes RFC 2460. ^ Google
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IPv6
Internet
Internet
look like?. Event occurs at 13:35.  ^ a b c Bradner, S.; Mankin, A. (January 1995). The Recommendation for the IP Next Generation Protocol. IETF. doi:10.17487/RFC1752. RFC 1752. https://tools.ietf.org/html/rfc1752.  ^ Rashid, Fahmida. " IPv4
IPv4
Address Exhaustion Not Instant Cause for Concern with IPv6
IPv6
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IPv6
Multicast
Multicast
Address, P. Savola, B. Haberman (November 2004) ^ RFC 2908, The Internet
Internet
Multicast
Multicast
Address Allocation Architecture, D. Thaler, M. Handley, D. Estrin (September 2000) ^ RFC 3306, Unicast-Prefix-based IPv6
IPv6
Multicast
Multicast
Addresses, B. Haberman, D. Thaler (August 2002) ^ RFC 2894, Router Renumbering for IPv6, M. Crawford, August 2000. ^ RFC 4301, " IPv6
IPv6
Node Requirements", J. Loughney (April 2006) ^ RFC 6434, " IPv6
IPv6
Node Requirements", E. Jankiewicz, J. Loughney, T. Narten (December 2011) ^ RFC 3963, Network Mobility (NEMO) Basic Protocol Support, V. Devarapalli, R. Wakikawa, A. Petrescu, P. Thubert (January 2005) ^ Gont, F.; Linkova, J.; Chown, T.; Liu, S. (October 2015). "Observations on the Dropping of Packets with IPv6
IPv6
Extension Headers in the Real World". draft-ietf-v6ops-ipv6-ehs-in-real-world-01.  ^ RFC 2675, IPv6
IPv6
Jumbograms, D. Borman, S. Deering, R. Hinden (August 1999) ^ Statement on IPv6
IPv6
Address Privacy, Steve Deering & Bob Hinden, Co-Chairs of the IETF's IP Next Generation Working Group, 6 November 1999. ^ "Neues Internet-Protokoll erschwert anonymes Surfen". Spiegel.de. Retrieved 19 February 2012.  ^ Marten, T; Draves, R (January 2001). Privacy Extensions for Stateless Address Autoconfiguration in IPv6.  ^ IPv6
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Essentials by Silvia Hagen, p. 28, chapter 3.5. ^ Privacy Extensions (IPv6), Elektronik Kompendium. ^ Overview of the Advanced Networking Pack for Windows XP, Revision: 8.14 ^ IPv6: Privacy Extensions einschalten, Reiko Kaps, 13 April 2011 ^ "Comment #61 : Bug #176125 : Bugs: "procps" package: Ubuntu". Bugs.launchpad.net. Retrieved 19 February 2012.  ^ Gont, F (April 2014). A Method for Generating Semantically Opaque Interface Identifiers with IPv6
IPv6
Stateless Address Autoconfiguration (SLAAC). doi:10.17487/RFC7217. RFC 7217. https://tools.ietf.org/html/rfc7217.  ^ Fernando Gont (September 2016). "Recommendation on Stable IPv6 Interface Identifiers".  ^ RFC 4291, p. 9 ^ a b RFC 3315, R. Droms, J. Bound, B. Volz, T. Lemon, C. Perkins, and M. Carney, Dynamic Host Configuration Protocol
Dynamic Host Configuration Protocol
for IPv6 (DHCPv6), July 2003 (Proposed Standard) ^ Graziani, Rick (2012). IPv6
IPv6
Fundamentals: A Straightforward Approach to Understanding IPv6. Cisco Press. p. 55. ISBN 978-0-13-303347-2.  ^ Coffeen, Tom (2014). IPv6
IPv6
Address Planning: Designing an Address Plan for the Future. O'Reilly Media. p. 170. ISBN 978-1-4919-0326-1.  ^ S. Kawamura (August 2010). "A Recommendation for IPv6
IPv6
Address Text Representation". section 4.2.2. RFC 5952 .  ^ S. Kawamura (August 2010). "A Recommendation for IPv6
IPv6
Address Text Representation". RFC 5952 .  Missing or empty url= (help) ^ a b c Narten, T. (August 1999). "Neighbor discovery and stateless autoconfiguration in IPv6". IEEE Internet
Internet
Computing. 3 (4): 54–62. doi:10.1109/4236.780961.  ^ S. Thomson (September 2007). " IPv6
IPv6
Stateless Address Autoconfiguration". section 5.5.1. RFC 4862 .  ^ T. Narten (September 2007). "Neighbor Discovery for IP version 6 (IPv6)". section 6.3.7. RFC 4861 .  ^ S. Thomson; T. Narten; T. Jinmei (September 2007). " IPv6
IPv6
Stateless Address Autoconfiguration". RFC 4862 .  ^ " IPv6
IPv6
Address Allocation and Assignment Policy". RIPE NCC. 8 February 2011. Retrieved 27 March 2011.  ^ " Comcast
Comcast
Activates First Users With IPv6
IPv6
Native Dual Stack Over DOCSIS". Comcast.com. Comcast. 31 January 2011.  ^ " IPv6
IPv6
Transition Mechanism / Tunneling Comparison". Sixxs.net. Retrieved 20 January 2012.  ^ "Advisory Guidelines for 6to4
6to4
Deployment". IETF. RFC 6343 .  Missing or empty url= (help); access-date= requires url= (help) ^ "Basic Transition Mechanisms for IPv6
IPv6
Hosts and Routers". IETF. RFC 4213 .  Missing or empty url= (help); access-date= requires url= (help) ^ "IPv6: Dual stack where you can; tunnel where you must". www.networkworld.com. 5 September 2007. Retrieved 27 November 2012.  ^ Sun, Charles C. (1 May 2014). "Stop using Internet Protocol
Internet Protocol
Version 4!". Computerworld.  ^ "DS-Lite – IPv4
IPv4
over IPv6
IPv6
and NAT". 2012-03-22.  ^ RFC 3056, Connection of IPv6
IPv6
Domains via IPv4
IPv4
Clouds, B. Carpenter, February 2001. ^ RFC 4380, Teredo: Tunneling IPv6
IPv6
over UDP through Network Address Translations (NATs), C. Huitema, Februari 2006 ^ "The Windows Vista
Windows Vista
Developer Story: Application Compatibility Cookbook". Msdn2.microsoft.com. 24 April 2006. Retrieved 20 January 2012.  ^ RFC 5214, Intra-Site Automatic Tunnel Addressing Protocol (ISATAP), F. Templin, T. Gleeson, D. Thaler, March 2008. ^ RFC 3053, IPv6
IPv6
Tunnel Broker, A. Durand, P. Fasano, I. Guardini, D. Lento (January 2001) ^ RFC 4966, Reasons to Move the Network Address Translator-Protocol Translator (NAT-PT) to Historic Status ^ "Web sites must support IPv6
IPv6
by 2012, expert warns". Network World. 21 January 2010. Retrieved 30 September 2010.  ^ "IP Version 6 Addressing Architecture". IETF. February 2006. RFC 4291 . Retrieved 2017-11-28.  ^ inet6(4) –  OpenBSD
OpenBSD
Kernel Interfaces Manual ^ "Basic Socket Interface Extensions for IPv6". IETF. February 2003. p. 22. RFC 3493 . Retrieved 2017-11-28.  ^ " DOCSIS 2.0 Interface". Cablemodem.com. 29 October 2007. Archived from the original on 4 September 2009. Retrieved 31 August 2009.  ^ "RMV6TF.org" (PDF). Archived from the original (PDF) on 5 January 2012. Retrieved 20 January 2012.  ^ Mullins, Robert (April 5, 2012), Shadow Networks: an Unintended IPv6 Side Effect, retrieved March 2, 2013  ^ Cicileo, Guillermo; Gagliano, Roque; O’Flaherty, Christian; et al. (October 2009). IPv6
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For All: A Guide for IPv6
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Usage and Application in Different Environments (PDF). p. 5. Retrieved March 2, 2013.  ^ Jun-ichiro itojun Hagino (October 2003). "IPv4-Mapped Addresses on the Wire Considered Harmful".  ^ " IPv4
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Address Report". Potaroo.net. Retrieved 20 January 2012.  ^ Mike Leber (2 October 2010). "Global IPv6
IPv6
Deployment Progress Report". Hurricane Electric. Retrieved 19 October 2011.  ^ "Beijing2008.cn leaps to next-generation Net" (Press release). The Beijing Organizing Committee for the Games of the XXIX Olympiad. 30 May 2008. Archived from the original on 4 February 2009.  ^ Das, Kaushik (2008). " IPv6
IPv6
and the 2008 Beijing Olympics". IPv6.com. Retrieved 15 August 2008. As thousands of engineers, technologists have worked for a significant time to perfect this (IPv6) technology, there is no doubt, this technology brings considerable promises but this is for the first time that it will showcase its strength when in use for such a mega-event.  ^ Derek Morr (9 June 2009). "Verizon Mandates IPv6
IPv6
Support for Next-Gen Cell Phones". CircleID.  ^ theipv6guy (31 July 2012). "T-Mobile USA Launches External IPv6". T-Mobile. Archived from the original on 19 October 2013.  ^ van Beijnum, Iljitsch. " IPv6
IPv6
adoption starting to add up to real numbers: 0.6 percent". Ars Technica. Retrieved 9 April 2015.  ^ David Frost (20 April 2011). "Ipv6 traffic volumes going backwards". iTWire. Retrieved 19 February 2012.  ^ "Traffic Graphs www.seattleix.net". www.seattleix.net. Retrieved 2017-10-30.  ^ "Amsterdam Internet
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Exchange Ether Type". ams-ix.net. Retrieved 2015-10-06.  ^ "IPv6". Google
Google
Statistics. Google. Retrieved 27 April 2015.  ^ "6lab IPv6
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website". 6lab.cisco.com. Retrieved 2015-01-28. 

External links[edit]

Wikiversity has learning resources about IPv6

IPv6
IPv6
in the Linux Kernel by Rami Rosen. Free Pool of IPv4
IPv4
Address Space Depleted An Introduction and Statistics about IPV6

v t e

Internet Protocol
Internet Protocol
version 6

General

IPv6 IPv6
IPv6
address IPv6
IPv6
packet Mobile IPv6

Deployment

IPv6
IPv6
deployment World IPv6
IPv6
Day and World IPv6
IPv6
Launch Day Comparison of IPv6
IPv6
support in operating systems List of IPv6
IPv6
tunnel brokers

IPv4
IPv4
to IPv6
IPv6
topics

IPv4
IPv4
address exhaustion IPv6
IPv6
transition mechanism

Related protocols

DHCPv6 ICMPv6

Neighbor Discovery Protocol Multicast
Multicast
Listener Discovery Secure Neighbor Discovery Multicast
Multicast
router discovery

Site Multihoming by IPv6
IPv6
Intermediation

Authority control

.