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Internet Protocol version 6 (IPv6) is the next-generation Internet Protocol version designated as the successor to IPv4, the first implementation used in the Internet that is still in dominant use currently. It is an Internet Layer protocol for packet-switched internetworks. The main driving force for the redesign of Internet Protocol is the foreseeable IPv4 address exhaustion. IPv6 was defined in December 1998 by the Internet Engineering Task Force (IETF) with the publication of an Internet standard specification, RFC 2460.

IPv6 has a vastly larger address space than IPv4. This results from the use of a 128-bit address, whereas IPv4 uses only 32 bits. The new address space thus supports 2128 (about 3.4×1038) addresses. This expansion provides flexibility in allocating addresses and routing traffic and eliminates the primary need for network address translation (NAT), which gained widespread deployment as an effort to alleviate IPv4 address exhaustion.

IPv6 also implements new features that simplify aspects of address assignment (stateless address autoconfiguration) and network renumbering (prefix and router announcements) when changing Internet connectivity providers. The IPv6 subnet size has been 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 media addressing information (MAC address).

Network security is integrated into the design of the IPv6 architecture. Internet Protocol Security (IPsec) was originally developed for IPv6, but found widespread optional deployment first in IPv4 (into which it was back-engineered). The IPv6 specifications mandate IPsec implementation as a fundamental interoperability requirement.

In December 2008, despite marking its 10th anniversary as a Standards Track protocol, IPv6 was only in its infancy in terms of general worldwide deployment. A 2008 study[1] by Google Inc. indicated that penetration was still less than one percent of Internet-enabled hosts in any country. IPv6 has been implemented on all major operating systems in use in commercial, business, and home consumer environments.[2]

Contents

Motivation and origins

The first publicly used version of the Internet Protocol, Version 4 (IPv4), provides an addressing capability of about 4 billion addresses (232). This was deemed sufficient in the early design stages of the Internet when the explosive growth and worldwide proliferation of networks was not anticipated.

During the first decade of operation of the TCP/IP-based Internet, by the late 1980s, it became apparent that methods had to be developed to conserve address space. In the early 1990s, even after the introduction of classless network redesign, it became clear that this would not suffice to prevent IPv4 address exhaustion and that further changes to the Internet infrastructure were needed.[3] By the beginning of 1992, several proposed systems were being circulated, and by the end of 1992, the IETF announced a call for white papers (RFC 1550) and the creation of the "IP Next Generation" (IPng) area of working groups.[3][4]

The Internet Engineering Task Force adopted IPng on July 25, 1994, with the formation of several IPng working groups.[3] By 1996, a series of RFCs were released defining Internet Protocol Version 6 (IPv6), starting with RFC 2460.

The technical discussion, development and introduction of IPv6 was not without controversy and the design has been criticized for lack of interoperability with IPv4 and other aspects, for example by noted computer scientist D. J. Bernstein.[5]

Incidentally, the IPng architects could not use version number 5 as a successor to IPv4, because it had been assigned to an experimental flow-oriented streaming protocol (Internet Stream Protocol), similar to IPv4, intended to support video and audio.

It is widely expected that IPv4 will be supported alongside IPv6 for the foreseeable future. IPv4-only nodes are not able to communicate directly with IPv6 nodes, and will need assistance from an intermediary; see Transition mechanisms below.

IPv4 exhaustion

Estimates of the time frame until complete exhaustion of IPv4 addresses varied widely. In 2003, Paul Wilson (director of APNIC) stated that, based on then-current rates of deployment, the available space would last for one or two decades.[6] In September 2005, a report by Cisco Systems suggested that the pool of available addresses would dry up in as little as 4 to 5 years.[7] As of May 2009, a daily updated report projected that the IANA pool of unallocated addresses would be exhausted in June 2011, with the various Regional Internet Registries using up their allocations from IANA in March 2012.[8] There is now consensus among Regional Internet Registries that final milestones of the exhaustion process will be passed in 2010 or 2011 at the latest, and a policy process has started for the end-game and post-exhaustion era.[9]

Features and differences from IPv4

In most regards, 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 network-layer addresses, such as FTP or NTPv3.

IPv6 specifies a new packet format, designed to minimize packet-header processing. Since the headers of IPv4 packets and IPv6 packets are significantly different, the two protocols are not interoperable.

Larger address space

The most important feature of IPv6 is a much larger address space than that of IPv4: addresses in IPv6 are 128 bits long, compared to 32-bit addresses in IPv4.

An illustration of an IP address (version 6), in hexadecimal and binary.

The very large IPv6 address space supports a total of 2128 (about 3.4×1038) addresses—or approximately 5×1028 (roughly 295) addresses for each of the roughly 6.5 billion (6.5×109) people alive in 2006.[10] In another perspective, there is the same number of IP addresses per person as the number of atoms in a metric ton of carbon.

While these numbers are impressive, it was not the intent of the designers of the IPv6 address space to assure geographical saturation with usable addresses. Rather, the longer addresses allow a better, systematic, hierarchical allocation of addresses and efficient route aggregation. With IPv4, complex Classless Inter-Domain Routing (CIDR) techniques were developed to make the best use of the small address space. Renumbering an existing network for a new connectivity provider with different routing prefixes is a major effort with IPv4, as discussed in RFC 2071 and RFC 2072. 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.

The size of a subnet in IPv6 is 264 addresses (64-bit subnet mask), the square of the size of the entire IPv4 Internet. Thus, actual address space utilization rates will likely be small in IPv6, but network management and routing will be more efficient because of the inherent design decisions of large subnet space and hierarchical route aggregation.

Stateless address autoconfiguration

IPv6 hosts can configure themselves automatically when connected to a routed IPv6 network using ICMPv6 router discovery messages. When first connected to a network, a host sends a link-local multicast router solicitation request for its configuration parameters; if configured suitably, routers respond to such a request with a router advertisement packet that contains network-layer configuration parameters.[11]

If IPv6 stateless address autoconfiguration is unsuitable for an application, a network may use stateful configuration with the Dynamic Host Configuration Protocol for IPv6 (DHCPv6) or hosts may be configured statically.

Routers present a special case of requirements for address configuration, as they often are sources for autoconfiguration information, such as router and prefix advertisements. Stateless configuration for routers can be achieved with a special router renumbering protocol.[12]

Multicast

Multicast, the ability to send a single packet to multiple destinations, is part of the base specification in IPv6. This is unlike IPv4, where it is optional (although usually implemented).

IPv6 does not implement broadcast, which is the ability to send a packet to all hosts on the attached link. The same effect can be achieved by sending a packet to the link-local all hosts multicast group. It therefore lacks the notion of a broadcast address—the highest address in a subnet (the broadcast address for that subnet in IPv4) is considered a normal address in IPv6.

Most environments, however, do not currently have their network infrastructures configured to route multicast packets; multicasting on single subnet will work, but global multicasting might not.

IPv6 multicast shares common features and protocols with IPv4 multicast, but also provides changes and improvements. When even the smallest IPv6 global routing prefix is assigned to an organization, the organization is also assigned the use of 4.2 billion globally routable source-specific IPv6 multicast groups to assign for inner-domain or cross-domain multicast applications [RFC 3306]. In IPv4 it was very difficult for an organization to get even one globally routable cross-domain multicast group assignment and implementation of cross-domain solutions was very arcane [RFC 2908]. IPv6 also supports new multicast solutions, including Embedded Rendezvous Point [RFC 3956] which simplifies the deployment of cross domain solutions.

Mandatory network layer security

Internet Protocol Security (IPsec), the protocol for IP encryption and authentication, forms an integral part of the base protocol suite in IPv6. IPsec support is mandatory in IPv6; this is unlike IPv4, where it is optional (but usually implemented). IPsec, however, is not widely used at present except for securing traffic between IPv6 Border Gateway Protocol routers.

Simplified processing by routers

A number of simplifications have been made to the packet header, and the process of packet forwarding has been simplified, in order to make packet processing by routers simpler and hence more efficient. Specifically:

  • The packet header in IPv6 is simpler than that used in IPv4, with many rarely used fields moved to separate options; in effect, although the addresses in IPv6 are four times larger, the (option-less) IPv6 header is only twice the size of the (option-less) IPv4 header.
  • IPv6 routers do not perform fragmentation. IPv6 hosts are required to either perform PMTU discovery, perform end-to-end fragmentation, or to send packets smaller than the IPv6 minimum MTU size of 1280 octets.
  • The IPv6 header is not protected by a checksum; integrity protection is assumed to be assured by both a link layer checksum and a higher layer (TCP, UDP, etc.) checksum. In effect, IPv6 routers do not need to recompute a checksum when header fields (such as the TTL or Hop Count) change. This improvement may have been made less necessary by the development of routers that perform checksum computation at link speed using dedicated hardware, but it is still relevant for software based routers.
  • The Time-to-Live 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.

Mobility

Unlike mobile IPv4, Mobile IPv6 (MIPv6) avoids triangular routing and is therefore as efficient as normal IPv6. IPv6 routers may also support Network Mobility (NEMO) [RFC 3963] which allows entire subnets to move to a new router connection point without renumbering. However, since neither MIPv6 nor MIPv4 or NEMO are widely deployed today, this advantage is mostly theoretical.

Options extensibility

IPv4 has a fixed size (40 octets) of option parameters. In IPv6, 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 allows IPv6 to be easily 'extended' to support future services for QoS, security, mobility, etc. without a redesign of the basic protocol.

Jumbograms

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.

Packet format

The IPv6 packet is composed of three main parts: the fixed header, optional extension headers and the payload.

Fixed header

The fixed header makes up the first 40 octets (320 bits) of an IPv6 data packet. The format of the fixed header is presented in the table below. The octet (byte) offsets are in hexadecimal (base 16) and the bit offsets are in decimal (base 10).

Octet Offset 0 1 2 3
Bit Offset 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
0 0 Version Traffic Class Flow Label
4 32 Payload Length Next Header Hop Limit
8 64 Source Address
C 96
10 128
14 160
18 192 Destination Address
1C 224
20 256
24 288

The fields used in the header are:

  • Version: The number 6 encoded (bit sequence 0110).
  • Traffic class: The packet priority (8 bits). Priority values subdivide into ranges: traffic where the source provides congestion control and non-congestion control traffic.
  • Flow label: Used for QoS management (20 bits). Originally created for giving real-time applications special service, but currently unused.[13]
  • Payload length: The size of the payload in octets (16 bits). When cleared to zero, the option is a "Jumbo payload" (hop-by-hop).
  • Next header: Specifies the next encapsulated protocol. The values are compatible with those specified for the IPv4 protocol field (8 bits).
  • Hop limit: Replaces the time to live field of IPv4 (8 bits).
  • Source and destination addresses: 128 bits each.

The protocol field of IPv4 is replaced with a next header field. This field usually specifies the transport layer protocol used by a packet's payload. In the presence of options, however, the next header field specifies the presence of one or more out of six extension headers, which then follow the IPv6 header in distinct order; the payload's protocol itself is specified in the next header field of the last extension header.

Extension header

Extension Header Type Size Description RFC
Hop-By-Hop Options 0 variable Options that need to be examined by all devices on the path. RFC 2460
Routing 43 variable Methods to specify the route for a datagram. (Used with Mobile IPv6) RFC 2460, RFC 3775, RFC 5095
Fragment 44 64 bits Contains parameters for fragmentation of datagrams. RFC 2460
Authentication Header (AH) 51 variable Contains information used to verify the authenticity of most parts of the packet. (See IPsec) RFC 4302
Encapsulating Security Payload (ESP) 50 variable Carries encrypted data for secure communication. (See IPsec). RFC 4303
Destination Options 60 variable Options that need to be examined only by the destination of the packet. RFC 2460
No Next Header 59 empty A placeholder indicating no next header. RFC 2460

Payload

The payload can have a size of up to 64 KB in standard mode, or larger with a "jumbo payload" option in a Hop-By-Hop Options extension header.

Fragmentation is handled only in the sending host in IPv6: routers never fragment a packet, and hosts are expected to use Path MTU discovery.

Addressing

The increased length of network addresses emphasizes a most important change when moving from IPv4 to IPv6. IPv6 addresses are 128 bits long[14], whereas IPv4 addresses are 32 bits; where the IPv4 address space contains roughly 4.3×109 (4.3 billion) addresses, IPv6 has enough room for 3.4×1038 (340 trillion trillion trillion) unique addresses.

IPv6 addresses are normally written with hexadecimal digits and colon separators like 2001:db8:85a3::8a2e:370:7334, as opposed to the dot-decimal notation of the 32 bit IPv4 addresses. IPv6 addresses are typically composed of two logical parts: a 64-bit (sub-)network prefix, and a 64-bit host part.

IPv6 addresses are classified into three types: unicast addresses which uniquely identify network interfaces, anycast addresses which identify a group of interfaces—mostly at different locations—for which traffic flows to the nearest one, and multicast addresses which are used to deliver one packet to many interfaces. Broadcast addresses are not used in IPv6. Each IPv6 address also has a 'scope', which specifies in which part of the network it is valid and unique. Some addresses have node scope or link scope; most addresses have global scope (i.e. they are unique globally).

Some IPv6 addresses are used for special purposes, like the loopback address. Also, some address ranges are considered special, like link-local addresses (for use in the local network only) and solicited-node multicast addresses (used in the Neighbor Discovery Protocol).

IPv6 in the Domain Name System

A quad-A record (AAAA) is defined in the DNS for returning IPv6 addresses to forward queries; a new format of PTR record is also defined for reverse queries.

Transition mechanisms

Until IPv6 completely supplants IPv4, a number of transition mechanisms[15] are needed to enable IPv6-only hosts to reach IPv4 services and to allow isolated IPv6 hosts and networks to reach the IPv6 Internet over the IPv4 infrastructure.

For the period while IPv6 hosts and routers co-exist with IPv4 systems various proposals have been made:

  • RFC 2893 (Transition Mechanisms for IPv6 Hosts and Routers), obsoleted by RFC 4213 (Basic Transition Mechanisms for IPv6 Hosts and Routers)
  • RFC 2766 (Network Address Translation - Protocol Translation NAT-PT), obsoleted as explained in RFC 4966 (Reasons to Move the Network Address Translator - Protocol Translator NAT-PT to Historic Status)
  • RFC 2185 (Routing Aspects of IPv6 Transition)
  • RFC 3493 (Basic Socket Interface Extensions for IPv6)
  • RFC 3056 (Connection of IPv6 Domains via IPv4 Clouds)
  • RFC 4380 (Teredo: Tunneling IPv6 over UDP through Network Address Translations NATs)
  • RFC 4214 (Intra-Site Automatic Tunnel Addressing Protocol ISATAP)
  • RFC 3053 (IPv6 Tunnel Broker)
  • RFC 3142 (An IPv6-to-IPv4 Transport Relay Translator)

Dual IP stack implementation

A fundamental IPv4-to-IPv6 transition technology involves the presence of two Internet Protocol software implementations in an operating system, one for IPv4 and another for IPv6. Such dual-stack IP hosts may run IPv4 and IPv6 completely independently, or they may use a hybrid implementation, which is the form commonly implemented in modern operating systems on server and end-user computers. Dual-stack hosts are described in RFC 4213.

Modern hybrid dual-stack implementations of TCP/IP allow programmers to write networking code that works transparently on IPv4 or IPv6. The software may use hybrid sockets designed to accept both IPv4 and IPv6 packets. When used in IPv4 communications, hybrid stacks use IPv6 semantics internally and represent IPv4 addresses in a special IPv6 address format, the IPv4-mapped address.

IPv4-mapped addresses

Hybrid dual-stack IPv6/IPv4 implementations typically support a special class of addresses, the IPv4-mapped addresses. This address type has its first 80 bits set to zero and the next 16 set to one while its last 32 bits are filled with the IPv4 address. These addresses are commonly represented in the standard IPv6 format, but having the last 32 bits written in the customary dot-decimal notation of IPv4; for example, ::ffff:192.0.2.128 is the IPv4-mapped IPv6 address for IPv4 address 192.0.2.128.

Because of the significant internal differences between IPv4 and IPv6, some of the lower level functionality available to programmers in the IPv6 stack might not work with IPv4 mapped addresses. Some common IPv6 stacks do not support the IPv4-mapped address feature, either because the IPv6 and IPv4 stacks are separate implementations (e.g., Microsoft Windows 2000, XP, and Server 2003), or because of security concerns (OpenBSD). On these operating systems, it is necessary to open a separate socket for each IP protocol that is to be supported. On some systems (e.g., Linux, NetBSD, FreeBSD) this feature is controlled by the socket option IPV6_V6ONLY as specified in RFC 3493.

Tunneling

In order to reach the IPv6 Internet, an isolated host or network must use the existing IPv4 infrastructure to carry IPv6 packets. This is done using a technique known as tunneling which consists of encapsulating IPv6 packets within IPv4, in effect using IPv4 as a link layer for IPv6.

The direct encapsulation of IPv6 datagrams within IPv4 packets is indicated by IP protocol number 41. IPv6 can also be encapsulated within UDP packets e.g. in order to cross a router or NAT device that blocks protocol 41 traffic. Other encapsulation schemes, such as used in AYIYA or GRE, are also popular.

Automatic tunneling

Automatic tunneling refers to a technique where the routing infrastructure automatically determines the tunnel endpoints. RFC 3056 recommends 6to4 tunneling for automatic tunneling, which uses protocol 41 encapsulation.[16] Tunnel endpoints are determined by using a well-known IPv4 anycast address on the remote side, and embedding IPv4 address information within IPv6 addresses on the local side. 6to4 is widely deployed today.

Teredo is an automatic tunneling technique that uses UDP encapsulation and can allegedly cross multiple NAT boxes.[17] IPv6, including 6to4 and Teredo tunneling, are enabled by default in Windows Vista.[18] Most Unix systems only implement native support for 6to4, but Teredo can be provided by third-party software such as Miredo.

ISATAP[19] treats the IPv4 network as a virtual IPv6 local link, with mappings from each IPv4 address to a link-local IPv6 address. Unlike 6to4 and Teredo, which are inter-site tunnelling mechanisms, ISATAP is an intra-site mechanism, meaning that it is designed to provide IPv6 connectivity between nodes within a single organisation.

Configured and automated tunneling (6in4)

In configured tunneling, the tunnel endpoints are explicitly configured, either by an administrator manually or the operating system's configuration mechanisms, or by an automatic service known as a tunnel broker[20], 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 behaviour of configured tunneling.

Raw encapsulation of IPv6 packets using 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

After the Regional Internet Registries have exhausted their pools of available IPv4 addresses, it is likely that hosts newly added to the Internet might only have IPv6 connectivity. For these clients to have backward-compatible connectivity to existing IPv4-only resources, suitable translation mechanisms must be deployed.

One form of translation is the use of a dual-stack application-layer proxy; for example a web proxy.

NAT-like techniques for application-agnostic translation at the lower layers have also been proposed. Most have been found to be too unreliable in practice because of the wide range of functionality required by common application-layer protocols, and are considered by many to be obsolete.

IPv6 readiness

Adoption issues

Issues of IPv6 adoption include:

  • legacy equipment where
    • the manufacturer no longer exists to provide support
    • the manufacturer refuses to produce updates to support IPv6 or provides them but only at a prohibitive cost.
    • software upgrades are impossible (for example: software in permanent ROM)
    • the device has insufficient resources to implement the IPv6 stack (usually a lack of ROM or RAM)
    • the device can handle IPv6 but only at a much lower performance than IPv4 (an issue with many older routers)
  • manufacturers providing new equipment with sufficient resources for IPv6
  • manufacturers investing in developing new software for IPv6 support
  • publicity to persuade end-users to prepare to upgrade existing equipment
  • publicity to educate or inform end-users about IPv4 obsolescence to create demand for IPv6-capable equipment
  • ISPs not investing technical resources into preparing for IPv6

There are two distinct classes of users of networking equipment, informed (mainly commercial and professional), and uninformed (mainly consumer). The former understand that network devices are specialist computers which may need software upgrades for security and performance fixes. The latter generally treat their networking equipment as appliances, which are configured only when first unboxed, if at all, and only ever undergo firmware upgrades when absolutely necessary. Inevitably it is the latter group who have no knowledge of IPv4 or v6, but who are most likely to suffer when their equipment has to be replaced, since commercial grade equipment has generally handled IPv6 for quite a few years.

Most equipment such as hosts and routers require explicit IPv6 support. Fewer problems arise with equipment which only does low-level transport, such as cables, most ethernet adapters, and most layer-2 switches.

As of 2007, IPv6 readiness is currently not considered in most consumer purchasing decisions. If such equipment is not IPv6-capable, it might need to be upgraded or replaced prematurely if connectivity from or to new users and to servers using IPv6 addresses is required.

As with the year-2000 compatibility, IPv6 compatibility is mainly a software/firmware issue. However, unlike the year-2000 issue, there seems to be virtually no effort to ensure compatibility of older equipment and software by manufacturers. Furthermore, even compatibility of products now available is unlikely for many types of software and equipment. This is caused by only a recent realisation that IPv4 exhaustion is imminent, and the hope that we will be able to get by for a relatively long time with a combined IPv4/IPv6 situation. There is a tug-of-war going on in the internet community whether the transition will/should be rapid or long. Specifically, an important question is whether almost all internet servers should be ready to serve to new IPv6-only clients by 2012. Universal access to IPv6-only servers will be even more of a challenge.

Most equipment would be fully IPv6 capable with a software/firmware update if the device has sufficient code and data space to support the additional protocol stack. However, as with 64-bit Windows and Wi-Fi Protected Access support, manufacturers are likely to try to save on development costs for hardware which they no longer sell, and to try to get more sales from new "IPv6-ready" equipment. Even when chipset makers develop new drivers for their chipsets, device manufacturers might not pass these on to the consumers. Moreover, as IPv6 gets implemented, optional features might become important, such as IPv6 mobile.

Home routers are usually not IPv6 ready.[citation needed] As for the CableLabs consortium, the 160 Mbit/s DOCSIS 3.0 IPv6-ready specification for cable modems has only been issued in August 2006. IPv6 capable Docsis 2.0b was skipped while the widely used DOCSIS 2.0 does not support IPv6. The new 'DOCSIS 2.0 + IPv6' standard also supports IPv6, which may on the cable modem side only require a firmware upgrade.[21][22] It is expected that only 60% of cable modems' servers and 40% of cable modems will be DOCSIS 3.0 by 2011.[23] Other equipment which is typically not IPv6-ready range from Skype and SIP phones to oscilloscopes and printers. Professional network routers in use should be IPv6-ready. Most personal computers should also be IPv6-ready, because the network stack resides in the operating system. Most applications with network capabilities are not ready, but could be upgraded with support from the developers. Since February 2002, with J2SE 1.4, all applications that are 100% Java have implicit support for IPv6 addresses.[24]

ADSL services offer a problem if the access networks of the incumbent telephone connection cannot support IPv6, such that independent ADSL providers cannot provide native IPv6 connectivity.

IPv6 conformance testing and evaluation

A few organizations are involved, locally and internationally, with IPv6 testing and evaluation ranging from the United States Department of Defense to the University of New Hampshire. Fuzzing, Fault injection and mutation test equipment and software is available from companies such as Mu Dynamics, Ixia, Candela Technologies[25]; and Codenomicon[26]; which all also provide capability for creating and customizing your own IPv6 tests. Other classes of test equipment, including load and performance and conformance are available from companies like Spirent, Ixia, Candela Technologies and Agilent Technologies.

Deployment

Although IPv4 address exhaustion has been slowed by the introduction of classless inter-domain routing (CIDR) and the extensive use of network address translation (NAT), address uptake has accelerated again in recent years.[citation needed] Most forecasts expect complete depletion between 2010 and 2012.[8]

As of 2008, IPv6 accounts for a minuscule fraction of the used addresses and the traffic in the publicly-accessible Internet which is still dominated by IPv4.[27]

The 2008 Summer Olympic Games were a notable event in terms of IPv6 deployment, being the first time a major world event has had a presence on the IPv6 Internet at http://ipv6.beijing2008.cn/en (IP addresses 2001:252:0:1::2008:6 and 2001:252:0:1::2008:8) and all network operations of the Games were conducted using IPv6.[28] It is believed that the Olympics provided the largest showcase of IPv6 technology since the inception of IPv6.[29]

Cellular telephone systems present a large deployment field for Internet Protocol devices as mobile telephone service is being transitioned from 3G systems to next generation (4G) technologies in which voice is provisioned as a Voice over Internet Protocol (VoIP) service. This mandates the use of IPv6 for such networks due to the impending IPv4 address exhaustion. In the U.S., cellular operator Verizon has released technical specifications for devices operating on its future networks.[30] The specification mandates IPv6 operation according to the 3GPP Release 8 Specifications (March 2009) and deprecates IPv4 as an optional capability.

Some implementations of the BitTorrent peer-to-peer file transfer protocol make extensive use of IPv6 to avoid NAT issues[31].

Major announcements and availability

Year Announcements and availability
1996 Alpha quality IPv6 support in Linux kernel development version 2.1.8.[32]
6bone (an IPv6 virtual network for testing) is started.
1997 By the end of 1997 IBM's AIX 4.3 is the first commercial platform supporting IPv6.[33][34]
Also in 1997, Early Adopter Kits for DEC's operating systems, Tru64 and OpenVMS, are made available.[35]
1998 Microsoft Research[36] releases its first experimental IPv6 stack. This support is not intended for use in a production environment.
1999 The Freenet6 tunnel broker service is launched.
2000 Production-quality BSD support for IPv6 becomes generally available in early to mid-2000 in FreeBSD, OpenBSD, and NetBSD via the KAME project.[37]
Microsoft releases an IPv6 technology preview version for Windows 2000 in March 2000.[36]
Sun Solaris supports IPv6 in Solaris 8 in February.[38]
Compaq ships IPv6 with Tru64.[35]
2001 In January, Compaq ships IPv6 with OpenVMS.[35]
Cisco Systems introduces IPv6 support on Cisco IOS routers and L3 switches.[39]
HP introduces IPv6 with HP-UX 11i v1.[40]
2002 Microsoft Windows NT 4.0 and Windows 2000 SP1 have limited IPv6 support for research and testing since at least 2002.
Microsoft Windows XP (2001) supports IPv6 for developmental purposes. In Windows XP SP1 (2002) and Windows Server 2003, IPv6 is included as a core networking technology, suitable for commercial deployment.[41]
IBM z/OS supports IPv6 since version 1.4 (generally availability in September 2002).[42]
2003 Apple Mac OS X v10.3 "Panther" (2003) supports IPv6 which is enabled by default.[43]
In July, ICANN announces that IPv6 address records for the Japan (jp) and Korea (kr) country code top-level domain nameservers are visible in the DNS root server zone files with serial number 2004072000. The IPv6 records for France (fr) are added later. This makes IPv6 DNS publicly operational.
2005 Linux 2.6.12 removes experimental status from its IPv6 implementation.[44]
2007 Microsoft Windows Vista (2007) supports IPv6 which is enabled by default.[41]
Apple's AirPort Extreme 802.11n base station includes an IPv6 gateway in its default configuration. It uses 6to4 tunneling and manually configured static tunnels.[45] (Note: 6to4 was disabled by default in later firmware revisions.)
2008 On February 4, 2008, IANA adds AAAA records for the IPv6 addresses of six root name servers.[46][47] With this transition, it is now possible for two Internet hosts to fully communicate without using IPv4.
On March 12, 2008, Google launches a public IPv6 web interface to its popular search engine at the URL http://ipv6.google.com.[48]
2009 In January 2009, Google extends its IPv6 initiative with Google over IPv6, which offers IPv6 support for Google services to compatible networks.
2010 In January 2010, Comcast announces public trials of IPv6 on its production network.[49][50]

See also

References

  1. ^ Global IPv6 Statistics - Measuring the current state of IPv6 for ordinary users, S.H. Gunderson (Google), RIPE 57 (Dubai, Oct 2008)
  2. ^ Google: more Macs mean higher IPv6 usage in US
  3. ^ a b c RFC 1752 The Recommendation for the IP Next Generation Protocol, S. Bradner, A. Mankin, January 1995.
  4. ^ History of the IPng Effort
  5. ^ "The IPV6 Mess". Internet Archive. http://cr.yp.to/djbdns/ipv6mess.html. 
  6. ^ Exec: No shortage of Net addresses By John Lui, CNETAsia
  7. ^ A Pragmatic Report on IPv4 Address Space Consumption by Tony Hain, Cisco Systems
  8. ^ a b IPv4 Address Report
  9. ^ Proposed Global Policy for the Allocation of the Remaining IPv4 Address Space
  10. ^ U.S. Census Bureau
  11. ^ RFC 4862 IPv6 Stateless Address Autoconfiguration, S. Thomson, T. Narten, T. Jinmei, September 2007.
  12. ^ RFC 2894 Router Renumbering for IPv6, M. Crawford, August 2000.
  13. ^ RFC 2460 Internet Protocol, Version 6 (IPv6), S. Deering, R Hinden, December 1998.
  14. ^ RFC 4291 IP Version 6 Addressing Architecture, R. Hinden, S. Deering, February 2006.
  15. ^ IPv6 Transition Mechanism / Tunneling Comparison
  16. ^ RFC 3056 Connection of IPv6 Domains via IPv4 Clouds, B. Carpenter, Februari 2001.
  17. ^ RFC 4380 Teredo: Tunneling IPv6 over UDP through Network Address Translations (NATs), C. Huitema, Februari 2006
  18. ^ The Windows Vista Developer Story: Application Compatibility Cookbook
  19. ^ RFC 5214 Intra-Site Automatic Tunnel Addressing Protocol (ISATAP), F. Templin, T. Gleeson, D. Thaler, March 2008.
  20. ^ RFC 3053 IPv6 Tunnel Broker, A. Durand, P. Fasano, I. Guardini, D. Lento, January 2001.
  21. ^ "DOCSIS 2.0 Interface". Cablemodem.com. 2007-10-29. http://www.cablemodem.com/specifications/specifications20.html. Retrieved 2009-08-31. 
  22. ^ [1]
  23. ^ ABI Research (2007-08-23). "DOCSIS 3.0 Network Equipment Penetration to Reach 60% by 2011". Press release. http://www.abiresearch.com/abiprdisplay.jsp?pressid=710. Retrieved 2007-09-30. 
  24. ^ "Networking IPv6 User Guide for JDK/JRE 5.0". http://java.sun.com/j2se/1.5.0/docs/guide/net/ipv6_guide/index.html. Retrieved 2007-09-30. 
  25. ^ Candela Technologies
  26. ^ Codenomicon Defensics: IPv6 test suite datasheet
  27. ^ Geoff Huston - An Update on IPv6 Deployment (RIPE 56)
  28. ^ The Beijing Organizing Committee for the Games of the XXIX Olympiad (2008-05-30). "Beijing2008.cn leaps to next-generation Net". Press release. http://en.beijing2008.cn/news/official/preparation/n214384681.shtml. 
  29. ^ Das, Kaushik (2008). "IPv6 and the 2008 Beijing Olympics". IPv6.com. http://ipv6.com/articles/general/IPv6-Olympics-2008.htm. Retrieved 2008-08-15. "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." 
  30. ^ Derek Morr (2009-06-09). "Verizon Mandates IPv6 Support for Next-Gen Cell Phones". CircleID. http://www.circleid.com/posts/20090609_verizon_mandates_ipv6_support_for_next_gen_cell_phones/. 
  31. ^ Rob Issac (2008), Welcome to your IPv6 enabled transit network. Whether you like it, or not, http://www.ausnog.net/files/ausnog-03/presentations/ausnog03-ward-IPv6_enabled_network.pdf 
  32. ^ Linux IPv6 Development Project
  33. ^ IPv6 support shipping in AIX 3.3
  34. ^ Its AIX 4.3.
  35. ^ a b c DEC/Compaq IPv6 history
  36. ^ a b Internet Protocol Version 6 (old Microsoft Research IPv6 release)
  37. ^ KAME project
  38. ^ Sun Solaris 8 changes from Solaris 7
  39. ^ Cisco main IPv6 site
  40. ^ HP main IPv6 site
  41. ^ a b Microsofts main IPv6 site
  42. ^ "IBM: z/OS operating system". 03.ibm.com. http://www-03.ibm.com/servers/eserver/zseries/announce/zos_r4/. Retrieved 2009-08-31. 
  43. ^ Mac OS X 10.3 Using IPv6 *** Document not found error message *** 2008-11-14
  44. ^ Linux 2.6.12 changelog
  45. ^ Apple AirPort Extreme technical specifications.
  46. ^ IPv6: coming to a root server near you
  47. ^ IANA - IPv6 Addresses for the Root Servers
  48. ^ Official Google Blog
  49. ^ http://www.comcast6.net/
  50. ^ http://www.networkworld.com/news/2010/012710-comcast-ipv6-trials.html?hpg1=bn

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Internet Protocol Version 6 (IPv6) is a version of the Internet Protocol that is designed to succeed Internet Protocol version 4 (IPv4), the first publicly used Internet Protocol in operation since 1981. IPv6 is an Internet Layer protocol for packet-switched internetworking. The main driving force for the redesign of Internet Protocol was the foreseeable IPv4 address exhaustion. IPv6 was developed by the Internet Engineering Task Force (IETF), and is described in Internet standard document RFC 2460, published in December 1998.[1]

IPv6 has a vastly larger address space than IPv4. This results from the use of a 128-bit address, whereas IPv4 uses only 32 bits. The new address space thus supports 2128 (about 3.4×1038) addresses. This expansion provides flexibility in allocating addresses and routing traffic and eliminates the primary need for network address translation (NAT), which gained widespread deployment as an effort to alleviate IPv4 address exhaustion.

IPv6 also implements many other new features. It simplifies aspects of address assignment (stateless address autoconfiguration) and network renumbering (prefix and router announcements) when changing Internet connectivity providers. The IPv6 subnet size has been 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 media addressing information (MAC address). Network security is also integrated into the design of the IPv6 architecture, and the IPv6 specification mandates support for IPsec as a fundamental interoperability requirement.

For deployment, IPv6 is largely incompatible with IPv4 at the packet level, and translation services have practical issues that make them controversial.[2] IPv6 and IPv4 are therefore treated as almost entirely separate networks with devices having two separate protocol stacks if they need to access both networks, with tunneling of IPv6 on IPv4 and vice versa. In December 2008, despite marking its 10th anniversary as a Standards Track protocol, IPv6 was only in its infancy in terms of general worldwide deployment. A 2008 study[3] by Google Inc. indicated that penetration was still less than one percent of Internet-enabled hosts in any country. IPv6 has been implemented on all major operating systems in use in commercial, business, and home consumer environments.[4]

Contents

Motivation and origins

The first publicly used version of the Internet Protocol, Version 4 (IPv4), provides an addressing capability of about 4 billion addresses (232). This was deemed sufficient in the early design stages of the Internet when the explosive growth and worldwide proliferation of networks was not anticipated.

During the first decade of operation of the Internet, by the late 1980s, 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 address exhaustion, and that further changes to the Internet infrastructure were needed.[5]

By the beginning of 1992, several proposals appeared and by the end of 1992, the IETF announced a call for white papers[6] and the creation of the IP Next Generation (IPng) area of working groups.[5][7] [[File:|thumb|IPv4 address exhaustion from 1995 to 2010.]] The Internet Engineering Task Force adopted the IPng model on July 25, 1994, with the formation of several IPng working groups.[5] By 1996, a series of RFCs was released defining Internet Protocol version 6 (IPv6), starting with RFC 1883.

The IETF assigned version 6 for the new protocol as a successor to version 4, because version 5 had previously been assigned to an experimental protocol, the Internet Stream Protocol, similar to IPv4, intended to support video and audio.

It is widely expected that IPv4 will be supported alongside IPv6 for the foreseeable future. IPv4-only nodes are not able to communicate directly with IPv6 nodes and need assistance from an intermediary gateway or must use other transition mechanisms.

IPv4 exhaustion

Estimates of the time of complete IPv4 address exhaustion varied widely in the early 2000s, but all converge now on the time frame from 2011 to 2012. In 2003, Paul Wilson (director of APNIC) stated that, based on then-current rates of deployment, the available space would last for one or two decades.[8] In September 2005, a report by Cisco Systems suggested that the pool of available addresses would dry up in as little as 4 to 5 years.[9] As of September 2010, a daily updated report projected that the IANA pool would be exhausted in mid-2011, with the various regional Internet registries using up their allocations from IANA in early 2012.[10] As of 2008, a policy process has started for the end-game and post-exhaustion era.[11]

Features and differences from IPv4

In most regards, 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.

IPv6 specifies a new packet format, designed to minimize packet header processing by routers.[1][12] Because the headers of IPv4 packets and IPv6 packets are significantly different, the two protocols are not interoperable.

Larger address space

The most important feature of IPv6 is a much larger address space than in IPv4: addresses for IPv6 are 128 bits long, compared to 32 bits in IPv4.[1]

The very large IPv6 address space supports a total of 2128 (about 3.4×1038) addresses—or approximately 5×1028 (roughly 295) addresses for each of the roughly 6.8 billion (6.8×109) people alive in 2010.[13] In another perspective, this is the same number of IP addresses per person as the number of atoms in a metric ton of carbon.

While these numbers are impressive, it was not the intent of the designers of the IPv6 address space to assure geographical saturation with usable addresses. Rather, the longer addresses allow a better, systematic, hierarchical allocation of addresses and efficient route aggregation. With IPv4, complex Classless Inter-Domain Routing (CIDR) techniques were developed to make the best use of the small address space. Renumbering an existing network for a new connectivity provider with different routing prefixes is a major effort with IPv4.[14][15] 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.

The size of a subnet in IPv6 is always 264 addresses, the square of the size of the entire IPv4 address space, which is 232. Thus, actual address space utilization rates will be small in IPv6, but network management and routing is expected to be more efficient because of the inherent design decisions of large subnet space and hierarchical route aggregation.

Stateless address autoconfiguration

IPv6 hosts can configure themselves automatically when connected to a routed IPv6 network using 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; if configured suitably, routers respond to such a request with a router advertisement packet that contains network-layer configuration parameters.[16]

If IPv6 stateless address autoconfiguration 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 statically.

Routers present a special case of requirements for address configuration, as they often are sources for autoconfiguration information, such as router and prefix advertisements. Stateless configuration for routers can be achieved with a special router renumbering protocol.[17]

Multicast

Multicast, the transmission of a packet to multiple destinations in a single send operation, is part of the base specification in IPv6. In IPv4 this is an optional although commonly implemented feature.[18]

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 multicast to address 224.0.0.1.

IPv6 multicast addressing shares common features and protocols with IPv4 multicast, but also provides changes and improvements by eliminating the need for certain protocols.

Unicast address assignments by a local Internet registry for IPv6 have at least a 64-bit routing prefix, yielding the smallest subnet size available in IPv6 (also 64 bits). With such an assignment it is possible to embed the unicast address prefix into the 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 subnet automatically has available a set of globally routable source-specific multicast groups for multicast applications (RFC 3306).

In IPv4 it was very difficult for an organization to get even one globally routable multicast group assignment and implementation of inter-domain solutions was very arcane.[19]

IPv6 also supports new multicast solutions, including embedding Rendezvous Point addresses in an IPv6 multicast group address which simplifies the deployment of inter-domain solutions.[20]

Mandatory support for network layer security

Internet Protocol Security (IPsec) was originally developed for IPv6, but found widespread deployment first in IPv4, into which it was back-engineered. IPsec is an integral part of the base protocol suite in IPv6.[1] IPsec support is mandatory in IPv6; this is unlike IPv4, where it is optional.

Simplified processing by routers

In IPv6, the packet header and the process of packet forwarding have been simplified to make packet processing by routers more efficient,[1][12] and 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 options; as a result, although the addresses in IPv6 are four times as large, the option-less IPv6 header is only twice the size of the option-less IPv4 header.
  • IPv6 routers do not perform fragmentation. IPv6 hosts are required to either perform PMTU 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.[note 1] Therefore, IPv6 routers do not need to recompute a checksum when header fields (such as the time to live (TTL) or hop count) change.[note 2]
  • 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.

Mobility

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.[21]

Options extensibility

The IPv4 protocol header has a fixed size (40 octets) for option parameters. In IPv6, 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.[1]

Jumbograms

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.[22]

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 64KiB without special options, or larger with a jumbo payload option in a Hop-By-Hop Options extension header.

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.

Addressing

The most important feature of IPv6 is a much larger address space than in IPv4. IPv6 addresses are 128 bits long, compared to only 32 bits previously.[23] While the IPv4 address space contains only about 4.3×109 (4.3 billion) addresses, IPv6 supports approximately 3.4×1038 (340 undecillion) unique addresses, deemed enough for the foreseeable future.[citation needed]

IPv6 addresses are written groups of four hexadecimal digits separated by colons, for example, 2001:db8:1f70::999:de8:7648:6e8. IPv6 addresses are logically divided into two parts: a 64-bit (sub-)network prefix, and a 64-bit interface identifier.

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 which are used to deliver one packet to many interfaces. The broadcast method is not implemented in IPv6. Each 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 addresses are used for special purposes, such as the address for loopback. Also, some address ranges are considered special, such as link-local addresses for use in the local network only, and solicited-node multicast addresses used in the Neighbor Discovery Protocol.

IPv6 in the Domain Name System

In the Domain Name System, hostnames are mapped to IPv6 addresses by AAAA resource records, so-called quad-A records. For reverse resolution, the 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 address. This scheme is defined in RFC 3596.

Transition mechanisms

Until IPv6 completely supplants IPv4, a number of transition mechanisms[24] are needed to enable IPv6-only hosts to reach IPv4 services and to allow isolated IPv6 hosts and networks to reach the IPv6 Internet over the IPv4 infrastructure.

For the period while IPv6 hosts and routers co-exist with IPv4 systems various proposals have been made:

  • RFC 2893, Transition Mechanisms for IPv6 Hosts and Routers, obsoleted by RFC 4213 Basic Transition Mechanisms for IPv6 Hosts and Routers
  • RFC 2766, Network Address Translation — Protocol Translation NAT-PT, obsoleted as explained in RFC 4966 Reasons to Move the Network Address Translator — Protocol Translator NAT-PT to Historic Status
  • RFC 2185, Routing Aspects of IPv6 Transition
  • RFC 3493, Basic Socket Interface Extensions for IPv6
  • RFC 3056, Connection of IPv6 Domains via IPv4 Clouds
  • RFC 4380, Teredo: Tunneling IPv6 over UDP through Network Address Translations NATs
  • RFC 4214, Intra-Site Automatic Tunnel Addressing Protocol ISATAP
  • RFC 3053, IPv6 Tunnel Broker
  • RFC 3142, An IPv6-to-IPv4 Transport Relay Translator
  • RFC 5569, IPv6 Rapid Deployment on IPv4 Infrastructures (6rd)
  • RFC 5572, IPv6 Tunnel Broker with the Tunnel Setup Protocol (TSP)

Dual IP stack implementation

The dual-stack protocol implementation in an operating system is a fundamental IPv4-to-IPv6 transition technology. It implements IPv4 and IPv6 protocol stacks either independently or in a hybrid form. The hybrid form is commonly implemented in modern operating systems supporting IPv6. Dual-stack hosts are described in RFC 4213.

Modern hybrid dual-stack implementations of IPv4 and IPv6 allow programmers to write networking code that works transparently on IPv4 or IPv6. The software may use hybrid sockets designed to accept both IPv4 and IPv6 packets. When used in IPv4 communications, hybrid stacks use an IPv6 application programming interface and represent IPv4 addresses in a special address format, the IPv4-mapped IPv6 address.

IPv4-mapped IPv6 addresses

Hybrid dual-stack IPv6/IPv4 implementations support a special class of addresses, the IPv4-mapped IPv6 addresses. This address type has its first 80 bits set to zero and the next 16 set to one, while its last 32 bits are filled with the IPv4 address. These addresses are commonly represented in the standard IPv6 format, but having the last 32 bits written in the customary dot-decimal notation of IPv4; for example, ::ffff:192.0.2.128 represents the IPv4 address 192.0.2.128.

Because of the significant internal differences between IPv4 and IPv6, some of the lower level functionality available to programmers in the IPv6 stack do not work identically with IPv4 mapped addresses. Some common IPv6 stacks do not support the IPv4-mapped address feature, either because the IPv6 and IPv4 stacks are separate implementations (e.g., Microsoft Windows 2000, XP, and Server 2003), or because of security concerns (OpenBSD).[citation needed] On these operating systems, it is necessary to open a separate socket for each IP protocol that is to be supported. 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.

Tunneling

In order to reach the IPv6 Internet, an isolated host or network must use the existing IPv4 infrastructure to carry IPv6 packets. This is done using a technique known as tunneling which consists of encapsulating IPv6 packets within IPv4, in effect using IPv4 as a link layer for IPv6.

The direct encapsulation of IPv6 datagrams within IPv4 packets is indicated by IP protocol number 41. IPv6 can also be encapsulated within UDP packets e.g. in order to cross a router or NAT device that blocks protocol 41 traffic. Other encapsulation schemes, such as used in AYIYA or GRE, are also popular.

Automatic tunneling

Automatic tunneling refers to a technique where the routing infrastructure automatically determines the tunnel endpoints. RFC 3056 recommends 6to4 tunneling for automatic tunneling, which uses protocol 41 encapsulation.[25] Tunnel endpoints are determined by using a well-known IPv4 anycast address on the remote side, and embedding IPv4 address information within IPv6 addresses on the local side. 6to4 is widely deployed today.

Teredo is an automatic tunneling technique that uses UDP encapsulation and can allegedly cross multiple NAT boxes.[26] IPv6, including 6to4 and Teredo tunneling, are enabled by default in Windows Vista.[27] Most Unix systems only implement native support for 6to4, but Teredo can be provided by third-party software such as Miredo.

ISATAP[28] treats the IPv4 network as a virtual IPv6 local link, with mappings from each IPv4 address to a link-local IPv6 address. Unlike 6to4 and Teredo, which are inter-site tunnelling mechanisms, ISATAP is an intra-site mechanism, meaning that it is designed to provide IPv6 connectivity between nodes within a single organisation.

Configured and automated tunneling (6in4)

In configured tunneling, the tunnel endpoints are explicitly configured, either by an administrator manually or the operating system's configuration mechanisms, or by an automatic service known as a tunnel broker;[29] 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 behaviour of configured tunneling.

Raw encapsulation of IPv6 packets using 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

After the regional Internet registries have exhausted their pools of available IPv4 addresses, it is likely that hosts newly added to the Internet might only have IPv6 connectivity. For these clients to have backward-compatible connectivity to existing IPv4-only resources, suitable 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 have been proposed. Most have been found to be unreliable[2] in practice because of the wide range of functionality required by common application-layer protocols, and are considered by many to be obsolete.[citation needed]

IPv6 readiness

Barriers to IPv6 adoption include:

  • Legacy Equipment
    • manufacturer no longer exists
    • manufacturer refuses to support IPv6 or makes updates prohibitively expensive
    • software upgrades are impossible (software in permanent ROM)
    • device has insufficient resources to implement the IPv6 stack
    • IPv6 is supported but performance is poor
  • New Equipment
    • IPv6 hardware support increases cost to the consumer
    • IPv6 software development is expensive
  • Consumer Apathy
    • Consumers aren't interested until they need to be
    • Applications work fine right now
    • Publicity and education are expensive; who will pay?

Even though consumers are most likely to suffer when their equipment has to be replaced they tend to look at networking devices like household appliances that only rarely need repairs and never have to be configured or updated. Commercial grade equipment is more likely to support IPv6, so it is the small consumer with his cost-effective disposable networking technology who will be most affected by the eventual change from IPv4 to IPv6.

Smart equipment that contains software needs explicit IPv6 support. Lower-level equipment like cables, network adapters, and switches may not be affected by the change. In general, layer-1 and layer-2 equipment won't require updates.

IPv6 compatibility is mainly a software/firmware issue like the year-2000. Unlike the year-2000 issue, there is little interest in ensuring compatibility of older equipment and software by manufacturers.[citation needed] The realization that IPv4 exhaustion is imminent is recent and manufacturers haven't shown much initiative in updating equipment. There is hope that a combined IPv4/IPv6 internet will streamline the transition. The internet community is divided on the issue of whether the transition should be a quick switch or a longer process. The American Registry for Internet Numbers suggests that all internet servers be prepared to serve IPv6-only clients by January 2012.[30] Universal access to IPv6-only servers will be even more of a challenge.

Most equipment would be fully IPv6 capable with a software or firmware update if the device has sufficient storage and memory space for the new IPv6 stack. However, as with 64-bit Windows, UEFI and Wi-Fi Protected Access support, manufacturers are unlikely to spend on development costs for hardware they have already sold when they are poised to make more sales from "IPv6-ready" equipment.

The CableLabs consortium published the 160 Mbit/s DOCSIS 3.0 IPv6-ready specification for cable modems in August 2006. The widely used DOCSIS 2.0 does not support IPv6. The new 'DOCSIS 2.0 + IPv6' standard also supports IPv6, which may on the cable modem side only require a firmware upgrade.[31][32] It is expected that only 60% of cable modems' servers and 40% of cable modems will be DOCSIS 3.0 by 2011.[33]

Other equipment which is typically not IPv6-ready ranges from Skype and SIP phones to oscilloscopes and printers. Professional network routers in use should be IPv6-ready. Most personal computers should also be IPv6-ready because the network stack resides in the operating system. Most applications with network capabilities are not ready but could be upgraded with support from the developers. Since Java 1.4 (February 2002) all applications that are 100% Java compatible have support for IPv6 addresses.[34]

Deployment

The introduction of Classless Inter-Domain Routing (CIDR) in the Internet routing and IP address allocation methods in 1993 and the extensive use of network address translation (NAT) has delayed the inevitable IPv4 address exhaustion. Final exhaustion is predicted for the 2011 to 2012 time frame at the major allocation levels.[10]

In 2008, IPv6 accounted for a minuscule fraction of the used addresses and the traffic in the publicly-accessible Internet which is still dominated by IPv4.[35] In October 2010, 243 (83%) of the 294 top-level domains (TLDs) in the Internet supported IPv6 to access their domain name servers, and 203 (69%) zones contained IPv6 glue records, and approximately 1.4 million domains (1%) had IPv6 address records in their zones.[36] Of all networks in the global BGP routing table, 7.2% have IPv6 protocol support.

The 2008 Summer Olympic Games were a notable event in terms of IPv6 deployment, being the first time a major world event has had a presence on the IPv6 Internet at http://ipv6.beijing2008.cn/en (IP addresses 2001:252:0:1::2008:6 and 2001:252:0:1::2008:8) and all network operations of the Games were conducted using IPv6.[37] At the time of the event, it was believed that the Olympics provided the largest showcase of IPv6 technology since the inception of IPv6.[38] Since that time, major providers of Internet services, such as Google, have begun to implement IPv6 access into their products.[39]

Cellular telephone systems present a large deployment field for Internet Protocol devices as mobile telephone service is being transitioned from 3G systems to next generation (4G) technologies in which voice is provisioned as a Voice over Internet Protocol (VoIP) service. This mandates the use of IPv6 for such networks. In the U.S., cellular operator Verizon has released technical specifications for devices operating on its future networks.[40] The specification mandates IPv6 operation according to the 3GPP Release 8 Specifications (March 2009) and deprecates IPv4 as an optional capability.

Some implementations of the BitTorrent peer-to-peer file transfer protocol make use of IPv6 to avoid NAT issues common for IPv4 private networks.[41]

All major operating systems in use as of 2010 on personal computers and server systems have production quality IPv6 implementations. Microsoft Windows has supported IPv6 since Windows 2000, and in production ready state beginning with Windows XP. Windows Vista and later have improved IPv6 support[42] Mac OS X Panther (10.3), GNU/Linux 2.6, FreeBSD, and Solaris also have mature production implementations.

Major milestones

Year Major development and availability milestones
1996 Alpha quality IPv6 support in Linux kernel development version 2.1.8.[43]
6bone (an IPv6 virtual network for testing) is started.
1997 By the end of 1997 IBM's AIX 4.3 is the first commercial platform supporting IPv6.[44][45]
Also in 1997, Early Adopter Kits for DEC's operating systems, Tru64 and OpenVMS, are made available.[46]
1998 Microsoft Research[47] releases its first experimental IPv6 stack. This support is not intended for use in a production environment.
2000 Production-quality BSD support for IPv6 becomes generally available in early to mid-2000 in FreeBSD, OpenBSD, and NetBSD via the KAME project.[48]
Microsoft releases an IPv6 technology preview version for Windows 2000 in March 2000.[47]
Sun Solaris supports IPv6 in Solaris 8 in February.[49]
Compaq ships IPv6 with Tru64.[46]
2001 In January, Compaq ships IPv6 with OpenVMS.[46]
Cisco Systems introduces IPv6 support on Cisco IOS routers and L3 switches.[50]
HP introduces IPv6 with HP-UX 11i v1.[51]
2002 Microsoft Windows NT 4.0 and Windows 2000 SP1 have limited IPv6 support for research and testing since at least 2002.
Microsoft Windows XP (2001) supports IPv6 for developmental purposes. In Windows XP SP1 (2002) and Windows Server 2003, IPv6 is included as a core networking technology, suitable for commercial deployment.[52]
IBM z/OS supports IPv6 since version 1.4 (generally availability in September 2002).[53]
2003 Apple Mac OS X v10.3 "Panther" (2003) supports IPv6 which is enabled by default.[54]
2004 In July, ICANN announces that IPv6 address records for the Japan (jp) and Korea (kr) country code top-level domain nameservers are visible in the DNS root server zone files with serial number 2004072000. The IPv6 records for France (fr) are added later. This makes IPv6 DNS publicly operational.
2005 Linux 2.6.12 removes experimental status from its IPv6 implementation.[55]
2007 Microsoft Windows Vista (2007) supports IPv6 which is enabled by default.[52]
Apple's AirPort Extreme 802.11n base station includes an IPv6 gateway in its default configuration. It uses 6to4 tunneling and manually configured static tunnels.[56] (Note: 6to4 was disabled by default in later firmware revisions.)
2008 On February 4, 2008, IANA adds AAAA records for the IPv6 addresses of six root name servers.[57][58] With this transition, it is now possible for two Internet hosts to fully communicate without using IPv4.
On March 12, 2008, Google launches a public IPv6 web interface to its popular search engine at the URL http://ipv6.google.com.[39]
2009 In January 2009, Google extends its IPv6 initiative with Google over IPv6, which offers IPv6 support for Google services to compatible networks.
2010 In May/June 2010, Facebook became accessible on IPv6 via http://www.v6.facebook.com/

See also

Notes

  1. ^ UDP/IPv4 may actually have a checksum of 0, indicating no checksum; IPv6 requires UDP to have its own checksum.
  2. ^ This improvement may have been made less necessary by the development of routers that perform checksum computation at link speed using dedicated hardware, but it is still relevant for software based routers.

References

  1. ^ a b c d e f RFC 2460, Internet Protocol, Version 6 (IPv6) Specification, S. Deering, R. Hinden (December 1998)
  2. ^ a b RFC 4966 Reasons to Move the Network Address Translator - Protocol Translator (NAT-PT) to Historic Status
  3. ^ Global IPv6 Statistics - Measuring the current state of IPv6 for ordinary users, S. H. Gunderson (Google), RIPE 57 (Dubai, Oct 2008)
  4. ^ Google: more Macs mean higher IPv6 usage in US
  5. ^ a b c RFC 1752 The Recommendation for the IP Next Generation Protocol, S. Bradner, A. Mankin, January 1995.
  6. ^ RFC 1550, IP: Next Generation (IPng) White Paper Solicitation, S. Bradner, A. Mankin (December 1993)
  7. ^ History of the IPng Effort
  8. ^ Exec: No shortage of Net addresses By John Lui, CNETAsia
  9. ^ A Pragmatic Report on IPv4 Address Space Consumption by Tony Hain, Cisco Systems
  10. ^ a b IPv4 Address Report
  11. ^ Proposed Global Policy for the Allocation of the Remaining IPv4 Address Space
  12. ^ a b RFC 1726, Technical Criteria for Choosing IP The Next Generation (IPng), Partridge C., Kastenholz F. (December 1994)
  13. ^ U.S. Census Bureau
  14. ^ RFC 2071, Network Renumbering Overview: Why would I want it and what is it anyway?, P. Ferguson, H. Berkowitz (January 1997)
  15. ^ RFC 2072, Router Renumbering Guide, H. Berkowitz (January 1997)
  16. ^ RFC 4862, IPv6 Stateless Address Autoconfiguration, S. Thomson, T. Narten, T. Jinmei (September 2007)
  17. ^ RFC 2894, Router Renumbering for IPv6, M. Crawford, August 2000.
  18. ^ RFC 1112, Host extensions for IP multicasting, S. Deering (August 1989)
  19. ^ RFC 2908, The Internet Multicast Address Allocation Architecture, D. Thaler, M. Handley, D. Estrin (September 2000)
  20. ^ RFC 3956, Embedding the Rendezvous Point (RP) Address in an IPv6 Multicast Address, P. Savola, B. Haberman (November 2004)
  21. ^ RFC 3963, Network Mobility (NEMO) Basic Protocol Support, V. Devarapalli, R. Wakikawa, A. Petrescu, P. Thubert (January 2005)
  22. ^ RFC 2675, IPv6 Jumbograms, D. Borman, S. Deering, R. Hinden (August 1999)
  23. ^ RFC 4291 IP Version 6 Addressing Architecture, R. Hinden, S. Deering (February 2006)
  24. ^ IPv6 Transition Mechanism / Tunneling Comparison
  25. ^ RFC 3056 Connection of IPv6 Domains via IPv4 Clouds, B. Carpenter, Februari 2001.
  26. ^ RFC 4380 Teredo: Tunneling IPv6 over UDP through Network Address Translations (NATs), C. Huitema, Februari 2006
  27. ^ The Windows Vista Developer Story: Application Compatibility Cookbook
  28. ^ RFC 5214 Intra-Site Automatic Tunnel Addressing Protocol (ISATAP), F. Templin, T. Gleeson, D. Thaler, March 2008.
  29. ^ RFC 3053, IPv6 Tunnel Broker, A. Durand, P. Fasano, I. Guardini, D. Lento (January 2001)
  30. ^ Web sites must support IPv6 by 2012, expert warns, Network World, 21 January 2010, http://www.networkworld.com/news/2010/012110-ipv6-warning.html, retrieved 2010-09-30 
  31. ^ "DOCSIS 2.0 Interface". Cablemodem.com. 2007-10-29. http://www.cablemodem.com/specifications/specifications20.html. Retrieved 2009-08-31. 
  32. ^ RMV6TF.org
  33. ^ ABI Research (2007-08-23). "DOCSIS 3.0 Network Equipment Penetration to Reach 60% by 2011". Press release. http://www.abiresearch.com/abiprdisplay.jsp?pressid=710. Retrieved 2007-09-30. 
  34. ^ "Networking IPv6 User Guide for JDK/JRE 5.0". http://java.sun.com/j2se/1.5.0/docs/guide/net/ipv6_guide/index.html. Retrieved 2007-09-30. 
  35. ^ Geoff Huston - An Update on IPv6 Deployment (RIPE 56)
  36. ^ Mike Leber (2010-10-02). "Global IPv6 Deployment Progress Report". Hurricane Electric. http://bgp.he.net/ipv6-progress-report.cgi. Retrieved 2010-10-02. 
  37. ^ The Beijing Organizing Committee for the Games of the XXIX Olympiad (2008-05-30). "Beijing2008.cn leaps to next-generation Net". Press release. http://en.beijing2008.cn/news/official/preparation/n214384681.shtml. 
  38. ^ Das, Kaushik (2008). "IPv6 and the 2008 Beijing Olympics". IPv6.com. http://ipv6.com/articles/general/IPv6-Olympics-2008.htm. Retrieved 2008-08-15. "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." 
  39. ^ a b Official Google Blog announcing IPv6 support
  40. ^ Derek Morr (2009-06-09). "Verizon Mandates IPv6 Support for Next-Gen Cell Phones". CircleID. http://www.circleid.com/posts/20090609_verizon_mandates_ipv6_support_for_next_gen_cell_phones/. 
  41. ^ Rob Issac (2008), Welcome to your IPv6 enabled transit network. Whether you like it, or not, http://www.ausnog.net/files/ausnog-03/presentations/ausnog03-ward-IPv6_enabled_network.pdf 
  42. ^ Vista: How PPPv6 support works?
  43. ^ Linux IPv6 Development Project
  44. ^ IPv6 support shipping in AIX 3.3
  45. ^ Its AIX 4.3.
  46. ^ a b c DEC/Compaq IPv6 history
  47. ^ a b Internet Protocol Version 6 (old Microsoft Research IPv6 release)
  48. ^ KAME project
  49. ^ Sun Solaris 8 changes from Solaris 7
  50. ^ Cisco main IPv6 site
  51. ^ HP main IPv6 site
  52. ^ a b Microsofts main IPv6 site
  53. ^ "IBM: z/OS operating system". 03.ibm.com. http://www-03.ibm.com/servers/eserver/zseries/announce/zos_r4/. Retrieved 2009-08-31. 
  54. ^ Mac OS X 10.3 Using IPv6 *** Document not found error message *** 2008-11-14
  55. ^ Linux 2.6.12 changelog
  56. ^ Apple AirPort Extreme technical specifications.
  57. ^ IPv6: coming to a root server near you
  58. ^ IANA - IPv6 Addresses for the Root Servers

External links


Study guide

Up to date as of January 14, 2010

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IPv6 (IPng or InternetProtocol next generation) it is a replacement for IPv4. it improves the flexibility and security of the IPv4 packet structure.

More IPs

The old way of using the TCP/IP_Model Model called for IPv4, but due to a limit in the number of unique addresses a new method was created. IPv6 uses a different method to create IPs, and allow for 128bit IP addresses. The number of available IPs available when the IPv6 protocol finally takes effect will increase from 4,294,967,296 to 340,282,366,920,938,463,463,374,607,431,768,211,456. This should allow for 5*10^48 IP addresses for every one of the approximently 6.5 billion peaple on the planet.

See also


Wiktionary

Up to date as of January 15, 2010

Definition from Wiktionary, a free dictionary

English

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IPv6

  1. Internet Protocol version 6, successor to IPv4 as formally adopted for general use.







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