Internet Protocol version 6 (
IPv6) is a version of the
Internet ProtocolThe Internet Protocol is the principal communications protocol used for relaying datagrams across an internetwork using the Internet Protocol Suite...
(IP). It is designed to succeed the
Internet Protocol version 4Internet Protocol version 4 is the fourth revision in the development of the Internet Protocol and the first version of the protocol to be widely deployed. Together with IPv6, it is at the core of standards-based internetworking methods of the Internet...
(IPv4). The
InternetThe Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
operates by transferring data between hosts in small packets that are independently
routedRouting is the process of selecting paths in a network along which to send network traffic. Routing is performed for many kinds of networks, including the telephone network , electronic data networks , and transportation networks...
across networks as specified by an international
communications protocolA communications protocol is a system of digital message formats and rules for exchanging those messages in or between computing systems and in telecommunications...
known as the Internet Protocol.
Each host or computer on the Internet requires an IP address in order to communicate. The growth of the Internet has created a need for more addresses than are possible with IPv4. IPv6 was developed by the
Internet Engineering Task ForceThe Internet Engineering Task Force develops and promotes Internet standards, cooperating closely with the W3C and ISO/IEC standards bodies and dealing in particular with standards of the TCP/IP and Internet protocol suite...
(IETF) to deal with this long-anticipated IPv4 address exhaustion, and is described in
Internet standardIn computer network engineering, an Internet Standard is a normative specification of a technology or methodology applicable to the Internet. Internet Standards are created and published by the Internet Engineering Task Force .-Overview:...
document RFC 2460, published in December 1998. Like IPv4, IPv6 is an internet-layer protocol for packet-switched
internetworkingInternetworking is the practice of connecting a computer network with other networks through the use of gateways that provide a common method of routing information packets between the networks...
and provides end-to-end
datagramA datagram is a basic transfer unit associated with a packet-switched network in which the delivery, arrival time, and order are not guaranteed....
transmission across multiple IP networks. While IPv4 allows 32 bits for an
Internet Protocol addressAn Internet Protocol address is a numerical label assigned to each device participating in a computer network that uses the Internet Protocol for communication. An IP address serves two principal functions: host or network interface identification and location addressing...
, and can therefore support 2
32 (4,294,967,296) addresses, IPv6 uses 128-bit addresses, so the new address space supports 2
128 (approximately 340 undecillion or ) addresses. This expansion allows for many more devices and users on the internet as well as extra flexibility in allocating addresses and efficiency for routing traffic. It also eliminates the primary need for
network address translationIn computer networking, network address translation is the process of modifying IP address information in IP packet headers while in transit across a traffic routing device....
(NAT), which gained widespread deployment as an effort to alleviate IPv4 address exhaustion.
IPv6 also implements additional features not present in IPv4. It simplifies aspects of address assignment (stateless address autoconfiguration), network renumbering and router announcements when changing Internet connectivity providers. The IPv6
subnetA subnetwork, or subnet, is a logically visible subdivision of an IP network. The practice of dividing a network into subnetworks is called subnetting....
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 addressA Media Access Control address is a unique identifier assigned to network interfaces for communications on the physical network segment. MAC addresses are used for numerous network technologies and most IEEE 802 network technologies, including Ethernet...
).
Network securityIn the field of networking, the area of network security consists of the provisions and policies adopted by the network administrator to prevent and monitor unauthorized access, misuse, modification, or denial of the computer network and network-accessible resources...
is also integrated into the design of the IPv6 architecture, and the IPv6 specification mandates support for
IPsecInternet Protocol Security is a protocol suite for securing Internet Protocol communications by authenticating and encrypting each IP packet of a communication session...
as a fundamental interoperability requirement.
The last top level (
/8) block of free IPv4 addresses was assigned in February 2011 by
IANAThe Internet Assigned Numbers Authority is the entity that oversees global IP address allocation, autonomous system number allocation, root zone management in the Domain Name System , media types, and other Internet Protocol-related symbols and numbers...
to the 5
RIRsA regional Internet registry is an organization that manages the allocation and registration of Internet number resources within a particular region of the world...
, although many free addresses still remain in most assigned blocks and each RIR will continue with standard policy until it is at its last /8. After that, only 1024 addresses (a /22) are made available from the RIR for each
LIRA local Internet registry is an organization that has been allocated a block of IP addresses by a regional Internet registry , and that assigns most parts of this block to its own customers. Most LIRs are Internet service providers, enterprises, or academic institutions. Membership in an RIR is...
– currently, only APNIC has already reached this stage. While IPv6 is supported on all major operating systems in use in commercial, business, and home consumer environments, IPv6 does not implement interoperability features with IPv4, and creates essentially a parallel, independent network. Exchanging traffic between the two networks requires special translator gateways, but modern computer operating systems implement dual-protocol software for transparent access to both networks either natively or using a
tunneling protocolComputer networks use a tunneling protocol when one network protocol encapsulates a different payload protocol...
such as
6to46to4 is an Internet transition mechanism for migrating from IPv4 to IPv6, a system that allows IPv6 packets to be transmitted over an IPv4 network without the need to configure explicit tunnels...
,
6in46in4 is an Internet transition mechanism for migrating from Internet Protocol version 4 to IPv6. 6in4 uses tunneling to encapsulate IPv6 traffic over explicitly-configured IPv4 links as defined in RFC 4213 . The 6in4 traffic is sent over the IPv4 Internet inside IPv4 packets whose IP headers have...
, or
TeredoIn computer networking, Teredo is a transition technology that gives full IPv6 connectivity for IPv6-capable hosts which are on the IPv4 Internet but which have no direct native connection to an IPv6 network...
. In December 2010, despite marking its 12th anniversary as a Standards Track protocol, IPv6 was only in its infancy in terms of general worldwide
deploymentInternet Protocol Version 6 is the next generation of the Internet Protocol that is currently in various stages of deployment on the Internet...
. A 2008 study by Google Inc. indicated that penetration was still less than one percent of Internet-enabled hosts in any country at that time.
IPv4
The first publicly used version of the Internet Protocol, Version 4 (IPv4), provides an addressing capability of 2
32 or approximately 4.3 billion addresses. Address exhaustion was not initially a concern in IPv4 as this version was originally presumed to be an internal test within ARPA, and not intended for public use.
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.
Working-group proposal
By the beginning of 1992, several proposals appeared and by the end of 1992, the IETF announced a call for white papers. In September 1993, the IETF created a temporary, ad-hoc
IP Next Generation (IPng) area to deal specifically with IPng issues. The new area was led by Allison Mankin and
Scott BradnerScott Bradner is a senior figure in the area of Internet governance. He serves as the secretary to the Internet Society and was formerly a trustee. He is on the board of ARIN, the North American IP address registry. He has also held numerous senior leadership roles on the Internet Engineering Task...
, and had a directorate with 15 engineers from diverse backgrounds for direction-setting and preliminary document review:
[The working-group members were J. Allard (Microsoft), Steve Bellovin]Steven M. Bellovin is a researcher on computer networking and security. He is currently a Professor in the Computer Science department at Columbia University, having previously been a Fellow at AT&T Labs Research in Florham Park, New Jersey.- Career :...
(AT&T), Jim Bound (Digital Equipment Corporation), Ross Callon (Wellfleet), Brian Carpenter (CERN), Dave ClarkDavid Dana Clark is an American computer scientist. He graduated from Swarthmore College in 1966. In 1968, he received his Master's and Engineer's degrees in Electrical Engineering from the Massachusetts Institute of Technology, where he worked on the I/O architecture of Multics under Jerry...
(MIT), John CurranJohn Curran is an early Internet executive, and the President and CEO of the American Registry for Internet Numbers . He was a founder of ARIN and served as the Chairman from inception through 2009...
(NEARNET), Steve DeeringStephen Deering is a former Technical Leader at Cisco Systems, where he worked on the development and standardization of architectural enhancements to the Internet Protocol...
(Xerox), Dino Farinacci (Cisco), Paul Francis (NTT), Eric Fleischmann (Boeing), Mark Knopper (Ameritech), Greg Minshall (Novell), Rob Ullmann (Lotus), and Lixia Zhang (Xerox).
The Internet Engineering Task Force adopted the IPng model on July 25, 1994, with the formation of several IPng working groups. By 1996, a series of
RFCsIn computer network engineering, a Request for Comments is a memorandum published by the Internet Engineering Task Force describing methods, behaviors, research, or innovations applicable to the working of the Internet and Internet-connected systems.Through the Internet Society, engineers and...
was released defining Internet Protocol version 6 (IPv6), starting with RFC 1883. (Version 5 was used by the experimental Internet Stream Protocol.)
It is widely expected that IPv4 will be supported alongside IPv6 for the foreseeable future. IPv4-only and IPv6-only nodes cannot communicate directly, and need assistance from an intermediary gateway or must use other transition mechanisms.
Exhaustion of IPv4 addresses
On February 3, 2011, in a ceremony in Miami, the
Internet Assigned Numbers AuthorityThe Internet Assigned Numbers Authority is the entity that oversees global IP address allocation, autonomous system number allocation, root zone management in the Domain Name System , media types, and other Internet Protocol-related symbols and numbers...
(IANA) assigned the last batch of 5
/8CIDR notation is a compact specification of an Internet Protocol address and its associated routing prefix. Classless Inter-Domain Routing is an Internet Protocol address allocation and route aggregation methodology used within the Internet addressing architecture that replaced the IPv4 classful...
address blocks to the Regional Internet Registries., officially depleting the global pool of completely fresh blocks of addresses. Each of the address blocks represents approximately 16.7 million possible addresses, or over 80 million combined potential addresses.
These addresses could well be fully consumed within three to six months of that time at current rates of allocation.
APNICThe Asia Pacific Network Information Centre is the Regional Internet Registry for the Asia Pacific region.APNIC provides number resource allocation and registration services that support the global operation of the Internet...
was the first RIR to exhaust its regional pool on 15 April 2011, except for a small amount of address space reserved for the transition to IPv6, which will be allocated in a much more restricted way.
In 2003, the director of
Asia-Pacific Network Information CentreThe Asia Pacific Network Information Centre is the Regional Internet Registry for the Asia Pacific region.APNIC provides number resource allocation and registration services that support the global operation of the Internet...
(APNIC), Paul Wilson, stated that, based on then-current rates of deployment, the available space would last for one or two decades. In September 2005, a report by
Cisco SystemsCisco Systems, Inc. is an American multinational corporation headquartered in San Jose, California, United States, that designs and sells consumer electronics, networking, voice, and communications technology and services. Cisco has more than 70,000 employees and annual revenue of US$...
suggested that the pool of available addresses would exhaust in as little as 4 to 5 years. In 2008, a policy process started for the end-game and post-exhaustion era. In 2010, a daily updated report projected the global address pool exhaustion by the first quarter of 2011, and depletion at the five
regional Internet registriesA regional Internet registry is an organization that manages the allocation and registration of Internet number resources within a particular region of the world...
before the end of 2011.
Comparison to IPv4
IPv6 specifies a new
packet formatAn IPv6 packet is the smallest message entity exchanged via the Internet Protocol across an Internet Protocol version 6 network.Packets consist of control information for addressing and routing, and a payload consisting of user data. The control information in IPv6 packets is subdivided into a...
, designed to minimize packet header processing by routers. Because the headers of IPv4 packets and IPv6 packets are significantly different, the two protocols are not interoperable. However, in most respects, IPv6 is a conservative extension of IPv4. Most transport and application-layer protocols need little or no change to operate over IPv6; exceptions are application protocols that embed internet-layer addresses, such as
FTPFile Transfer Protocol is a standard network protocol used to transfer files from one host to another host over a TCP-based network, such as the Internet. FTP is built on a client-server architecture and utilizes separate control and data connections between the client and server...
and
NTPv3The Network Time Protocol is a protocol and software implementation for synchronizing the clocks of computer systems over packet-switched, variable-latency data networks. Originally designed by David L...
.
Larger address space
The most important feature of IPv6 is a much larger address space than in IPv4. The length of an IPv6 address is 128 bits, compared to 32 bits in IPv4. The address space therefore supports 2
128 or approximately addresses. By comparison, this amounts to approximately addresses for each of the seven billion people alive in 2011. In addition, the IPv4 address space is poorly allocated, with approximately 14% of all available addresses utilized. While these numbers are large, it was not the intent of the designers of the IPv6 address space to assure geographical saturation 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 RoutingClassless Inter-Domain Routing is a method for allocating IP addresses and routing Internet Protocol packets. The Internet Engineering Task Force introduced CIDR in 1993 to replace the previous addressing architecture of classful network design in the Internet...
(CIDR) methods were developed to make the best use of the small address space. The standard size of a subnet in IPv6 is 2
64 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 is 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. 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.
Multicasting
MulticastIn computer networking, multicast is the delivery of a message or information to a group of destination computers simultaneously in a single transmission from the source creating copies automatically in other network elements, such as routers, only when the topology of the network requires...
ing, 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. IPv6 multicast addressing shares common features and protocols with IPv4 multicast, but also provides changes and improvements by eliminating the need for certain protocols. 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 also supports new multicast solutions, including embedding rendezvous point addresses in an IPv6 multicast group address which simplifies the deployment of inter-domain solutions.
In IPv4 it was very difficult for an organization to get even one globally routable multicast group assignment and the implementation of inter-domain solutions was very arcane. Unicast address assignments by a
local Internet registryA local Internet registry is an organization that has been allocated a block of IP addresses by a regional Internet registry , and that assigns most parts of this block to its own customers. Most LIRs are Internet service providers, enterprises, or academic institutions. Membership in an RIR is...
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.
(SLAAC)
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-localA link-local address is an Internet Protocol address that is intended only for communications within the segment of a local network or a point-to-point connection that a host is connected to. Routers do not forward packets with link-local addresses....
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.
If IPv6 stateless address autoconfiguration is unsuitable for an application, a network may use stateful configuration with the
Dynamic Host Configuration Protocol version 6DHCPv6 is the Dynamic Host Configuration Protocol for IPv6. Although IPv6's stateless address autoconfiguration can also be used to acquire IPv6 access, DHCPv6 may be a more suitable solution to assign addresses, nameservers and other configuration information as being done today with DHCP for IPv4...
(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.
Mandatory support for network-layer security
Internet Protocol SecurityInternet Protocol Security is a protocol suite for securing Internet Protocol communications by authenticating and encrypting each IP packet of a communication session...
(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. IPsec support is mandatory in IPv6 but optional for IPv4.
Simplified processing by routers
In IPv6, the packet header and the process of packet forwarding have been simplified. Although IPv6 packet headers are at least twice the size of IPv4 packet headers, packet processing by routers is generally more efficient, thereby extending the
end-to-end principleThe end-to-end principle is a classic design principle of computer networking which states that application specific functions ought to reside in the end hosts of a network rather than in intermediary nodes, provided they can be implemented "completely and correctly" in the end hosts...
of Internet design. Specifically:
- The packet header in IPv6 is simpler than that used in IPv4, with many rarely used fields moved to separate optional header extensions.
- IPv6 routers do not perform fragmentation
The Internet Protocol implements datagram fragmentation, so that packets may be formed that can pass through a link with a smaller maximum transmission unit than the original datagram size....
. IPv6 hosts are required to either perform path MTU discoveryPath MTU Discovery is a standardized technique in computer networking for determining the maximum transmission unit size on the network path between two Internet Protocol hosts, usually with the goal of avoiding IP fragmentation...
, perform end-to-end fragmentation, or to send packets no larger than the IPv6 default minimum MTUIn computer networking, the maximum transmission unit of a communications protocol of a layer is the size of the largest protocol data unit that the layer can pass onwards. MTU parameters usually appear in association with a communications interface...
size of 1280 octetsAn octet is a unit of digital information in computing and telecommunications that consists of eight bits. The term is often used when the term byte might be ambiguous, as there is no standard for the size of the byte.-Overview:...
.
- The IPv6 header is not protected by a checksum
A checksum or hash sum is a fixed-size datum computed from an arbitrary block of digital data for the purpose of detecting accidental errors that may have been introduced during its transmission or storage. The integrity of the data can be checked at any later time by recomputing the checksum and...
; integrity protection is assumed to be assured by both link-layer and higher-layer (TCP, UDP, etc.) error detection.[UDP/IPv4 may actually have a checksum of 0, indicating no checksum; IPv6 requires UDP to have its own checksum.] Therefore, IPv6 routers do not need to recompute a checksum when header fields (such as the time to liveTime to live is a mechanism that limits the lifespan of data in a computer or network. TTL may be implemented as a counter or timestamp attached to or embedded in the data. Once the prescribed event count or timespan has elapsed, data is discarded. In computer networking, TTL prevents a data...
(TTL) or hop countIn computer networking, hop count refers to the number of routers through which data must pass between source and destination. Each router along the data path constitutes a hop, as the data is moved from one Layer 3 network to another...
) 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 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 routingTriangular routing is routing that sends a packet to a proxy system before transmission to the intended destination. Triangular routing is a problem in mobile IP, however it finds applications in other networking scenarios, for example to avoid problems associated with network address translation ,...
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.
Options extensibility
The IPv6 protocol header has a fixed size (40 octets). Options are implemented as additional extension headers after the IPv6 header, which limits their size only by the size of an entire packet. The extension header mechanism provides extensibility to support future services for
quality of serviceThe quality of service refers to several related aspects of telephony and computer networks that allow the transport of traffic with special requirements...
, security, mobility, and others, without redesign of the basic protocol.
Jumbograms
IPv4 limits packets to (2
16 – 1) octets of payload. IPv6 has optional support for packets over this limit, referred to as
jumbogramIn packet-switched computer networks, a jumbogram is a packet of any size exceeding the standard Maximum Transmission Unit of the underlying network technology at either the Link Layer or the Internet Layer....
s, which can be as large as (2
32 – 1) octets. The use of jumbograms may improve performance over high-
MTUIn computer networking, the maximum transmission unit of a communications protocol of a layer is the size of the largest protocol data unit that the layer can pass onwards. MTU parameters usually appear in association with a communications interface...
links. The use of jumbograms is indicated by the Jumbo Payload Option header.
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
octetsAn octet is a unit of digital information in computing and telecommunications that consists of eight bits. The term is often used when the term byte might be ambiguous, as there is no standard for the size of the byte.-Overview:...
(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
payloadIn military aircraft or space exploration, the payload is the carrying capacity of an aircraft or space ship, including cargo, munitions, scientific instruments or experiments. External fuel, when optionally carried, is also considered part of the 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
IPsecInternet Protocol Security is a protocol suite for securing Internet Protocol communications by authenticating and encrypting each IP packet of a communication session...
framework.
The payload can have a size of up to without special options, or larger with a jumbo payload option in a
Hop-By-Hop Options extension header.
Unlike in IPv4, fragmentation is handled only in the end points of a communication session; routers never fragment a packet, and hosts are expected to use
Path MTU DiscoveryPath MTU Discovery is a standardized technique in computer networking for determining the maximum transmission unit size on the network path between two Internet Protocol hosts, usually with the goal of avoiding IP fragmentation...
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 addressAn Internet Protocol Version 6 address is a numerical label that is used to identify a network interface of a computer or other network node participating in an IPv6-enabled computer network....
es are 128 bits long, compared to only 32 bits previously. While the IPv4 address space contains only about (4.3
billion1,000,000,000 is the natural number following 999,999,999 and preceding 1,000,000,001.In scientific notation, it is written as 109....
) addresses, IPv6 supports approximately (340 undecillion) unique addresses, deemed enough for the foreseeable future.
IPv6 addresses are written in eight groups of four
hexadecimalIn mathematics and computer science, hexadecimal is a positional numeral system with a radix, or base, of 16. It uses sixteen distinct symbols, most often the symbols 0–9 to represent values zero to nine, and A, B, C, D, E, F to represent values ten to fifteen...
digits separated by colons, for example,
2001:0db8:85a3:0000:0000:8a2e:0370:7334. IPv6 unicast addresses other than those that start with binary 000 are logically divided into two parts: a 64-bit (sub-)network prefix, and a 64-bit interface identifier.
For stateless address autoconfiguration (SLAAC) to work, subnets require a /64 address block as defined in RFC 4291 section 2.5.1. Local Internet registries get assigned at least /32 blocks, which they divide among ISPs. The obsolete RFC 3177 recommended the assignment of a /48 to end consumer sites. 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
ComcastComcast Corporation is the largest cable operator, home Internet service provider, and fourth largest home telephone service provider in the United States, providing cable television, broadband Internet, and telephone service to both residential and commercial customers in 39 states and the...
customers have been given a single /64 network.
IPv6 addresses are classified by three types of networking methodologies:
unicastright|200pxIn computer networking, unicast transmission is the sending of messages to a single network destination identified by a unique address.-Addressing methodologies:...
addresses identify each network interface,
anycastAnycast is a network addressing and routing methodology in which datagrams from a single sender are routed to the topologically nearest node in a group of potential receivers all identified by the same destination address.-Addressing methodologies:...
addresses identify a group of interfaces, usually at different locations of which the nearest one is automatically selected, and
multicastIn computer networking, multicast is the delivery of a message or information to a group of destination computers simultaneously in a single transmission from the source creating copies automatically in other network elements, such as routers, only when the topology of the network requires...
addresses 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 reserved for special purposes, such as the address for
loopbackLoopback describes ways of routing electronic signals, digital data streams, or flows of items from their originating facility back to the source without intentional processing or modification...
,
6to46to4 is an Internet transition mechanism for migrating from IPv4 to IPv6, a system that allows IPv6 packets to be transmitted over an IPv4 network without the need to configure explicit tunnels...
tunneling,
Teredo tunnelingIn computer networking, Teredo is a transition technology that gives full IPv6 connectivity for IPv6-capable hosts which are on the IPv4 Internet but which have no direct native connection to an IPv6 network...
and several more. See 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 ProtocolThe Neighbor Discovery Protocol is a protocol in the Internet Protocol Suite used with Internet Protocol Version 6 . It operates in the Link Layer of the Internet model and is responsible for address autoconfiguration of nodes, discovery of other nodes on the link, determining the Link Layer...
.
IPv6 in the Domain Name System
In the
Domain Name SystemThe Domain Name System is a hierarchical distributed naming system for computers, services, or any resource connected to the Internet or a private network. It associates various information with domain names assigned to each of the participating entities...
,
hostnameA hostname is a label that is assigned to a device connected to a computer network and that is used to identify the device in various forms of electronic communication such as the World Wide Web, e-mail or Usenet...
s are mapped to IPv6 addresses by
AAAA resource records, so-called
quad-A records. For
reverse resolutionIn computer networking, reverse DNS lookup or reverse DNS resolution is the determination of a domain name that is associated with a given IP address using the Domain Name System of the Internet....
, the IETF reserved the domain
ip6.arpaThe domain name arpa is a top-level domain in the Domain Name System of the Internet. It is used exclusively for technical infrastructure purposes...
, where the name space is hierarchically divided by the 1-digit
hexadecimalIn mathematics and computer science, hexadecimal is a positional numeral system with a radix, or base, of 16. It uses sixteen distinct symbols, most often the symbols 0–9 to represent values zero to nine, and A, B, C, D, E, F to represent values ten to fifteen...
representation of
nibbleIn computing, a nibble is a four-bit aggregation, or half an octet...
units (4 bits) of the IPv6 address. This scheme is defined in RFC 3596.
Address Format
IPv6 addresses have two logical parts: a 64-bit network prefix, and a 64-bit host address part. (The host address is often automatically generated from the interface MAC address.) An IPv6 address is represented by 8 groups of 16-bit hexadecimal values separated by colons (:) shown as follows:
- 2001:0db8:85a3:0000:0000:8a2e:0370:7334
The hexadecimal digits are case-insensitive.
The 128-bit IPv6 address can be abbreviated with the following rules:
- Rule one: Leading zeroes within a 16-bit value may be omitted. For example, the address
fe80:0000:0000:0000:0202:b3ff:fe1e:8329 may be written as fe80:0:0:0:202:b3ff:fe1e:8329
- Rule two: One group of consecutive zeroes within an address may be replaced by a double colon. For example,
fe80:0:0:0:202:b3ff:fe1e:8329 becomes fe80::202:b3ff:fe1e:8329
A single IPv6 address can be represented in several different ways, such as
2001:db8::1:0:0:1 and
2001:0DB8:0:0:1::1. RFC 5952 recommends a canonical textual representation.
Transition mechanisms
Until IPv6 completely supplants IPv4, a number of transition mechanisms 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 2185, Routing Aspects of IPv6 Transition
- 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 3053, IPv6 Tunnel Broker
- RFC 3056, 6to4
6to4 is an Internet transition mechanism for migrating from IPv4 to IPv6, a system that allows IPv6 packets to be transmitted over an IPv4 network without the need to configure explicit tunnels...
. Connection of IPv6 Domains via IPv4 Clouds
- RFC 3142, An IPv6-to-IPv4 Transport Relay Translator
- RFC 4213, Basic Transition Mechanisms for IPv6 Hosts and Routers
- RFC 4380, Teredo: Tunneling IPv6 over UDP through Network Address Translations NATs
- RFC 4798, Connecting IPv6 Islands over IPv4 MPLS Using IPv6 Provider Edge Routers (6PE)
- RFC 5214, Intra-Site Automatic Tunnel Addressing Protocol ISATAP
- RFC 5569, IPv6 Rapid Deployment on IPv4 Infrastructures (6rd)
- RFC 5572, IPv6 Tunnel Broker with the Tunnel Setup Protocol (TSP)
- RFC 6180, Guidelines for Using IPv6 Transition Mechanisms during IPv6 Deployment
- RFC 6343, Advisory Guidelines for 6to4 Deployment
Dual IP stack implementation
The dual-stack protocol implementation in an
operating systemAn operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer 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
socketsThe Berkeley sockets application programming interface comprises a library for developing applications in the C programming language that perform inter-process communication, most commonly for communications across a computer network....
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
IPv4Internet Protocol version 4 is the fourth revision in the development of the Internet Protocol and the first version of the protocol to be widely deployed. Together with IPv6, it is at the core of standards-based internetworking methods of the Internet...
address. These addresses are commonly represented in the standard IPv6 format, but having the last 32 bits written in the customary
dot-decimal notationDot-decimal notation is a presentation format for numerical data. It consists of a string of decimal numbers, each pair separated by a full stop ....
of IPv4; for example,
::ffff:192.0.2.128 represents the IPv4 address
192.0.2.128. It substitutes the old and deprecated IPv4-compatible IPv6 address formed by
::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 WindowsMicrosoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
2000, XP, and Server 2003), or because of security concerns (
OpenBSDOpenBSD is a Unix-like computer operating system descended from Berkeley Software Distribution , a Unix derivative developed at the University of California, Berkeley. It was forked from NetBSD by project leader Theo de Raadt in late 1995...
)
. 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 kernelThe Linux kernel is an operating system kernel used by the Linux family of Unix-like operating systems. It is one of the most prominent examples of free and open source software....
,
NetBSDNetBSD is a freely available open source version of the Berkeley Software Distribution Unix operating system. It was the second open source BSD descendant to be formally released, after 386BSD, and continues to be actively developed. The NetBSD project is primarily focused on high quality design,...
, and
FreeBSDFreeBSD is a free Unix-like operating system descended from AT&T UNIX via BSD UNIX. Although for legal reasons FreeBSD cannot be called “UNIX”, as the direct descendant of BSD UNIX , FreeBSD’s internals and system APIs are UNIX-compliant...
, 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
tunnelingComputer networks use a tunneling protocol when one network protocol encapsulates a different payload protocol...
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
GREGeneric Routing Encapsulation is a tunneling protocol developed by Cisco Systems that can encapsulate a wide variety of network layer protocols inside virtual point-to-point links over an Internet Protocol internetwork.-Overview:...
, are also popular.
Conversely, on IPv6-only internet links, when access to IPv4 network facilities are needed, tunneling of IPv4 over IPv6 protocol occurs, using the IPv6 as a link layer for IPv4.
Automatic tunneling
Automatic tunneling refers to a technique where the routing infrastructure automatically determines the tunnel endpoints.
6to46to4 is an Internet transition mechanism for migrating from IPv4 to IPv6, a system that allows IPv6 packets to be transmitted over an IPv4 network without the need to configure explicit tunnels...
is recommended by RFC 3056 tunneling method for automatic tunneling, which uses protocol 41 encapsulation. 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.
TeredoIn computer networking, Teredo is a transition technology that gives full IPv6 connectivity for IPv6-capable hosts which are on the IPv4 Internet but which have no direct native connection to an IPv6 network...
is an automatic tunneling technique that uses UDP encapsulation and can allegedly cross multiple NAT boxes. IPv6, including 6to4 and Teredo tunneling, are enabled by default in
Windows VistaWindows Vista is an operating system released in several variations developed by Microsoft for use on personal computers, including home and business desktops, laptops, tablet PCs, and media center PCs...
and Windows 7. Most Unix systems only implement native support for 6to4, but Teredo can be provided by third-party software such as
MiredoMiredo is an open-source Teredo IPv6 tunneling software included in many Linux and BSD operating systems and is also available for recent versions of Mac OS X.It includes working implementations of:* a Teredo client,* a Teredo relay and* a Teredo server....
.
ISATAPISATAP is an IPv6 transition mechanism meant to transmit IPv6 packets between dual-stack nodes on top of an IPv4 network....
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 brokerIn the context of computer networking, a tunnel broker is a service which provides a network tunnel. These tunnels can provide encapsulated connectivity over existing infrastructure to a new infrastructure....
; 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
IPv4The Internet Protocol is the principal communications protocol used for relaying datagrams across an internetwork using the Internet Protocol Suite...
protocol number 41 is recommended for configured tunneling; this is sometimes known as
6in46in4 is an Internet transition mechanism for migrating from Internet Protocol version 4 to IPv6. 6in4 uses tunneling to encapsulate IPv6 traffic over explicitly-configured IPv4 links as defined in RFC 4213 . The 6in4 traffic is sent over the IPv4 Internet inside IPv4 packets whose IP headers have...
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 registriesA regional Internet registry is an organization that manages the allocation and registration of Internet number resources within a particular region of the world...
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 serverIn computer networks, a proxy server is a server that acts as an intermediary for requests from clients seeking resources from other servers. A client connects to the proxy server, requesting some service, such as a file, connection, web page, or other resource available from a different 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 due to a number of criticisms, however more recently the continued low adoption of IPv6 has prompted a new standardization effort under the name NAT64.
Application transition
RFC 4038,
Application Aspects of IPv6 Transition, is an informational RFC that covers the topic of IPv4 to IPv6 application transition mechanisms. Other RFCs that pertain IPv6 at the application level are:
- RFC 3493, Basic Socket Interface Extensions for IPv6
- RFC 3542, Advanced Sockets Application Program Interface (API) for IPv6
Similar to the OS-level WAN stack, applications can be:
- IPv4 only
- IPv6 only
- dual set of IPv4 and IPv6 only
- hybrid IPv4 and IPv6
IPv6 readiness
Compatibility with 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. The
American Registry for Internet NumbersThe American Registry for Internet Numbers is the Regional Internet Registry for Canada, many Caribbean and North Atlantic islands, and the United States. ARIN manages the distribution of Internet number resources, including IPv4 and IPv6 address space and AS numbers. ARIN opened its doors for...
(ARIN) suggests that all Internet servers be prepared to serve IPv6-only clients by January 2012.
Software
Most personal computers running recent
operating systemAn operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
versions are IPv6-ready. Most popular applications with network capabilities are ready, and most others could be easily upgraded with support from the developers. Java applications adhering to Java 1.4 (February 2002) standards have support for IPv6.
Hardware and embedded systems
Low-level equipment like network adapters and
network switchA network switch or switching hub is a computer networking device that connects network segments.The term commonly refers to a multi-port network bridge that processes and routes data at the data link layer of the OSI model...
es may not be affected by the change, since they transmit link-layer frames without inspecting the contents. Networking devices that obtain IP addresses or perform routing based on IP address do need IPv6 support.
Most equipment would be IPv6 capable with a software or firmware update if the device has sufficient storage and memory space for the new IPv6 stack. However, manufacturers may be reluctant to spend on software development costs for hardware they have already sold when they are poised for new sales from IPv6-ready equipment.
In some cases, non-compliant equipment needs to be replaced because the manufacturer no longer exists or software updates are not possible, for example, because the network stack is implemented in permanent
read-only memoryRead-only memory is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware .In its strictest sense, ROM refers only...
.
Consumers view networking devices as household appliances that do not need maintenance. Little effort has been made to educate consumers about the need to upgrade.
The
CableLabsFounded in 1988 by cable television operating companies, Cable Television Laboratories, Inc. is a not-for-profit research and development consortium that has cable operators as its members. System operators from around the world are eligible to be members. Members dues are based on revenue...
consortium published the 160 Mbit/s
DOCSISData Over Cable Service Interface Specification is an international telecommunications standard that permits the addition of high-speed data transfer to an existing cable TV system...
3.0 IPv6-ready specification for
cable modemA cable modem is a type of network bridge and modem that provides bi-directional data communication via radio frequency channels on a HFC and RFoG infrastructure. Cable modems are primarily used to deliver broadband Internet access in the form of cable Internet, taking advantage of the high...
s 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. It is expected that only 60% of cable modems' servers and 40% of cable modems will be DOCSIS 3.0 by 2011.
Other equipment which is typically not IPv6-ready ranges from Voice over Internet Protocol devices to laboratory equipment and printers.
Deployment
The introduction of
Classless Inter-Domain RoutingClassless Inter-Domain Routing is a method for allocating IP addresses and routing Internet Protocol packets. The Internet Engineering Task Force introduced CIDR in 1993 to replace the previous addressing architecture of classful network design in the Internet...
(CIDR) in the Internet routing and IP address allocation methods in 1993 and the extensive use of
network address translationIn computer networking, network address translation is the process of modifying IP address information in IP packet headers while in transit across a traffic routing device....
(NAT) delayed the inevitable IPv4 address exhaustion, but the final phase of exhaustion started on February 3, 2011. However, despite a decade long development and implementation history as a Standards Track protocol, general worldwide deployment is still in its infancy. As of October 2011, about 3% of domain names and 12% of the networks on the internet have IPv6 protocol support.
Nevertheless, IPv6 has been implemented on all major operating systems in use in commercial, business, and home consumer environments. Since 2008, the
domain name systemThe Domain Name System is a hierarchical distributed naming system for computers, services, or any resource connected to the Internet or a private network. It associates various information with domain names assigned to each of the participating entities...
can be used in IPv6 as major web sites like
GoogleGoogle Inc. is an American multinational public corporation invested in Internet search, cloud computing, and advertising technologies. Google hosts and develops a number of Internet-based services and products, and generates profit primarily from advertising through its AdWords program...
, although sometimes with extra configuration. IPv6 was first used in a major world event during the 2008 Summer Olympic Games, the largest showcase of IPv6 technology since the inception of IPv6. Countries like
ChinaChinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
or the
Federal U.S. GovernmentThe federal government of the United States is the national government of the constitutional republic of fifty states that is the United States of America. The federal government comprises three distinct branches of government: a legislative, an executive and a judiciary. These branches and...
are also starting to require support for IPv6 on their equipment.
Finally, modern cellular telephone specifications mandate IPv6 operation and deprecate IPv4 as an optional capability.
Controversy
Privacy extensions are, except for the Windows platform and Mac OS X since 10.7 as well as iOS since version 4.3, not enabled by default. The fact that the unique MAC address is exposed to the Internet and therefore makes devices trackable has led to criticism in various countries. Two actions are necessary to guarantee the same level as with today's IPv4 networks: the client device has the privacy extensions enabled, and the provider dynamically assigns a varying address block to the client device.
See also
- 3GPP
The 3rd Generation Partnership Project is a collaboration between groups of telecommunications associations, known as the Organizational Partners...
- China Next Generation Internet
The China Next Generation Internet project is a five year plan initiated by the Chinese government with the purpose of gaining a significant position in the future development of the Internet through the early adoption of IPv6.-Key CNGI goals:...
- Comparison of IPv6 application support
This is a comparison of popular Internet applications in regards to their support of the IPv6 protocol.-Applications:-External links:**: last updated in 7-2007.**: last updated in 3-2003.*: chapter 21 of TLDP's Linux IPv6 HOWTO....
- Comparison of IPv6 support by major transit providers
Internet Protocol Version 6 is not yet universally available as of 2011, but support by major ISPs and transit providers is steadily increasing. Many major transit providers offer an IPv6 service to their customers, but do not have a ubiquitous view of all other IPv6 networks...
- Comparison of IPv6 support in operating systems
This is a comparison of operating systems in regards to their support of the IPv6 protocol.- Notes :* Operating systems that do not support either DHCPv6 or ND RDNSS cannot automatically configure name servers in an IPv6-only environment.-External links:...
- Comparison of IPv6 support in routers
This is a comparison of consumer and commercial network routers in regards to their support of the IPv6 protocol.-Third-party firmwares with IPv6 support:-Consumer routers with 6to4 support:* Apple's Airport Extreme & Airport Express base station...
- List of IPv6 tunnel brokers
- Miredo
Miredo is an open-source Teredo IPv6 tunneling software included in many Linux and BSD operating systems and is also available for recent versions of Mac OS X.It includes working implementations of:* a Teredo client,* a Teredo relay and* a Teredo server....
- SATSIX
SATSIX is a demonstration of IPv6 integration of hybrid satellite and Wireless local loop and is funded by the Sixth Framework Programme through Information Society Technologies. The project will help in the implementation of the European Space Policy and the i2010 European Initiative...
- University of New Hampshire InterOperability Laboratory
The University of New Hampshire InterOperability Laboratory provides independent, broad-based interoperability and standards conformance testing for data, telecommunications and storage networking products and technologies...
involvement in the IPv6 Ready Logo Program
- The US DoD Joint Interoperability Test Command DoD IPv6 Product Certification
- Historical Testing Program :As of February 2009, the DoD ceased the requirement for IPv6-only testing for certification and entry into the Unified Capabilities Approved Products List...
Program
External links