Internet Protocol version 6 (
IPv6) is the next-generation
Internet ProtocolThe Internet Protocol is a protocol used for communicating data across a packet-switched internetwork using the Internet Protocol Suite, also referred to as TCP/IP....
version designated as the successor to
IPv4Internet Protocol version 4 is the fourth revision in the development of the Internet Protocol and it is 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...
, the first implementation used in the
InternetThe Internet is a global system of interconnected computer networks that use the standardized Internet Protocol Suite to serve billions of users worldwide...
and still in dominant use .
It is an
Internet LayerThe Internet Layer is a group of internetworking methods in the TCP/IP protocol suite which is the foundation of the Internet . It is the group of methods, protocols, and specifications which are used to transport datagrams from the originating host across network boundaries, if necessary, to the...
protocol for packet-switched
internetworksInternetworking involves connecting two or more computer networks via gateways using a common routing technology. The result is called an internetwork...
. The main driving force for the redesign of Internet Protocol was the foreseeable IPv4 address exhaustion. IPv6 was defined in December 1998 by the
Internet Engineering Task ForceThe Internet Engineering Task Force develops and promotes Internet standards, cooperating closely with the W3C and ISO/IEC standard bodies and dealing in particular with standards of the TCP/IP and Internet protocol suite...
(IETF) with the publication of an
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:...
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 2
128 (about 3.4×10
38) addresses. This expansion provides flexibility in allocating addresses and routing traffic and eliminates the primary need for
network address translationIn computer networking, network address translation is the process of modifying network address information in datagram packet headers while in transit across a traffic routing device for the purpose of remapping a given address space into another....
(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
subnetA subnetwork, or subnet, describes a logically visible sub-section of a single Internet network. This division groups networked computers and devices that have a common, designated IP address routing prefix into a separate network....
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 LayerIn computer networking, the Link Layer is the lowest layer in the Internet Protocol Suite, the networking architecture of the Internet . It is the group of methods or protocols that only operate on a host's link...
media addressing information (
MAC addressIn computer networking, a Media Access Control address is a unique identifier assigned to most network adapters or network interface cards by the manufacturer for identification, and used in the Media Access Control protocol sublayer. If assigned by the manufacturer, a MAC address usually...
).
Network securityIn the field of networking, the specialist area of network security consists of the provisions made in an underlying computer network infrastructure, policies adopted by the network administrator to protect the network and the network-accessible resources from unauthorized access, and consistent...
is integrated into the design of the IPv6 architecture.
Internet Protocol Security (IPsec)Internet Protocol Security is a protocol suite for securing Internet Protocol communications by authenticating and encrypting each IP packet of a data stream. IPsec also includes protocols for establishing mutual authentication between agents at the beginning of the session and negotiation of...
was originally developed for IPv6, but found widespread optional deployment first in IPv4 (into which it was back-engineered). The IPv6 specifications mandate
IPsecInternet Protocol Security is a protocol suite for securing Internet Protocol communications by authenticating and encrypting each IP packet of a data stream. IPsec also includes protocols for establishing mutual authentication between agents at the beginning of the session and negotiation of...
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
deploymentThis article attempts to provide an overview of Internet Protocol Version 6 deployment around the world.In February 1999, The IPv6 Forum was founded by the IETF Deployment WG to drive deployment worldwide. This resulted in the creation of regional and local IPv6 Task Forces.A global view into the...
. A 2008 study 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.
Motivation and origins
The first publicly used version of the
Internet ProtocolThe Internet Protocol is a protocol used for communicating data across a packet-switched internetwork using the Internet Protocol Suite, also referred to as TCP/IP....
, Version 4 (
IPv4Internet Protocol version 4 is the fourth revision in the development of the Internet Protocol and it is 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...
), provides an addressing capability of about 4 billion addresses (2
32). This was deemed sufficient in the early design stages of the
InternetThe Internet is a global system of interconnected computer networks that use the standardized Internet Protocol Suite to serve billions of users worldwide...
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. 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.
The Internet Engineering Task Force adopted IPng 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...
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. BernsteinDaniel Julius Bernstein is a professor at the University of Illinois at Chicago, a mathematician, a cryptologist, and a programmer. Bernstein is the author of the computer software qmail, publicfile and djbdns...
.
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
streamingStreaming media are multimedia that are constantly received by, and normally presented to, an end-user while being delivered by a streaming provider . The name refers to the delivery method of the medium rather than to the medium itself...
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 used to vary 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. In September 2005, a report by
Cisco SystemsCisco Systems, Inc. is a multinational corporation with more than 65,000 employees and annual revenue of US$36.10 billion as of 2009. Headquartered in San Jose, California, it designs and sells networking and communications technology and services....
suggested that the pool of available addresses would dry up in as little as 4 to 5 years. , a daily updated report projected that the
IANAThe Internet Assigned Numbers Authority is the entity that oversees global IP address allocation, root zone management for the Domain Name System , media types, and other Internet Protocol related assignments...
pool of unallocated addresses would be exhausted in June 2011, with the various
Regional Internet RegistriesA regional Internet registry is an organization overseeing the allocation and registration of Internet number resources within a particular region of the world...
using up their allocations from IANA in March 2012. 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.
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
FTPFile Transfer Protocol is a standard network protocol used to exchange and manipulate files over a TCP/IP 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 applications...
or
NTPv3The Network Time Protocol is a protocol for synchronizing the clocks of computer systems over packet-switched, variable-latency data networks. NTP uses UDP on port 123 as its transport layer. It is designed particularly to resist the effects of variable latency by using a jitter buffer...
.
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.
The very large IPv6 address space supports a total of 2
128 (about 3.4×10
38) addresses—or approximately 5×10
28 (roughly 2
95) addresses for each of the roughly 6.5 billion (6.5×10
9) people alive in 2006. In a different perspective, this is 2
52 addresses for every observable star in the known universe.
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 RoutingClassless Inter-Domain Routing is a methodology of allocating IP addresses and routing Internet Protocol packets. It was introduced in 1993 to replace the prior addressing architecture of classful network design in the Internet with the goal to slow the growth of routing tables on routers across...
(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 2
64 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
ICMPv6Internet Control Message Protocol Version 6 is the implementation of the Internet Control Message Protocol for Internet Protocol version 6 . ICMPv6 is an integral part of IPv6 and performs error reporting, diagnostic functions , neighbor discovery, and a framework for extensions to implement...
router discovery messages. When first connected to a network, a host sends a
link-localLink-local can refer to:* The data link layer, which is layer 2 of the OSI network model* Link-local addresses, which are intended only for use in the local layer 2 domain...
multicastMulticast addressing is a network technology for the delivery of information to a group of destinations simultaneously using the most efficient strategy to deliver the messages over each link of the network only once, creating copies only when the links to the multiple destinations split.The word...
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.
If IPv6 stateless address autoconfiguration is unsuitable for an application, a network may use stateful configuration with the
Dynamic Host Configuration ProtocolThe Dynamic Host Configuration Protocol is a computer networking protocol used by devices to obtain configuration information for operation in an Internet Protocol network...
for IPv6 (
DHCPv6DHCPv6 is the Dynamic Host Configuration Protocol for IPv6. Although IPv6's stateless address autoconfiguration removes the primary motivation for DHCP in IPv4, DHCPv6 can still be used to statefully assign addresses if the network administrator desires more control over addressing...
) 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 specified in RFC 2894.
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 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)Internet Protocol Security is a protocol suite for securing Internet Protocol communications by authenticating and encrypting each IP packet of a data stream. IPsec also includes protocols for establishing mutual authentication between agents at the beginning of the session and negotiation of...
, 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).
IPsecInternet Protocol Security is a protocol suite for securing Internet Protocol communications by authenticating and encrypting each IP packet of a data stream. IPsec also includes protocols for establishing mutual authentication between agents at the beginning of the session and negotiation of...
, however, is not widely used at present except for securing traffic between IPv6
Border Gateway ProtocolThe Border Gateway Protocol is the core routing protocol of the Internet. It maintains a table of IP networks or 'prefixes' which designate network reachability among autonomous systems . It is described as a path vector 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. Concretely,
- 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
Path MTU discovery is a 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 smaller than the IPv6 minimum MTUIn computer networking, the maximum transmission unit of a layer of a communications protocol is the size of the largest protocol data unit that it can pass onwards. MTU parameters usually appear in association with a communications interface...
size of 1280 bytes.
- 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 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
Time to live is a limit on the period of time or number of iterations or transmissions in computer and computer network technology that a unit of data can experience before it should be discarded.-IP packets:...
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 IPv6Mobile IPv6 is a version of Mobile IP - a network layer IP standard used by electronic devices to exchange data across a packet switched internetwork...
(MIPv6) avoids
triangular routingTriangular routing is routing which sends a packet to a proxy system before sending to the intended destination. Triangular routing is a problem in Mobile IP, however Skype uses triangular routing to communicate through NAT-enabled routers....
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 bytes) 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
QoSIn the field of computer networking and other packet-switched telecommunication networks, the traffic engineering term quality of service refers to resource reservation control mechanisms rather than the achieved service quality...
, security, mobility, etc. without a redesign of the basic protocol.
Jumbograms
IPv4 limits packets to 64
KiBA kibibyte is a unit of information or computer storage, established by the International Electrotechnical Commission in 2000. Its symbol is KiB...
of payload. IPv6 has optional support for packets over this limit, referred to as
jumbogramIn packet-switching computer networks, a jumbogram is a packet that is larger than the usual size limit for a given technology.- IPv6 jumbograms :...
s, which can be as large as 4
GiBThe gibibyte is a standards-based binary multiple of the byte, a unit of digital information storage...
. The use of jumbograms may improve performance over high-
MTUIn computer networking, the maximum transmission unit of a layer of a communications protocol is the size of the largest protocol data unit that it can pass onwards. MTU parameters usually appear in association with a communications interface...
networks. 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
octetsIn computing, an octet is a grouping of eight bits.Octet, with the only exception noted below, always refers to an entity having exactly eight bits. As such, it is often used where the term byte might be ambiguous. For that reason, computer networking standards almost exclusively use octet...
(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
hexadecimalIn mathematics and computer science, hexadecimal is a 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.Its primary use is as a...
(base 16) and the bit offsets are in
decimalThe decimal numeral system has ten as its base. It is the most widely used numeral base.- Decimal notation :...
(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
In the field of computer networking and other packet-switched telecommunication networks, the traffic engineering term quality of service refers to resource reservation control mechanisms rather than the achieved service quality...
management (20 bits). Originally created for giving real-time applications special service, but currently unused.
- 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
Time to live is a limit on the period of time or number of iterations or transmissions in computer and computer network technology that a unit of data can experience before it should be discarded.-IP packets:...
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 Mobile IPv6 is a version of Mobile IP - a network layer IP standard used by electronic devices to exchange data across a packet switched internetwork...
) |
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 Internet Protocol Security is a protocol suite for securing Internet Protocol communications by authenticating and encrypting each IP packet of a data stream. IPsec also includes protocols for establishing mutual authentication between agents at the beginning of the session and negotiation of...
) |
RFC 4302 |
| Encapsulating Security Payload (ESP) |
50 |
variable |
Carries encrypted data for secure communication. (See IPsec Internet Protocol Security is a protocol suite for securing Internet Protocol communications by authenticating and encrypting each IP packet of a data stream. IPsec also includes protocols for establishing mutual authentication between agents at the beginning of the session and negotiation of...
). |
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 64KB 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 discoveryPath MTU discovery is a 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....
.
128-bit length
The length of network addresses emphasize a most important change when moving from IPv4 to IPv6. IPv6 addresses are 128 bits long (as defined by RFC 4291), whereas IPv4 addresses are 32 bits; where the IPv4 address space contains roughly 4.3×10
9 (4.3 billion) addresses, IPv6 has enough room for 3.4×10
38 unique addresses.
IPv6 addresses are typically composed of two logical parts: a 64-bit (sub-)network prefix, and a 64-bit host part, which is either automatically generated from the interface's
MAC addressIn computer networking, a Media Access Control address is a unique identifier assigned to most network adapters or network interface cards by the manufacturer for identification, and used in the Media Access Control protocol sublayer. If assigned by the manufacturer, a MAC address usually...
or assigned sequentially. Because the globally unique MAC addresses offer an opportunity to track user equipment, and so users, across time and IPv6 address changes, RFC 4941 was developed to reduce the prospect of user identity being permanently tied to an IPv6 address, thus restoring some of the possibilities of anonymity existing at IPv4. RFC 4941 specifies a mechanism by which time-varying random bit strings can be used as interface circuit identifiers, replacing unchanging and traceable MAC addresses.
Notation
IPv6 addresses are normally written as eight groups of four
hexadecimalIn mathematics and computer science, hexadecimal is a 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.Its primary use is as a...
digits, where each group is separated by a colon (:). For example,
2001:0db8:85a3:0000:0000:8a2e:0370:7334
is a valid IPv6 address. To shorten the writing and presentation of addresses, several simplifications to the notation are permitted.
Any leading zeros in a group may be omitted; thus, the given example becomes
2001:db8:85a3:0:0:8a2e:370:7334
One or any number of consecutive groups of 0 value may be replaced with two colons (::):
2001:db8:85a3::8a2e:370:7334
This substitution with double-colon may be performed only once in an address, because multiple occurrences would lead to ambiguity. For example, the illegal address notation
2001::FFD3::57ab, could represent any of the following:
2001:0:0:0:0:FFD3:0:57ab
2001:0:0:0:FFD3:0:0:57ab
2001:0:0:FFD3:0:0:0:57ab
2001:0:FFD3:0:0:0:0:57ab
Using the double-colon reduction the localhost (loopback) address, fully written as
0000:0000:0000:0000:0000:0000:0000:0001, may be reduced to
::1 and the undetermined IPv6 address (zero value), i.e., all bits are zero, is simply
::.
For example, the addresses below are all valid and equivalent:
2001:0db8:0000:0000:0000:0000:1428:57ab
2001:0db8:0000:0000:0000::1428:57ab
2001:0db8:0:0:0:0:1428:57ab
2001:0db8:0:0::1428:57ab
2001:0db8::1428:57ab
2001:db8::1428:57ab
The sequence of the last 4 bytes of the IPv6 address may optionally be written in
dot-decimal notationIn computer networking, dot-decimal notation is a method of writing binary numbers in octet grouped base-10 numbers separated by dots ....
, in the style of
IPv4Internet Protocol version 4 is the fourth revision in the development of the Internet Protocol and it is 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...
addresses. This notation is convenient when working in a mixed (
dual-stackA dual-stack host provides two discrete network implementations in the Network Layer . The term stack here refers to the protocol stack or suite of protocols used in computer networking software....
) environment of IPv4 and IPv6 addresses, and IPv6 addresses are derived from IPv4 ones. The general form of the notation is
x:x:x:x:x:x:d.d.d.d, where the x's are the 6 high-order groups of hexadecimal digits and the d's represent the decimal digit groups of the four low-order
octetsIn computing, an octet is a grouping of eight bits.Octet, with the only exception noted below, always refers to an entity having exactly eight bits. As such, it is often used where the term byte might be ambiguous. For that reason, computer networking standards almost exclusively use octet...
of the address. For example,
::ffff:12.34.56.78 is the same address as
::ffff:0c22:384e. Usage of this notation may not be widely supported.
RFC 4291 (IP Version 6 Addressing Architecture) provides additional information.
Prefix and network notation
An IPv6 network is a contiguous group of IPv6 addresses. The size of this block must be a power of 2, and the beginning of a block must be aligned on a bit boundary of the address space. The leading set of bits of the addresses, which are identical for all hosts in a given network, are called the network's address prefix.
Networks are written in
CIDR notationThe Classless Inter-Domain Routing address specification or CIDR notation, begins with the Internet Protocol address followed by a "/" character and a decimal number specifying the number of consecutive bits of the routing prefix, or for IPv4, the subnet mask....
: a network is denoted by the first address in the network and the size in bits of the prefix, separated by a slash "/". For example, the network written
2001:0db8:1234::/48 starts at address
2001:0db8:1234:0000:0000:0000:0000:0000 and ends at
2001:0db8:1234:ffff:ffff:ffff:ffff:ffff.
Network addresses should not be confused with the notation used for interface addresses under some operating systems. Under such systems, an interface address is written by combining the address of the interface with the prefix length of the network it is connected to. For example, an interface with address
2001:db8:a::123 connected to a
/64 subnet is written
2001:db8:a::123/64.
IPv6 address types
IPv6 addresses are classified into three types:
- A unicast
right|250pxIn computer networking, unicast transmission is the sending of messages to a single network destination host on a packet switching network....
address identifies a single network interface. The protocol delivers packets sent to a unicast address to that specific interface. Unicast IPv6 addresses can have a scope which is reflected in more specific address names: global unicast address, link-local address, and unique local unicast addressA unique local address is an IPv6 address in the block fc00::/7. The address block defined in RFC 4193. They are supposed to be used for systems that are not connected to the Internet...
.
- An anycast
Anycast is a network addressing and routing scheme whereby data is routed to the "nearest" or "best" destination as viewed by the routing topology.The term is intended to echo the terms unicast, broadcast and multicast....
address is assigned to a group of interfaces, usually belonging to different nodes. A packet sent to an anycast address is delivered to just one of the member interfaces, typically the “nearest” according to the routing protocol’s choice of distance. Anycast addresses cannot be identified easily: they have the structure of normal unicast addresses, and differ only by being injected into the routing protocol at multiple points in the network.
- A multicast
Multicast addressing is a network technology for the delivery of information to a group of destinations simultaneously using the most efficient strategy to deliver the messages over each link of the network only once, creating copies only when the links to the multiple destinations split.The word...
address is also assigned to a set of interfaces that typically belong to different nodes. A packet that is sent to a multicast address is delivered to all interfaces identified by that address. Multicast addresses begin with an octet of one (1) bits, i.e., they have prefix FF00::/8. The four least-significant bits of the second address octet identify the address scope, i.e. the span over which the multicast address is propagated.
- Commonly implemented scopes are node-local (0x1), link-local (0x2), site-local (0x5), organization-local (0x8), and global (0xE). The least-significant 112 bits of a multicast address form the multicast group identifier. Only the low-order 32 bits of the group ID are commonly used, because of traditional methods of forming 32 bit identifiers from Ethernet addresses
In computer networking, a Media Access Control address is a unique identifier assigned to most network adapters or network interface cards by the manufacturer for identification, and used in the Media Access Control protocol sublayer. If assigned by the manufacturer, a MAC address usually...
. Defined group IDs are 0x1 for all-nodes multicast addressing and 0x2 for all-routers multicast addressing.
- Another group of multicast addresses are solicited-node multicast addresses which are formed with the prefix FF02::1:FF00:0/104, and where the rest of the group ID (least significant 24 bits) is filled from the interface's unicast or anycast address. These addresses allow link-layer address resolution via Neighbor Discovery Protocol
The Neighbor Discovery Protocol is a protocol in the Internet Protocol Suite used with IPv6. It operates in the Link Layer and is responsible for discovery of other nodes on the link, determining the link layer addresses of other nodes, finding available routers, and maintaining reachability...
(NDP) on the link without disturbing all nodes on the local network.
Special addresses
IANA maintains the official
list of the IPv6 address space. Global unicast assignments can be found at the various RIRs or at the
GRH DFP pages.
There are a number of addresses with special meaning in IPv6:
Unspecified address
- ::/128 — the address with all zero bits is called the unspecified address. This address must never be assigned to an interface and is to be used only in software before the application has learned its host's source address appropriate for a pending connection. Routers must not forward packets with the unspecified address.
Link local addresses
- ::1/128 — the loopback
The term loopback is generally used to describe methods or procedures of routing electronic signals, digital data streams, or other flows of items, from their originating facility quickly back to the same source entity without intentional processing or modification...
address is a unicast localhostIn computer networking, localhost is the standard hostname given to the address of the loopback network interface. The name is also a reserved domain name In computer networking, localhost (meaning "this computer") is the standard hostname given to the address of the loopback network interface....
address. If an application in a host sends packets to this address, the IPv6 stack will loop these packets back on the same virtual interface (corresponding to 127.0.0.1 in IPv4).
- fe80::/10 — The link-local prefix specifies that the address is only valid on a single link. This is analogous to the autoconfiguration IP addresses 169.254.0.0/16 in IPv4.
Unique local addresses
- fc00::/7 — unique local address
A unique local address is an IPv6 address in the block fc00::/7. The address block defined in RFC 4193. They are supposed to be used for systems that are not connected to the Internet...
es (ULA) are routable only within a set of cooperating sites. They were defined in RFC 4193 as a replacement for site-local addresses (see below). The addresses include a 40-bit pseudorandom number in the routing prefix that intends to minimize the risk of conflicts if sites merge or packets are misrouted into the Internet. Despite the restricted, local usage of these addresses, their address scope is global. This is a departure from the prior definitions of site-local addresses.
Multicast addresses
- ff00::/8 — The multicast prefix designates multicast address
In computer networking a multicast address is an identifier for a group of hosts that have joined a multicast group. Multicast addressing can be used in the Link Layer , such as Ethernet Multicast, as well as at the Internet Layer as IPv4 or IPv6 Multicast.- IPv4 multicast addresses :IPv4...
es as defined in "IP Version 6 Addressing Architecture" (RFC 4291). Some of these have been assigned to specific protocols, for example ff02::101 will reach all link-local NTP servers (RFC 2375).
Solicited-node multicast addresses
- ff02::1:FFXX:XXXX — XX:XXXX are the 3 low order octets of the corresponding unicast or anycast address.
IPv4 transition
- ::ffff:0:0/96 — this prefix is used for IPv4 mapped addresses (see Transition mechanisms below).
- 2001::/32 — Used for Teredo tunneling
Teredo is a tunneling protocol designed to grant IPv6 connectivity to nodes that are located behind IPv6-unaware NAT devices. It defines a way of encapsulating IPv6 packets within IPv4 UDP datagrams that can be routed through NAT devices and on the IPv4 internet.- Purpose :6to4, the most common...
.
- 2002::/16 — this prefix is used for 6to4
6to4 is a system that allows IPv6 packets to be transmitted over an IPv4 network without the need to configure explicit tunnels. Routing conventions are also in place that allow 6to4 hosts to communicate with hosts on the IPv6 internet...
addressing.
ORCHID
- 2001:10::/28 — ORCHID (Overlay Routable Cryptographic Hash Identifiers) as per (RFC 4843). These are non-routed IPv6 addresses used for Cryptographic Hash Identifiers.
Documentation
- 2001:db8::/32 — this prefix is used in documentation (RFC 3849). The addresses should be used anywhere an example IPv6 address is given or model networking scenarios are described.
Deprecated or obsolete addresses
- ::/96 — This is a 96-bit zero-value prefix originally known as IPv4-compatible addresses. This class of addresses were used to represent IPv4
Internet Protocol version 4 is the fourth revision in the development of the Internet Protocol and it is 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...
addresses within an IPv6 transition technology. Such an IPv6 address has its first 96 bits set to zero, while its last 32 bits are the IPv4 address that is represented. The Internet Engineering Task Force (IETF) has deprecated the use of IPv4-compatible addresses with publication RFC 4291. The only remaining use of this address format is to represent an IPv4 address in a table or database with fixed size members that must also be able to store an IPv6 address.
- fec0::/10 — The site-local prefix specifies that the address is valid only within the site network of an organization. Its use has been deprecated in September 2004 by RFC 3879 and new systems must not support this special type of address. New specifications replace this address type with unique local addresses.
Link-local addresses and zone indices
All interfaces have an associated
link-local address, that is only guaranteed to be unique on the attached link. Link local addresses are defined by the address prefix
fe80::/10, with the only allocated subnet (54 bits) being zero, such that a standards-based link-local address has an effective format
fe80::/64. The least significant 64 bits are usually chosen as the interface hardware address constructed in modified
EUI-64In computer networking, a Media Access Control address is a unique identifier assigned to most network adapters or network interface cards by the manufacturer for identification, and used in the Media Access Control protocol sublayer. If assigned by the manufacturer, a MAC address usually...
format.
Because all link-local addresses in a host have a common prefix, normal routing procedures cannot be used to choose the outgoing interface when sending packets to a link-local destination. A special identifier, known as a
zone index, is needed to provide the additional routing information; in the case of link-local addresses, zone indices correspond to interface identifiers.
When an address is written textually, the zone index is appended to the address, separated by a percent sign "
%". The actual syntax of zone indices depends on the operating system:
- the Microsoft Windows IPv6 stack uses numeric zone indexes, e.g., fe80::3%1. The index is determined by the interface number.
- Some Unix-like systems (e.g., BSD and Linux) use the interface name as a zone index: fe80::3%eth0.
- Mac OS X (10.5.7) also uses the interface name (e.g. en0) as a zone index: fe80::3%en0.
Zone index notations cause syntax conflicts when used in Uniform Resource Identifiers (URI), as the '%' character also designates
percent-encodingPercent-encoding, also known as URL encoding, is a mechanism for encoding information in a Uniform Resource Identifier under certain circumstances. Although it is known as URL encoding it is, in fact, used more generally within the main Uniform Resource Identifier set, which includes both Uniform...
.
Relatively few
IPv6-capable applicationsThis is a comparison of popular Internet applications in regards to their support of the IPv6 protocol.-IPv6 support table:-Programs that bridge IPv4 with IPv6:*http://toxygen.net/6tunnel/ 6tunnel & NT6tunnel: IPv4-IPv6 port proxy...
understand address scope syntax at the user level, thus rendering link-local addressing inappropriate for many user applications. However, link-local addresses are not intended for most of such application usage and their primary benefit is in low-level network management functions , for example for logging into a router that for some reason has become unreachable.
Literal IPv6 addresses in network resource identifiers
Since an IPv6 address contains colon (":") characters, network administrators must take care to avoid conflicts with other syntactic meanings of the colon in network resource labels.
In IPv4 the colon is used to separate an IP address from a transport protocol port number. This usage has been extended to IPv6, however, when a port is specified in an address string, the proper IPv6 address must be enclosed in square brackets ("[", "]"). This convention is used in other more complex identifiers.
Example: In a
URLIn computing, a Uniform Resource Locator is a subset of the Uniform Resource Identifier that specifies where an identified resource is available and the mechanism for retrieving it. In popular usage and in many technical documents and verbal discussions it is often incorrectly used as a synonym...
the IPv6 address is enclosed in brackets, e.g.,
http://[2001:0db8:85a3:08d3:1319:8a2e:0370:7348]/.
If the URL also contains a port number the notation is:
https://[2001:0db8:85a3:08d3:1319:8a2e:0370:7344]:443/
This is not only useful but mandated when using the short form:
https://[2001:db8::1428:57ab]:443/
Additional information can be found in "RFC 2732 - Format for Literal IPv6 Addresses in URL's" and "RFC 3986 - Uniform Resource Identifier (URI): Generic Syntax."
In
Microsoft WindowsMicrosoft Windows is a series of software operating systems and graphical user interfaces produced by Microsoft. Microsoft first introduced an operating environment named Windows in November 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces...
operating systems, IP addresses were also allowed in Uniform Naming Convention (UNC) path names. Since the colon is an illegal character in a UNC path name, the use of IPv6 addresses is also illegal in UNC names. For this reason,
MicrosoftMicrosoft Corporation is a multinational computer technology corporation that develops, manufactures, licenses, and supports a wide range of software products for computing devices...
has registered a
second-level Internet domainIn the Domain Name System hierarchy, a second-level domain is a domain that is directly below a top-level domain . For example, in example.com, example is the second-level domain of the .com TLD....
, ipv6-literal.net, as a means to facilitate symbolic substitution. IPv6 addresses may be transcribed in the following fashion:
2001:0db8:85a3:08d3:1319:8a2e:0370:7348
is written as
2001-db8-85a3-8d3-1319-8a2e-370-7348.ipv6-literal.net
This notation is automatically resolved by Microsoft software without DNS queries to any name servers. If the IPv6 address contains a zone index, it is appended to the address portion after an 's' character:
fe80--1s4.ipv6-literal.net
IPv6 addresses in the Domain Name System
IPv6 addresses are represented in the
Domain Name SystemThe Domain Name System is a hierarchical 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 participants...
by
AAAA resource records (so-called
quad-A records) for forward lookups.
Reverse lookupIn 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....
takes place under
ip6.arpaarpa is an Internet top-level domain used exclusively for Internet infrastructure purposes. The name is a backronym for Address and Routing Parameter Area....
(previously
ip6.intint is a sponsored top-level domain used in the Domain Name System of the Internet.According to current Internet Assigned Numbers Authority policy, the int sTLD is reserved for international treaty-based organizations, United Nations agencies and organizations or entities having...
), where name space is allocated by the
ASCIIThe American Standard Code for Information Interchange is a character-encoding scheme based on the ordering of the English alphabet. ASCII codes represent text in computers, communications equipment, and other devices that use text...
representation of
nibbleIn computing, a nibble is a four-bit aggregation, or half an octet. As a nibble contains 4 bits, there are sixteen possible values, so a nibble corresponds to a single hexadecimal digit .A full byte is represented by two hexadecimal digits; therefore, it is common to display a byte...
units (digits) of the hexadecimal IP address. This scheme, which is an adaptation of the IPv4 method under
in-addr.arpa, is defined in RFC 3596.
AAAA record fields
| NAME |
Domain name |
| TYPE |
AAAA (28) |
| CLASS |
Internet (1) |
| TTL Time to live is a limit on the period of time or number of iterations or transmissions in computer and computer network technology that a unit of data can experience before it should be discarded.-IP packets:...
|
Time to live in seconds |
| RDLENGTH |
Length of RDATA field |
| RDATA |
String form of the IPV6 address as described in RFC 4291 |
RFC 3484 specifies how applications should select an IPv6 or IPv4 address for use, including addresses retrieved from DNS.
The DNS protocol is independent of its transport layer. Queries and replies may be transmitted over IPv6 or IPv4 transports regardless of the address family of the data requested.
At the design stage of the IPv6 DNS architecture, the AAAA scheme faced a rival proposal. This alternate approach, designed to facilitate network renumbering, uses
A6 records for the forward lookup and a number of other innovations such as
bit-string labels and
DNAME records. It is defined in RFC 2874 and its references (with further discussion of the pros and cons of both schemes in RFC 3364), but has been deprecated to experimental status (RFC 3363).
Transition challenges
As of 2009, many DNS resolvers in home-networking NAT devices and routers still handle AAAA records improperly. Some of these simply drop DNS requests for such records, instead of properly returning the appropriate negative DNS response. Because the request is dropped, the host sending the request has to wait for a timeout to trigger. This often causes a perceived slow down when connecting to IPv6 hosts.
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 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 stack
Since IPv6 represents a conservative extension of IPv4, it is relatively easy to write a network stack that supports both IPv4 and IPv6 while sharing most of the code. Such an implementation is called a
dual stack, and a host implementing a dual stack is called a
dual-stack host. This approach is described in RFC 4213.
Most current implementations of IPv6 use a dual stack. Some early experimental implementations used independent IPv4 and IPv6 stacks.
IPv4 mapped addresses
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 represent an
IPv4Internet Protocol version 4 is the fourth revision in the development of the Internet Protocol and it is 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. For example,
::ffff:c000:280 is the IPv4 mapped address for the IPv4 address
192.0.2.128.
As an exception to standard IPv6 addresses notation, IPv4 mapped addresses are commonly represented with their last 32 bits written in the customary
dot-decimal notationIn computer networking, dot-decimal notation is a method of writing binary numbers in octet grouped base-10 numbers separated by dots ....
of IPv4, appended to the standard IPv6 notation of the leading bits, e.g.,
::ffff:c000:280 could be written as
::ffff:192.0.2.128.
This address type allows the transparent use of the
Transport LayerIn computer networking, the Transport Layer is a group of methods and protocols within a layered architecture of network components within which it is responsible for encapsulating application data blocks into data units suitable for transfer to the network infrastructure for transmission to the...
protocols over IPv4 through the IPv6 networking API. A beneficial feature of this mechanism is that server applications only need to open a single listening
socketThe 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....
to handle connections from clients using IPv6 or IPv4 protocols. IPv6 clients will be handled natively by default, and IPv4 clients appear as IPv6 clients with an appropriately mapped address. It can also be used to establish IPv4
connectionConnectivity, in the context of computer science, refers to the use of computer networks to link computers to one another, and provide information resources between computer systems and their final users...
s specifically with an IPv6 socket. While the network protocol on the transmission medium is IPv4, the connection is presented as an IPv6 interface to the application.
Because of the significant internal differences between IPv4 and IPv6 at all levels of the IP stack, some of the lower level functionality that may be exposed by the IPv6 stack might not work with IPv4 mapped addresses, if there is no direct translation to IPv4.
Some common IPv6 stacks do not support the IPv4 mapped address feature, either because the IPv6 and IPv4 stacks are separate implementations (
Microsoft WindowsMicrosoft Windows is a series of software operating systems and graphical user interfaces produced by Microsoft. Microsoft first introduced an operating environment named Windows in November 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces...
prior to Vista/Longhorn: e.g. XP/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.,
LinuxLinux is a generic term referring to Unix-like computer operating systems based on the Linux kernel. Their development is one of the most prominent examples of free and open source software collaboration; typically all the underlying source code can be used, freely modified, and redistributed,...
,
NetBSDNetBSD is a freely redistributable, open source version of the Unix-derivative Berkeley Software Distribution computer operating system. It was the second open source BSD descendant to be formally released, after 386BSD, and continues to be actively developed...
,
FreeBSDFreeBSD is a free Unix-like operating system descended from AT&T UNIX via the Berkeley Software Distribution . It has been characterized as "the unknown giant among free operating systems". It is not a clone of UNIX, but works like UNIX, with UNIX-compliant internals and system APIs. FreeBSD is...
) 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 that can encapsulate a wide variety of network layer protocol packet types inside IP tunnels, creating a virtual point-to-point link to Cisco routers at remote points over an IP internetwork.-Overview:GRE tunnels are designed...
, are also popular.
Automatic tunneling
Automatic tunneling refers to a technique where the routing infrastructure automatically determines the tunnel endpoints. RFC 3056 recommends
6to46to4 is a system that allows IPv6 packets to be transmitted over an IPv4 network without the need to configure explicit tunnels. Routing conventions are also in place that allow 6to4 hosts to communicate with hosts on the IPv6 internet...
tunneling 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.
TeredoTeredo is a tunneling protocol designed to grant IPv6 connectivity to nodes that are located behind IPv6-unaware NAT devices. It defines a way of encapsulating IPv6 packets within IPv4 UDP datagrams that can be routed through NAT devices and on the IPv4 internet.- Purpose :6to4, the most common...
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 a line of operating systems developed by Microsoft for use on personal computers, including home and business desktops, laptops, tablet PCs, and media center PCs...
. 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 for Linux and BSD operating systems as well as recent versions of Mac OS X.It includes working implementations of:* a Teredo client,* a Teredo relay and* a Teredo server.- External links :*...
.
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 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....
. Configured tunneling is usually more deterministic and easier to debug than automatic tunneling, and is therefore recommended for large, well-administered networks.
Raw encapsulation of IPv6 packets using
IPv4The Internet Protocol is a protocol used for communicating data across a packet-switched internetwork using the Internet Protocol Suite, also referred to as TCP/IP....
protocol number 41 is recommended for configured tunnelling; 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...
tunnelling. As with automatic tunnelling, 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 overseeing 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
translation mechanismsIPv6 transition mechanisms are used to allow IPv6-connected hosts to access IPv4-only Internet resources and hosts. Some IPv6 transition mechanisms were first defined in RFC 1933 but this RFC has been obsoleted by RFC 4213....
must be deployed.
One form of translation is the use of a dual-stack
application-layer proxyIn 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 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.
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-2000The Year 2000 problem was a notable problem for both digital and non-digital documentation and data storage situations which resulted from the practice of abbreviating a four-digit year to two digits.In computer program design, the practice of representing the year...
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 AccessWi-Fi Protected Access is a certification program created by the Wi-Fi Alliance to indicate compliance with the security protocol created by the Wi-Fi Alliance to secure wireless computer networks...
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. As for 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, the 160 Mbit/s
DOCSISData Over Cable Service Interface Specification is an international standard developed by CableLabs and contributing companies that include ARRIS, BigBand Networks, Broadcom, Cisco, Conexant, Correlant, Harmonic, Intel, Motorola, Netgear, Terayon, and Texas Instruments...
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 cable television infrastructure. Cable modems are primarily used to deliver broadband Internet access in the form of cable Internet, taking advantage of the high...
s 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. 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 range from
SkypeSkype is a software application that allows users to make voice calls over the Internet. Calls to other users of the service and, in some countries, to free-of-charge numbers, are free, while calls to other landlines and mobile phones can be made for a fee...
and
SIPThe Session Initiation Protocol is a signaling protocol, widely used for controlling multimedia communication sessions such as voice and video calls over Internet Protocol . Other feasible application examples include video conferencing, streaming multimedia distribution, instant messaging,...
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.
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.
Fault injectionIn software testing, fault injection is a technique for improving the coverage of a test by introducing faults to test code paths, in particular error handling code paths, that might otherwise rarely be followed. It is often used with stress testing and is widely considered to be an important part...
and mutation test equipment is available from companies such as
Mu DynamicsMu Dynamics is a private venture-funded company that makes hardware and software to test network services, allowing its users to quantify their product's or service's reliability, availability and security....
, whereby tests can be customized. Other classes of test equipment, including load and performance and conformance are available from companies like
SpirentSpirent Communications plc is a British telecommunications company based in Crawley, West Sussex. It is listed on the London Stock Exchange and is a constituent of the FTSE 250 Index.-History:...
, Ixia and
Agilent TechnologiesAgilent Technologies , or Agilent, is a company which designs and manufactures instruments and equipment for measurement and evaluation. The company's headquarters are in Santa Clara, California....
.
Deployment
Although IPv4 address exhaustion has been slowed by the introduction of
classless inter-domain routingClassless Inter-Domain Routing is a methodology of allocating IP addresses and routing Internet Protocol packets. It was introduced in 1993 to replace the prior addressing architecture of classful network design in the Internet with the goal to slow the growth of routing tables on routers across...
(CIDR) and the extensive use of
network address translationIn computer networking, network address translation is the process of modifying network address information in datagram packet headers while in transit across a traffic routing device for the purpose of remapping a given address space into another....
(NAT), address uptake has accelerated again in recent years. Some forecasts expect complete depletion by the year 2012.
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.
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. It is believed that the Olympics provided the largest showcase of IPv6 technology since the inception of IPv6.
Cellular telephone systems present a large deployment field for Internet Protocol devices as mobile telephone service is being transitioned from
3GInternational Mobile Telecommunications-2000 , better known as 3G or 3rd Generation, is a family of standards for mobile telecommunications defined by the International Telecommunication Union, which includes GSM EDGE, UMTS, and CDMA2000 as well as DECT and WiMAX...
systems to next generation (
4G4G refers to the fourth generation of cellular wireless and is a successor to 3G and 2G standards. The rest of this article associates 4G with International Mobile Telecommunications-Advanced , though 4G is a broader term and could include standards outside IMT-Advanced...
) 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. The specification mandates IPv6 operation according to the
3GPP Release 8 Specifications (March 2009) and deprecates IPv4 as an optional capability.
Major announcements and availability
| Year |
Announcements and availability |
| 1996 |
Alpha quality IPv6 support in 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....
development version 2.1.8. |
| 6bone The 6bone was a testbed for Internet Protocol version 6; it was an outgrowth of the IETF IPng project that created the IPv6 protocols intended to eventually replace the current Internet network layer protocols known as IPv4...
(an IPv6 virtual network for testing) was started. |
| 1997 |
By the end of 1997, a large number of interoperable IPv6 implementations exist. |
By the end of 1997 IBMInternational Business Machines Corporation, abbreviated IBM, is a multinational computer technology and IT consulting corporation headquartered in Armonk, Town of North Castle, New York, United States. The company is one of the few information technology companies with a continuous history dating...
's AIX 4.3 is the first commercial platform supporting IPv6. |
| Also in 1997, Early Adopter Kits for DEC's Digital Equipment Corporation was a pioneering American company in the computer industry. It is often referred to within the computing industry as DEC...
operating systems, Tru64 and OpenVMSOpenVMS , previously known as VAX-11/VMS, VAX/VMS or VMS, is the name of a high-end computer server operating system that runs on VAX, Alpha and Itanium-based families of computers...
, were available. |
| 1998 |
Microsoft Research Microsoft Research is a division of Microsoft created in 1991 for researching various computer science topics and issues. It currently employs Turing Award winners C.A.R...
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 FreeBSDFreeBSD is a free Unix-like operating system descended from AT&T UNIX via the Berkeley Software Distribution . It has been characterized as "the unknown giant among free operating systems". It is not a clone of UNIX, but works like UNIX, with UNIX-compliant internals and system APIs. FreeBSD is...
, 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...
, and NetBSDNetBSD is a freely redistributable, open source version of the Unix-derivative Berkeley Software Distribution computer operating system. It was the second open source BSD descendant to be formally released, after 386BSD, and continues to be actively developed...
via the KAME projectThe KAME project was a joint effort of six organizations in Japan which aimed to provide a free IPv6 and IPsec protocol stack implementation for variants of the BSD Unix computer operating-system...
. |
Microsoft releases an IPv6 technology preview version for Windows 2000Windows 2000 is a line of operating systems produced by Microsoft for use on business desktops, notebook computers, and servers. Released on February 17, 2000, it was the successor to Windows NT 4.0, and is the final release of Microsoft Windows to display the "Windows NT" designation...
in March 2000. |
SunSun Microsystems, Inc. is a multinational vendor of computers, computer components, computer software, and information technology services, founded on February 24, 1982...
SolarisSolaris is a UNIX-based operating system introduced by Sun Microsystems in 1992 as the successor to SunOS.Solaris is known for its scalability, especially on SPARC systems, and for originating many innovative features such as DTrace and ZFS...
supports IPv6 in Solaris 8 in February. |
CompaqCompaq Computer Corporation was an American personal computer company founded in 1982, and is now a brand name of Hewlett-Packard.The company was formed by Rod Canion, Jim Harris and Bill Murto — former Texas Instruments senior managers...
ships IPv6 with Tru64. |
| 2001 |
In January, CompaqCompaq Computer Corporation was an American personal computer company founded in 1982, and is now a brand name of Hewlett-Packard.The company was formed by Rod Canion, Jim Harris and Bill Murto — former Texas Instruments senior managers...
ships IPv6 with OpenVMSOpenVMS , previously known as VAX-11/VMS, VAX/VMS or VMS, is the name of a high-end computer server operating system that runs on VAX, Alpha and Itanium-based families of computers...
. |
Cisco SystemsCisco Systems, Inc. is a multinational corporation with more than 65,000 employees and annual revenue of US$36.10 billion as of 2009. Headquartered in San Jose, California, it designs and sells networking and communications technology and services....
introduces IPv6 support on Cisco IOSCisco IOS is the software used on the vast majority of Cisco Systems routers and current Cisco network switches. . IOS is a package of routing, switching, internetworking and telecommunications functions tightly integrated with a multitasking operating system...
routers and L3 switches. |
| HP introduces IPv6 with HP-UX HP-UX is Hewlett-Packard's proprietary implementation of the Unix operating system, based on System V . It runs on the HP 9000 PA-RISC-based range of processors and HP Integrity Intel's Itanium-based systems, and was also available for later Apollo/Domain systems...
11i v1. |
| 2002 |
MicrosoftMicrosoft Corporation is a multinational computer technology corporation that develops, manufactures, licenses, and supports a wide range of software products for computing devices...
Windows NT 4.0Windows NT 4.0 is a preemptive, graphical and business-oriented operating system designed to work with either uniprocessor or symmetric multi-processor computers. It was the next release of Microsoft's Windows NT line of operating systems and was released to manufacturing on 31 July 1996...
and Windows 2000Windows 2000 is a line of operating systems produced by Microsoft for use on business desktops, notebook computers, and servers. Released on February 17, 2000, it was the successor to Windows NT 4.0, and is the final release of Microsoft Windows to display the "Windows NT" designation...
SP1 have limited IPv6 support for research and testing since at least 2002. |
Microsoft Windows XPWindows XP is a line of operating systems produced by Microsoft for use on personal computers, including home and business desktops, laptops, and media centers. The name "XP" is short for "eXPerience"...
(2001) supports IPv6 for developmental purposes. In Windows XPWindows XP is a line of operating systems produced by Microsoft for use on personal computers, including home and business desktops, laptops, and media centers. The name "XP" is short for "eXPerience"...
SP1 (2002) and Windows Server 2003Windows Server 2003 is a server operating system produced by Microsoft. Introduced on 24 April 2003 as the successor to Windows 2000 Server, it is considered by Microsoft to be the cornerstone of its Windows Server System line of business server products. An updated version, Windows Server 2003...
, IPv6 is included as a core networking technology, suitable for commercial deployment. |
IBM z/OSz/OS is a 64-bit operating system for mainframe computers, created by IBM. It is the successor to OS/390, which in turn followed MVS and combined a number of formerly separate, related products. z/OS offers the attributes of modern operating systems but also retains much of the functionality...
supports IPv6 since version 1.4 (generally availability in September 2002). |
| 2003 |
Apple Mac OS X v10.3 "Panther" Mac OS X version 10.3 “Panther” is the fourth major release of Mac OS X, Apple’s desktop and server operating system. It followed Mac OS X v10.2 “Jaguar” and preceded Mac OS X v10.4 “Tiger”...
(2003) supports IPv6 which is enabled by default. |
| In July, ICANN ICANN is the Internet Corporation for Assigned Names and Numbers. Headquartered in Marina Del Rey, California, United States, ICANN is a non-profit corporation that was created on September 18, 1998 and incorporated September 30, 1998 in order to oversee a number of Internet-related tasks...
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 a later. This makes IPv6 publicly operational. |
| 2005 |
LinuxLinux is a generic term referring to Unix-like computer operating systems based on the Linux kernel. Their development is one of the most prominent examples of free and open source software collaboration; typically all the underlying source code can be used, freely modified, and redistributed,...
2.6.12 removes experimental status from its IPv6 implementation. |
| 2007 |
Microsoft Windows VistaWindows Vista is a line of operating systems developed by Microsoft for use on personal computers, including home and business desktops, laptops, tablet PCs, and media center PCs...
(2007) supports IPv6 which is enabled by default. |
| 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. |
| 2008 |
On February 4, 2008, IANA adds AAAA records for the IPv6 addresses of six root name servers. With this transition, it is now possible for two Internet hosts to fully communicate without using IPv4. |
On March 12, 2008, GoogleGoogle Inc. is an American public corporation, earning revenue from advertising related to its Internet search, e-mail, online mapping, office productivity, social networking, and video sharing services as well as selling advertising-free versions of the same technologies. Google has also...
launches a public IPv6 web interface to its popular search engine at the URL http://ipv6.google.com. |
On July 18, 2008, Internode SystemsInternode, founded on 8 May 1991 by Managing Director Simon Hackett, is an Australian Internet Service Provider. The company focuses primarily on ADSL-based Internet access, but also provides business-class access , web hosting, co-location, Voice over IP, and a variety of related...
launches a national IPv6 service, the first in AustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the continental mainland , the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans...
. |
| On December 11, 2008, Hurricane Electric Hurricane Electric founded in 1995, is a global Internet backbone , with a specific focus on IPv6.Hurricane Electric also operates datacenters in the Northern California Bay Area.-IP Backbone:...
became the first network in the world to connect over 300 IPv6 networks. |
| 2009 |
In January 2009, Google extended its IPv6 initiative with Google over IPv6, which offers IPv6 support for Google services to compatible networks. |
| On January 19, 2009, The Pirate Bay The Pirate Bay is a Swedish website that indexes and tracks BitTorrent files. It bills itself as "the world's largest BitTorrent tracker" and is ranked as the 104th most popular website by Alexa Internet. The website is primarily funded with advertisements shown next to torrent listings...
announces native IPv6 support. Both trackers and web servers are IPv6 enabled (main website at the URL: http://ipv6.thepiratebay.org/). |
| On June 15, 2009, Limelight Networks Limelight Networks is a Content Delivery Network service provider. The company is based in Tempe, Arizona, U.S.A., with offices in San Francisco, New York, London, Paris, Frankfurt, and Tokyo.The company operates a global fiber-optic network that helps content publishers avoid sending files over...
announced IPv6 support. Limelight Networks will run IPv4 and IPv6 simultaneously across its entire network platform. |
IPv6 network address translation
Network address translationIn computer networking, network address translation is the process of modifying network address information in datagram packet headers while in transit across a traffic routing device for the purpose of remapping a given address space into another....
, a widely spread method to delay IPv4 address space exhaustion, was not considered for implementation in the IPv6 core definitions. However, due to its popularity, proponents desire re-implementation in IPv6 for other reasons. The
Internet Architecture BoardThe Internet Architecture Board is the committee charged with oversight of the technical and engineering development of the Internet by the Internet Society ....
has engaged in the ongoing debate.
See also
- IPv4 address exhaustion
- IPv6 deployment
This article attempts to provide an overview of Internet Protocol Version 6 deployment around the world.In February 1999, The IPv6 Forum was founded by the IETF Deployment WG to drive deployment worldwide. This resulted in the creation of regional and local IPv6 Task Forces.A global view into the...
- Comparison of IPv6 application support
This is a comparison of popular Internet applications in regards to their support of the IPv6 protocol.-IPv6 support table:-Programs that bridge IPv4 with IPv6:*http://toxygen.net/6tunnel/ 6tunnel & NT6tunnel: IPv4-IPv6 port proxy...
- 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....
- List of IPv6 tunnel brokers
- Miredo
Miredo is an open-source Teredo IPv6 tunneling software for Linux and BSD operating systems as well as recent versions of Mac OS X.It includes working implementations of:* a Teredo client,* a Teredo relay and* a Teredo server.- External links :*...
- ICMPv6
Internet Control Message Protocol Version 6 is the implementation of the Internet Control Message Protocol for Internet Protocol version 6 . ICMPv6 is an integral part of IPv6 and performs error reporting, diagnostic functions , neighbor discovery, and a framework for extensions to implement...
- University of New Hampshire InterOperability Laboratory
The Interoperability Laboratory is a non-profit service based organisation. Its members are typically companies invested in a specific technology, usually networking or data related. The IOL invests resources to de-construct relative specifications and deployment scenarios into test suites...
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
- 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...
External links