What this IPv6 means? This article is ment to explain you a very accurate describtion of what this protocol is and how it works. We are sure that only few people is prepared to really understand all the words and specific terminology used here. Anyway we decide to give you a full explanation of this argument. Internet Protocol Version 6 (IPv6) is a version of the Internet Protocol that is designed to succeed Internet Protocol version 4 (IPv4). IPv4 is the first publicly used Internet Protocol and has been in operation since 1981. IPv6 is an Internet Layer protocol for packet-switched internetworking and provides end-to-end datagram transmission across multiple IP networks. As a datagram service it does not guarantee reliability, a function provided at the Transport Layer. The main driving force for the redesign of Internet Protocol was the foreseeable IPv4 address exhaustion. IPv6 was developed by the Internet Engineering Task Force (IETF), and is described in Internet standard document RFC 2460, published in December 1998. IPv6 uses a 128-bit address, whereas IPv4 uses only 32 bits. The new address space supports 2128 (about 3.4×1038) addresses. This expansion provides considerable flexibility in allocating addresses and routing traffic.
It also eliminates the primary need for network address translation (NAT), which gained widespread deployment as an effort to alleviate IPv4 address exhaustion. IPv6 also implements many other new features. It simplifies aspects of address assignment (stateless address autoconfiguration) and network renumbering (prefix and router announcements) when changing Internet connectivity providers. The IPv6 subnet size has been standardized by fixing the size of the host identifier portion of an address to 64 bits to facilitate an automatic mechanism for forming the host identifier from link layer media addressing information (MAC address). Network security is also integrated into the design of the IPv6 architecture, and the IPv6 specification mandates support for IPsec as a fundamental interoperability requirement. For deployment, IPv6 is largely incompatible with IPv4 at the packet level, and translation services have practical issues that make them controversial.
IPv6 and IPv4 are therefore treated as almost entirely separate networks with devices having two separate protocol stacks if access to both networks is needed, with tunneling of IPv6 on IPv4 and vice versa. In December 2008, despite marking its 10th anniversary as a Standards Track protocol, IPv6 was only in its infancy in terms of general worldwide deployment. A 2008 study 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. The first publicly used version of the Internet Protocol, Version 4 (IPv4), provides an addressing capability of about 4 billion addresses. This was deemed sufficient in the early design stages of the Internet when the explosive growth and worldwide proliferation of networks was not anticipated. During the first decade of operation of the Internet, by the late 1980s, it became apparent that methods had to be developed to conserve address space. In the early 1990s, even after the redesign of the addressing system using a classless network model, it became clear that this would not suffice to prevent IPv4 address exhaustion, and that further changes to the Internet infrastructure were needed. By the beginning of 1992, several proposals appeared and by the end of 1992, the IETF announced a call for white papers and the creation of the IP Next Generation (IPng) area of working groups. IPv4 address exhaustion from 1995 to 2011.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 RFCs 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. IPv4 exhaustionEstimates of the time of complete IPv4 address exhaustion varied widely in the early 2000s, but all converge now[update] on the time frame from 2011 to 2012. In 2003, Paul Wilson (director of APNIC) stated that, based on then-current rates of deployment, the available space would last for one or two decades. In September 2005, a report by Cisco Systems suggested that the pool of available addresses would dry up in as little as 4 to 5 years. As of January 2011, a daily updated report projected that the IANA pool would be exhausted in the first quarter of 2011, with the various regional Internet registries using up their allocations from IANA before the end of 2011. As of 2008, a policy process has started for the end-game and post-exhaustion era. Comparison to IPv4IPv6 specifies a new packet format, designed to minimize packet header processing by routers. Because the headers of IPv4 packets and IPv6 packets are significantly different, the two protocols are not interoperable. However, in most regards, IPv6 is a conservative extension of IPv4. Most transport and application-layer protocols need little or no change to operate over IPv6; exceptions are application protocols that embed internet-layer addresses, such as FTP and NTPv3. Decomposition of an IPv6 address into its binary formThe most important feature of IPv6 is a much larger address space than in IPv4. The size of IPv6 addresses is 128 bits, compared to 32 bits in IPv4.
The address space therefore supports 2128 or approximately 3.4×1038 addresses. By comparison, this amounts to approximately 5×1028 addresses for each of the 6.8 billion people alive in 2010. 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 simplify allocation of addresses, enable efficient route aggregation, and implementation of special addressing features. In IPv4, complex Classless Inter-Domain Routing (CIDR) methods were developed to make the best use of the small address space. The standard size of a subnet in IPv6 is 264 addresses, the square of the size of the entire IPv4 address space. Thus, actual address space utilization rates will be small in IPv6, but network management and routing efficiency 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. Multicast, the transmission of a packet to multiple destinations in a single send operation, is part of the base specification in IPv6. In IPv4 this is an optional although commonly implemented feature. 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 implementation of inter-domain solutions was very arcane.[18] Unicast address assignments by a local Internet registry for IPv6 have at least a 64-bit routing prefix, yielding the smallest subnet size available in IPv6 (also 64 bits). With such an assignment it is possible to embed the unicast address prefix into the IPv6 multicast address format, while still providing a 32-bit block, the least significant bits of the address, or approximately 4.2 billion multicast group identifiers. Thus each user of an IPv6 subnet automatically has available a set of globally routable source-specific multicast groups for multicast applications. Stateless address autoconfiguration (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-local router solicitation multicast request for its configuration parameters; if configured suitably, routers respond to such a request with a router advertisement packet that contains network-layer configuration parameters. If IPv6 stateless address autoconfiguration is unsuitable for an application, a network may use stateful configuration with the Dynamic Host Configuration Protocol version 6 (DHCPv6) or hosts may be configured statically. Routers present a special case of requirements for address configuration, as they often are sources for autoconfiguration information, such as router and prefix advertisements.
Stateless configuration for routers can be achieved with a special router renumbering protocol. Mandatory support for network layer securityInternet Protocol Security (IPsec) was originally developed for IPv6, but found widespread deployment first in IPv4, into which it was back-engineered. IPsec is an integral part of the base protocol suite in IPv6. IPsec support is mandatory in IPv6 but optional for IPv4. Simplified processing by routersIn IPv6, the packet header and the process of packet forwarding have been simplified to make packet processing by routers more efficient and thereby extending the end-to-end principle of Internet design. The packet header in IPv6 is simpler than that used in IPv4, with many rarely used fields moved to separate options; as a result, although the addresses in IPv6 are four times as large, the option-less IPv6 header is only twice the size of the option-less IPv4 header. IPv6 routers do not perform fragmentation. IPv6 hosts are required to either perform PMTU discovery, perform end-to-end fragmentation, or to send packets no larger than the IPv6 default minimum MTU size of 1280 octets. The IPv6 header is not protected by a checksum; integrity protection is assumed to be assured by both link layer and higher layer (TCP, UDP, etc.) error detection. Therefore, IPv6 routers do not need to recompute a checksum when header fields (such as the time to live (TTL) or hop count) change. The TTL field of IPv4 has been renamed to Hop Limit, reflecting the fact that routers are no longer expected to compute the time a packet has spent in a queue. MobilityUnlike mobile IPv4, mobile IPv6 avoids triangular routing and is therefore as efficient as native IPv6. IPv6 routers may also support network mobility which allows entire subnets to move to a new router connection point without renumbering. Options extensibilityThe IPv6 protocol header has a fixed size (40 octets). Options are implemented as additional extension headers after the IPv6 header, which limits their size only by the size of an entire packet. The extension header mechanism provides extensibility to support future services for quality of service, security, mobility, and others, without redesign of the basic protocol. JumbogramsIPv4 limits packets to 65535 (216 – 1) octets of payload.
IPv6 has optional support for packets over this limit, referred to as jumbograms, which can be as large as 4294967295 (232 – 1) octets. The use of jumbograms may improve performance over high-MTU links. The use of jumbograms is indicated by the Jumbo Payload Option header. The IPv6 packet is composed of two parts: the packet header and the payload. The header consists of a fixed portion with minimal functionality required for all packets and may contain optional extension to implement special features. The fixed header occupies the first 40 octets (320 bits) of the IPv6 packet. It contains the source and destination addresses, traffic classification options, a hop counter, and a pointer for extension headers if any. The Next Header field, present in each extension as well, points to the next element in the chain of extensions. The last field points to the upper-layer protocol that is carried in the packet’s payload. Extension headers carry options that are used for special treatment of a packet in the network, e.g., for routing, fragmentation, and for security using the IPsec framework. The payload can have a size of up to 64KiB without special options, or larger with a jumbo payload option in a Hop-By-Hop Options extension header. Fragmentation is handled only in the end points of a communication session; routers never fragment a packet, and hosts are expected to use Path MTU Discovery to select a packet size that can traverse the entire communications path. The most important feature of IPv6 is a much larger address space than in IPv4. IPv6 addresses are 128 bits long, compared to only 32 bits previously.
While the IPv4 address space contains only about 4.3×109 (4.3 billion) addresses, IPv6 supports approximately 3.4×1038 (340 undecillion) unique addresses, deemed enough for the foreseeable future. IPv6 addresses are written in groups of four hexadecimal digits separated by colons, for example, 2001:db8:1f70::999:de8:7648:6e8. IPv6 addresses are logically divided into two parts: a 64-bit (sub-)network prefix, and a 64-bit interface identifier. IPv6 addresses are classified by three types of networking methodologies: unicast addresses identify each network interface, anycast addresses identify a group of interfaces, usually at different locations of which the nearest one is automatically selected, and multicast addresses are used to deliver one packet to many interfaces. The broadcast method is not implemented in IPv6. Each IPv6 address has a scope, which specifies in which part of the network it is valid and unique. Some addresses are unique only on the local (sub-)network; Others are globally unique. Some IPv6 addresses are used for special purposes, such as the address for loopback. Also, some address ranges are considered special, such as link-local addresses for use in the local network only, and solicited-node multicast addresses used in the Neighbor Discovery Protocol.