Technicalities of IPv6.

Implementation of IPv6 in a complex network.

Internet.
The definition of internet with respect to the perspective of Internet Protocol (IP) is like; Internet operates by transferring data in small packets that are independently routed across the networks as specified by an international communication protocol known as IP (Internet protocol). Each data packet contains two numeric addresses that are the packets origin and destination devices.

In the beginning IPv4 ( predecessor of IPv6 ) has performed the role of data transferring as data carrier or in other words as a routed protocol and it is also still the foundation for most internet communication. But as communication networks has grown and become complex IPv4 couldn't fulfil the current requirement of the corporate world and businesses and now IPv6 has replaced and is replacing IPv4 in various parts of the world.

Vocabulary words.
1) Alleviate: To reduce or relieve.
2) rendezvous: An agreement between two or more persons to meet at a certain time.

IPv6.
Like IPv4, IPv6 is an internet layer protocol for packet switched networking and also provides end to end datagram transmission across multiple IP networks. Due to its large address space ,as discussed in my previous article, It allows for many more devices and users on the internet as well as extra flexibility in allocating addresses and efficiency for routing traffic. It also eliminates the primary need for network address translation (NAT), which gained widespread deployment as an effort to alleviate  IPv4 address exhaustion.

Some new features in IPv6.
IPv6 implements additional features not present in IPv4 such as

1. Larger address space, which has been discussed in my previous article.
2. Multicasting as a default behavior.
3. It simplifies aspects of address assignment (stateless address auto-configuration).
4. Network renumbering and router announcements when changing internet connectivity providers.
5. Network security is also integrated in to the design of the IPv6 architecture, and the IPv6 specification mandates support for IPsec as a fundamental interoperability requirement.

• we will talk about on all these new features later in detail.

IPv6 is now supported on all major operating systems in use in commercial, business, and home consumer environments.

IPv6 does not implement interoperability features with IPv4 and creates essentially a parallel, independent network. Exchanging traffic between two networks requires special translator gateways, but modern computer operating systems implement "Dual-protocol" software for transparent access to both networks using "Tunneling."

Not this kind of Tunneling.

Explanation of new features.


Multicasting.

• Multicast, the transmission of a packet to multiple destinations in a single send operation, is part of the base specification in IPv6 which means this is a default behavior.
• 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 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 acheived 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.

Stateless address auto-configuration.


IPv6 hosts can configure themselves automatically when connected to a routed IPv6 network using ICMPv6 (Internet Control Message version 6 ) 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 auto-configuration is unsuitable for an application, a network may use stateful configuration with the DHCPv6 ( Dynamic Host Configuration Protocol version 6 ) or hosts may be configured statically.

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

Mandatory support for network layer security.


Internet protocol security (IPsec) was originally developed for IPv6, but found widespread deployment first in IPv4, in to which it was back-engineered. IPsec is an integral part of the base protocol suite in IPv6. IPsec support is mandatory in IPv6 but optional for IPV4.

Simplified processing by routers.


In IPv6, the packet headers and the process of packet forwarding have been simplified. Although IPv6 packets headers are at least twice the size of IPv4 packet headers, packet processing by routers is generally more efficient, thereby extending the end-to-end principle of internet design, specifically

• The packet headers in IPv6 is simpler than that used in IPv4, with many rarely used fields moved to separate optional header extensions.
• IPv6 routers do not perform fragmentation, IPv6 hosts are required to either perform path MTU 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 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.

Mobility.

Not like 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.