Internet Protocol version 6 (IPv6) is an Internet Layer protocol for packet-switched internetworks. The Internet Engineering Task Force (IETF) has designated IPv6 as the successor of IPv4.
IPv6 has a much larger address space than IPv4, which allows flexibility in allocating addresses and routing traffic. The extended address length eliminates the need to use network address translation to avoid address exhaustion, and also simplifies aspects of address assignment and renumbering when changing Internet connectivity providers.
The very large IPv6 address space supports 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 today.
Features and differences from IPv4:-
To a great extent, IPv6 functions as a conservative extension of IPv4. Most transport- and application-layer protocols need little or no change to work over IPv6; exceptions are applications protocols that embed network-layer addresses.
Pv6 specifies a new packet format, designed to minimize packet-header processing. Since the headers of IPv4 and IPv6 are significantly different, the two protocols are not interoperable.
Larger address space
In particular, IPv6 features a larger address space than that of IPv4: addresses in IPv6 are 128 bits long versus 32 bits in IPv4.
IPv6 includes three types of addresses: unicast, anycast, and multicast. An address with the first octet set to "one" (1) bits identifies a multicast address.
Address scopes
IPv6 introduces the concept of address scopes. An address scope defines the "region" or "span" where an address can be defined as a unique identifier of an interface. These spans are the local link, the site network, and the global network.
Stateless address autoconfiguration
IPv6 hosts can configure themselves automatically when connected to a routed IPv6 network using ICMPv6 router discovery messages. When first connected to a network, a host sends a link-local multicast router solicitation request for its configuration parameters; if configured suitably, routers respond to such a request with a router advertisement packet that contains network-layer configuration parameters.
Multicast vs. broadcast
IPv6 does not define broadcast addresses as used in IPv4. Instead, it accomplishes broadcasting at the internetworking layer with a new implementation of multicast addressing that does not disturb all interfaces on a link. For this purpose IPv6 defines a reserved address format for multicasting that is part of the base specifications of IPv6
Mandatory network layer security
Internet Protocol Security (IPsec), the protocol for IP encryption and authentication, forms an integral part of the base protocol suite in IPv6. IP packet header support is mandatory in IPv6; this is unlike IPv4, where it is optional (but usually implemented). IPsec, however, is not widely used at present except for securing traffic between IPv6 Border Gateway Protocol routers.
Router handling for delivery prioritization
The IPv6 packet header contains a new "Flow Label" field for prioritizing packet delivery by routers. The Flow Label replaces the "Service Type" field in IPv4.
Hop-Limit vs. TTL
The Time-to-Live field of IPv4 has been replaced by a Hop-Limit field.
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.
Jumbograms
IPv4 limits packets to 64 KiB of payload. IPv6 has optional support for packets over this limit, referred to as jumbograms, which can be as large as 4 GiB. The use of jumbograms may improve performance over high-MTU networks. The presence of jumbograms is indicated by the Jumbo Payload Option header.
IPv6 packet format:-
The IPv6 packet is composed of two main parts: the header and the payload.
The header is in the first 40 octets (320 bits) of the packet and contains:
* Version - version 6 (4-bit IP version).
* Traffic class - packet priority (8-bits). Priority values subdivide into ranges: traffic where the source provides congestion control and non-congestion control traffic.
* Flow label - QoS management (20 bits). Originally created for giving real-time applications special service, but currently unused.
* Payload length - payload length in bytes (16 bits). When cleared to zero, the option is a "Jumbo payload" (hop-by-hop).
* Next header - Specifies the next encapsulated protocol. The values are compatible with those specified for the IPv4 protocol field (8 bits).
* Hop limit - replaces the time to live field of IPv4 (8 bits).
* Source and destination addresses - 128 bits each.
IPv6 has a much larger address space than IPv4, which allows flexibility in allocating addresses and routing traffic. The extended address length eliminates the need to use network address translation to avoid address exhaustion, and also simplifies aspects of address assignment and renumbering when changing Internet connectivity providers.
The very large IPv6 address space supports 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 today.
Features and differences from IPv4:-
To a great extent, IPv6 functions as a conservative extension of IPv4. Most transport- and application-layer protocols need little or no change to work over IPv6; exceptions are applications protocols that embed network-layer addresses.
Pv6 specifies a new packet format, designed to minimize packet-header processing. Since the headers of IPv4 and IPv6 are significantly different, the two protocols are not interoperable.
Larger address space
In particular, IPv6 features a larger address space than that of IPv4: addresses in IPv6 are 128 bits long versus 32 bits in IPv4.
IPv6 includes three types of addresses: unicast, anycast, and multicast. An address with the first octet set to "one" (1) bits identifies a multicast address.
Address scopes
IPv6 introduces the concept of address scopes. An address scope defines the "region" or "span" where an address can be defined as a unique identifier of an interface. These spans are the local link, the site network, and the global network.
Stateless address autoconfiguration
IPv6 hosts can configure themselves automatically when connected to a routed IPv6 network using ICMPv6 router discovery messages. When first connected to a network, a host sends a link-local multicast router solicitation request for its configuration parameters; if configured suitably, routers respond to such a request with a router advertisement packet that contains network-layer configuration parameters.
Multicast vs. broadcast
IPv6 does not define broadcast addresses as used in IPv4. Instead, it accomplishes broadcasting at the internetworking layer with a new implementation of multicast addressing that does not disturb all interfaces on a link. For this purpose IPv6 defines a reserved address format for multicasting that is part of the base specifications of IPv6
Mandatory network layer security
Internet Protocol Security (IPsec), the protocol for IP encryption and authentication, forms an integral part of the base protocol suite in IPv6. IP packet header support is mandatory in IPv6; this is unlike IPv4, where it is optional (but usually implemented). IPsec, however, is not widely used at present except for securing traffic between IPv6 Border Gateway Protocol routers.
Router handling for delivery prioritization
The IPv6 packet header contains a new "Flow Label" field for prioritizing packet delivery by routers. The Flow Label replaces the "Service Type" field in IPv4.
Hop-Limit vs. TTL
The Time-to-Live field of IPv4 has been replaced by a Hop-Limit field.
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.
Jumbograms
IPv4 limits packets to 64 KiB of payload. IPv6 has optional support for packets over this limit, referred to as jumbograms, which can be as large as 4 GiB. The use of jumbograms may improve performance over high-MTU networks. The presence of jumbograms is indicated by the Jumbo Payload Option header.
IPv6 packet format:-
The IPv6 packet is composed of two main parts: the header and the payload.
The header is in the first 40 octets (320 bits) of the packet and contains:
* Version - version 6 (4-bit IP version).
* Traffic class - packet priority (8-bits). Priority values subdivide into ranges: traffic where the source provides congestion control and non-congestion control traffic.
* Flow label - QoS management (20 bits). Originally created for giving real-time applications special service, but currently unused.
* Payload length - payload length in bytes (16 bits). When cleared to zero, the option is a "Jumbo payload" (hop-by-hop).
* Next header - Specifies the next encapsulated protocol. The values are compatible with those specified for the IPv4 protocol field (8 bits).
* Hop limit - replaces the time to live field of IPv4 (8 bits).
* Source and destination addresses - 128 bits each.