IPv6 Header Format
Version. 4 bits.
IPv6 version number.
Traffic Class. 8 bits.
Internet traffic priority delivery value.
Flow Label. 20 bits.
Used for specifying special router handling from source to destination(s) for a sequence of packets.
Payload Length. 16 bits unsigned.
Specifies the length of the data in the packet. When cleared to zero, the option is a hop-by-hop Jumbo payload.
Next Header. 8 bits.
Specifies the next encapsulated protocol. The values are compatible with those specified for the IPv4 protocol field.
Hop Limit. 8 bits unsigned.
For each router that forwards the packet, the hop limit is decremented by 1. When the hop limit field reaches zero, the packet is discarded. This replaces the TTL field in the IPv4 header that was originally intended to be used as a time based hop limit.
Source address. 16 bytes.
The IPv6 address of the sending node.
Destination address. 16 bytes.
The IPv6 address of the destination node.
(RFC 2461) An identifier for a set of interfaces (typically belonging to different nodes). A packet sent to an anycast address is delivered to one of the interfaces identified by that address (the "nearest" one, according to the routing protocol's measure of distance). Note that an anycast address is syntactically indistinguishable from a unicast address. Thus, nodes sending packets to anycast addresses don't generally know that an anycast address is being used.
(RFC 1971) An address assigned to an interface whose use is discouraged, but not forbidden. A deprecated address should no longer be used as a source address in new communications, but packets sent to deprecated addresses are delivered as expected. A deprecated address may continue to be used as a source address in communications where switching to a preferred address causes hardship to a specific upper-layer activity (e.g., an existing TCP connection).
(RFC 1981) A sequence of packets sent from a particular source to a particular (unicast or multicast) destination for which the source desires special handling by the intervening routers.
(RFC 1981) A combination of a source address and a non-zero flow label.
(RFC 2675) An IPv6 packet containing a payload longer than 65,535 bytes. Jumbograms are relevant only to IPv6 nodes that may be attached to links with a link MTU greater than 65,575 bytes, and need not be implemented or understood by IPv6 nodes that do not support attachment to links with such large MTUs.
NLA, Next-Level Aggregation Identifier.
An address that is assigned to an interface on a specified link.
An address that is not assigned to any interfaces on the specified link.
The set of links traversed by a packet between a source node and a destination node.
PMTU, Path MTU.
The minimum link MTU of all the links in a path between a source node and a destination node.
(RFC 1971) An address assigned to an interface whose use by upper layer protocols is unrestricted. Preferred addresses may be used as the source (or destination) address of packets sent from (or to) the interface.
(RFC 2461) A router that responds to Neighbor Discovery query messages on behalf of another node. A router acting on behalf of a mobile node that has moved off-link could potentially act as a proxy for the mobile node.
SLA, Site-Level Aggregation Identifier.
This field is used by an individual organization to create its own local addressing hierarchy and to identify subnets. Assignment of the SLA ID field is the responsibility of each individual organization.
(RFC 1971) An address whose uniqueness on a link is being verified, prior to its assignment to an interface. A tentative address is not considered assigned to an interface in the usual sense. An interface discards received packets addressed to a tentative address, but accepts Neighbor Discovery packets related to Duplicate Address Detection for the tentative address.
TLA, Top-Level Aggregation Identifier.