{{short description|Smallest message entity exchanged using Internet Protocol version 6}}
An '''IPv6 packet''' is the smallest message entity exchanged using [[IPv6|Internet Protocol version 6]] (IPv6). [[Network packet|Packet]]sPackets consist of control information for addressing and routing and a [[payload (computing)|payload]] of user data. The control information in IPv6 packets is subdivided into a mandatory fixed [[header (computing)|header]] and optional extension headers. The payload of an IPv6 packet is typically a [[datagram]] or segment of the higher-level [[transport layer]] protocol, but may be data for an [[internet layer]] (e.g., [[ICMPv6]]) or [[link layer]] (e.g., [[OSPF]]) instead.
IPv6 packets are typically transmitted over the link layer (i.e., over [[Ethernet]] or [[Wi-Fi]]), which encapsulates each packet in a [[frame (networking)|frame]]. Packets may also be transported over a higher-layer [[tunneling protocol]], such as [[IPv4]] when using [[6to4]] or [[Teredo tunneling|Teredo]] transition technologies.
In contrast to IPv4, [[router (computing)|routers]] do not fragment IPv6 packets larger than the [[maximum transmission unit]] (MTU), it is the sole responsibility of the originating node. A minimum MTU of 1,280 [[octet (computing)|octets]] is mandated by IPv6, but [[Host (network)|hosts]] are "strongly recommended" to use [[Path MTU Discovery]] to take advantage of MTUs greater than the minimum.{{Ref RFC|820085}}
Since July 2017, the [[Internet Assigned Numbers Authority]] (IANA) is responsible for registering all IPv6 parameters that are used in IPv6 packet headers.<ref name=rfc8200/>
