IPv6 packet: Difference between revisions

Revision as of 16:20, 24 October 2019

Revision as of 16:55, 24 October 2019

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; ''Traffic Class'' (6+2 bits) : The bits of this field hold two values. The six most-significant bits hold the [[Differentiated Services]] (DS) field, which is used to classify packets.<ref name=rfc2474>{{Cite IETF|rfc=2474|author=K. Nickols|author2=S. Blake|authorlink3=Fred Baker (IETF chair)|author3=F. Baker|author4=D. Black|date=December 1998|title=Definition of the Differentiated Service Field (DS Field) in the IPv4 and IPv6 Headers}}</ref><ref name=rfc3260>{{Cite IETF|rfc=3260|author=D. Grossman|date=April 2002|title=New Terminology and Clarifications for DiffServ}}</ref> Currently, all standard DS fields end with a '0'&nbsp;bit. Any DS field that ends with two '1'&nbsp;bits is intended for local or experimental use.<ref name=rfc4727></ref>

: The remaining two bits are used for [[Explicit Congestion Notification]] (ECN);<ref name=rfc3168>{{Cite IETF|rfc=3168|author=K. Ramakrishnan|author2=S. Floyd|author3=D. Black|date=September 2001|title=The Addition of Explicit Congestion Notification (ECN) to IP}}</ref> priority values subdivide into ranges: traffic where the source provides congestion control and non-congestion control traffic.

; ''Flow Label'' (20 bits): OriginallyA createdhigh-entropy foridentifier givingof [[real-timea computing|real-timeflow applications]]of specialpackets service.<refbetween name=rfc8200a />source and Whendestination. set toA aflow non-zerois valuegroup of packets, ite.g., servesa asTCP session or a hintmedia tostream. routersThe andspecial switchesflow withlabel multiple0 outboundmeans pathsthe thatpacket thesedoes packetsnot shouldbelong stayto onany theflow same(using path,this soscheme). thatAn theyolder willscheme notidentifies beflow reordered.<refby name=rfc3595>{{Citesource IETF|rfc=3595|author=B.address Wijnen|date=Septemberand 2003|title=Textualport, Conventionsdestination foraddress IPv6and Flowport, Label}}</ref>protocol (value of the last ''Next Header'' field).<ref name=rfc6437>{{Cite IETF|rfc=6437|author=S. Amante|author2=B. Carpenter|author3=S. Jiang|author4=J. Rajahalme|date=November 2011|title=IPv6 Flow Label Specification}}</ref> It has further been suggested that the flow label be used to help detect spoofed packets.<ref>[http://tools.ietf.org/html/draft-blake-ipv6-flow-label-nonce-02 draft-blake-ipv6-flow-label-nonce-02]</ref>

; ''Payload Length'' (16 bits): The size of the payload in octets, including any extension headers. The length is set to zero when a ''Hop-by-Hop'' extension header carries a [[#Jumbogram|Jumbo Payload]] option.<ref name=rfc2675>{{Cite IETF|rfc=2675|author=D. Borman|authorlink2=Steve Deering|author2=S. Deering|author3=R. Hinden|date=August 1999|title=IPv6 Jumbograms}}</ref>

; ''Next Header'' (8 bits): Specifies the type of the next header. This field usually specifies the [[transport layer]] protocol used by a packet's payload. When extension headers are present in the packet this field indicates which extension header follows. The values are [[List of IP protocol numbers|shared]] with those used for the IPv4 protocol field, as both fields have the same function (see [[List of IP protocol numbers]]).