Editing EtherType

{{short description|Field in Ethernet frames indicating which protocol is encapsulated in the payload}}
{{Use American English|date = March 2019}}

'''EtherType''' is a two-[[Octet (computing)|octet]] field in an [[Ethernet frame]].  It is used to indicate which [[Communications protocol|protocol]] is [[Encapsulation (networking)|encapsulated]] in the payload of the frame and is used at the receiving end by the [[data link layer]] to determine how the payload is processed. The same field is also used to indicate the size of some Ethernet frames.

EtherType is also used as the basis of [[802.1Q VLAN tagging]], [[Encapsulation (networking)|encapsulating]] packets from VLANs for transmission multiplexed with other VLAN traffic over an [[Ethernet trunk]].

EtherType was first defined by the [[Ethernet II framing]] standard and later adapted for the [[IEEE 802.3]] standard. EtherType values are assigned by the [[IEEE Registration Authority]].

== Overview ==
[[Image:EthernetFrame.jpg|thumb|center|700px|An Ethernet frame including the EtherType field. Each lower slot designates an octet; the EtherType is two octets long.]]

In modern implementations of Ethernet, the field within the Ethernet frame used to describe the EtherType can also be used to represent the size of the payload of the Ethernet Frame.  Historically, depending on the type of Ethernet framing that was in use on an Ethernet segment, both interpretations were simultaneously valid, leading to potential ambiguity.  [[Ethernet II framing]] considered these octets to represent EtherType while the original IEEE 802.3 framing considered these octets to represent the size of the payload in bytes.

In order to allow Ethernet II and IEEE 802.3 framing to be used on the same Ethernet segment, a unifying standard, IEEE 802.3x-1997, was introduced that required that EtherType values be greater than or equal to 1536.  That value was chosen because the maximum length ([[Maximum Transmission Unit|MTU]]) of the data field of an Ethernet 802.3 frame is 1500 bytes and 1536 is represented by the number 600 in the [[hexadecimal]] numeral system. Thus, values of 1500 and below for this field indicate that the field is used as the size of the payload of the Ethernet frame while values of 1536 and above indicate that the field is used to represent an EtherType.  The interpretation of values 1501–1535, inclusive, is undefined.<ref>IEEE Std 802.3-2005, 3.2.6</ref>

The end of a frame is signaled by a valid [[frame check sequence]] followed by loss of carrier or by a special symbol or sequence in the [[line code|line coding scheme]] for a particular [[Ethernet physical layer]], so the length of the frame does not always need to be encoded as a value in the Ethernet frame.  However, as the minimum payload of an Ethernet frame is 46 bytes, a protocol that uses EtherType must include its own length field if that is necessary for the recipient of the frame to determine the length of short packets (if allowed) for that protocol.

== VLAN tagging==
[[File:Ethernet 802.1Q Insert.svg|center|thumb|950px|Insertion of the [[802.1Q VLAN tag]] (four octets) into an Ethernet-II frame, with a typical VLAN arrangement of a tag protocol identifier (TPID) EtherType value of 0x8100. A [[QinQ]] arrangement would add another four-octet tag containing a two-octet TPID using various EtherType values.]]

[[802.1Q VLAN tagging]] uses a 0x8100 EtherType value. The payload following includes a 2-byte tag control identifier (TCI) followed by an Ethernet frame beginning with a second (original) EtherType field for consumption by [[end station]]s. [[IEEE 802.1ad]] extends this tagging with further nested EtherType and TCI pairs.

== Jumbo frames ==
The size of the payload of non-standard [[jumbo frame]]s, typically ~9000 Bytes long, collides with the range used by EtherType, and cannot be used for indicating the length of such a frame. The proposition to resolve this conflict was to substitute the special EtherType value 0x8870 when a length would otherwise be used.<ref>{{cite IETF |draft=draft-ietf-isis-ext-eth-01 |title=Extended Ethernet Frame Size Support |date=November 2001}}</ref> However, the proposition (its use case was bigger packets for [[IS-IS]]) was not accepted and it is defunct. The chair of IEEE 802.3 at the time, Geoff Thompson, responded to the draft outlining IEEE 802.3's official position and the reasons behind the position. The draft authors also responded to the chair's letter, but no subsequent answer from the IEEE 802.3 has been recorded.<ref name="jumbo">{{cite news |url=https://datatracker.ietf.org/doc/draft-kaplan-isis-ext-eth/ |title=Extended Ethernet Frame Size Support |author=Kaplan |newspaper=Ietf Datatracker |publisher=[[Internet Engineering Task Force]] |date=2000-05-26|display-authors=etal}}</ref>

While defunct, this draft was implemented and is used in Cisco routers in their IS-IS implementation (for IIH Hello packets padding).<ref>{{cite mailing list |url=http://permalink.gmane.org/gmane.comp.security.scapy.general/5154 |title=Fwd: Re: ISIS in SCAPY and Jumbo frames |first=Marcel |last=Patzlaff |mailing-list=scapy-ml |date=2015-04-08 |access-date=2017-05-09 |archive-url=https://web.archive.org/web/20180331104715/http://permalink.gmane.org/gmane.comp.security.scapy.general/5154 |archive-date=2018-03-31 |url-status=dead }}</ref>

== Use beyond Ethernet ==
With the advent of the [[IEEE 802]] suite of standards, a [[Subnetwork Access Protocol]] (SNAP) header combined with an [[IEEE 802.2]] [[Logical Link Control|LLC]] header is used to transmit the EtherType of a payload for IEEE 802 networks other than Ethernet, as well as for non-IEEE networks that use the IEEE 802.2 LLC header, such as [[FDDI]]. However, for Ethernet, Ethernet II framing is still used.

== Registration ==

EtherTypes are assigned by the IEEE Registration Authority,<ref>{{citation |url=https://standards.ieee.org/wp-content/uploads/import/documents/tutorials/ethertype.pdf |title=Use of the IEEE Assigned Ethertype with IEEE Std 802.3 Local and Metropolitan Area Networks |access-date=2022-02-03}}</ref> which publishes them in list format.<ref name="ieee.org">{{cite web |url=http://standards-oui.ieee.org/ethertype/eth.txt |title=Public EtherType list |publisher=[[IEEE]] |access-date=2018-09-08}}</ref>  The [[Internet Assigned Numbers Authority]] has a separate list of some EtherType registrations, compiled from several sources, including the IEEE Registration Authority's list and some other lists.<ref name="ethtypes">{{cite web|url=https://www.iana.org/assignments/ieee-802-numbers/ieee-802-numbers.xhtml#ieee-802-numbers-1|title=IEEE 802 Numbers|date=2015-10-06|publisher=[[Internet Assigned Numbers Authority]]|access-date=2016-09-23}}</ref>

== Values ==
<!-- please don't add any protocol you find here. This is for [[WP:N|NOTABLE]] protocols. Any protocol added should minimally have an article elsewhere on Wikipedia. -->
{| class="wikitable"
|+ EtherType values for some notable protocols<ref name="ethtypes"/>
! EtherType value ([[hexadecimal]]) !! Protocol
|-
| 0x0800 || [[Internet Protocol version 4]] (IPv4)
|-
| 0x0806 || [[Address Resolution Protocol]] (ARP) 
|-
| 0x0842 || [[Wake-on-LAN]]<ref>{{cite web|url=https://wiki.wireshark.org/WakeOnLAN|title=WakeOnLAN|website=Wireshark Wiki|access-date=2018-10-16}}</ref>
|-
| 0x22EA || [[Stream Reservation Protocol]]
|-
| 0x22F0 || [[Audio Video Bridging#IEEE1722|Audio Video Transport Protocol]] (AVTP)
|-
| 0x22F3 || [[TRILL|IETF TRILL Protocol]]
|-
| 0x6002 || [[Digital Equipment Corporation|DEC]] [[Maintenance Operations Protocol|MOP]] RC
|-
| 0x6003 || [[DECnet]] Phase IV, DNA Routing
|-
| 0x6004 || [[Digital Equipment Corporation|DEC]] [[Local Area Transport|LAT]]
|-
| 0x8035 || [[Reverse Address Resolution Protocol]] (RARP)
|-
| 0x809B || [[AppleTalk]] (EtherTalk)
|-
| 0x80D5 || [[IEEE_802.2|LLC]] [[Protocol_data_unit|PDU]] (in particular, [[IBM]] [[Systems_Network_Architecture|SNA]]), preceded by 2 bytes length and 1 byte padding<ref>{{Cite web |last=IBM |date=May 1996 |title=LAN Technical Reference: IEEE 802.2 and NetBIOS Application Program Interfaces. IBM Document Number SC30-3587-01 |url=https://www.ardent-tool.com/docs/boo/bk8p7001.boo |at=sections 1.16-1.16.1 |format=BOO (IBM Book Manager) |edition=2nd}}</ref>
|-
| 0x80F3 || [[AppleTalk]] Address Resolution Protocol (AARP)
|-
| 0x8100 || VLAN-tagged frame ([[IEEE 802.1Q]]) and Shortest Path Bridging [[IEEE 802.1aq]] with [[Network-to-network interface|NNI]] compatibility<ref name="Avaya">{{cite web|url=https://downloads.avaya.com/css/P8/documents/100128510|title=Configuration - Shortest Path Bridging MAC (SPBM)|date=June 2012|publisher=Avaya|page=35|access-date=23 June 2017}}</ref>
|-
| 0x8102 || [[Simple Loop Prevention Protocol]] (SLPP)
|-
| 0x8103 || [[Virtual Link Aggregation Control Protocol]] (VLACP)
|-
| 0x8137 || [[IPX]]
|-
| 0x8204 || [[QNX#Transparent Distributed Processing|QNX Qnet]]
|-
| 0x86DD || [[Internet Protocol Version 6]] (IPv6)
|-
| 0x8808 || [[Ethernet flow control]]
|-
| 0x8809 || Ethernet Slow Protocols<ref>{{cite book|url=https://ieeexplore.ieee.org/servlet/opac?punumber=8457467|title=IEEE Std 802.3-2018|doi=10.1109/IEEESTD.2018.8457469|date=August 31, 2018|chapter=Annex 57A|isbn=978-1-5044-5090-4 }}</ref> such as the [[Link Aggregation Control Protocol]] (LACP)
|-
| 0x8819 || [[CobraNet]]
|-
| 0x8847 || [[MPLS]] unicast
|-
| 0x8848 || [[MPLS]] multicast
|-
| 0x8863 || [[PPPoE]] Discovery Stage
|-
| 0x8864 || [[PPPoE]] Session Stage
|-
| 0x887B || [[HomePlug|HomePlug 1.0 MME]]
|-
| 0x888E || EAP over LAN ([[IEEE 802.1X]])
|-
| 0x8892 || [[PROFINET]] Protocol
|-
| 0x889A || [[HyperSCSI]] (SCSI over Ethernet)
|-
| 0x88A2 || [[ATA over Ethernet]]
|-
| 0x88A4 || [[EtherCAT]] Protocol
|-
| 0x88A8 ||[[IEEE 802.1ad|Service VLAN tag identifier (S-Tag) on Q-in-Q tunnel]]
|-
| 0x88AB || [[Ethernet Powerlink]]{{citation needed|reason=No discussion of this EtherType in target article|date=January 2013}}
|-
| 0x88B8 || [[GOOSE]] (Generic Object Oriented Substation event)
|-
| 0x88B9 || GSE ([[Generic Substation Events]]) Management Services
|-
| 0x88BA || [[IEC 61850|SV (Sampled Value Transmission)]]
|-
|0x88BF
|[https://help.mikrotik.com/docs/display/ROS/RoMON MikroTik RoMON] (unofficial)
|-
| 0x88CC || [[Link Layer Discovery Protocol]] (LLDP)
|-
| 0x88CD || [[SERCOS III]]
|-
| 0x88E1 || [[HomePlug#HomePlug Green PHY|HomePlug Green PHY]]
|-
| 0x88E3 || [[Media Redundancy Protocol]] (IEC62439-2)
|-
| 0x88E5 || [[IEEE 802.1AE]] MAC security (MACsec)
|-
| 0x88E7 || Provider Backbone Bridges (PBB) ([[IEEE 802.1ah]])
|-
| 0x88F7 || [[Precision Time Protocol]] (PTP) over IEEE 802.3 Ethernet
|-
| 0x88F8 || [[NC-SI]]
|-
| 0x88FB || [[Parallel Redundancy Protocol]] (PRP)
|-
| 0x8902 || [[IEEE 802.1ag]] [[Connectivity Fault Management]] (CFM) Protocol / [[ITU-T Recommendation Y.1731]] ([[OA&M|OAM]])
|-
| 0x8906 || [[Fibre Channel over Ethernet]] (FCoE)
|-
| 0x8914 || [[FCoE]] Initialization Protocol
|-
| 0x8915 || [[RDMA over Converged Ethernet]] (RoCE)
|-
| 0x891D || [[TTEthernet]] Protocol Control Frame (TTE)
|-
| 0x893a || [[IEEE 1905|1905.1]] IEEE Protocol
|-
| 0x892F || [[High-availability Seamless Redundancy]] (HSR)
|-
| 0x9000 || [[Ethernet Configuration Testing Protocol]]<ref>{{cite book|url=http://decnet.ipv7.net/docs/dundas/aa-k759b-tk.pdf|title=The Ethernet, A Local Area Network Data Link and Physical Layer Specification Version 2.0|date=November 1982|section=8. Ethernet Configuration Testing Protocol}}</ref>
|-
| 0xF1C1 || Redundancy Tag ([[Time-Sensitive Networking|IEEE 802.1CB Frame Replication and Elimination for Reliability]])
|}

== See also ==

*[[Port (computer networking)]]

== References ==
{{Reflist}}

== External links ==
*[https://standards.ieee.org/products-programs/regauth/tut/ IEEE Registration Authority Tutorials]
*[https://standards.ieee.org/products-programs/regauth/ethertype/ IEEE EtherType Registration Authority]

{{Ethernet}}

{{DEFAULTSORT:Ethertype}}
[[Category:Ethernet]]