EtherType
Encyclopedia
EtherType is a two-octet
field in an Ethernet frame
. It is used to indicate which protocol
is encapsulated
in the PayLoad of an Ethernet Frame. This field was first defined by the Ethernet II framing networking standard, and later adapted for the IEEE 802.3 Ethernet networking standard.
EtherType numbering generally starts from 0x0800. In modern implementations of Ethernet, the field within the Ethernet frame used to describe the EtherType also can 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 ambiguity. Ethernet v2 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 packets using Ethernet v2 framing and packets using the 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 (0x0600). That value was chosen because the maximum length (MTU
) of the data field of an Ethernet 802.3 frame was 1500 bytes (0x05DC). Thus, values of 1500 (0x05DC) 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 EtherType. The interpretation of values between 1500 and 1536, exclusive, is undefined. The size of the payload of non-standard jumbo frames
, typically ~9000 Bytes long, falls within the range used by EtherType; this conflict is resolved by substituting the special EtherType value 0x8870 when a length would otherwise be used. The network stack can replace this special EtherType with the actual length of the packet on receive, or when bridging to non-Ethernet networks like FDDI.
Ethernet MAC Frame.
Note that the ABOVE figure does not show any Virtual LAN
tags, which increase the size of the frame by 32-bits per tag.
Multiprotocol Label Switching
also uses 32-bits per label and a stacking arrangement.
The figure below shows a typical VLAN arrangement with a TPID EtherType value of 0x8100.
A QinQ arrangement would add another 32-bit tag with 16-bit TPID using various EtherType values.
Triple Tagging QinQinQ has three 32-bit tags besides the original 16-bit EtherType field.
With 802.1q VLAN Tagging and QinQ the sparse 16-bit EtherType is being completely used. The 16-bit EtherType not only tags the PayLoad Class, it also serves to help end any VLAN Tagging or QinQ stacking. Via look-ahead peeking in streams, the 16-bit EtherType can help to confirm or package a QinQ 32+32+16=80 bit Header between the 48-bit MAC addresses and the PayLoad. Of those 80-bits only 32-bits are used for dynamic information. For a full 66-bit addressing system, 18 bits are needed beyond the MAC. Thus, additional EtherType values are required and used for Triple Tagging QinQinQ. Inefficient and conservative use of a 16-bit Tag Protocol Identifier (TPID) on each 32-bit VLAN Tag, followed by the trailing lone 16-bits creates a 48-bit Signature that can not easily be mistaken as part of the PayLoad. Vendor implementations may avoid wasting band-width sending those 48-bits in proprietary link compression schemes. The EtherType is not expected to contain any CRC or FCS information.
With the advent of the IEEE 802
suite of standards, a SNAP
header combined with an IEEE 802.2
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, the Ethernet II header is still used.
EtherType for some common protocols
Note that even very well known de facto uses of EtherTypes are not always recorded in the IEEE list of EtherType values. For example, EtherType 0x0806 (used by ARP
) appears in the IEEE list only as "Symbolics, Inc., Protocol unavailable."
Octet (computing)
An octet is a unit of digital information in computing and telecommunications that consists of eight bits. The term is often used when the term byte might be ambiguous, as there is no standard for the size of the byte.-Overview:...
field in an Ethernet frame
Ethernet frame
A data packet on an Ethernet link is called an Ethernet frame. A frame begins with Preamble and Start Frame Delimiter. Following which, each Ethernet frame continues with an Ethernet header featuring destination and source MAC addresses. The middle section of the frame is payload data including any...
. It is used to indicate which protocol
Communications protocol
A communications protocol is a system of digital message formats and rules for exchanging those messages in or between computing systems and in telecommunications...
is encapsulated
Encapsulation (networking)
In computer networking, encapsulation is a method of designing modular communication protocols in which logically separate functions in the network are abstracted from their underlying structures by inclusion or information hiding within higher level objects....
in the PayLoad of an Ethernet Frame. This field was first defined by the Ethernet II framing networking standard, and later adapted for the IEEE 802.3 Ethernet networking standard.
EtherType numbering generally starts from 0x0800. In modern implementations of Ethernet, the field within the Ethernet frame used to describe the EtherType also can 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 ambiguity. Ethernet v2 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 packets using Ethernet v2 framing and packets using the 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 (0x0600). That value was chosen because the maximum length (MTU
Maximum transmission unit
In computer networking, the maximum transmission unit of a communications protocol of a layer is the size of the largest protocol data unit that the layer can pass onwards. MTU parameters usually appear in association with a communications interface...
) of the data field of an Ethernet 802.3 frame was 1500 bytes (0x05DC). Thus, values of 1500 (0x05DC) 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 EtherType. The interpretation of values between 1500 and 1536, exclusive, is undefined. The size of the payload of non-standard jumbo frames
Jumbo Frames
In computer networking, jumbo frames are Ethernet frames with more than 1500 bytes of payload. Conventionally, jumbo frames can carry up to 9000 bytes of payload, but variations exist and some care must be taken when using the term. Many Gigabit Ethernet switches and Gigabit Ethernet network...
, typically ~9000 Bytes long, falls within the range used by EtherType; this conflict is resolved by substituting the special EtherType value 0x8870 when a length would otherwise be used. The network stack can replace this special EtherType with the actual length of the packet on receive, or when bridging to non-Ethernet networks like FDDI.
Note that the ABOVE figure does not show any Virtual LAN
Virtual LAN
A virtual local area network, virtual LAN or VLAN, is a group of hosts with a common set of requirements that communicate as if they were attached to the same broadcast domain, regardless of their physical location...
tags, which increase the size of the frame by 32-bits per tag.
Multiprotocol Label Switching
Multiprotocol Label Switching
Multiprotocol Label Switching is a mechanism in high-performance telecommunications networks that directs data from one network node to the next based on short path labels rather than long network addresses, avoiding complex lookups in a routing table. The labels identify virtual links between...
also uses 32-bits per label and a stacking arrangement.
The figure below shows a typical VLAN arrangement with a TPID EtherType value of 0x8100.
A QinQ arrangement would add another 32-bit tag with 16-bit TPID using various EtherType values.
Triple Tagging QinQinQ has three 32-bit tags besides the original 16-bit EtherType field.
With 802.1q VLAN Tagging and QinQ the sparse 16-bit EtherType is being completely used. The 16-bit EtherType not only tags the PayLoad Class, it also serves to help end any VLAN Tagging or QinQ stacking. Via look-ahead peeking in streams, the 16-bit EtherType can help to confirm or package a QinQ 32+32+16=80 bit Header between the 48-bit MAC addresses and the PayLoad. Of those 80-bits only 32-bits are used for dynamic information. For a full 66-bit addressing system, 18 bits are needed beyond the MAC. Thus, additional EtherType values are required and used for Triple Tagging QinQinQ. Inefficient and conservative use of a 16-bit Tag Protocol Identifier (TPID) on each 32-bit VLAN Tag, followed by the trailing lone 16-bits creates a 48-bit Signature that can not easily be mistaken as part of the PayLoad. Vendor implementations may avoid wasting band-width sending those 48-bits in proprietary link compression schemes. The EtherType is not expected to contain any CRC or FCS information.
With the advent of the IEEE 802
IEEE 802
IEEE 802 refers to a family of IEEE standards dealing with local area networks and metropolitan area networks.More specifically, the IEEE 802 standards are restricted to networks carrying variable-size packets. IEEE 802 refers to a family of IEEE standards dealing with local area networks and...
suite of standards, a SNAP
Subnetwork Access Protocol
The Subnetwork Access Protocol is a mechanism for multiplexing, on networks using IEEE 802.2 LLC, more protocols than can be distinguished by the 8-bit 802.2 Service Access Point fields. SNAP supports identifying protocols by Ethernet type field values; it also supports vendor-private protocol...
header combined with an IEEE 802.2
IEEE 802.2
IEEE 802.2 is the IEEE 802 standard defining Logical Link Control , which is the upper portion of the data link layer of the OSI Model. The LLC sublayer presents a uniform interface to the user of the data link service, usually the network layer...
LLC
Logical Link Control
The logical link control data communication protocol layer is the upper sub-layer of the data link layer in the seven-layer OSI reference model...
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
Fiber distributed data interface
Fiber Distributed Data Interface provides a 100 Mbit/s optical standard for data transmission in a local area network that can extend in range up to . Although FDDI logical topology is a ring-based token network, it does not use the IEEE 802.5 token ring protocol as its basis; instead, its...
. However, for Ethernet, the Ethernet II header is still used.
EtherType for some common protocols
| EtherType | Protocol |
|---|---|
| 0x0800 | Internet Protocol, Version 4 (IPv4 IPv4 Internet Protocol version 4 is the fourth revision in the development of the Internet Protocol and the first version of the protocol to be widely deployed. Together with IPv6, it is at the core of standards-based internetworking methods of the Internet... ) |
| 0x0806 | Address Resolution Protocol (ARP Address Resolution Protocol Address Resolution Protocol is a telecommunications protocol used for resolution of network layer addresses into link layer addresses, a critical function in multiple-access networks. ARP was defined by RFC 826 in 1982. It is Internet Standard STD 37... ) |
| 0x0842 | Wake-on-LAN Magic Packet Wake-on-LAN Wake-on-LAN is an Ethernet computer networking standard that allows a computer to be turned on or woken up by a network message.... , as used by ether-wake and Sleep Proxy Service Sleep Proxy Service Apple's Bonjour Sleep Proxy service is an open sourcecomponent of zero configuration networking, designed to assist in reducing power consumption of networked electronic devices. A device acting as a sleep proxy server will respond to Multicast DNS queries for another, compatible device which has... |
| 0x1337 | SYN-3 heartbeat protocol (SYNdog) |
| 0x22F3 | IETF TRILL Protocol TRILL (computing) TRILL is a IETF Standard implemented by devices called RBridges or Routing Bridges. TRILL combines the advantages of bridges and routers and is the application of link state routing to the VLAN-aware customer-bridging problem. RBridges are compatible with and can incrementally replace previous... |
| 0x6003 | DECnet DECnet DECnet is a suite of network protocols created by Digital Equipment Corporation, originally released in 1975 in order to connect two PDP-11 minicomputers. It evolved into one of the first peer-to-peer network architectures, thus transforming DEC into a networking powerhouse in the 1980s... Phase IV |
| 0x8035 | Reverse Address Resolution Protocol (RARP) |
| 0x809B | AppleTalk AppleTalk AppleTalk is a proprietary suite of protocols developed by Apple Inc. for networking computers. It was included in the original Macintosh released in 1984, but is now unsupported as of the release of Mac OS X v10.6 in 2009 in favor of TCP/IP networking... (Ethertalk) |
| 0x80F3 | AppleTalk AppleTalk AppleTalk is a proprietary suite of protocols developed by Apple Inc. for networking computers. It was included in the original Macintosh released in 1984, but is now unsupported as of the release of Mac OS X v10.6 in 2009 in favor of TCP/IP networking... Address Resolution Protocol (AARP) |
| 0x8100 | VLAN-tagged frame (IEEE 802.1Q IEEE 802.1Q IEEE 802.1Q is the networking standard that supports Virtual LANs on an Ethernet network. The standard defines a system of VLAN tagging for Ethernet frames and the accompanying procedures to be used by bridges and switches in handling such frames... ) |
| 0x8137 | Novell IPX IPX Internetwork Packet Exchange is the OSI-model Network layer protocol in the IPX/SPX protocol stack.The IPX/SPXM protocol stack is supported by Novell's NetWare network operating system. Because of Netware's popularity through the late 1980s into the mid 1990s, IPX became a popular internetworking... (alt) |
| 0x8138 | Novell Novell Novell, Inc. is a multinational software and services company. It is a wholly owned subsidiary of The Attachmate Group. It specializes in network operating systems, such as Novell NetWare; systems management solutions, such as Novell ZENworks; and collaboration solutions, such as Novell Groupwise... |
| 0x8204 | QNX Qnet |
| 0x86DD | Internet Protocol, Version 6 (IPv6 IPv6 Internet Protocol version 6 is a version of the Internet Protocol . It is designed to succeed the Internet Protocol version 4... ) |
| 0x8808 | MAC Control |
| 0x8809 | Slow Protocols (IEEE 802.3 IEEE 802.3 IEEE 802.3 is a working group and a collection of IEEE standards produced by the working group defining the physical layer and data link layer's media access control of wired Ethernet. This is generally a local area network technology with some wide area network applications... ) |
| 0x8819 | CobraNet Cobranet CobraNet is a combination of software, hardware and network protocols designed to deliver uncompressed, multi-channel, low-latency digital audio over a standard Ethernet network... |
| 0x8847 | MPLS Multiprotocol Label Switching Multiprotocol Label Switching is a mechanism in high-performance telecommunications networks that directs data from one network node to the next based on short path labels rather than long network addresses, avoiding complex lookups in a routing table. The labels identify virtual links between... unicast |
| 0x8848 | MPLS Multiprotocol Label Switching Multiprotocol Label Switching is a mechanism in high-performance telecommunications networks that directs data from one network node to the next based on short path labels rather than long network addresses, avoiding complex lookups in a routing table. The labels identify virtual links between... multicast |
| 0x8863 | PPPoE Point-to-Point Protocol over Ethernet The Point-to-Point Protocol over Ethernet is a network protocol for encapsulating Point-to-Point Protocol frames inside Ethernet frames. It is used mainly with DSL services where individual users connect to the DSL modem over Ethernet and in plain Metro Ethernet networks... Discovery Stage |
| 0x8864 | PPPoE Session Stage |
| 0x886F | Microsoft NLB heartbeat |
| 0x8870 | Jumbo Frames |
| 0x887B | HomePlug 1.0 MME HomePlug HomePlug is the family name for various power line communications specifications that support networking over existing home electrical wiring. Several specifications exist under the HomePlug moniker, with each offering unique performance capabilities and coexistence or compatibility with other... |
| 0x888E | EAP over LAN (IEEE 802.1X IEEE 802.1X IEEE 802.1X is an IEEE Standard for port-based Network Access Control . It is part of the IEEE 802.1 group of networking protocols. It provides an authentication mechanism to devices wishing to attach to a LAN or WLAN.... ) |
| 0x8892 | PROFINET Protocol |
| 0x889A | HyperSCSI HyperSCSI HyperSCSI was a computer network protocol for accessing storage by sending and receiving SCSI commands.It was developed by researchers at the Data Storage Institute in Singapore in 2000 to 2003.... (SCSI over Ethernet) |
| 0x88A2 | ATA over Ethernet ATA over Ethernet ATA over Ethernet is a network protocol developed by the Brantley Coile Company, designed for simple, high-performance access of SATA storage devices over Ethernet networks. It is used to build storage area networks with low-cost, standard technologies.- Protocol description :AoE runs on layer 2... |
| 0x88A4 | EtherCAT EtherCAT EtherCAT - Ethernet for Control Automation Technology - is an open high performance Ethernet-based fieldbus system. The development goal of EtherCAT was to apply Ethernet to automation applications which require short data update times with low communication jitter and low hardware costs.-... Protocol |
| 0x88A8 | Provider Bridging (IEEE 802.1ad) |
| 0x88AB | Ethernet Powerlink Ethernet Powerlink Ethernet Powerlink is a deterministic real-time protocol for standard Ethernet. It is an open protocol managed by the Ethernet POWERLINK Standardization Group... |
| 0x88CC | LLDP Link Layer Discovery Protocol The Link Layer Discovery Protocol is a vendor-neutral Link Layer protocol in the Internet Protocol Suite used by network devices for advertising their identity, capabilities, and neighbors on a IEEE 802 local area network, principally wired Ethernet... |
| 0x88CD | SERCOS III SERCOS III sercos III is the third generation of the sercos interface, a globally standardized open digital interface for the communication between industrial controls, motion devices, and input/output devices . sercos III merges the hard real-time aspects of the sercos interface with Ethernet. It is based... |
| 0x88D8 | Circuit Emulation Services over Ethernet (MEF-8) |
| 0x88E1 | HomePlug AV MME HomePlug HomePlug is the family name for various power line communications specifications that support networking over existing home electrical wiring. Several specifications exist under the HomePlug moniker, with each offering unique performance capabilities and coexistence or compatibility with other... |
| 0x88E5 | MAC security (IEEE 802.1AE IEEE 802.1AE 802.1AE is the IEEE MAC Security standard which defines connectionless data confidentiality and integrity for media access independent protocols... ) |
| 0x88F7 | Precision Time Protocol Precision Time Protocol The Precision Time Protocol is a protocol used to synchronize clocks throughout a computer network. On a local area network it achieves clock accuracy in the sub-microsecond range, making it suitable for measurement and control systems.... (IEEE 1588) |
| 0x8902 | IEEE 802.1ag Connectivity Fault Management Connectivity Fault Management IEEE 802.1ag IEEE Standard for Local and Metropolitan Area Networks Virtual Bridged Local Area Networks Amendment 5: Connectivity Fault Management is a standard defined by IEEE. It defines protocols and practices for OAM for paths through 802.1 bridges and local area networks... (CFM) Protocol / ITU-T Recommendation Y.1731 (OAM OA&M Operations, administration and management or operations, administration and maintenance is a general term used to describe the processes, activities, tools, standards, etc involved with operating, administering, managing and maintaining any system... ) |
| 0x8906 | Fibre Channel over Ethernet Fibre Channel over Ethernet Fibre Channel over Ethernet is an encapsulation of Fibre Channel frames over Ethernet networks. This allows Fibre Channel to use 10 Gigabit Ethernet networks while preserving the Fibre Channel protocol... |
| 0x8914 | FCoE Initialization Protocol |
| 0x9000 | Configuration Test Protocol (Loop) |
| 0x9100 | Q-in-Q |
| 0xCAFE | Veritas Low Latency Transport (LLT) |
Note that even very well known de facto uses of EtherTypes are not always recorded in the IEEE list of EtherType values. For example, EtherType 0x0806 (used by ARP
Address Resolution Protocol
Address Resolution Protocol is a telecommunications protocol used for resolution of network layer addresses into link layer addresses, a critical function in multiple-access networks. ARP was defined by RFC 826 in 1982. It is Internet Standard STD 37...
) appears in the IEEE list only as "Symbolics, Inc., Protocol unavailable."