IEEE802.3(7) Standards, Environments, and Macros IEEE802.3(7)


ieee802.3 - IEEE 802.3 Ethernet parameters and statistics


The IEEE 802.3 standard specifies the details for Ethernet networking.
This page describes the various statistics and tunables that device drivers
supporting Ethernet commonly offer. Note that not every device or driver
supports every one of these values, and many devices offer additional
statistics and tunables that are specific to that hardware. See the device
driver's documentation for those specific details.

Values that are statistics are visible kstat(8), whereas properties are
visible using the dladm(8) show-linkprop subcommand. Tunables are
properties that can be changed using the dladm(8) set-linkprop subcommand.
A more useful summary of current operational state can be seen with the
dladm(8) show-ether subcommand.


The following statistics are accessible with kstat(8). Note that some
statistics are available in both 32- and 64-bit counters, in which case the
name of the 64 bit statistic will be the same as the 32-bit, but with "64"
appended. For example, ipackets64 is the 64-bit version of the ipackets
statistic. These are indicated with the special suffix [64] in the table

adv_cap_10hdx Advertises 10 Mbps half-duplex support.

adv_cap_10fdx Advertises 10 Mbps full-duplex support.

adv_cap_100hdx Advertises 100 Mbps half-duplex support.

adv_cap_100T4 Advertises 100BASE-T4 support.

adv_cap_100fdx Advertises 100 Mbps full-duplex support.

adv_cap_1000hdx Advertises 1000 Mbps half-duplex support.

adv_cap_1000fdx Advertises 1000 Mbps full-duplex support.

adv_cap_2500fdx Advertises 2.5 Gbps support.

adv_cap_5000fdx Advertises 5 Gbps support.

adv_cap_10gfdx Advertises 10 Gbps support.

adv_cap_25gfdx Advertises 25 Gbps support.

adv_cap_40gfdx Advertises 40 Gbps support.

adv_cap_50gfdx Advertises 50 Gbps support.

adv_cap_100gfdx Advertises 100 Gbps support.

adv_cap_200gfdx Advertises 200 Gbps support.

adv_cap_400gfdx Advertises 400 Gbps support.

adv_cap_autoneg Advertises auto-negotiation support.

adv_cap_asmpause Advertises asymmetric flow control support.

adv_cap_pause Advertises flow control support.

adv_rem_fault Remote fault status sent to peer.

align_errors Mis-aligned frames received.

brdcstrcv Broadcast frames received.

brdcstxmt Broadcast frames transmitted.

cap_10hdx Device supports 10 Mbps half-duplex.

cap_10fdx Device supports 10 Mbps full-duplex.

cap_100hdx Device supports 100 Mbps half-duplex.

cap_100T4 Device supports 100BASE-T4.

cap_100fdx Device supports 100 Mbps full-duplex.

cap_1000hdx Device supports 1000 Mbps half-duplex.

cap_1000fdx Device supports 1000 Mbps full-duplex.

cap_2500fdx Device supports 2.5 Gbps.

cap_5000fdx Device supports 5 Gbps.

cap_10gfdx Device supports 10 Gbps.

cap_25gfdx Device supports 25 Gbps.

cap_40gfdx Device supports 40 Gbps.

cap_50gfdx Device supports 50 Gbps.

cap_100gfdx Device supports 100 Gbps.

cap_200gfdx Device supports 200 Gbps.

cap_400gfdx Device supports 400 Gbps.

cap_asmpause Device supports asymmetric flow control.

cap_autoneg Device supports auto-negotiation.

cap_pause Device supports symmetric flow control.

cap_rem_fault Device supports remote fault notification.

carrier_errors Frames dropped due to loss of link.

collisions Collisions.

defer_xmts Transmits deferred due to link activity.

ex_collisions Frames dropped due to too many collisions.

fcs_errors Frames received with bad frame checksum.

first_collisions Frames with at least one collision.

ierrors Receive errors.

ifspeed Link speed in bits per second.

ipackets[64] Frames received successfully.

jabber_errors Jabber errors.

link_asmpause Asymmetric flow control; works together with
link_pause. See the description for it below.

link_autoneg Link was auto-negotiated.

link_duplex Link duplex status, values as follows:

0 Unknown.
1 Half-duplex.
2 Full-duplex.

link_pause Link flow control available; works together with
link_asmpause. The meanings of these bits are:

pause asmpause meaning
0 0 No flow control.
1 0 Symmetric flow control.
0 1 Honor received pause frames.
1 1 Send pause frames when congested.

link_state Link state; 0 for down, 1 for up.

link_up Link is up if 1.

lp_cap_10hdx Peer supports 10 Mbps half-duplex.

lp_cap_10fdx Peer supports 10 Mbps full-duplex.

lp_cap_100T4 Peer supports 100BASE-T4.

lp_cap_100hdx Peer supports 100 Mbps half-duplex.

lp_cap_100fdx Peer supports 100 Mbps full-duplex.

lp_cap_1000fdx Peer supports 1000 Mbps full-duplex.

lp_cap_1000hdx Peer supports 1000 Mbps half-duplex.

lp_cap_2500fdx Peer supports 2.5 Gbps.

lp_cap_5000fdx Peer supports 5 Gbps.

lp_cap_10gfdx Peer supports 10 Gbps.

lp_cap_25gfdx Peer supports 25 Gbps.

lp_cap_40gfdx Peer supports 40 Gbps.

lp_cap_50gfdx Peer supports 50 Gbps.

lp_cap_100gfdx Peer supports 100 Gbps full-duplex.

lp_cap_200gfdx Peer supports 200 Gbps full-duplex.

lp_cap_400gfdx Peer supports 400 Gbps full-duplex.

lp_cap_asmpause Peer supports asymmetric flow control.

lp_cap_autoneg Peer supports auto-negotiation.

lp_cap_pause Peer advertises flow control support.

lp_rem_fault Peer announces a remote fault.

macrv_errors Generic receive errors.

macxmt_errors Generic transmit errors.

multi_collisions Frames with more than one collision.

multircv Multicast frames received.

multixmt Multicast frames transmitted.

norcvbuf Receive frames dropped due to lack of resources.

noxmtbuf Transmit frames dropped due to lack of resources.

obytes[64] Bytes (octets) transmitted successfully.

oerrors Transmit errors.

oflo Overflow errors.

opackets[64] Frames successfully transmitted.

promisc Interface is in promiscuous mode.

rbytes[64] Bytes (octets) received successfully.

runt_errors Frames received that were too short.

sqe_errors Squelch errors.

toolong_errors Frames received that were too long.

tx_late_collisions Late collisions on transmit.

uflo Underflow errors.

unknowns Frames received with no local recipient.

xcvr_addr Transceiver address.

xcvr_id Transceiver vendor and device ID.

xcvr_inuse Identifies the type of transceiver in use. Ethernet-
specific media values are defined in <sys/mac_ether.h>.
For more information see the section on MAC_PROP_MEDIA
in mac(9E).


The following parameters are accessible with dladm(8). Some of these are
normally read-only. Other properties that are not specific to IEEE 802.3 /
Ethernet links are also available via dladm(8), and are documented in its
man page rather than here.

speed Link speed, in Mbps per second (dladm only).

duplex Link duplex, either "full" or "half".

state Link state, either "up" or "down".

mtu Maximum link frame size in bytes. See Jumbo Frames.

flowctrl Flow control setting, one of "no", "tx", "rx", or "bi".
See Flow Control.

fec FEC settings, one of "none", "auto", "rs", or "base-r".
See Forward Error Correction.

adv_10hdx_cap Advertising 10 Mbps half-duplex support.

en_10fhdx_cap Enable 10 Mbps full-duplex.

en_10fhdx_cap Enable 10 Mbps half-duplex.

adv_10fdx_cap Advertising 10 Mbps full-duplex support.

adv_100hdx_cap Advertising 100 Mbps half-duplex support.

en_100hdx_cap Enable 100 Mbps half-duplex.

adv_100fdx_cap Advertising 100 Mbps full-duplex support.

en_100fdx_cap Enable 100 Mbps full-duplex.

adv_1000hdx_cap Advertising 1000 Mbps half-duplex support.

en_1000hdx_cap Enable 1000 Mbps half-duplex.

adv_1000fdx_cap Advertising 1000 Mbps full-duplex support.

en_1000fdx_cap Enable 1000 Mbps full-duplex.

adv_10gfdx_cap Advertising 10 Gbps support.

en_10gfdx_cap Enable 10 Gbps support.

adv_25gfdx_cap Advertising 25 Gbps support.

en_25gfdx_cap Enable 25 Gbps support.

adv_40gfdx_cap Advertising 40 Gbps support.

en_40gfdx_cap Enable 40 Gbps support.

adv_50gfdx_cap Advertising 50 Gbps support.

en_50gfdx_cap Enable 50 Gbps support.

adv_100gfdx_cap Advertising 100 Gbps support.

en_100gfdx_cap Enable 100 Gbps support.

adv_200gfdx_cap Advertising 200 Gbps support.

en_200gfdx_cap Enable 200 Gbps support.

adv_400gfdx_cap Advertising 400 Gbps support.

en_400gfdx_cap Enable 400 Gbps support.

With modern devices, auto-negotiation is normally handled automatically.
With 1 Gbps, 10 Gbps, and higher speeds it is mandatory (10GBASE-T also
requires full-duplex operation). It is also strongly recommended for use
whenever possible; without auto-negotiation the link will usually not
operate unless both partners are configured to use the same link mode.

Auto-negotiation, when enabled, takes place by comparing the local
capabilities that have been advertised (which must also be supported by the
local device), with the capabilities that have been advertised by the link
partner (peer). The first of the following modes that is supported by both
partners is selected as the link negotiation result:

+o 400 Gbps (400gfdx)
+o 200 Gbps (200gfdx)
+o 100 Gbps (100gfdx)
+o 50 Gbps (50gfdx)
+o 40 Gbps (40gfdx)
+o 25 Gbps (25gfdx)
+o 10 Gbps (10gfdx)
+o 5 Gbps (5000fdx)
+o 2.5 Gbps (2500fdx)
+o 1000 Mbps full-duplex (1000fdx)
+o 1000 Mbps half-duplex (1000hdx)
+o 100 Mbps full-duplex (100fdx)
+o 100BASE-T4 (100T4)
+o 100 Mbps half-duplex (100hdx)
+o 10 Mbps full-duplex (10fdx)
+o 10 Mbps half-duplex (10hdx)

Advertisement of these modes can be enabled or disabled by setting the
appropriate en_ property in dladm(8).

Auto-negotiation may also be disabled, by setting the adv_autoneg_cap
property to 0. In this case, the highest enabled link mode (using the
above list) is "forced" for the link.

Flow Control

Link layer flow control is available on many modern devices, and is
mandatory for operation at 10 Gbps. It requires that the link be auto-
negotiated, and that the link be full-duplex, in order to function.

Flow control is applied when a receiver becomes congested. In this case
the receiver can send a special frame, called a pause frame, to request its
partner cease transmitting for a short period of time.

Flow control can be said to be either symmetric, in which case both
partners can send and honor pause frames, or asymmetric, in which case one
partner may not transmit pause frames.

The flow control mode used is driven by the flowctrl property. It has the
following meanings:

"no" Neither send, nor honor pause frames.
"tx" Send pause frames, provided that the peer can support them, but
do not honor them.
"rx" Receive and honor pause frames.
"bi" Both send and receive (and honor) pause frames.

The statistics for flow control (adv_cap_pause, adv_cap_asmpause,
lp_cap_pause, lp_cap_asmpause, link_pause, and link_asmpause) are based on
the properties exchanged in the auto-negotiation and are confusing as a
result. Administrators are advised to use the flowctrl property instead.

Forward Error Correction

Beginning with 25 Gbit per-lane Ethernet (100 Gbit QSFP devices use 4 lanes
of 25 GbE) the various IEEE Ethernet standards allowed the optional use of
forward error correction, often abbreviated FEC. In 25/100 Gbit Ethernet,
FEC is considered an optional part of the standard and is subject to auto-
negotiation. In 25/100 Gbit Ethernet, there are two explicit types of FEC
that are defined and two meta options:

rs This is a Reed-Solomon based code (RS(514,528)) This is considered
the stronger of the two FEC modes and operates on both a per-lane
basis and the entire channel.

base-r This is known as FireCode and comes from IEEE 802.3 clause 74.
FireCode operates on each lane indepenently. It cannot correct as
much as the rs FEC; however, it has lower latency.

auto This indicates that the device should perform auto-negotiation to
determine the type of FEC that should be used.

none This indicates the devie should not use FEC at all.

Due to the evolution of FEC support in 25/100 Gbit Ethernet, not all
devices support FEC auto-negotiation. Sometimes to form a working link, a
particular FEC must be explicitly selected.

With 50 Gbit per-lane Ethernet and higher single-lane and combined speeds,
the use of FEC is no longer something separate that is part of auto-
negotiation. Instead, it is a mandatory part of higher-speed

Jumbo Frames

The IEEE 802.3 standard specifies a standard frame size of 1518 bytes,
which includes a 4-byte frame checksum, a 14-byte header, and 1500 bytes of
payload. Most devices support larger frame sizes than this, and when all
possible parties on the same local network can do so, it may be
advantageous to choose a larger frame size; 9000 bytes is the most common
option, as it allows a transport layer to convey 8 KB (8192) of data, while
leaving room for various link, network, and transport layer headers.

Note that the use of frames carrying more than 1500 bytes of payload is not
standardized, even though it is common practice.

The mtu property is used to configure the frame size. Note that this is
the size of the payload, and excludes the preamble, checksum, and header.
It also excludes the tag for devices that support tagging (see Virtual LANs

Care must be taken to ensure that all communication parties agree on the
same size, or communication may cease to function properly.

Note that the mtu property refers to the link layer property. It may be
necessary to configure upper layer protocols such as IP to use a different
size when this changes. See ifconfig(8).

Virtual LANs

Most devices support virtual LANs (and also priority control tagging)
though the use of a 4-byte tag inserted between the frame header and
payload. The details of configuration of this are covered in the dladm(8)

Data Link Provider Interface (DLPI) Details
The correct method for applications to access Ethernet devices directly is
to use the DLPI. See dlpi(4P) and libdlpi(3LIB) for further information.

The following DLPI parameters are presented to applications.

Maximum SDU 1500 (or larger, as determined by the mtu
Minimum SDU 0
Address length 6
SAP length -2
Service mode DL_CLDLS
Broadcast address ff:ff:ff:ff:ff:ff (6 bytes with all bits set)

Note that if the application binds to SAP of 0, then standard IEEE 802.3
mode is assumed and the frame length is stored in place of the Ethernet
type. Frames that arrive with the type field set to 1500 or less, are
delivered to applications that bind to SAP 0.

Ethernet drivers on the support both DLPI style 1 and style 2 operation.
Additionally, it is possible to configure provide "vanity" names to
interfaces using the dladm(8) rename-link subcommand. Such vanity names
are only accessible using DLPI style 1.


There may be other mechanisms available to configure link layer properties.
Historically the ndd(8) command, and driver.conf(5) files could be used to
do this. These methods are deprecated in favor of dladm(8) properties.


When present, the statistics and properties presented here are Committed.
However, note that not every Ethernet device supports all of these, and
some devices may support additional statistics and properties.

The DLPI and IEEE 802.3 itself are Standard.


libdlpi(3LIB), dlpi(4P), driver.conf(5), dladm(8), ifconfig(8), kstat(8),
ndd(8), netstat(8)

IEEE 802.3: Ethernet, IEEE Standards Association.

Data Link Provider Interface (DLPI), The Open Group, 1997.

STREAMs Programming Guide, Sun Microsystems, Inc., January 2005.

illumos July 25, 2023 illumos