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) subcommand. Tunables are properties that can be changed using the dladm(8) subcommand. A more useful summary of current operational state can be seen with the dladm(8) 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, is the 64-bit version of the ipackets statistic. These are indicated with the special suffix [64] in the table below.

Advertises 10 Mbps half-duplex support.
Advertises 10 Mbps full-duplex support.
Advertises 100 Mbps half-duplex support.
Advertises 100BASE-T4 support.
Advertises 100 Mbps full-duplex support.
Advertises 1000 Mbps half-duplex support.
Advertises 1000 Mbps full-duplex support.
Advertises 2.5 Gbps support.
Advertises 5 Gbps support.
Advertises 10 Gbps support.
Advertises 25 Gbps support.
Advertises 40 Gbps support.
Advertises 50 Gbps support.
Advertises 100 Gbps support.
Advertises 200 Gbps support.
Advertises 400 Gbps support.
Advertises auto-negotiation support.
Advertises asymmetric flow control support.
Advertises flow control support.
Remote fault status sent to peer.
Mis-aligned frames received.
Broadcast frames received.
Broadcast frames transmitted.
Device supports 10 Mbps half-duplex.
Device supports 10 Mbps full-duplex.
Device supports 100 Mbps half-duplex.
Device supports 100BASE-T4.
Device supports 100 Mbps full-duplex.
Device supports 1000 Mbps half-duplex.
Device supports 1000 Mbps full-duplex.
Device supports 2.5 Gbps.
Device supports 5 Gbps.
Device supports 10 Gbps.
Device supports 25 Gbps.
Device supports 40 Gbps.
Device supports 50 Gbps.
Device supports 100 Gbps.
Device supports 200 Gbps.
Device supports 400 Gbps.
Device supports asymmetric flow control.
Device supports auto-negotiation.
Device supports symmetric flow control.
Device supports remote fault notification.
Frames dropped due to loss of link.
Collisions.
Transmits deferred due to link activity.
Frames dropped due to too many collisions.
Frames received with bad frame checksum.
Frames with at least one collision.
Receive errors.
Link speed in bits per second.
[64]
Frames received successfully.
Jabber errors.
Asymmetric flow control; works together with link_pause. See the description for it below.
Link was auto-negotiated.
Link duplex status, values as follows:
0 Unknown.
1 Half-duplex.
2 Full-duplex.
Link flow control available; works together with link_asmpause. The meanings of these bits are:
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; 0 for down, 1 for up.
Link is up if 1.
Peer supports 10 Mbps half-duplex.
Peer supports 10 Mbps full-duplex.
Peer supports 100BASE-T4.
Peer supports 100 Mbps half-duplex.
Peer supports 100 Mbps full-duplex.
Peer supports 1000 Mbps full-duplex.
Peer supports 1000 Mbps half-duplex.
Peer supports 2.5 Gbps.
Peer supports 5 Gbps.
Peer supports 10 Gbps.
Peer supports 25 Gbps.
Peer supports 40 Gbps.
Peer supports 50 Gbps.
Peer supports 100 Gbps full-duplex.
Peer supports 200 Gbps full-duplex.
Peer supports 400 Gbps full-duplex.
Peer supports asymmetric flow control.
Peer supports auto-negotiation.
Peer advertises flow control support.
Peer announces a remote fault.
Generic receive errors.
Generic transmit errors.
Frames with more than one collision.
Multicast frames received.
Multicast frames transmitted.
Receive frames dropped due to lack of resources.
Transmit frames dropped due to lack of resources.
[64]
Bytes (octets) transmitted successfully.
Transmit errors.
Overflow errors.
[64]
Frames successfully transmitted.
Interface is in promiscuous mode.
[64]
Bytes (octets) received successfully.
Frames received that were too short.
Squelch errors.
Frames received that were too long.
Late collisions on transmit.
Underflow errors.
Frames received with no local recipient.
Transceiver address.
Transceiver vendor and device ID.
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.

Link speed, in Mbps per second (dladm only).
Link duplex, either "full" or "half".
Link state, either "up" or "down".
Maximum link frame size in bytes. See Jumbo Frames.
Flow control setting, one of “no”, “tx”, “rx”, or “bi”. See Flow Control.
FEC settings, one of “none”, “auto”, “rs”, or “base-r”. See Forward Error Correction.
Advertising 10 Mbps half-duplex support.
Enable 10 Mbps full-duplex.
Enable 10 Mbps half-duplex.
Advertising 10 Mbps full-duplex support.
Advertising 100 Mbps half-duplex support.
Enable 100 Mbps half-duplex.
Advertising 100 Mbps full-duplex support.
Enable 100 Mbps full-duplex.
Advertising 1000 Mbps half-duplex support.
Enable 1000 Mbps half-duplex.
Advertising 1000 Mbps full-duplex support.
Enable 1000 Mbps full-duplex.
Advertising 10 Gbps support.
Enable 10 Gbps support.
Advertising 25 Gbps support.
Enable 25 Gbps support.
Advertising 40 Gbps support.
Enable 40 Gbps support.
Advertising 50 Gbps support.
Enable 50 Gbps support.
Advertising 100 Gbps support.
Enable 100 Gbps support.
Advertising 200 Gbps support.
Enable 200 Gbps support.
Advertising 400 Gbps support.
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 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:

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

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

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

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.

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 specifications.

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 below).

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).

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) manual.

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 property.)
Minimum SDU 0
Address length 6
MAC type
SAP length -2
Service mode
Broadcast address (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.

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 . 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 .

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.

July 25, 2023 OmniOS