IEEE802.3(5) Standards, Environments, and Macros IEEE802.3(5)

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(1M), whereas properties are visible using the dladm(1M) show-linkprop subcommand. Tunables are properties that can be changed using the dladm(1M) set-linkprop subcommand. A more useful summary of current operational state can be seen with the dladm(1M) show-ether subcommand.

The following statistics are accessible with kstat(1M). 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 below.
adv_cap_1000fdx
Advertises 1000 Mbps full-duplex support.
adv_cap_1000hdx
Advertises 1000 Mbps half-duplex support.
adv_cap_100fdx
Advertises 100 Mbps full-duplex support.
adv_cap_100gfdx
Advertises 100 Gbps support.
adv_cap_100hdx
Advertises 100 Mbps half-duplex support.
adv_cap_100T4
Advertises 100BASE-T4 support.
adv_cap_10fdx
Advertises 10 Mbps full-duplex support.
adv_cap_10gfdx
Advertises 10 Gbps support.
adv_cap_10hdx
Advertises 10 Mbps half-duplex support.
adv_cap_2500fdx
Advertises 2.5 Gbps support.
adv_cap_50gfdx
Advertises 50 Gbps support.
adv_cap_40gfdx
Advertises 40 Gbps support.
adv_cap_25gfdx
Advertises 25 Gbps support.
adv_cap_5000fdx
Advertises 5 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_1000fdx
Device supports 1000 Mbps full-duplex.
cap_1000hdx
Device supports 1000 Mbps half-duplex.
cap_100fdx
Device supports 100 Mbps full-duplex.
cap_100gfdx
Device supports 100 Gbps.
cap_100hdx
Device supports 100 Mbps half-duplex.
cap_100T4
Device supports 100BASE-T4.
cap_10fdx
Device supports 10 Mbps full-duplex.
cap_10gfdx
Device supports 10 Gpbs.
cap_10hdx
Device supports 10 Mbps half-duplex.
cap_2500fdx
Device supports 2.5 Gbps.
cap_50gfdx
Device supports 50 Gpbs.
cap_40gfdx
Device supports 40 Gpbs.
cap_25gfdx
Device supports 25 Gpbs.
cap_5000fdx
Device supports 5 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_1000fdx
Peer supports 1000 Mbps full-duplex.
lp_cap_1000hdx
Peer supports 1000 Mbps half-duplex.
lp_cap_100fdx
Peer supports 100 Mbps full-duplex.
lp_cap_100gfdx
Peer supports 100 Gbps full-duplex.
lp_cap_100hdx
Peer supports 100 Mbps half-duplex.
lp_cap_100T4
Peer supports 100BASE-T4.
lp_cap_10fdx
Peer supports 10 Mbps full-duplex.
lp_cap_10gfdx
Peer supports 10 Gbps.
lp_cap_10hdx
Peer supports 10 Mbps half-duplex.
lp_cap_2500fdx
Peer supports 2.5 Gbps.
lp_cap_5000fdx
Peer supports 5 Gbps.
lp_cap_50gfdx
Peer supports 50 Gbps.
lp_cap_40gfdx
Peer supports 40 Gbps.
lp_cap_25gfdx
Peer supports 25 Gbps.
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. Values are as follows:
0 Unknown or undefined.
1 None.
2 10 Mbps
3 100BASE-T4
4 100BASE-X
5 100BASE-T2
6 1000BASE-X
7 1000BASE-T

The following parameters are accessible with dladm(1M). Some of these are normally read-only. Other properties that are not specific to IEEE 802.3 / Ethernet links are also available via dladm(1M), 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.
adv_10gfdx_cap
Advertising 10 Gbps support.
en_10gfdx_cap
Enable 10 Gbps support.
adv_1000fdx_cap
Advertising 1000 Mbps full-duplex support.
en_1000fdx_cap
Enable 1000 Mbps full-duplex.
adv_1000hdx_cap
Advertising 1000 Mbps half-duplex support.
en_1000hdx_cap
Enable 1000 Mbps half-duplex.
adv_100fdx_cap
Advertising 100 Mbps full-duplex support.
en_100fdx_cap
Enable 100 Mbps full-duplex.
adv_100hdx_cap
Advertising 100 Mbps half-duplex support.
en_100hdx_cap
Enable 100 Mbps half-duplex.
adv_10fdx_cap
Advertising 10 Mbps full-duplex support.
en_10fhdx_cap
Enable 100 Mbps full-duplex.
adv_10hdx_cap
Advertising 10 Mbps half-duplex support.
en_10fhdx_cap
Enable 10 Mbps half-duplex.

With modern devices, auto-negotiation is normally handled automatically. With 10 Gbps and 1000 Gbps, 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:

  • 10 Gbps (10gfdx)
  • 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 en_ property in dladm(1M).

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.

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.

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(1M).

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(1M) manual.
The correct method for applications to access Ethernet devices directly is to use the DLPI. See dlpi(7P) 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.

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(1M) 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(1M) command, and driver.conf(4) files could be used to do this. These methods are deprecated in favor of dladm(1M) 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.

dladm(1M), ifconfig(1M), kstat(1M), ndd(1M), netstat(1M), libdlpi(3LIB), driver.conf(4), dlpi(7P)

IEEE 802.3: Ethernet, IEEE Standards Association.

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

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

November 23, 2016 OmniOS