man/man7/ieee802.3.7

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.Dd "July 25, 2023"
.Dt IEEE802.3 7
.Os
.Sh NAME
.Nm ieee802.3
.Nd IEEE 802.3 Ethernet parameters and statistics
.Sh DESCRIPTION
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.
.
.Lp
Values that are statistics are visible
.Xr kstat 8 ,
whereas properties are visible using the
.Xr dladm 8
.Sy show-linkprop
subcommand.
Tunables are properties that can be changed using the
.Xr dladm 8
.Sy set-linkprop
subcommand.
A more useful summary of current operational state can be seen with the
.Xr dladm 8
.Sy show-ether
subcommand.
.
.Ss Statistics
The following statistics are accessible with
.Xr 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
.Dq Sy 64
appended.
For example,
.Sy ipackets64
is the 64-bit version of the
.Sy ipackets
statistic.
These are indicated with the special suffix
.Op Sy 64
in the table below.
.
.Bl -tag -width tx_late_collisions
.It Sy adv_cap_10hdx
Advertises 10 Mbps half-duplex support.
.It Sy adv_cap_10fdx
Advertises 10 Mbps full-duplex support.
.It Sy adv_cap_100hdx
Advertises 100 Mbps half-duplex support.
.It Sy adv_cap_100T4
Advertises 100BASE-T4 support.
.It Sy adv_cap_100fdx
Advertises 100 Mbps full-duplex support.
.It Sy adv_cap_1000hdx
Advertises 1000 Mbps half-duplex support.
.It Sy adv_cap_1000fdx
Advertises 1000 Mbps full-duplex support.
.It Sy adv_cap_2500fdx
Advertises 2.5 Gbps support.
.It Sy adv_cap_5000fdx
Advertises 5 Gbps support.
.It Sy adv_cap_10gfdx
Advertises 10 Gbps support.
.It Sy adv_cap_25gfdx
Advertises 25 Gbps support.
.It Sy adv_cap_40gfdx
Advertises 40 Gbps support.
.It Sy adv_cap_50gfdx
Advertises 50 Gbps support.
.It Sy adv_cap_100gfdx
Advertises 100 Gbps support.
.It Sy adv_cap_200gfdx
Advertises 200 Gbps support.
.It Sy adv_cap_400gfdx
Advertises 400 Gbps support.
.It Sy adv_cap_autoneg
Advertises auto-negotiation support.
.It Sy adv_cap_asmpause
Advertises asymmetric flow control support.
.It Sy adv_cap_pause
Advertises flow control support.
.It Sy adv_rem_fault
Remote fault status sent to peer.
.It Sy align_errors
Mis-aligned frames received.
.It Sy brdcstrcv
Broadcast frames received.
.It Sy brdcstxmt
Broadcast frames transmitted.
.It Sy cap_10hdx
Device supports 10 Mbps half-duplex.
.It Sy cap_10fdx
Device supports 10 Mbps full-duplex.
.It Sy cap_100hdx
Device supports 100 Mbps half-duplex.
.It Sy cap_100T4
Device supports 100BASE-T4.
.It Sy cap_100fdx
Device supports 100 Mbps full-duplex.
.It Sy cap_1000hdx
Device supports 1000 Mbps half-duplex.
.It Sy cap_1000fdx
Device supports 1000 Mbps full-duplex.
.It Sy cap_2500fdx
Device supports 2.5 Gbps.
.It Sy cap_5000fdx
Device supports 5 Gbps.
.It Sy cap_10gfdx
Device supports 10 Gbps.
.It Sy cap_25gfdx
Device supports 25 Gbps.
.It Sy cap_40gfdx
Device supports 40 Gbps.
.It Sy cap_50gfdx
Device supports 50 Gbps.
.It Sy cap_100gfdx
Device supports 100 Gbps.
.It Sy cap_200gfdx
Device supports 200 Gbps.
.It Sy cap_400gfdx
Device supports 400 Gbps.
.It Sy cap_asmpause
Device supports asymmetric flow control.
.It Sy cap_autoneg
Device supports auto-negotiation.
.It Sy cap_pause
Device supports symmetric flow control.
.It Sy cap_rem_fault
Device supports remote fault notification.
.It Sy carrier_errors
Frames dropped due to loss of link.
.It Sy collisions
Collisions.
.It Sy defer_xmts
Transmits deferred due to link activity.
.It Sy ex_collisions
Frames dropped due to too many collisions.
.It Sy fcs_errors
Frames received with bad frame checksum.
.It Sy first_collisions
Frames with at least one collision.
.It Sy ierrors
Receive errors.
.It Sy ifspeed
Link speed in bits per second.
.It Sy ipackets Ns Op Sy 64
Frames received successfully.
.It Sy jabber_errors
Jabber errors.
.It Sy link_asmpause
Asymmetric flow control; works together with
.Sy link_pause .
See the description for it below.
.It Sy link_autoneg
Link was auto-negotiated.
.It Sy link_duplex
Link duplex status, values as follows:
.Bl -column "0" infinity
.It 0 Ta Unknown.
.It 1 Ta Half-duplex.
.It 2 Ta Full-duplex.
.El
.It Sy link_pause
Link flow control available; works together with
.Sy link_asmpause .
The meanings of these bits are:
.Bl -column "pause" "asmpause"
.It Sy pause Ta Sy asmpause Ta Sy meaning
.It 0 Ta 0 Ta "No flow control."
.It 1 Ta 0 Ta Symmetric flow control.
.It 0 Ta 1 Ta Honor received pause frames.
.It 1 Ta 1 Ta Send pause frames when congested.
.El
.It Sy link_state
Link state; 0 for down, 1 for up.
.It Sy link_up
Link is up if 1.
.It Sy lp_cap_10hdx
Peer supports 10 Mbps half-duplex.
.It Sy lp_cap_10fdx
Peer supports 10 Mbps full-duplex.
.It Sy lp_cap_100T4
Peer supports 100BASE-T4.
.It Sy lp_cap_100hdx
Peer supports 100 Mbps half-duplex.
.It Sy lp_cap_100fdx
Peer supports 100 Mbps full-duplex.
.It Sy lp_cap_1000fdx
Peer supports 1000 Mbps full-duplex.
.It Sy lp_cap_1000hdx
Peer supports 1000 Mbps half-duplex.
.It Sy lp_cap_2500fdx
Peer supports 2.5 Gbps.
.It Sy lp_cap_5000fdx
Peer supports 5 Gbps.
.It Sy lp_cap_10gfdx
Peer supports 10 Gbps.
.It Sy lp_cap_25gfdx
Peer supports 25 Gbps.
.It Sy lp_cap_40gfdx
Peer supports 40 Gbps.
.It Sy lp_cap_50gfdx
Peer supports 50 Gbps.
.It Sy lp_cap_100gfdx
Peer supports 100 Gbps full-duplex.
.It Sy lp_cap_200gfdx
Peer supports 200 Gbps full-duplex.
.It Sy lp_cap_400gfdx
Peer supports 400 Gbps full-duplex.
.It Sy lp_cap_asmpause
Peer supports asymmetric flow control.
.It Sy lp_cap_autoneg
Peer supports auto-negotiation.
.It Sy lp_cap_pause
Peer advertises flow control support.
.It Sy lp_rem_fault
Peer announces a remote fault.
.It Sy macrv_errors
Generic receive errors.
.It Sy macxmt_errors
Generic transmit errors.
.It Sy multi_collisions
Frames with more than one collision.
.It Sy multircv
Multicast frames received.
.It Sy multixmt
Multicast frames transmitted.
.It Sy norcvbuf
Receive frames dropped due to lack of resources.
.It Sy noxmtbuf
Transmit frames dropped due to lack of resources.
.It Sy obytes Ns Op Sy 64
Bytes (octets) transmitted successfully.
.It Sy oerrors
Transmit errors.
.It Sy oflo
Overflow errors.
.It Sy opackets Ns Op Sy 64
Frames successfully transmitted.
.It Sy promisc
Interface is in promiscuous mode.
.It Sy rbytes Ns Op Sy 64
Bytes (octets) received successfully.
.It Sy runt_errors
Frames received that were too short.
.It Sy sqe_errors
Squelch errors.
.It Sy toolong_errors
Frames received that were too long.
.It Sy tx_late_collisions
Late collisions on transmit.
.It Sy uflo
Underflow errors.
.It Sy unknowns
Frames received with no local recipient.
.It Sy xcvr_addr
Transceiver address.
.It Sy xcvr_id
Transceiver vendor and device ID.
.It Sy xcvr_inuse
Identifies the type of transceiver in use.
Ethernet-specific media values are defined in
.In sys/mac_ether.h .
For more information see the section on
.Dv MAC_PROP_MEDIA
in
.Xr mac 9E .
.El
.Ss Properties
The following parameters are accessible with
.Xr 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
.Xr dladm 8 ,
and are documented in its man page rather than here.
.
.Bl -tag -width adv_1000hdx_cap
.It Sy speed
Link speed, in Mbps per second (dladm only).
.It Sy duplex
Link duplex, either "full" or "half".
.It Sy state
Link state, either "up" or "down".
.It Sy mtu
Maximum link frame size in bytes.
See
.Sx Jumbo Frames .
.It Sy flowctrl
Flow control setting, one of
.Dq no ,
.Dq tx ,
.Dq rx ,
or
.Dq bi .
See
.Sx Flow Control .
.It Sy fec
FEC settings, one of
.Dq none ,
.Dq auto ,
.Dq rs ,
or
.Dq base-r .
See
.Sx Forward Error Correction .
.It Sy adv_10hdx_cap
Advertising 10 Mbps half-duplex support.
.It Sy en_10fhdx_cap
Enable 10 Mbps full-duplex.
.It Sy en_10fhdx_cap
Enable 10 Mbps half-duplex.
.It Sy adv_10fdx_cap
Advertising 10 Mbps full-duplex support.
.It Sy adv_100hdx_cap
Advertising 100 Mbps half-duplex support.
.It Sy en_100hdx_cap
Enable 100 Mbps half-duplex.
.It Sy adv_100fdx_cap
Advertising 100 Mbps full-duplex support.
.It Sy en_100fdx_cap
Enable 100 Mbps full-duplex.
.It Sy adv_1000hdx_cap
Advertising 1000 Mbps half-duplex support.
.It Sy en_1000hdx_cap
Enable 1000 Mbps half-duplex.
.It Sy adv_1000fdx_cap
Advertising 1000 Mbps full-duplex support.
.It Sy en_1000fdx_cap
Enable 1000 Mbps full-duplex.
.It Sy adv_10gfdx_cap
Advertising 10 Gbps support.
.It Sy en_10gfdx_cap
Enable 10 Gbps support.
.It Sy adv_25gfdx_cap
Advertising 25 Gbps support.
.It Sy en_25gfdx_cap
Enable 25 Gbps support.
.It Sy adv_40gfdx_cap
Advertising 40 Gbps support.
.It Sy en_40gfdx_cap
Enable 40 Gbps support.
.It Sy adv_50gfdx_cap
Advertising 50 Gbps support.
.It Sy en_50gfdx_cap
Enable 50 Gbps support.
.It Sy adv_100gfdx_cap
Advertising 100 Gbps support.
.It Sy en_100gfdx_cap
Enable 100 Gbps support.
.It Sy adv_200gfdx_cap
Advertising 200 Gbps support.
.It Sy en_200gfdx_cap
Enable 200 Gbps support.
.It Sy adv_400gfdx_cap
Advertising 400 Gbps support.
.It Sy en_400gfdx_cap
Enable 400 Gbps support.
.El
.Ss Auto-negotiation
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
.Em 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.
.Lp
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:
.Lp
.Bl -bullet -offset indent -compact
.It
400 Gbps (400gfdx)
.It
200 Gbps (200gfdx)
.It
100 Gbps (100gfdx)
.It
50 Gbps (50gfdx)
.It
40 Gbps (40gfdx)
.It
25 Gbps (25gfdx)
.It
10 Gbps (10gfdx)
.It
5 Gbps (5000fdx)
.It
2.5 Gbps (2500fdx)
.It
1000 Mbps full-duplex (1000fdx)
.It
1000 Mbps half-duplex (1000hdx)
.It
100 Mbps full-duplex (100fdx)
.It
100BASE-T4 (100T4)
.It
100 Mbps half-duplex (100hdx)
.It
10 Mbps full-duplex (10fdx)
.It
10 Mbps half-duplex (10hdx)
.El
.Lp
Advertisement of these modes can be enabled or disabled by setting the
appropriate
.Sy en_
property in
.Xr dladm 8 .
.Lp
Auto-negotiation may also be disabled, by setting the
.Sy adv_autoneg_cap
property to 0.
In this case, the highest enabled link mode (using the above list) is
.Dq forced
for the link.
.Ss 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.
.Lp
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.
.Lp
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.
.Lp
The flow control mode used is driven by the
.Sy flowctrl
property.
It has the following meanings:
.Lp
.Bl -column -compact -offset indent Dv
.It Dq no Ta Neither send, nor honor pause frames.
.It Dq tx Ta Send pause frames, provided that the peer can support them,
but do not honor them.
.It Dq rx Ta Receive and honor pause frames.
.It Dq bi Ta Both send and receive (and honor) pause frames.
.El
.Lp
The statistics for flow control
.Po Sy adv_cap_pause , adv_cap_asmpause , lp_cap_pause , lp_cap_asmpause ,
.Sy link_pause ,
and
.Sy link_asmpause
.Pc
are based on the properties exchanged in the auto-negotiation and are
confusing as a result.
Administrators are advised to use the
.Sy flowctrl
property instead.
.
.Ss Forward Error Correction
Beginning with 25 Gbit per-lane Ethernet
.Pq 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:
.Bl -tag -width Ds
.It rs
This is a Reed-Solomon based code
.Po
.Pf RS Pq 514,528
.Pc
This is considered the stronger of the two FEC modes and operates on
both a per-lane basis and the entire channel.
.It 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.
.It auto
This indicates that the device should perform auto-negotiation to
determine the type of FEC that should be used.
.It none
This indicates the devie should not use FEC at all.
.El
.Pp
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.
.Pp
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.
.Ss 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.
.Lp
Note that the use of frames carrying more than 1500 bytes of payload is
not standardized, even though it is common practice.
.Lp
The
.Sy 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
.Sx Virtual LANs
below).
.Lp
Care must be taken to ensure that all communication parties agree on the same
size, or communication may cease to function properly.
.Lp
Note that the
.Sy 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
.Xr ifconfig 8 .
.
.Ss 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
.Xr dladm 8
manual.
.
.Ss Data Link Provider Interface (DLPI) Details
.
The correct method for applications to access Ethernet devices directly
is to use the DLPI.
See
.Xr dlpi 4P
and
.Xr libdlpi 3LIB
for further information.
.Lp
The following DLPI parameters are presented to applications.
.Bl -column -offset indent "Broadcast address"
.It Maximum SDU Ta 1500 (or larger, as determined by the Sy mtu No property.)
.It Minimum SDU Ta 0
.It Address length Ta 6
.It MAC type Ta Dv DL_ETHER
.It SAP length Ta -2
.It Service mode Ta Dv DL_CLDLS
.It Broadcast address Ta Li ff:ff:ff:ff:ff:ff No (6 bytes with all bits set)
.El
.Lp
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.
.Lp
Ethernet drivers on the support both DLPI style 1 and style 2 operation.
Additionally, it is possible to configure provide
.Dq vanity
names to interfaces using the
.Xr dladm 8
.Sy rename-link
subcommand.
Such vanity names are only accessible using DLPI style 1.
.Sh NOTES
There may be other mechanisms available to configure link layer properties.
Historically the
.Xr ndd 8
command, and
.Xr driver.conf 5
files could be used to do this.
These methods are deprecated in favor of
.Xr dladm 8
properties.
.
.Sh INTERFACE STABILITY
When present, the statistics and properties presented here
are
.Sy Committed .
However, note that not every Ethernet device supports all of these,
and some devices may support additional statistics and properties.
.Lp
The DLPI and IEEE 802.3 itself are
.Sy Standard .
.Sh SEE ALSO
.Xr libdlpi 3LIB ,
.Xr dlpi 4P ,
.Xr driver.conf 5 ,
.Xr dladm 8 ,
.Xr ifconfig 8 ,
.Xr kstat 8 ,
.Xr ndd 8 ,
.Xr netstat 8
.Rs
.%T IEEE 802.3: Ethernet
.%Q IEEE Standards Association
.Re
.Rs
.%B Data Link Provider Interface (DLPI)
.%Q The Open Group
.%D 1997
.Re
.Rs
.%B STREAMs Programming Guide
.%Q Sun Microsystems, Inc.
.%D January 2005
.Re