IFMEDIA(4)

NAME
ifmedia - network interface media settings

SYNOPSIS
#include <sys/socket.h>
#include <net/if.h>
#include <net/if_media.h>

DESCRIPTION
The ifmedia interface provides a consistent method for querying and setting network interface media and media options. The media is typically set using the ifconfig(8) command.

Currently these link types are supported by ifmedia:

IFM_ETHER
    Ethernet
IFM_FDDI
    FDDI
IFM_IEEE80211
    IEEE802.11 Wireless LAN
IFM_TDM
    Time Division Multiplex
IFM_CARP
    CARP

The following sections describe the possible media settings for each link type. Not all of these are supported by every device; refer to your device's manual page for more information.

The lists below provide the possible names of each media type or option. The first name in the list is the canonical name of the media type or option. Additional names are acceptable aliases for the media type or option.

COMMON MEDIA TYPES AND OPTIONS
The following media types are shared by all link types:

IFM_AUTO
    Autoselect the best media. [autoselect, auto]
IFM_MANUAL
    Jumper or switch on device selects media. [manual]
IFM_NONE
    Deselect all media. [none]

The following media options are shared by all link types:

IFM_FDX
    Place the device into full-duplex mode. This option only has meaning if the device is normally not full-duplex.

IFM_HDX
    Place the device into half-duplex mode. This option only has meaning if the device is normally not half-duplex. [half-duplex, hdx]

IFM_FLOW
    Enable hardware flow control on device.

IFM_FLAG0
    Driver-defined flag. [flag0]

IFM_FLAG1
    Driver-defined flag. [flag1]

IFM_FLAG2
    Driver-defined flag. [flag2]

IFM_LOOP
    Place the device into hardware loopback mode. [loopback, hw-loopback, loop]

MEDIA TYPES AND OPTIONS FOR ETHERNET
The following media types are defined for Ethernet:

IFM_10_T
    10BASE-T, 10Mb/s over unshielded twisted pair, RJ45 connector. [10baseT, UTP, 10UTP]

IFM_10_2
    10BASE2, 10Mb/s over coaxial cable, BNC connector; also called Thinnet. [10base2, BNC, 10BNC]

IFM_10_5
    10BASE5, 10Mb/s over 15-wire cables, DB15 connector; also called AUI. [10base5, AUI, 10AUI]

IFM_10_STP
    10BASE-STP, 10Mb/s over shielded twisted pair, DB9 connector. [10baseSTP, STP, 10STP]

IFM_10_FL
    10BASE-FL, 10Mb/s over fiber optic cables. [10baseFL, FL, 10FL]

IFM_100_TX
    100BASE-TX, 100Mb/s over unshielded twisted pair, RJ45 connector. [100baseTX, 100TX]

IFM_100_FX
    100BASE-FX, 100Mb/s over fiber optic cables. [100baseFX, 100FX]

IFM_100_T4
    100BASE-T4, 100Mb/s over 4-wire (category 3) unshielded twisted pair, RJ45 connector. [100baseT4, 100T4]

IFM_100_T2
    100BASE-T2. [100baseT2, 100T2]

IFM_100_VG
    100VG-AnyLAN. [100baseVG, 100VG]

IFM_1000_SX
    1000BASE-SX, 1Gb/s over multi-mode fiber optic cables. [1000baseSX, 1000SX]

IFM_1000_LX
    1000BASE-LX, 1Gb/s over single-mode fiber optic cables. [1000baseLX, 1000LX]

IFM_1000_CX
    1000BASE-CX, 1Gb/s over shielded twisted pair. [1000baseCX, 1000CX]

IFM_1000_T
    1000BASE-T, 1Gb/s over category 5 unshielded twisted pair, RJ45 connector. [1000baseT, 1000T]

IFM_1000_TX
    Compatibility for 1000BASE-T. [1000baseTX, 1000TX]

IFM_2500_SX
    2500BASE-SX, 2.5Gb/s over multi-mode fiber optic cables. [2500baseSX, 2500SX]

IFM_2500_T
    2500BASE-T, 2.5Gb/s over unshielded twisted pair, RJ45 connector. [2500baseT, 2500BASE-T]

IFM_10G_CX4
    10GBASE-CX4, 10Gb/s over XAUI 4-lane PCS and copper cables. [10GbaseCX4, 10GCX4, 10GBASE-CX4]

IFM_10G_LR
    10GBASE-LR, 10Gb/s over single-mode fiber optic cables. [10GbaseLR, 10GLR, 10GBASE-LR]

IFM_10G_SFP_CU
    10GSFP+Cu, 10Gb/s over SFP+ Direct Attach cables. [10GSFP+Cu, 10GCu]

IFM_10G_SR
    10GBASE-SR, 10Gb/s over multi-mode fiber optic cables. [10GbaseSR, 10GSR, 10GBASE-SR]

IFM_10G_T
    10GBASE-T, 10Gb/s over unshielded twisted pair, RJ45 connector. [10GbaseT, 10GT, 10GBASE-T]

IFM_HPNA_1
    HomePNA 1.0, 1Mb/s over 2-wire (category 3) unshielded twisted pair [HomePNA1, HPNA1]

The following media options are defined for Ethernet:

IFM_ETH_MASTER
    Configure a 1000BASE-T PHY as a MASTER PHY.

IFM_ETH_RXPAUSE
    Receive flow control is enabled on the 1000BASE-T PHY.

IFM_ETH_TXPAUSE
    Transmit flow control is enabled on the 1000BASE-T PHY.

MEDIA TYPES AND OPTIONS FOR FDDI
The following media types are defined for FDDI:

IFM_FDDI_SMF
    Single-mode fiber. [Single-mode, SMF]
IFM_FDDI_MMF
    Multi-mode fiber. [Multi-mode, MMF]
IFM_FDDI_UTP
    Unshielded twisted pair, RJ45 connector. [UTP, CDDI]

The following media options are defined for FDDI:

IFM_FDDI_DA
    Dual-attached station vs. Single-attached station. [dual-attach, das]

MEDIA TYPES AND OPTIONS FOR IEEE802.11 WIRELESS LAN
The following media modes are defined for IEEE802.11 Wireless LAN:

IFM_IEEE80211_11A
    5GHz, OFDM mode. [11a]
IFM_IEEE80211_11B
    2GHz, DSSS/CCK mode. [11b]
IFM_IEEE80211_11G
    2GHz, DSSS/CCK/OFDM mode. [11g]
IFM_IEEE80211_FH
    2GHz, GFSK mode. [fh]
IFM_IEEE80211_11N
    2GHz/5GHz, HT mode. [11n]
IFM_IEEE80211_11AC
    5GHz, VHT mode. [11ac]

The following media options are defined for IEEE802.11 Wireless LAN:

IFM_IEEE80211_ADHOC
    Ad-hoc mode. [adhoc]
IFM_IEEE80211_HOSTAP
    Host Access Point mode. [hostap]
IFM_IEEE80211_IBSS
    IBSS mode. [ibss]
IFM_IEEE80211_IBSSMASTER
    IBSS master mode. [ibssmaster]
IFM_IEEE80211_MONITOR
    Monitor mode. [monitor]

All of the above media options are mutually exclusive. If no media option is used, the wireless interface will try to find an access point to connect to. hostap mode allows the wireless interface to act as an access point for other 802.11 devices. ibss mode is the standardized method of operating without an access point, with each participating device taking on part of the role of an access point. adhoc mode, more accurately known as ad-hoc demo mode, is not specified by the IEEE 802.11 standard and only works with wi(4) devices. Likewise, ibssmaster mode only works with wi(4) devices. On standard 802.11 networks the IBSS master role is assigned automatically.

The channels detailed below are defined for IEEE802.11 Wireless LAN in the 2.4GHz band. The list of available frequencies is dependent on radio regulations specified by regional authorities. Recognized regulatory authorities include the FCC (United States), ETSI (Europe), and Japan. Frequencies in the table are specified in MHz.
Channel | FCC | ETSI | Japan
1 | 2412 | 2412 | 2412
2 | 2417 | 2417 | 2417
3 | 2422 | 2422 | 2422
4 | 2427 | 2427 | 2427
5 | 2432 | 2432 | 2432
6 | 2437 | 2437 | 2437
7 | 2442 | 2442 | 2442
8 | 2447 | 2447 | 2447
9 | 2452 | 2452 | 2452
10 | 2457 | 2457 | 2457
11 | 2462 | 2462 | 2462
12 | - | 2467 | 2467
13 | - | 2472 | 2472
14 | - | - | 2484

The channels do overlap; the bandwidth required for each channel is about 20MHz. When using multiple channels in close proximity, it is suggested that channels be separated by at least 25MHz. In the US, this means that only channels 1, 6, and 11 may be used simultaneously without interference.

Channels in the 5GHz band are too numerous to list here. Regulation of their use, particularly outdoors, varies between countries. Users are advised to inform themselves about applicable regulations before configuring wireless LAN devices for use in the 5GHz band.

The following media types are defined for IEEE802.11 Wireless LAN:

IFM_IEEE80211_FH1
    Frequency Hopping 1Mbps. [FH1]
IFM_IEEE80211_FH2
    Frequency Hopping 2Mbps. [FH2]
IFM_IEEE80211_DS1
    Direct Sequence 1Mbps. [DS1]
IFM_IEEE80211_DS2
    Direct Sequence 2Mbps. [DS2]

The above media types were first introduced in the IEEE 802.11-1997 standard and are used in the 2.4GHz band only. Frequency Hopping Spread Spectrum modulation is incompatible with modern 802.11 networks. Direct Sequence Spread Spectrum modulation (DSSS) frames can still be used if backwards compatibility to 802.11b is enabled.

IFM_IEEE80211_DS5
    Direct Sequence 5.5Mbps. [DS5]
IFM_IEEE80211_DS11
    Direct Sequence 11Mbps. [DS11]
IFM_IEEE80211_DS22
    Direct Sequence 22Mbps. [DS22]

The above media types were first introduced in the IEEE 802.11b-1999 standard and are used in the 2.4GHz band only. They use Complementary Code Keying (CCK) which, compared to frames sent at 1Mbps or 2Mbps, reduces the possible distance between transmitter and receiver.

Modern 802.11 networks remain compatible with 802.11b, even though DSSS frames are incompatible with modern 802.11 frames using OFDM. Co-existence with 802.11b requires OFDM transmitters to either risk frame collisions or “reserve” the medium with a separate preceding transmission that DSSS receivers are able to decode. This causes additional overhead which some 802.11 deployments avoid by deliberately disabling backwards compatibility with 802.11b.

IFM_IEEE80211_OFDM6
    OFDM 6Mbps. [OFDM6]
IFM_IEEE80211_OFDM9
    OFDM 9Mbps. [OFDM9]
IFM_IEEE80211_OFDM12
    OFDM 12Mbps. [OFDM12]
IFM_IEEE80211_OFDM18
    OFDM 18Mbps. [OFDM18]
IFM_IEEE80211_OFDM24
    OFDM 24Mbps. [OFDM24]
IFM_IEEE80211_OFDM36
    OFDM 36Mbps. [OFDM36]
IFM_IEEE80211_OFDM48
    OFDM 48Mbps. [OFDM48]
IFM_IEEE80211_OFDM54
    OFDM 54Mbps. [OFDM54]
IFM_IEEE80211_OFDM72
    OFDM 72Mbps. [OFDM72]

The above media types were first introduced in the IEEE 802.11a-1999 standard for the 5GHz band, and in the IEEE 802.11g-2003 standard for the 2.4GHz band. OFDM with 72Mbps is a proprietary extension and was never standardized by IEEE.

Orthogonal Frequency Division Multiplexing (OFDM) is the current standard modulation technique for 802.11. Each 20MHz channel used by 802.11a and 802.11g provides space for 48 OFDM sub-carriers for data. The sub-carriers use BPSK, QPSK, 16QAM, or 64QAM modulation, combined with a particular coding rate for error correction at the receiver. The coding rate specifies how many data bits in a frame are transmitted without redundancy.
Modulation | Coding Rate | Mbit/s
BPSK | 1/2 | 6
BPSK | 3/4 | 9
QPSK | 1/2 | 12
QPSK | 3/4 | 18
16QAM | 1/2 | 24
16QAM | 3/4 | 36
64QAM | 1/2 | 48
64QAM | 3/4 | 52

The IEEE 802.11n-2009 standard for “High Throughput” (HT) wireless LAN defines additional sub-carriers, modulations, and coding rates. The channel bandwidth for data frame transmissions was optionally extended to 40MHz, with full backwards compatibility to 802.11a/b/g devices which cannot decode 40MHz transmissions. Several additional features were introduced, most notably MIMO (multiple-input, multiple-output). With MIMO, a data stream is divided across up to 4 “spatial streams”, which are transmitted in parallel by a corresponding amount of antennas. Each spatial stream is received with a dedicated antenna, and the spatial streams are de-multiplexed to obtain the original data stream.

802.11n assigns a numeric identifier to all possible combinations of modulation, coding rate, and number of spatial streams. This results in 77 distinct modulation and coding schemes, abbreviated as “MCS”.

ifmedia supports HT_MCS0 up to HT_MCS31:

IFM_IEEE80211_HT_MCSx
    HT OFDM MCS x (where x is in the range 0 - 31, inclusive). [HT-MCSx]

In practice, only MCS-0 to MCS-32 are supported by commonly available devices. The remaining MCS define combinations where distinct spatial streams employ distinct modulations, a feature which was not widely implemented by hardware vendors.

The IEEE 802.11ac-2013 standard for “Very High Throughput” (VHT) wireless LAN operates in the 5GHz band only. The channel bandwidth for data frame transmissions can be up to 160MHz wide. The MCS identifiers were redefined and vastly reduced in number. As a result, only VHT_MCS0 to VHT_MCS9 are defined for 802.11ac:

IFM_IEEE80211_VHT_MCSx
    VHT OFDM MCS x (where x is in the range 0 - 9, inclusive). [VHT-MCSx]

The number of spatial streams is no longer associated with a given VHT MCS identifier and must be specified as a separate “NSS” parameter. This parameter is not yet implemented by ifmedia.

MEDIA TYPES AND OPTIONS FOR TDM
The following media types are defined for TDM:

IFM_TDM_E1
    E1, 2048kb/s HDB3 encoded, G.703 clearchannel serial line. [e1]

IFM_TDM_E1_AMI
    E1, 2048kb/s AMI encoded, G.703 clearchannel serial line. [e1-ami]

IFM_TDM_E1_AMI_G704
    E1, 2048kb/s AMI encoded, G.704 structured serial line. [e1-ami-g.704]

IFM_TDM_E1_G704
    E1, 2048kb/s HDB3 encoded, G.704 structured serial line. [e1-g.704]

IFM_TDM_E1_G704_CRC4
    E1, 2048kb/s HDB3 encoded, G.704 structured serial line with CRC4 checksum. [e1-g.704-crc4]

IFM_TDM_E3
    E3, 34368kb/s HDB3 encoded, G.703 clearchannel serial line. [e3]

IFM_TDM_E3_G751
    E3, 34368kb/s HDB3 encoded, G.751 structured serial line. [e3-g.751]

IFM_TDM_E3_G832
    E3, 34368kb/s HDB3 encoded, G.832 structured serial line. [e3-g.832]

IFM_TDM_T1
    T1, 1536xkb/s B8ZS encoded, extended super frame (ESF) structured serial line. [t1]

IFM_TDM_T1_AMI
    T1, 1536kb/s AMI encoded, super frame (SF) structured serial line. [t1-ami]

IFM_TDM_T3
    T3, 44736kb/s B3ZS, C-bit structured serial line. [t3]

IFM_TDM_T3_M13
    T3, 44736kb/s B3ZS, M13 structured serial line. [t3-m13]

The following media options are defined for TDM:

IFM_TDM_HDLC_CRC16
    Cisco HDLC with 16-bit CRC checksum encoding. [hdlc-crc16]

IFM_TDM_FR_ANSI
    ANSI/ITU Framerelay encoding. [framerelay-ansi, framerelay-itu]

IFM_TDM_FR_CISCO
    Cisco Framerelay encoding. [framerelay-cisco]

IFM_TDM_PPP
    PPP encoding. [ppp]

By default TDM interfaces will use Cisco HDLC encoding with a 32-bit CRC checksum.

The following media modes are defined for TDM:

IFM_TDM_MASTER
    Use local clock source as master clock. [master]

MEDIA TYPES AND OPTIONS FOR CARP
carp(4) does not support any media types or options.

SEE ALSO
netintro(4), ifconfig(8)

HISTORY
The ifmedia interface first appeared in BSD/OS 3.0. The implementation that appeared in NetBSD 1.3 was written by Jonathan Stone and Jason R. Thorpe to be compatible with the BSDI API. It has since gone through several revisions which have extended the API while maintaining backwards compatibility with the original API.

Support for the IEEE802.11 Wireless LAN link type was added in NetBSD 1.5.

Host AP mode was added in OpenBSD 3.1.