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LMC(4)			 BSD Kernel Interfaces Manual			LMC(4)

NAME
     lmc — device driver for LMC (now SBE) wide-area network interface cards

SYNOPSIS
     To wire this driver into your kernel, add the following line to your ker‐
     nel configuration file:

	   device lmc

     Alternatively, to load this module at boot time, add

	   if_lmc_load="YES"

     to /boot/loader.conf; see loader.conf(5).

     To wire a line protocol into your kernel, add:

	   options NETGRAPH
	   device sppp

     It is not necessary to wire line protocols into your kernel, they can be
     loaded later with kldload(8).  The driver can send and receive raw IP
     packets even if neither SPPP nor Netgraph are configured into the kernel.
     Netgraph and SPPP can both be enabled; Netgraph will be used if the
     rawdata hook is connected.

DESCRIPTION
     This is an open-source UNIX device driver for PCI-bus WAN interface
     cards.  It sends and receives packets in HDLC frames over synchronous
     circuits.	A generic PC plus UNIX plus some LMC / SBE cards makes an open
     router.  This driver works with FreeBSD, NetBSD, OpenBSD, BSD/OS and
     Linux OSs.	 It has been tested on i386 (SMP 32-bit little-endian) and
     Sparc (64-bit big-endian) architectures.

     The lmc driver works with the following cards:

     ·	 SBE wanADAPT-HSSI (LMC5200)

	 High Speed Serial Interface, EIA612/613, 50-pin connector, 0 to 52
	 Mb/s, DTE only.

     ·	 SBE wanADAPT-T3 (LMC5245)

	 T3: two 75-ohm BNC connectors, C-Parity or M13 Framing, 44.736 Mb/s,
	 up to 950 ft.

     ·	 SBE wanADAPT-SSI (LMC1000)

	 Synchronous Serial Interface, V.35, X.21, EIA449, EIA530(A), EIA232,
	 0 to 10 Mb/s, DTE or DCE.

     ·	 SBE wanADAPT-T1E1 (LMC1200)

	 T1 or E1: RJ45 conn, 100 or 120 ohms, T1-ESF-B8ZS, T1-SF-AMI,
	 E1-(many)-HDB3, 1.544 Mb/s or 2.048 Mb/s, up to 6 Kft.

     Cards contain a high-performance PCI interface, an HDLC function and
     either integrated modems (T1, T3) or modem interfaces (HSSI and SSI).

     PCI    The PCI interface is a DEC 21140A "Tulip" Fast Ethernet chip.
	    This chip has an efficient PCI implementation with scatter/gather
	    DMA, and can run at 100 Mb/s full duplex (twice as fast as needed
	    here).

     HDLC   The HDLC functions (ISO-3309: flags, bit-stuffing, CRC) are imple‐
	    mented in a Field Programmable Gate Array (FPGA) which talks to
	    the Ethernet chip through a Media Independent Interface (MII).
	    The hardware in the FPGA translates between Ethernet packets and
	    HDLC frames on-the-fly; think it as a WAN PHY chip for Ethernet.

     Modem  The modem chips are the main differences between cards.  HSSI
	    cards use ECL10K chips to implement the EIA-612/613 interface.  T3
	    cards use a TranSwitch TXC-03401 framer chip.  SSI cards use Lin‐
	    ear Technology LTC1343 modem interface chips.  T1 cards use a
	    BrookTree/Conexant/Mindspeed Bt8370 framer and line interface
	    chip.

     Line protocols exist above device drivers and below internet protocols.
     They typically encapsulate packets in HDLC frames and deal with higher-
     level issues like protocol multiplexing and security.  This driver is
     compatible with several line protocol packages:

     Netgraph	   Netgraph(4) implements many basic packet-handling functions
		   as kernel loadable modules.	They can be interconnected in
		   a graph to implement many protocols.	 Configuration is done
		   from userland without rebuilding the kernel.	 Packets are
		   sent and received through this interface if the driver's
		   rawdata hook is connected, otherwise the ifnet interface
		   (SPPP and RawIP) is used.  ASCII configuration control mes‐
		   sages are not currently supported.

     SPPP	   sppp(4) implements Synchronous-PPP, Frame-Relay and Cisco-
		   HDLC in the kernel.

     RawIP	   This null line protocol, built into the driver, sends and
		   receives raw IPv4 and IPv6 packets in HDLC frames (aka IP-
		   in-HDLC) with no extra bytes of overhead and no state at
		   the end points.

EXAMPLES
   ifconfig and lmcconfig
     The program lmcconfig(8) manipulates interface parameters beyond the
     scope of ifconfig(8).  In normal operation only a few arguments are
     needed:

	   -X  selects the external SPPP line protocol package.
	   -x  selects the built-in RawIP line protocol package.
	   -Z  selects PPP line protocol.
	   -z  selects Cisco-HDLC line protocol.
	   -F  selects Frame-Relay line protocol.

     lmcconfig lmc0
	     displays interface configuration and status.

     lmcconfig lmc0 -D
	     enables debugging output from the device driver only.

     ifconfig lmc0 debug
	     enables debugging output from the device driver and from the line
	     protocol module above it.	Debugging messages that appear on the
	     console are also written to file /var/log/messages.  Caution:
	     when things go very wrong, a torrent of debugging messages can
	     swamp the console and bring a machine to its knees.

   Operation
     Activate a PPP link using SPPP and Netgraph with:

	   ngctl mkpeer lmc0: sppp rawdata downstream
	   ifconfig sppp0 10.0.0.1 10.0.0.2

     Activate a PPP link using only SPPP with:

	   lmcconfig lmc0 -XYZ
	   ifconfig lmc0 10.0.0.1 10.0.0.2

     Activate a Cisco-HDLC link using SPPP and Netgraph with:

	   ngctl mkpeer lmc0: sppp rawdata downstream
	   ifconfig sppp0 10.0.0.1 10.0.0.2 link2

     Activate a Cisco-HDLC link using only SPPP with:

	   lmcconfig lmc0 -XYz
	   ifconfig lmc0 10.0.0.1 10.0.0.2

     Activate a Cisco-HDLC link using only Netgraph with:

	   ngctl mkpeer lmc0: cisco rawdata downstream
	   ngctl mkpeer lmc0:rawdata iface inet inet
	   ifconfig ng0 10.0.0.1 10.0.0.2

     Activate a Frame-Relay DTE link using SPPP with:

	   lmcconfig lmc0 -XYF
	   ifconfig lmc0 10.0.0.1 10.0.0.2

     (SPPP implements the ANSI T1.617 annex D LMI.)

     Activate a Frame-Relay DTE link using Netgraph with:

	   ngctl mkpeer	 lmc0: frame_relay rawdata downstream
	   ngctl mkpeer	 lmc0:rawdata lmi dlci0 auto0
	   ngctl connect lmc0:rawdata dlci0 dlci1023 auto1023
	   ngctl mkpeer	 lmc0:rawdata rfc1490 dlci500 downstream
	   ngctl mkpeer	 lmc0:rawdata.dlci500 iface inet inet
	   ifconfig ng0 10.0.0.1 10.0.0.2
     This is ONE possible Frame Relay configuration; there are many.

     Activate a RAWIP link using only the driver with:

	   lmcconfig lmc0 -x
	   ifconfig lmc0 10.0.0.1 10.0.0.2

     Activate a RAWIP link using Netgraph with:

	   ngctl mkpeer lmc0: iface rawdata inet
	   ifconfig ng0 10.0.0.1 10.0.0.2

     If the driver is unloaded and then loaded, reconnect hooks by:

	   ngctl connect lmc0: ng0: rawdata inet

TESTING
   Testing with Loopbacks
     Testing with loopbacks requires only one card.  Packets can be looped
     back at many points: in the PCI chip, in the modem chips, through a loop‐
     back plug, in the local external equipment, or at the far end of a cir‐
     cuit.

     Activate the card with ifconfig(8):

	   ifconfig lmc0 10.0.0.1 10.0.0.1

     All cards can be looped through the PCI chip.  Cards with internal modems
     can be looped through the modem framer and the modem line interface.
     Cards for external modems can be looped through the driver/receiver
     chips.  See lmcconfig(8) for details.

     Loopback plugs test everything on the card.

     HSSI   Loopback plugs can be ordered from SBE (and others).  Transmit
	    clock is normally supplied by the external modem.  When an HSSI
	    card is operated with a loopback plug, the PCI bus clock must be
	    used as the transmit clock, typically 33 MHz.  When testing an
	    HSSI card with a loopback plug, configure it with lmcconfig(8):

		  lmcconfig lmc0 -a 2

	    “-a 2” selects the PCI bus clock as the transmit clock.

     T3	    Connect the two BNC jacks with a short coax cable.

     SSI    Loopback plugs can be ordered from SBE (only).  Transmit clock is
	    normally supplied by the external modem.  When an SSI card is
	    operated with a loopback plug, the on-board clock synthesizer must
	    be used.  When testing an SSI card with a loopback plug, configure
	    it with lmcconfig(8):

		  lmcconfig lmc0 -E -f 10000000

	    -E puts the card in DCE mode to source a transmit clock.  “-f
	    10000000” sets the internal clock source to 10 Mb/s.

     T1/E1  A loopback plug is a modular plug with two wires connecting pin 1
	    to pin 4 and pin 2 to pin 5.

     One can also test by connecting to a local modem (HSSI and SSI) or NI (T1
     and T3) configured to loop back.  Cards can generate signals to loopback
     remote equipment so that complete circuits can be tested; see
     lmcconfig(8) for details.

   Testing with a Modem
     Testing with a modem requires two cards of different types.

     T3/HSSI  If you have a T3 modem with an HSSI interface (made by Digital
	      Link, Larscom, Kentrox etc.) then use an HSSI card in one
	      machine and a T3 card in the other machine.  The T3 coax cables
	      must use the null modem configuration (see below).

     T1/V.35  If you have a T1 (or E1) modem with a V.35, X.21 or EIA530
	      interface, then use an SSI card in one machine and a T1 card in
	      the other machine.  Use a T1 null modem cable (see below).

   Testing with a Null Modem Cable
     Testing with a null modem cable requires two cards of the same type.

     HSSI   Three-meter HSSI null-modem cables can be ordered from SBE.	 In a
	    pinch, a 50-pin SCSI-II cable up to a few meters will work as a
	    straight HSSI cable (not a null modem cable).  Longer cables
	    should be purpose-built HSSI cables because the cable impedance is
	    different.	Transmit clock is normally supplied by the external
	    modem.  When an HSSI card is connected by a null modem cable, the
	    PCI bus clock can be used as the transmit clock, typically 33 MHz.
	    When testing an HSSI card with a null modem cable, configure it
	    with lmcconfig(8):

		  lmcconfig lmc0 -a 2

	    “-a 2” selects the PCI bus clock as the transmit clock.

     T3	    T3 null modem cables are just 75-ohm coax cables with BNC connec‐
	    tors.  TX OUT on one card should be connected to RX IN on the
	    other card.	 In a pinch, 50-ohm thin Ethernet cables usually work
	    up to a few meters, but they will not work for longer runs —
	    75-ohm coax is required.

     SSI    Three-meter SSI null modem cables can be ordered from SBE.	An SSI
	    null modem cable reports a cable type of V.36/EIA449.  Transmit
	    clock is normally supplied by the external modem.  When an SSI
	    card is connected by a null modem cable, an on-board clock synthe‐
	    sizer is used.  When testing an SSI card with a null modem cable,
	    configure it with lmcconfig(8):

		  lmcconfig lmc0 -E -f 10000000

	    -E puts the card in DCE mode to source a transmit clock.  “-f
	    10000000” sets the internal clock source to 10 Mb/s.

     T1/E1  A T1 null modem cable has two twisted pairs that connect pins 1
	    and 2 on one plug to pins 4 and 5 on the other plug.  Looking into
	    the cable entry hole of a plug, with the locking tab oriented
	    down, pin 1 is on the left.	 A twisted pair Ethernet cable makes
	    an excellent straight T1 cable.  Alas, Ethernet cross-over cables
	    do not work as T1 null modem cables.

OPERATION NOTES
   Packet Lengths
     Maximum transmit and receive packet length is unlimited.  Minimum trans‐
     mit and receive packet length is one byte.

     Cleaning up after one packet and setting up for the next packet involves
     making several DMA references.  This can take longer than the duration of
     a short packet, causing the adapter to fall behind.  For typical PCI bus
     traffic levels and memory system latencies, back-to-back packets longer
     than about 20 bytes will always work (53 byte cells work), but a burst of
     several hundred back-to-back packets shorter than 20 bytes will cause
     packets to be dropped.  This usually is not a problem since an IPv4
     packet header is at least 20 bytes long.

     This device driver imposes no constraints on packet size.	Most operating
     systems set the default Maximum Transmission Unit (MTU) to 1500 bytes;
     the legal range is usually (72..65535).  This can be changed with

	   ifconfig lmc0 mtu 2000

     SPPP enforces an MTU of (128..far-end-MRU) for PPP and 1500 bytes for
     Cisco-HDLC.  RAWIP sets the default MTU to 4032 bytes, but it can be
     changed to anything.

   BPF - Berkeley Packet Filter
     This driver has hooks for bpf(4), the Berkeley Packet Filter.  The line
     protocol header length reported to BPF is four bytes for SPPP and P2P
     line protocols and zero bytes for RawIP.

     To include BPF support into your kernel, add the following line to
     conf/YOURKERNEL:

	   device bpf

     To test the BPF kernel interface, bring up a link between two machines,
     then run ping(8) and tcpdump(1):

	   ping 10.0.0.1

     and in a different window:

	   tcpdump -i lmc0

     The output from tcpdump(1) should look like this:

	   03:54:35.979965 10.0.0.2 > 10.0.0.1: icmp: echo request
	   03:54:35.981423 10.0.0.1 > 10.0.0.2: icmp: echo reply

     Line protocol control packets will appear among the ping(8) packets occa‐
     sionally.

   Device Polling
     A T3 receiver can generate over 100K interrupts per second, This can
     cause a system to “live-lock”: spend all of its time servicing inter‐
     rupts.  FreeBSD has a polling mechanism to prevent live-lock.

     FreeBSD's mechanism permanently disables interrupts from the card and
     instead the card's interrupt service routine is called each time the ker‐
     nel is entered (syscall, timer interrupt, etc.) and from the kernel idle
     loop; this adds some latency.  The driver is permitted to process a lim‐
     ited number of packets.  The percentage of the CPU that can be consumed
     this way is settable.

     See the polling(4) manpage for details on how to enable the polling mode.

   SNMP: Simple Network Management Protocol
     This driver is aware of what is required to be a Network Interface Object
     managed by an Agent of the Simple Network Management Protocol.  The
     driver exports SNMP-formatted configuration and status information suffi‐
     cient for an SNMP Agent to create MIBs for:

	   RFC-2233: Interfaces group,
	   RFC-2496: DS3 interfaces,
	   RFC-2495: DS1/E1 interfaces,
	   RFC-1659: RS232-like interfaces.

     An SNMP Agent is a user program, not a kernel function.  Agents can
     retrieve configuration and status information by using Netgraph control
     messages or ioctl(2) system calls.	 User programs should poll
     sc->cfg.ticks which increments once per second after the SNMP state has
     been updated.

   HSSI and SSI LEDs
     The card should be operational if all three green LEDs are on (the upper-
     left one should be blinking) and the red LED is off.  All four LEDs turn
     on at power-on and module unload.

	   RED	     upper-right    No Transmit clock
	   GREEN     upper-left	    Device driver is alive if blinking
	   GREEN     lower-right    Modem signals are good
	   GREEN     lower-left	    Cable is plugged in (SSI only)

   T1E1 and T3 LEDs
     The card should be operational if the upper-left green LED is blinking
     and all other LEDs are off.  For the T3 card, if other LEDs are on or
     blinking, try swapping the coax cables!  All four LEDs turn on at power-
     on and module unload.

	   RED	     upper-right    Received signal is wrong
	   GREEN     upper-left	    Device driver is alive if blinking
	   BLUE	     lower-right    Alarm Information Signal (AIS)
	   YELLOW    lower-left	    Remote Alarm Indication (RAI)

     The green	   LED blinks if the device driver is alive.
     The red	   LED blinks if an outward loopback is active.
     The blue	   LED blinks if sending AIS, on solid if receiving AIS.
     The yellow	   LED blinks if sending RAI, on solid if receiving RAI.

   E1 Framing
     Phone companies usually insist that customers put a Frame Alignment
     Signal (FAS) in time slot 0.  A Cyclic Redundancy Checksum (CRC) can also
     ride in time slot 0.  Channel Associated Signalling (CAS) uses Time Slot
     16.  In telco-speak signalling is on/off hook, ringing, busy, etc.	 Sig‐
     nalling is not needed here and consumes 64 Kb/s.  Only use E1-CAS formats
     if the other end insists on it!  Use E1-FAS+CRC framing format on a pub‐
     lic circuit.  Depending on the equipment installed in a private circuit,
     it may be possible to use all 32 time slots for data (E1-NONE).

   T3 Framing
     M13 is a technique for multiplexing 28 T1s into a T3.  Muxes use the C-
     bits for speed-matching the tributaries.  Muxing is not needed here and
     usurps the FEBE and FEAC bits.  Only use T3-M13 format if the other end
     insists on it!  Use T3-CParity framing format if possible.	 Loop Timing,
     Fractional T3, and HDLC packets in the Facility Data Link are not sup‐
     ported.

   T1 & T3 Frame Overhead Functions
     Performance Report Messages (PRMs) are enabled in T1-ESF.
     Bit Oriented Protocol (BOP) messages are enabled in T1-ESF.
     In-band loopback control (framed or not) is enabled in T1-SF.
     Far End Alarm and Control (FEAC) msgs are enabled in T3-CPar.
     Far End Block Error (FEBE) reports are enabled in T3-CPar.
     Remote Alarm Indication (RAI) is enabled in T3-Any.
     Loopbacks initiated remotely time out after 300 seconds.

   T1/E1 'Fractional' 64 kb/s Time Slots
     T1 uses time slots 24..1; E1 uses time slots 31..0.  E1 uses TS0 for FAS
     overhead and TS16 for CAS overhead.  E1-NONE has no overhead, so all 32
     TSs are available for data.  Enable/disable time slots by setting 32
     1s/0s in a config param.  Enabling an E1 overhead time slot, or enabling
     TS0 or TS25-TS31 for T1, is ignored by the driver, which knows better.
     The default TS param, 0xFFFFFFFF, enables the maximum number of time
     slots for whatever frame format is selected.  56 Kb/s time slots are not
     supported.

   T1 Raw Mode
     Special gate array microcode exists for the T1/E1 card.  Each T1 frame of
     24 bytes is treated as a packet.  A raw T1 byte stream can be delivered
     to main memory and transmitted from main memory.  The T1 card adds or
     deletes framing bits but does not touch the data.	ATM cells can be
     transmitted and received this way, with the software doing all the work.
     But that is not hard; after all it is only 1.5 Mb/s second!

   T3 Circuit Emulation Mode
     Special gate array microcode exists for the T3 card.  Each T3 frame of
     595 bytes is treated as a packet.	A raw T3 signal can be packetized,
     transported through a packet network (using some protocol) and then
     reconstituted as a T3 signal at the far end.  The output transmitter's
     bit rate can be controlled from software so that it can be frequency
     locked to the distant input signal.

   HSSI and SSI Transmit Clocks
     Synchronous interfaces use two transmit clocks to eliminate skew caused
     by speed-of-light delays in the modem cable.  DCEs (modems) drive ST,
     Send Timing, the first transmit clock.  DTEs (hosts) receive ST and use
     it to clock transmit data, TD, onto the modem cable.  DTEs also drive a
     copy of ST back towards the DCE and call it TT, Transmit Timing, the sec‐
     ond transmit clock.  DCEs receive TT and TD and use TT to clock TD into a
     flip flop.	 TT experiences the same delay as (and has no skew relative
     to) TD.  Thus, cable length does not affect data/clock timing.

SEE ALSO
     tcpdump(1), ioctl(2), bpf(4), kld(4), netgraph(4), polling(4), sppp(4),
     loader.conf(5), ifconfig(8), lmcconfig(8), mpd(8) (ports/net/mpd),
     ngctl(8), ping(8), ifnet(9)

     http://www.sbei.com/

HISTORY
     Ron Crane had the idea to use a Fast Ethernet chip as a PCI interface and
     add an Ethernet-to-HDLC gate array to make a WAN card.  David Boggs
     designed the Ethernet-to-HDLC gate array and PC cards.  We did this at
     our company, LAN Media Corporation (LMC).	SBE Corp. acquired LMC and
     continues to make the cards.

     Since the cards use Tulip Ethernet chips, we started with Matt Thomas'
     ubiquitous de(4) driver.  Michael Graff stripped out the Ethernet stuff
     and added HSSI stuff.  Basil Gunn ported it to Solaris (lost) and Rob
     Braun ported it to Linux.	Andrew Stanley-Jones added support for three
     more cards and wrote the first version of lmcconfig(8).  David Boggs
     rewrote everything and now feels responsible for it.

AUTHORS
     David Boggs ⟨boggs@boggs.palo-alto.ca.us⟩

BSD				 May 20, 2006				   BSD
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