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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 kernel 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 implemented 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 Linear 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 messages 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 loopback plug, in the local external
     equipment, or at the far end of a circuit.

     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 connectors.  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 synthesizer 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 transmit 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 occasionally.

   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 interrupts.  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 kernel is entered (syscall, timer
     interrupt, etc.) and from the kernel idle loop; this adds some latency.  The driver is
     permitted to process a limited 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 sufficient 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.  Signalling 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 public 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
     supported.

   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 second
     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)

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>