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diff --git a/share/man/man4/lmc.4 b/share/man/man4/lmc.4 new file mode 100644 index 000000000000..dc8e47b10eaf --- /dev/null +++ b/share/man/man4/lmc.4 @@ -0,0 +1,766 @@ +.\" +.\" $FreeBSD$ +.\" +.\" Copyright (c) 2002-2005 David Boggs. (boggs@boggs.palo-alto.ca.us) +.\" All rights reserved. +.\" +.\" BSD License: +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" GNU General Public License: +.\" +.\" This program is free software; you can redistribute it and/or modify it +.\" under the terms of the GNU General Public License as published by the Free +.\" Software Foundation; either version 2 of the License, or (at your option) +.\" any later version. +.\" +.\" This program is distributed in the hope that it will be useful, but WITHOUT +.\" ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or +.\" FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for +.\" more details. +.\" +.\" You should have received a copy of the GNU General Public License along with +.\" this program; if not, write to the Free Software Foundation, Inc., 59 +.\" Temple Place - Suite 330, Boston, MA 02111-1307, USA. +.\" +.Dd May 20, 2006 +.Dt LMC 4 +.Os +.\" +.Sh NAME +.\" +.Nm lmc +.Nd device driver for +.Tn LMC +(now +.Tn SBE ) +wide-area network interface cards +.\" +.Sh SYNOPSIS +.\" +To wire this driver into your kernel, +add the following line to your kernel configuration file: +.Bd -ragged -offset indent +.Cd "device lmc" +.Ed +.Pp +Alternatively, to load this module at boot time, add +.Bd -literal -offset indent +if_lmc_load="YES" +.Ed +.Pp +to +.Pa /boot/loader.conf ; +see +.Xr loader.conf 5 . +.Pp +To wire a line protocol into your kernel, add: +.Bd -ragged -offset indent +.Cd "options NETGRAPH" +.Cd "device sppp" +.Ed +.Pp +It is not necessary to wire line protocols into your kernel, +they can be loaded later with +.Xr 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 +.Va rawdata +hook is connected. +.\" +.Sh DESCRIPTION +.\" +This is an open-source +.Ux +device driver for PCI-bus WAN interface cards. +It sends and receives packets in HDLC frames over synchronous circuits. +A generic PC plus +.Ux +plus some +.Tn LMC / SBE +cards makes an +.Em open +router. +This driver works with +.Fx , +.Nx , +.Ox , +.Bsx +and +.Tn Linux +OSs. +It has been tested on i386 (SMP 32-bit little-endian) and Sparc (64-bit big-endian) +architectures. +.Pp +The +.Nm +driver works with the following cards: +.Bl -bullet +.It +SBE wanADAPT-HSSI (LMC5200) +.Pp +High Speed Serial Interface, +EIA612/613, 50-pin connector, +0 to 52 Mb/s, DTE only. +.It +SBE wanADAPT-T3 (LMC5245) +.Pp +T3: two 75-ohm BNC connectors, +C-Parity or M13 Framing, +44.736 Mb/s, up to 950 ft. +.It +SBE wanADAPT-SSI (LMC1000) +.Pp +Synchronous Serial Interface, +V.35, X.21, EIA449, EIA530(A), EIA232, +0 to 10 Mb/s, DTE or DCE. +.It +SBE wanADAPT-T1E1 (LMC1200) +.Pp +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. +.El +.Pp +Cards contain a high-performance +.Sy "PCI" +interface, an +.Sy "HDLC" +function and +either integrated +.Sy "modems" +(T1, T3) or +.Sy "modem" +interfaces (HSSI and SSI). +.Bl -tag -width "Modem" +.It Sy "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). +.It Sy "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. +.It Sy "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. +.El +.Pp +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: +.Bl -tag -width "Generic HDLC" +.It Sy "Netgraph" +.Xr 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 +.Em rawdata +hook is connected, otherwise the ifnet interface (SPPP and RawIP) is used. +ASCII configuration control messages are +.Em not +currently supported. +.It Sy "SPPP" +.Xr sppp 4 +implements Synchronous-PPP, Frame-Relay and Cisco-HDLC in the kernel. +.It Sy "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. +.El +.\" +.Sh EXAMPLES +.\" +.Ss "ifconfig and lmcconfig" +.\" +The program +.Xr lmcconfig 8 +manipulates interface parameters beyond the scope of +.Xr ifconfig 8 . +In normal operation only a few arguments are needed: +.Pp +.Bl -tag -width ".Fl X" -offset indent -compact +.It Fl X +selects the external +SPPP +line protocol package. +.It Fl x +selects the built-in RawIP line protocol package. +.It Fl Z +selects PPP line protocol. +.It Fl z +selects Cisco-HDLC line protocol. +.It Fl F +selects Frame-Relay line protocol. +.El +.Bl -tag -width indent +.It Li "lmcconfig lmc0" +displays interface configuration and status. +.It Li "lmcconfig lmc0 -D" +enables debugging output from the device driver only. +.It Li "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 +.Pa "/var/log/messages" . +.Em Caution : +when things go very wrong, a torrent of debugging messages +can swamp the console and bring a machine to its knees. +.El +.\" +.Ss Operation +.\" +Activate a PPP link using SPPP and Netgraph with: +.Bd -literal -offset indent +ngctl mkpeer lmc0: sppp rawdata downstream +ifconfig sppp0 10.0.0.1 10.0.0.2 +.Ed +.Pp +Activate a PPP link using only SPPP with: +.Bd -literal -offset indent +lmcconfig lmc0 -XYZ +ifconfig lmc0 10.0.0.1 10.0.0.2 +.Ed +.Pp +Activate a Cisco-HDLC link using SPPP and Netgraph with: +.Bd -literal -offset indent +ngctl mkpeer lmc0: sppp rawdata downstream +ifconfig sppp0 10.0.0.1 10.0.0.2 link2 +.Ed +.Pp +Activate a Cisco-HDLC link using only SPPP with: +.Bd -literal -offset indent +lmcconfig lmc0 -XYz +ifconfig lmc0 10.0.0.1 10.0.0.2 +.Ed +.Pp +Activate a Cisco-HDLC link using only Netgraph with: +.Bd -literal -offset indent +ngctl mkpeer lmc0: cisco rawdata downstream +ngctl mkpeer lmc0:rawdata iface inet inet +ifconfig ng0 10.0.0.1 10.0.0.2 +.Ed +.Pp +Activate a Frame-Relay DTE link using SPPP with: +.Bd -literal -offset indent +lmcconfig lmc0 -XYF +ifconfig lmc0 10.0.0.1 10.0.0.2 +.Ed +.Pp +(SPPP implements the ANSI T1.617 annex D LMI.) +.Pp +Activate a Frame-Relay DTE link using Netgraph with: +.Bd -literal -offset indent +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 +.Ed +This is +.Em ONE +possible Frame Relay configuration; there are many. +.Pp +Activate a RAWIP link using only the driver with: +.Bd -literal -offset indent +lmcconfig lmc0 -x +ifconfig lmc0 10.0.0.1 10.0.0.2 +.Ed +.Pp +Activate a RAWIP link using Netgraph with: +.Bd -literal -offset indent +ngctl mkpeer lmc0: iface rawdata inet +ifconfig ng0 10.0.0.1 10.0.0.2 +.Ed +.Pp +If the driver is unloaded and then loaded, reconnect hooks by: +.Pp +.Dl "ngctl connect lmc0: ng0: rawdata inet" +.\" +.Sh TESTING +.\" +.Ss 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. +.Pp +Activate the card with +.Xr ifconfig 8 : +.Pp +.Dl "ifconfig lmc0 10.0.0.1 10.0.0.1" +.Pp +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 +.Xr lmcconfig 8 +for details. +.Pp +Loopback plugs test everything on the card. +.Bl -tag -width ".Sy T1/E1" +.It Sy 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 +.Xr lmcconfig 8 : +.Pp +.Dl "lmcconfig lmc0 -a 2" +.Pp +.Dq Fl a Li 2 +selects the PCI bus clock as the transmit clock. +.It Sy T3 +Connect the two BNC jacks with a short coax cable. +.It Sy 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 +.Xr lmcconfig 8 : +.Pp +.Dl "lmcconfig lmc0 -E -f 10000000" +.Pp +.Fl E +puts the card in DCE mode to source a transmit clock. +.Dq Fl f Li 10000000 +sets the internal clock source to 10 Mb/s. +.It Sy T1/E1 +A loopback plug is a modular plug with two wires +connecting pin 1 to pin 4 and pin 2 to pin 5. +.El +.Pp +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 +.Xr lmcconfig 8 +for details. +.\" +.Ss Testing with a Modem +.\" +Testing with a modem requires two cards of different types. +.Bl -tag -width ".Sy T3/HSSI" +.It Sy 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). +.It Sy 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). +.El +.\" +.Ss Testing with a Null Modem Cable +.\" +Testing with a null modem cable requires two cards of the same type. +.Bl -tag -width ".Sy T1/E1" +.It Sy 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 +.Xr lmcconfig 8 : +.Pp +.Dl "lmcconfig lmc0 -a 2 +.Pp +.Dq Fl a Li 2 +selects the PCI bus clock as the transmit clock. +.It Sy 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 +.Em usually +work up to a few meters, but they will +.Em not +work for longer runs \[em] 75-ohm coax is +.Em required . +.It Sy 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 +.Xr lmcconfig 8 : +.Pp +.Dl "lmcconfig lmc0 -E -f 10000000" +.Pp +.Fl E +puts the card in DCE mode to source a transmit clock. +.Dq Fl f Li 10000000 +sets the internal clock source to 10 Mb/s. +.It Sy 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. +.El +.\" +.Sh OPERATION NOTES +.\" +.Ss Packet Lengths +Maximum transmit and receive packet length is unlimited. +Minimum transmit and receive packet length is one byte. +.Pp +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. +.Pp +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 +.Pp +.Dl "ifconfig lmc0 mtu 2000" +.Pp +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. +.\" +.Ss BPF - Berkeley Packet Filter +.\" +This driver has hooks for +.Xr 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. +.Pp +To include BPF support into your kernel, +add the following line to +.Pa conf/YOURKERNEL : +.Pp +.Dl "device bpf" +.Pp +To test the BPF kernel interface, +bring up a link between two machines, then run +.Xr ping 8 +and +.Xr tcpdump 1 : +.Pp +.Dl "ping 10.0.0.1" +.Pp +and in a different window: +.Pp +.Dl "tcpdump -i lmc0" +.Pp +The output from +.Xr tcpdump 1 +should look like this: +.Bd -literal -offset indent +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 +.Ed +.Pp +Line protocol control packets will appear among the +.Xr ping 8 +packets occasionally. +.\" +.Ss Device Polling +.\" +A T3 receiver can generate over 100K interrupts per second, +This can cause a system to +.Dq live-lock : +spend all of its +time servicing interrupts. +.Fx +has a polling mechanism to prevent live-lock. +.Pp +.Fx Ns '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. +.Pp +See the +.Xr polling 4 +manpage for details on how to enable the polling mode. +.\" +.Ss 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: +.Pp +.Bl -item -offset indent -compact +.It +.%T "RFC-2233: Interfaces group" , +.It +.%T "RFC-2496: DS3 interfaces" , +.It +.%T "RFC-2495: DS1/E1 interfaces" , +.It +.%T "RFC-1659: RS232-like interfaces" . +.El +.Pp +An SNMP Agent is a user program, not a kernel function. +Agents can retrieve configuration and status information +by using +Netgraph control messages or +.Xr ioctl 2 +system calls. +User programs should poll +.Va sc->cfg.ticks +which increments once per second after the SNMP state has been updated. +.\" +.Ss 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. +.Pp +.Bl -column -compact -offset indent "YELLOW" "upper-right" "Software" +.It "RED" Ta "upper-right" Ta "No Transmit clock" +.It "GREEN" Ta "upper-left" Ta "Device driver is alive if blinking" +.It "GREEN" Ta "lower-right" Ta "Modem signals are good" +.It "GREEN" Ta "lower-left" Ta "Cable is plugged in (SSI only)" +.El +.\" +.Ss 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. +.Pp +.Bl -column -compact -offset indent "YELLOW" "upper-right" "Received" +.It "RED" Ta "upper-right" Ta "Received signal is wrong" +.It "GREEN" Ta "upper-left" Ta "Device driver is alive if blinking" +.It "BLUE" Ta "lower-right" Ta "Alarm Information Signal (AIS)" +.It "YELLOW" Ta "lower-left" Ta "Remote Alarm Indication (RAI)" +.El \" YELLOW +.Pp +.Bl -column -compact "The yellow" "LED" +.It "The green" Ta "LED blinks if the device driver is alive." +.It "The red" Ta "LED blinks if an outward loopback is active." +.It "The blue" Ta "LED blinks if sending AIS, on solid if receiving AIS." +.It "The yellow" Ta "LED blinks if sending RAI, on solid if receiving RAI." +.El \" LED +.\" +.Ss E1 Framing +.\" +Phone companies usually insist that customers put a +.Em Frame Alignment Signal +(FAS) in time slot 0. +A Cyclic Redundancy Checksum (CRC) can also ride in time slot 0. +.Em Channel Associated Signalling +(CAS) uses Time Slot 16. +In telco-speak +.Em 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). +.\" +.Ss 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 +.Em not +supported. +.\" +.Ss T1 & T3 Frame Overhead Functions +.\" +.Bl -item -compact +.It +Performance Report Messages (PRMs) are enabled in T1-ESF. +.It +Bit Oriented Protocol (BOP) messages are enabled in T1-ESF. +.It +In-band loopback control (framed or not) is enabled in T1-SF. +.It +Far End Alarm and Control (FEAC) msgs are enabled in T3-CPar. +.It +Far End Block Error (FEBE) reports are enabled in T3-CPar. +.It +Remote Alarm Indication (RAI) is enabled in T3-Any. +.It +Loopbacks initiated remotely time out after 300 seconds. +.El +.\" +.Ss 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 +.Em 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 +.Em not +supported. +.\" +.Ss 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! +.\" +.Ss 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 +.Em packetized , +transported through a +packet network (using some protocol) and then +.Em 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 +.Em frequency locked +to the distant input signal. +.\" +.Ss HSSI and SSI Transmit Clocks +.\" +Synchronous interfaces use two transmit clocks to eliminate +.Em 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 +.Em skew +relative to) TD. +Thus, cable length does not affect data/clock timing. +.\" +.Sh SEE ALSO +.\" +.Xr tcpdump 1 , +.Xr ioctl 2 , +.Xr bpf 4 , +.Xr kld 4 , +.Xr netgraph 4 , +.Xr polling 4 , +.Xr sppp 4 , +.Xr loader.conf 5 , +.Xr ifconfig 8 , +.Xr lmcconfig 8 , +.Xr mpd 8 Pq Pa ports/net/mpd , +.Xr ngctl 8 , +.Xr ping 8 , +.Xr ifnet 9 +.Pp +.Pa http://www.sbei.com/ +.\" +.Sh HISTORY +.\" +.An 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. +.An David Boggs +designed the Ethernet-to-HDLC gate array and PC cards. +We did this at our company, LAN Media Corporation +.Tn (LMC) . +.Tn SBE +Corp.\& acquired +.Tn LMC +and continues to make the cards. +.Pp +Since the cards use Tulip Ethernet chips, we started with +.An Matt Thomas Ns ' +ubiquitous +.Xr de 4 +driver. +.An Michael Graff +stripped out the Ethernet stuff and added HSSI stuff. +.An Basil Gunn +ported it to +.Tn Solaris +(lost) and +.Tn Rob Braun +ported it to +.Tn Linux . +.An Andrew Stanley-Jones +added support +for three more cards and wrote the first version of +.Xr lmcconfig 8 . +.An David Boggs +rewrote everything and now feels responsible for it. +.\" +.Sh AUTHORS +.\" +.An "David Boggs" Aq boggs@boggs.palo-alto.ca.us |