================================================================================ Telebit Corporation Revision 1.02 13 DEC 1990 ================================================================================ TELEBIT PEP MODEM CONSIDERATIONS FOR ADVERSE COMMUNICATIONS LINKS By TELEBIT CORPORATION Technical Support The Telebit modem's advanced multi-carrier design, utilizing the patented Packetized Ensemble Protocol (PEP), is ideally suited to operate over international circuits which can often cause insurmountable obstacles to standard "slow" or other high speed modems. There are several things to consider when attempting to establish a link over such a line that should help insure reliable connections with the maximum performance possible under the conditions. INTERNATIONAL CALLS When originating a call and dialing internationally, you should increase the time to wait for carrier from the default of 40 seconds, to about 80 seconds, to allow more time to dial, get a connection to the other end and then negotiate carrier. This is controlled in the modem by the S7 register, which can be set any- where up to 255 seconds as needed. Your software package may also have a parameter that controls the time to wait for carrier so be sure to set that accordingly. Leave the answering modem S7=40, because if 40 seconds has elapsed without establishing a connection, it is likely that it will fail to do so and it would be better to redial. If possible, set S50 =255 to force the modem to only send PEP connect tones. This will not allow the answering modem to connect at any slow speed. It is usually good to set S110=1, (only on a TrailBlazer Plus, T2000, or T2500) so the modems can negotiate to do data compression. Do not use the data compression feature if the files have been compressed prior to transmission. If you are going to use Kermit, Xmodem or UUCP to do a file transfer, set the S111 to the appropriate value to allow the modems to negotiate for protocol support. It is recommended that you use one of the supported protocols to optimize throughput to the maximum level the telephone line will allow. Zmodem and variations might also attain good results without any protocol support, but there is no need for complex sliding window protocols with the protocol support feature in TELEBIT modems. Echo suppression equipment on long distance circuits can cause timing delays that disrupt our packet transmission. The modem can be configured to compensate for this problem if S121=1. This is a negotiated feature, which means that it is not required to set S121 on both modems, only one of the two need be set to allow us to compensate for echo suppression. Experimentation is about the only way to determine if echo supression equipment is present on the circuits. If you seem to be able to operate without setting S121, don't change it. But if you are experiencing problems with frequent long delays in data transmission, try setting this and see if there is an improvement. CELLULAR, MICROWAVE, AND SATELLITE CALLS In satellite and microwave channels, Compansion may be an obstacle to obtaining good data throughput. Compansion is the Compression and Expansion (amplification) of an analog signal over a voice or data communications link. The use of Compansion to ensure the best voice quality possible over a satellite or microwave link may cause PEP packets to be "clipped" during a data connection. Uncompanded communications channels may be available from the satellite or microwave service provider. Experimentation is the best way to determine which type of service will best suit your application. The S121, S120, and J6 S36 registers will allow for a reliable and effective connection over either of these services. In cellular communications channels Compansion may also be a factor, but the leading obstacle is usually signal strength. Due to the use of passive or active RJ-11 adapters, the modem signal strength is crucial to maintaining a reliable and effective connection. The CellBlazer product has software registers (S175) which set signal strength on the modem. Other TELEBIT modems have the ability to set signal strength via an internal gain resistor or an external (RJ-45 connector) gain resistor. The S121, S120, and J6 S36 registers, in combination with the proper signal strength adjustments, will provide a reliable and effective connection over cellular channels. The communications equipment providing the RJ-11/RJ-45 interface to the modem may also be an important factor in cellular, microwave, or satellite connections. Active RJ-11/RJ-45 adapters are highly recommended for cellular use via cellular telephones. The satellite tracking mechanisms of a ship/earth station terminal may be just as important as its signal processing and transmission capabilities. The ability to adjust signal strength for any modem interfacing unit, along with the S121, S120, and J6 S36 registers, will provide a reliable and effective communications link. DIAGNOSING AND SOLVING MODEM COMMUNICATIONS PROBLEMS Some indications that your TELEBIT modem is experiencing difficulty in communicating are: 1) Inability to connect after several attempts at "Handshaking" (the PEP connect tones) resulting in a NO CARRIER status. 2) After connection, frequent pauses during which there is no response nor data received for 10 to 30 seconds at a time. 3) Disconnection after a delay of 60 seconds with no data transmission. In many cases, depending on the types of communications link, it is possible to "fine-tune" PEP to allow for more reliable connections and maximum performance. TELEBIT Technical Support prefers to troubleshoot these situations on a case by case basis. It is therefore recommended that they be consulted prior to modifying your TELEBIT modem modulation characteristics. TELEBIT Technical Support should be able correct most, if not all, of these problems. Contact TELEBIT Technical Support at 408-734-5200 (U.S.) or 1-800-TELEBIT (U.S.) or one of the TELEBIT international offices listed in this document. Many international calls will connect without any problems, but if difficulties in connecting or maintaining connections occur, the following settings are recommended. The three levels are in order of severity of line difficulties, from minor to major. Level 1. AT S120=12 J6 S36=1 Generally, Level 1 will have a very minor impact on performance, both in interactive use and file transfer. It is useful, however, for achieving a degree of reliability, even when the communication lines are very good. The J6 S36 register may be incremented up to 4 in order to better survive adverse line conditions. Level 2 AT S120=2 J6 S36=2 Level 2 will impact interactive performance severely while file transfers remain at close to normal performance. Level 3 AT S120=3 J6 S36=3 Level 3 is a last resort setting which will severly impact interactive performance and limit file transfer speeds to a maximum of 6000 bps. Data compression, S110=1, can make up some of the difference, but only if the data has not been previously compressed. ------------- Additional level: AT S120=2 J6 S36=4 |TOT REVIM ZADAET USTANOWO^NYJ TON S oboih KONCOW SWQZI, W TO WREMQ KAK S120=2 GASIT RABOTU S MIKRO-PAKETAMI. --------------- The S121=1 register will enable compensation for echo cancellation on the circuit, and can be enabled at any of these levels. If a stand alone modem is in use, the special register commands should be sent to the modem and saved to Non-Volatile Memory, by sending the save command "AT&W". In situations where a mixture of local and long distance calls are being placed, it is recommended that these special settings be made in a modem initialization file or that the A/B selection switch be used. THE PEP FINE TUNING REGISTERS The S120 register is a non-documented register that governs your PEP packet size. The modem operates on three different packet sizes: Micro Packets which are sent very frequently, Small Packets which are sent a little less frequent, and Long Packets which the modem automatically switches to when a file transfer begins. Sometimes over long-distance phone lines the modem has trouble staying in Micro Packet mode and has to perform a re-train, which you can hear by leaving your speaker on all the time with "ATM2". This is what you sometimes experience when you get long delays before you receive any data. Setting S120=12 eliminates Micro Packets and uses Small or Long Packets depending on the size of the file to be transmitted. Setting S120=2 eliminates Small Packets and only uses Long Packets. Configuring your modem to the proper settings is dependent on how bad the line quality is. The J6 S36 register adds a little tone in front of the packet being transmitted to keep the front of the PEP packet from getting "clipped off" during a long distance file transfer over adverse line conditions. Thus, if anything gets "clipped off" it will be this tone and not the data-carrying PEP packet. The more you increase the value of S36 the more tone you add to the front of the packet. Again, turn your speaker on to listen to the tones and set this register depending on how bad the line quality is. As a word of caution, J6 S36 should not be set above 4. This will result in a tone that is equal in size to the PEP packet and a 50% or more reduction in data throughput. The S120 and the J6 S36 are completely independent of each other. If S120 is set to a value other then default (S120=0) on one side only, the other side automatically negotiates to that value (i.e. setting S120=12 will force the other side to negotiate a value of S120=12 also). On the other hand J6 S36 is completely independent and must be set at each side. Sometimes it is only necessary to set one side, or which ever side has the most trouble transmitting data (answering modem is active vs. calling modem is passive). Please read your TELEBIT product reference manual for information on the S70-S76 registers and their functions. This will assist you in assessing which modem will need these registers set in accordance to its "instantaneous transmit rate" (ATS70?). Do not set S110=1 to enable Data Compression if the data you are transmitting has been previously compressed. Data compression on top of data compression adds too much overhead and will actually lower throughput on file transfers. UNIX In UNIX UUCP environments, it is recommended that the "chat script" in the L.sys file (Version2 UUCP) or the Dialers file (HoneyDANBER UUCP) be used to set these registers on a per site basis. These registers may also be added to "intelligent" dialers, such as the the dialTBIT dialer provided by SCO in their XENIX and UNIX systems. Here are some register entry examples: /usr/lib/uucp/Dialers (/etc/uucp/Dialers) This entry is one line: tbpepmod =W-, "" A\pA\pT OK ATS50=255S52=2S120=12J6S36=2DT\T CONNECT /usr/lib/uucp/L.sys (/etc/uucp/L.sys) This entry is one line: hostname Any cua0 19200 cua0 "" ATX0S50=255S52=2S120=12J6S36=2\r OK ATDNNNNNNNNNN\r CONNECT "" ""-\r-login: \r login: Uyoursysname ssword: XXXXXXXX /usr/lib/uucp/dialTBIT.c This section of the SCO dialTBIT.c dialer is the only one modified. The option is invoked via the dialing string in the L.sys or Systems file, with the appropriate entry to the L-devices or Devices file. LINES 204-209 [MODIFICATION]: /* * MDECHOSUP - Enable Echo Supressor Compensation * * S121=1 - Enable Echo Suppressor Compensation * S120=12 - Enable Long and Short PEP packets only * J6s36=2 - Enable calibration tone on the PEP packets */ #define MDECHOSUP "ATS120=12J6S36=2S121=1\r" /usr/lib/uucp/L.sys The "echo suppression" option is invoked by the "e" option in the following manner: hostname Any ACU 19200 NNNNNNNucpe "" \d ogin: Usys word: XXXXXX NOTES: u = UUCP protocol support enabled (S111=30) c = Data compression enabled (S110=1 ) p = PEP connection only enabled (S50=255) e = Echo suppression enabled (S121=1 ) Special registers: (S120=12) (J6S36=2) This document is meant to take a VERY general approach to the configuration of TELEBIT modems in interactive, file transfer, and networking applications over domestic, international, cellular, microwave, and satellite communications links. TELEBIT welcomes any questions, comments, and suggestions on this or any of our other product or configuration documents at the following U.S. or international mail address, telephone number, or network electronic mail account: Telebit Corporation 1315 Chesapeake Terrace Sunnyvale, CA 94089 1-800-TELEBIT Option 2....Technical Support. (408) 734-5200 (Direct Technical Support) UUCP: {ames, uunet, sun, pyramid}!telebit!modems INTERNET: modems@telebit.com Telebit Network Technologies, S.A. 255, Route d'Arlon L-18011 Strassen G.D. de Luxembourg +352 31 96 45 Mail accounts are also available for sales literature, special incentive programs, public relations, and special interest topics: sales corpcomm idndp slip ======================================================================== Add-on INFORMATION Unfortunatley there is no register that controls the number of retries before retraining. The "Cellblazer" (our Celleuar modem) has this feature because celluar lines can be very bad...like phone lines in Moscow! I've already given you all the info. we offer on S120 and J6s36. One more thing that the document doesn't mention is that if you set J6s36=4 the other end will automatically negotiate to that value. Normally J6S36 needs to be set AT EACH END. This may help you out. Also try S121=1 for echo suppression compensation. I would use S120=2 S121=1 J6S36=4. Good Luck.....Jim at Telebit. ===================================================================== ============================================================================ We hope this information is helpful, if not Please call us at the numbers listed below as E-Mail tends to lead to more questions which a phone call can easily resolve on a real-time basis....Thank You. |\\\\\\\| Telebit Technical Support |\\\\\\\| Telebit Corporation |\\\\\\\| 1315 Chesapeake Terrace T E L E B I T Sunnyvale, CA 94089 1-800-TELEBIT Direct Dial: (408) 734-5200 UUCP: {sun,pyramid,uunet,ames}!telebit!modems FAX: (408) 734-3333 INTERNET: modems@telebit.com TELEBIT: The modem of choice for the UNIX world. ============================================================================= ======================================================================== Telebit Corporation Revision 1.03 03 DECEMBER 1990 ======================================================================== A BRIEF TECHNICAL OVERVIEW OF TELEBIT MODEMS By Michael Ballard, Director, Network Systems, Telebit Corp. Edited by Telebit Technical Support. Before starting on this document, a caveat: this document is intended to address many of the questions and comments about TELEBIT modems that have appeared from the user community. We are striving to provide as much information as possible, in such a way that will be useful to the widest group of readers. This is NOT intended to be a Marketing Article, but rather a technical overview for the more sophisticated reader. Its purpose is to inform, not to sell product. If anyone is offended by Telebit taking this action, please mail directly to us first, to avoid cluttering the newsgroup. Thank you. I would like to provide some background for Unix users considering the use of a TELEBIT high-speed dialup modem. I served as project manager and principal programmer for Telebit's protocol support developement. The UUCP "g", Kermit, Xmodem and Ymodem protocols are directly supported in the firmware of all TELEBIT modems. Peter Honeyman, co-developer of ATT's HoneyDanBer/BNU UUCP, coded those portions of the firmware which support the "g" protocol. TELEBIT modems employs a patented multicarrier modulation scheme coined DAMQAM (Dynamically Adaptive Multicarrier Quadrature Amplitude Modulation). A CRC-16 based sliding window protocol with selective retransmission runs on top of this modulation scheme insuring data integrity across the phone line. This telephone line protocol is known as the Packetized Ensemble Protocol or PEP. PEP is the trademark by which all modems employing this technique can be recognized. This technique (DAMQAM) divides the voice bandwidth into 511 individual channels each capable of passing 2, 4, or 6 bits per baud based on the measured characteristics of the individual frequencies associated with each channel. On a typical phone connection, the modem uses a subset of about 400 of those channels. Each time the modem connects to a circuit established on the dialup Public Switched Telephone Network (PSTN), the TELEBIT modem measures the quality of the connection, and determines the usable subset of the 511 carriers. The aggregate sum of bits modulated on this subset of carriers multiplied times the baud rate yields a bit per second rate that on a local telephone connection (i.e. round trip through your local telco) is 18031 bps. This 18031 bps is then reduced by about 20% to allow for the CRC overhead, to about 14400 bps of data throughput. Long distance line quality varies with location and carrier, but you can expect this number to be in the 10000 to 17000 bps range under most conditions domestically. By choosing a high quality long distance carrier, you will ensure the best throughput overall. The modem operates at 7.35 and 88.26 baud, transparently changing baud rates to accomodate the pace and quantity of data traffic. When in "interactive mode" the modem sends data using 11 msec packets (which run at 88.26 baud). Each packet contains 15 bytes of data. In "file transfer mode" the modem uses 136 msec packets (that transfer at 7.35 baud) that contain 256 bytes of data. The TrailBlazer decides which packet size to use on an ongoing dynamic basis. No intervention from the user is required. At lower speeds, such as 300, 1200, and 2400 bps, TELEBIT modems provide emulation (performed in the DSP section, not by a "chip" modem) to support these standards. The 300 bps standard is called Bell 103C. At 1200 bps, two standards exist, Bell 212A and CCITT V.22. Both are supported. At 2400 bps, the standard is called CCITT V.22 bis. These speeds are all available with or without MNP Class 4 Error Correction and MNP 5 Data Compression. The TELEBIT T2500 modem provides the CCITT V.32 modulation standard for 9600 bps communication. This is accomplished by the use of the Rockwell V.32 modem "chip set". The addition of this "daughter" module allows the T2500 to use V.32 for asynchronous and synchronous communications. V.32 allows for 9600 bps, full-duplex communications. TELEBIT modems employs a Motorola 68000 and a Texas Instuments TMS32010 digital signal processor to accomplish this performance. Because of this substantial computer horsepower (about 7.5 MIPS), TELEBIT modmes are really communications processors, rather than conventional modems. The software defined architecture produces a flexible product platform that allows broad feature development capabilities while allowing the product's installed base to benefit from those developments by installing upgrade EPROM sets. All four protocols (Kermit, Xmodem/Ymodem, UUCP), V.22bis support, MNP at low speeds, multiple releases to improve the interactive performance (earlier TELEBIT modems utilized only one baud rate), a multitude of RS-232 behavior related features, leased line capabilities, remote command processor access, echo suppressor compensation, increased data rates, and a myriad of user requested features have found their way into current production modems and are available to earlier revisioned modems via the EPROM uprgrade kits. PEP modems provide a full duplex serial interface to an attached computer, however they employ a half duplex implementation on the telephone line. TELEBIT refers to this half duplex technique as "Adaptive Duplex". As the name implies, the ownership of the line (i.e. the ability to transmit) adapts to the quantity of data available to send at any single moment. Maximum efficiency is achieved by sending data in a nonstop data stream at 19.2 Kbps relying on serial interface flow control to moderate the data flow into and out of the modem. This allows the maximum amount of data to be available every time a transmitting modem takes ownership of the line. In this way the modem, not the DTE, controls the line turnarounds. The protocol provides a ceiling at about 3k of sent data before a transmitting modem must give up its turn and allow the other modem an opportunity to send. A continuous 19.2 Kbps data flow into the modem is required to ensure that there is always 3k of data to send each time a transmitting modem takes its turn. The serial interface speed must exceed the telephone line speed, potentially 18,031 bps, or the maximum efficiency of the modems can not be reached). UUCP's "g" protocol behavior on dialup lines was a clear contradiction of the desired behavior with the PEP protocol. Protocol "g" sends 3 small data packets at time and then waits for the remote UUCP to ACK or NAK their receipt. The resulting throughput when using UUCP "g" with TELEBIT modems was only a little better than a standard 1200 bps modem. This was unacceptable. TELEBIT decided to improve UUCP performance. TELEBIT modems can be configured to "spoof" the protocol by setting a register (S111) to one of several values. The spoof can support four different protocols: UUCP "g", Xmodem, Ymodem, and Kermit. "Spoof" means to fool the various protocols into thinking that they are getting their acknowledgment packets from the remote computer, when in reality they are getting them from the modem. All of these protocols are what are commonly referred to as "send and wait" protocols. This type of protocol builds a packet in computer A, sends it out through the modems, where it is received by computer B. Next, computer B looks at the packet to determine whether or not it arrived intact. If it did, it sends an ACK (acknowledgement) packet back to computer A. If it did not arrive intact, it sends a NAK (non-acknowledgement) packet. In either case, computer A can't send the next packet out until it gets the ACK from the first packet. This is slow! Since our modems are error-free between the modems, the only place data could get "broken" is between the modems and their respective computers. Let me draw the connection diagram below: Ca <======> Ta <----------------> Tb <======> Cb Ca = Computer A Cb = Computer B Ta = TELEBIT Modem A Tb = TELEBIT Modem B ====== RS-232 Cable ------ Phone Line When we are running our protocol support, we look at the packet coming from Ca. Ta checks the packet for validity and sends the ACK or NAK. Ca can begin building the next packet immediatly upon receipt of Ta's ACK. This results in Ca building and sending packets as fast as it can. Many packets are now forwarded to Tb. Tb now delivers the packets to Cb, observing the rules of the protocol. Tb will deliver the next packet or retransmit the previous packet based on the ACK or NAK received from Cb. Cb's ACKs and NAKs are then thrown away so as not to return to Ca. Protocol support can be configured to run in parallel with data compression enabled. The real world result of this is to increase protocol transfers from 2-3 Kbps to 10-19.2 Kbps. This covers most of the commonly asked questions about TELEBIT modems. If any of the above information is unclear, or you have questions regarding other aspects of modem technology or performance, send mail to: Michael Ballard Telebit Corporation 1315 Chesapeake Terrace Sunnyvale, CA 94089 1-800-TELEBIT UUCP: {ames, uunet, sun, pyramid, decwrl}!telebit!modems INTERNET: modems@telebit.com ================================================================================ Telebit Corporation Revision 1.03 03 DECEMBER 1990 ================================================================================ TELEBIT MODEM CONFIGURATION FOR UNIX DIAL-UP, UUCP, TCP/SLIP, AND POINT-TO-POINT PROTOCOL ENVIRONMENTS Written by Telebit Technical Support. This document is meant to simplify configuration of Telebit modems for use in UNIX dial-up and UUCP applications on a wide variety of systems. The configuration hints and examples presented in this document are meant to supplement the system specific configuration guides available from TELEBIT, as well as the TELEBIT modem reference manuals. Note that there are currently several configuration guides for specific systems. These configuration guides are available from TELEBIT and UUNET Communications Services via the U.S. Internet. The following networks and systems contain these documents as well: INTERNET: UUNET.UU.NET [192.48.96.2] EUNET: MCSUN.EU.NET [192.16.202.1] JUNET: FTP.CS.TITECH.AC.JP [131.112.16.39] ACSNET: DITMELA.CNG.DIT.CSIRO.AU [128.250.1.81] Internationally, on the European network, EUnet; on the Japanese network, JUnet; and in Australia via ACSnet. A listing of the archive is available by requesting the SETUPS.list or PRODUCTS.list files from TELEBIT and most of these systems via "anonymous" UUCP or FTP. Documentation on warranty, upgrades, Data Communications protocols, and a technical overview of TELEBIT product technology are also available. UUNET Communications Services makes these documents available via "anonymous" UUCP at 1-900-GOT-SRCS in the U.S.. This services is always available and carries a caller charge of $ .40 US per minute. UNIX DIAL-UP The first step in configuring a TELEBIT modem for use in either a UNIX dial-up or UUCP application is to connect to the modem through the system hardware and operating system. It is not enough to use a dumb terminal to configure the modem and then attach it to the system. While this may be the easiest method of configuration and integration of the modem, it does not provide for future maintenance and/or systems administrations capabilities. It is highly recommended that the operating system be used to access the modem through the systems hardware. Once this is accomplished, a login process (getty) can be established on the modem port to allow for dial-up interactive or UUCP usage. 1. THE HARDWARE TELEBIT modems use a DB25 (female), RS-232C interface. A modem cable comprised of two DB25 (one male and one male/female) connectors and 25 conductors end-to-end is usually required. Some systems may have a DB9 connector on the serial I/O port with which a modem cable comprised of one DB25 (male) and one DB9 (male/female) must be used. These cables are available (pre-assembled) in most computer supply and electronic parts stores or are supplied with the system. DB9-to-DB25 cables are a standard cable that is also readily available. Although a cable with conductors connecting the DB25/DB9 pins end-to-end is highly recommended, it may not always be possible. In pre-wired office or lab environments, a 25-conductor wire may not be available. In cases such as these, the modem cable may be modified to contain only the necessary conductors for modem use. The following table contains RS-232C signals and their corresponding DB25/DB9 pin assignments: RS-232C DB25 DB9 =================================== TD 2 3 RD 3 2 RTS 4 7 CTS 5 8 DSR 6 6 GND 7 5 DCD 8 1 DTR 20 4 In some cases, the modem cable may be reduced to a minimum of four conductors. Full modem control necessitates the use of at least eight conductors. If XON/XOFF flow control is enabled in the modem, the RTS/CTS signal leads may not be necessary, thus the conductors and corresponding pins may be removed. If the system does not require status signals from the modem, the DSR and DCD signal leads may not be necessary, thus the conductors and corresponding pins may be removed. Some systems may require cable modifications in order to provide special RS-232C signaling needed by the operating system. In such cases, the RS-232C signals between the modem and the systems serial I/O ports may require re-routing. If this is necessary, your system reference manuals or systems administrations manual may provide the correct modem cable configuration for your system. The TELEBIT modem reference manuals also contain common and custom wiring diagrams. An RS-232C break-out box may also be used to arrive at the final cable configuration. 2. USING THE OPERATING SYSTEM TO CONNECT TO THE MODEM Once the proper cable has been used to connect your TELEBIT modem and system, the operating system must be set-up to connect to the modem via the system hardware. The "tip" and/or "cu" commands are available in most UNIX systems to accomplish this. The KERMIT share software from Columbia University is also highly recommended, when available, in order to by-pass problems caused by system configuration files. KERMIT does not require the same operating system device description files that "tip" and/or "cu" are dependent upon. KERMIT's ability to attempt the use of the targeted modem port may result in the most immediate use of the modem. Error messages generated by the KERMIT software may also allow for better diagnosis of operating system or hardware problems related to the host systems inability to operate at high baud rates or possible cable configuration problems. NOTE: Not all systems may be capable of using serial I/O port speeds at or above 9600 bps. Some systems may require operating system or hardware modifications. Please refer to you systems manual or manufacturer for assistance if this is so. It is highly recommended that TELEBIT modems be connected to the serial I/O ports of the system cpu. Use of serial I/O multiplexors may limit modem speed to 9600 bps or lower due to flow control, cpu/bus interrupt, or memory buffering problems. USING TIP In systems where the "tip" command is available for connecting to serial I/O ports, the following entries to the /etc/remote file may be used as guidelines (all characters are literal, i.e. the ^ is 'shift 6' on most keyboards): tb9600:dv=/dev/TTTT:br#9600:el=^C^S^Q^U^D:ie=%$:oe=^D: tb19200:dv=/dev/TTTT:br#19200:el=^C^S^Q^U^D:ie=%$:oe=^D: The following /etc/remote may be used for autodialing: Note: Register X0 should be set when using this feature. TELEBIT|Autodial TELEBIT:\ :el=^D^U^C^S^Q^O@:du:at=hayes:ie=#$%:oe=^D:br#SSSSS:\ :pn=NNNNNNN:dv=/dev/TTTT: The "hayes" entry in the above autodialer uses:"AT V0 E0 S0=1 S2=255 S12=255" Where: TTTT = serial I/O port (tty) SSSSS = baud rate [9600/19200] NNNNNNN = phone number A direct connection to the modem or autodial is achieved by issuing the following command: tip tb9600 or tip hostname NOTE: Some systems may require an entry in L-devices (or Devices) that corresponds to the serial I/O port used in the /etc/remote entry. Please see the following section on entry guidelines for this file. USING CU In systems using the "cu" command to access the serial I/O ports, the/usr/lib/uucp/L-devices (or /usr/lib/uucp/Devices) contain the required serial I/O port definitions needed to access a direct connection. The following examples may be used as entry guidelines for these files: DIR tty000 0 9600 or Direct tty000 - 9600 direct A direct connection to the modem is achieved by issuing the following command: cu -s 9600 -l /dev/tty000 or cu -s 9600 -l /dev/tty000 dir If the modem can not be accessed through the operating system, there may be a cable or serial I/O port problem or operating system problem. Be sure to check for processes occupying the targeted serial I/O port or lock files (see section 4 on HDB UUCP). A good test of the serial I/O port-to-modem connection is to list the contents of an ASCII file and re-direct the output to the modem port. Create an ASCII text file comprised of alphanumeric characters (no special characters or metacharacters). This files hould be be about fifty lines in length. Place the modem where the TD and RD lights on the front panel are visible to you as you type. While monitoring the TD and RD lights on the modem, execute the following command: cat ascii.file > /dev/tty & If the TD and RD lights do not register the data passing through the modem, it is possible that the wrong serial I/O port name is being used, the port permissions may be set wrong, a LCK..tty000 may exist in /usr/spool/locks or /usr/spool/uucp, a serial I/O port problem may be present, or a cable problem may exist. The DTR light should also be lit as data passes through the modem. Note any error messages printed to the console for possible clues as to the problem and for use when referencing the problem to a UNIX Technical Support group. The "&" places the processing of this command in the background. Should this command hang or lock-up, a "kill -9 proc_num" may be done to cancel the command. 3. MODEM CONFIGURATION Contrary to popular belief, there are only 70 to 75 configurable S-registers in a TELEBIT modem. Only a dozen of these registers are required to configure the modem for use in a UNIX dial-up or UUCP environment. TELEBIT modems are most easily understood when they are divided into two parts. One half of the modem being the RS-232C serial I/O port interface and the other half, the RJ11/RJ45 PSTN (phone line) interface. THE SERIAL I/O PORT RS-232C INTERFACE The following table lists registers which define the RS-232C serial I/O port interface: S-REGISTER DESCRIPTION ================================================================= S48 Eight Bit Comparison S51 Interface Speed S52 DTR Interpretation S53 * DCD & DSR Interpretation S54 Break Signal Interpretation S55 Escape Char./Seq. Interpretation S56 XON Character S57 XOFF Character S58 Flow Control used by DTE S64 Dial/Answer Sequence Abort S65 XON/XOFF Failsafe S66 Lock Interface Speed S67 CTS Interpretation S68 Flow Control used by DCE S69 XON Signal Handling S130 * DSR Interpretation S131 * DCD Interpretation S150 Asynchronous/Synchronous Mode Selection * = New releases of modem firmware are made to be backwards compatible with previous releases. If an "S" register is missing, the feature has either been removed or the old register number maps to a new one(s). An "ERROR" message should not result from using re-mapped registers. THE RJ11/RJ45 PSTN (PHONE LINE) INTERFACE The following table lists registers which define the RJ11/RJ45 PSTN interface: S-REGISTER DESCRIPTION ================================================================= S0 Answer On Ring Number S7 Wait For Carrier Time S9 Carrier Detect Time (slow mode) S10 Carrier Loss To Detect Time (slow mode) S41 Inactivity Timer S50 Transmission Mode (PEP/V.32/V.22bis/...) S90 CCITT/BELL Mode Select (bell212a/V.22) S91 Guard Tone Selection (V.22 only) S92 Answer Sequence Selection (PEP/9600/...) S94 Transmission Speed Negotiation (fallback) S95 MNP Operating Mode (MNP4 or 5) S96 MNP Data Compression Enable (MNP5) S110 PEP Mode Data Compression Enable (Lempel-Ziv) S121 Echo Suppression Compensation MODEM TO SYSTEM INTERFACE The remainding registers are used to set the dialog and enable features to be used between the modem and system: S-REGISTER DESCRIPTION ===================================================================== En Echo ON/OFF Mn Speaker ON/OFF Qn Quiet Enable Vn Verbose ON/OFF Xn Result Code Basic/Extended S45 Remote Access Enable S61 Speaker Volume S100 Reverse Answer/Originate Mode S101 Continuous Answer/Originate (leased line) S104 Automatic Dialing Options S105 T/D (talk/data) Switch Enable S111 Asynchronous Protocols Support S112 Kermit Mark Character EXPLANATION OF TYPICAL REGISTER SETTINGS: Please use the chart below to select the most appropriate options for your UNIX environment and application. RESPONSE FLAGS ========================================================================================== Q4 For Dial-in -- modem result codes may cause a getty battle. X1 In HDB, it doesn't matter. In BSD, X0 is set in L.sys and /etc/remote. S-REGISTERS ========================================================================================== S45 "security" demands 0, debugging demands 255. S50 Most cases set S50=0. If the other modem has S92=1, set your modem to have S50=255 to send only PEP tones. S51 For autobauding, use either S51=255 or 254 and an -- A-pause-A-pause-A-pause . . . works every time. 255 presents data at 9600 bps for inbound calls. 254 presents data at 19200 bps for inbound calls. It is best to use a "hard set" baud rate (ie S51=5). S52 Recommend value of 2 (reset modem when DTR drops) S53 Recommend value of 3 (System V HDB systems may need 1 or 4). This register maps to S130/S131 when not listed in modem. S54 Recommend value of 3 (see modem reference manual) S58 Sets flow control. S58=2 (RTS/CTS) is recommended, when possible. S68=255 should also be set. S68=3 may be used whenever S58=0 for flow control during interactive use. S61 Volume of speaker. If it's an office environment, try a value of 45. If machine room, try 200. S66 S66=1 locks the interface speed and uses flow control for non-PEP modems. Hard setting the interface speed to 9600 or 19200 with S66=1 is highly recommended. S92 If low speed modems are also dialing in, set S92=1. Incoming PEP modem should have S50=255 set. S110 If you are sending/receiving text, set S110=1 to enable data compression. Otherwise, if sending news or binary files that are uncompressible (or pre-compressed), leave compression off by setting S110=0. S111 Use S111=30 or 255. At least one modem must have 30 for UUCP protocol support. CONFIGURATIONS FOR BSD4.2, BSD4.3, AND SYSTEM V UNIX SYSTEMS Below is a chart of the factory settings, along with typical BSD and SYSTEM V settings. Registers not shown are to be left at the factory settings: REG FACT BSD4.2 BSD4.3 HDB DESCRIPTION ========================================================================================== Ex E1 E0 E0 E0 Echo ON/OFF Mx M1 M1 M1 M1 Speaker ON/OFF Qx Q0 Q4 Q4 Q6 Quiet Enable Vx V1 V1 V1 V1 Verbose ON/OFF Xx X1 X1 X0 X3 Result Code Basic/Extended S45 000 255 255 255 Remote Access Enable S50 000 000 000 000 Transmission Mode S51 255 005 005 005 Interface Speed S52 000 002 002 002 DTR Interpretation S53 000 001 003 000 DCD & DSR Interpretation * S54 000 003 003 003 Break Signal Interpretation S55 000 000 000 000 Escape Char./Seq. Interp. S56 017 017 017 017 XON Character S57 019 019 019 019 XOFF Character S58 003 000 000 002 Flow Control used by DTE S130 002 002 004 002 DSR Interpretation * S131 002 001 001 003 DCD Interpretation * S64 000 000 000 000 Dial/Answer Sequence Abort S65 000 000 000 000 XON/XOFF Fail safe S66 000 001 001 001 Lock Interface Speed S67 000 000 000 000 CTS Interpretation S68 255 003 003 255 Flow Control used by DCE S90 000 000 000 000 V.22 Emulation Mode Enable S91 000 000 000 000 Guard Tone Selection S92 000 000 000 000 PEP tones before slow tones S95 000 000 000 000 MNP Error Correction S96 001 001 001 001 MNP Data Compression S110 255 255 255 255 Data Compression (PEP) S111 255 030 030 030 Protocol Support S112 001 001 001 001 Kermit Mark Character * = New releases of modem firmware are made to be backwards compatible with previous releases. If an "S" register is missing, the feature has either been removed or the old register number maps to a new one(s). An "ERROR" message should not result from using re-mapped registers. NOTE: Set S50=255 when calling UUNET Communications Services for UUCP use. S92=1 is set on ALL UUNET-TELEBIT modems. 4. DEFINING THE DIAL-IN PORT CHARACTERISTICS (GETTY/STTY) Once a direct connection to the modem through the operating system is operational and the modem registers are configured for your system and use, the dial-in port characteristics can be defined. These definitions can be altered upon succesful login by using the "stty" command which is standard to all UNIX systems.. The port on which the modem will be connected should be configured to run at either 9600 or 19200 bps. Use hardware (RTS/CTS) flow control where possible. Use software XON/XOFF flow control if RTS/CTS isn't available. Make sure that the flags in /etc/gettydefs (or /etc/gettytab) look something like: 19200m # B19200 CS8 ECHO IXON IXOFF HUPCL # B19200 CLOCAL IXON IXOFF IXON IXOFF TAB3 BRKINT OPOST ONCLR CS8 ISIG ICANON ECHO HUPCL #login: #19200m (note that the above should be entered as ONE line of data) or z|std.19200|19200-baud:\ :sp#19200: The use of a rotary or autobaud in getty is not recommended due to the modems ability to lock interface speed (S66=1). The modem can then arbitrate a slow modem connection to the hard-set interface speed without the need for interface speed matching. You should modify the baud rate entries to 9600 if your system only supports 9600 bps. In some systems this entry may be called "EXTA" or something similar. Keep in mind that every system may have slightly different names for the flags. If you do use a rotary or autobaud getty entry, don't forget to set the getty up to include 19200 in its cycle. You may have it trying 19.2 first and moving to 2400 on the first receipt of a break signal and to 1200 on the second receipt of a break. The order of the cycle is not important so long as the calling system knows to send breaks untilit sees the login sequence. 5. ESTABLISHING A LOGIN PROCESS (GETTY) The getty is established on the modem port by editing the /etc/ttys, /etc/ttytab, or /etc/inittab in order to add the modem port settings (described above) and to enable the getty. BSD UNIX GETTY These entry samples may be used in either the /etc/ttys or /etc/ttytab files to enable the modem port getty: 1zttya or name getty type status comments ttya "/usr/etc/getty std.19200" dialup on secure The process does not execute until "init" is restarted to include the new process. This is accomplished by issuing the command: kill -1 1 The new process (getty) may be verified by using the "ps" command. SYSTEM V GETTY This entry sample may be used in the /etc/inittab file to enable the modem port getty: 00:2:respawn:/etc/getty tty00 19200m The process does not execute until "init" is restarted to include the new process. This is accomplished by issuing the command: init q or telinit q The new process (getty) may be verified by using the "ps" command. NOTE: It is highly recommended that /etc/getty be used instead of /usr/lib/uucp/uugetty, due to various problems reported in the use of uugetty. The use of getty instead of uugetty does not prevent the modem port for dial-in and dial-out use. When getty is used on the modem port, the system init levels should be used to stop and restart the getty as needed for dial-out purposes. The following script give an example of how this may be done: #! /bin/sh init 3 chmod 666 /dev/tty cu -s 19200 -l /dev/tty (or uucico -r1 -x9 -ssys) init 2 UUCP Configuration of UUCP consists of additions and modifications to the UUCP files contained in /usr/lib/uucp or /etc/uucp. There are two UUCP environments available in BSD UNIX systems. These environments are Version2 UUCP and HoneyDANBER (HDB) UUCP. HoneyDANBER is native to SYSTEM V UNIX, but may also be found in some BSD UNIX systems. Version2 UUCP is found only in BSD UNIX systems. SYSTEM V UNIX has only one UUCP environment, HDB. Each environment has different file names, but basically the same workings in the execution of a UUCP session utilizing the "uucico" command. When working with UUCP, we have found the most useful resource for UUCP information has been the book "Managing UUCP and Usenet", published by O'Reilly & Associates. The book can be ordered directly from O'Reilly by calling their toll-free number, 1-(800)-338-6887 USA or 1-(800)-533-6887 CA. Their direct numbers are 1-(707)-829-0515 and 1-(707)-829-0104 FAX. The book costs $21.95 (US) and may save you hours of time when installing and troubleshooting your UUCP. These books are also available from UUNET Communications Services at 1-703-876-5050. "Managing UUCP and Usenet" covers both standard BSD and SYSTEM V UUCP. It is highly recommended for both novices to the UUCP environment and experienced UUCP System Administrators. Use the guidelines below as a starting point. Realize that many slight variations in UUCP behavior may require you to modify these instructions for your application. NOTE: Not all systems may be capable of using serial I/O port speeds at or above 9600 bps. Some systems may require operating system or hardware modifications. This includes the ability of UUCP (ie uucico) to function properly at 19200 bps. Please refer to your systems manual or manufacturer for assistance if this is so. It is highly recommended that TELEBIT modems be connected to the serial I/O ports of the system cpu. Use of serial I/O multiplexors may limit modem speed to 9600 bps or lower, when using UUCP, due to flow control, cpu/bus interrupt, or memory buffering problems. VERSION2 UUCP 1. MODIFY /usr/lib/uucp/L-devices (or /etc/uucp/L-devices) The L-devices file contains information that describes what types of devices the system has available for use in dialing other systems, and identifies the port(s) they are connected to. It also contains information about baud rate, and may also contain instructions for the modem on how to dial, or what dialer script (or program) to use. If you are running BSD or XENIX UUCP, you may need to modify the dialer for use with TELEBIT modems at high speeds. A good starting point is usually the Hayes dialer, either in script form or the program form. The dial program may be called "hayes", or "hayestone". If you have SCO XENIX, contact SCO Technical Support and ask for theTELEBIT utilities (on 5 1/4" or 3.5" floppy). These are available for SCO XENIX releases needing the "dialTBIT" dialer and new versions of the "uucico" and "cu" programs that have been enhanced to run at 19200 bps. This is not necessary for SCO UNIX 3.2 systems. If you think that your computer may need enhancements in order to run UUCP at high speeds, contact your vendor's Technical Support line for such information. Some examples of these entries are given below. Your system entries may appear slightly different. Use the guidelines below as a starting point. - ACU entries are for automatic dialing (using L.sys entries). - DIR entries are usually associated with "direct" connections from "cu" or "tip". - Modify the port number for the appropriate modem port on your system. - Use a standard dialer such as "hayes" or "hayestone" where available. - Use a custom dial program such as "dialTBIT" in XENIX. - Use "A\dA\dA\d" to synchronize the modem to different speeds when autobauding on outgoing calls, if necessary. - Set S50 to the appropriate speed when dialing out at low speeds, if necessary. EXAMPLE 1: /usr/lib/uucp/L-devices (XENIX, BSD 4.2 and 4.3 UUCP): ACU tty1A /usr/lib/uucp/dialTBIT 19200 DIR tty1A 0 19200 or ACU cua0 cua0 19200 DIR cua0 0 19200 2. MODIFY /usr/lib/uucp/L.sys (or /etc/uucp/L.sys) The only changes most systems require are to increase the baud rate from 1200 or 2400 up to 9600 or 19200. Everything else in the chat script should remain the same. Below is a typical L.sys entry, including the chat script. Do not copy this literally. Modify the information for your application: hostname Any ACU 19200 NNNNNNNNNN ogin:--ogin: Usysname ssword: XXXXXXXX NOTES: hostname = THEIR System name NNNNNNNNNN = THEIR System phone number Usysname = Your UUCP account on THEIR machine XXXXXXXX = Your UUCP passwd on THEIR machine The "chat" script is the most common point of wasted connection time and login failure. Be sure to test this entry rigorously to verify a successful login in the fastest time possible. 3. TEST UUCP UUCP can now be tested by issuing the following commands. The debugging level can be either -x4 or -x9: /usr/bin/uucp -r1 test.file testhost\!/test.directory [queue file transfer] /usr/lib/uucp/uucico -r1 -x4 -stesthost [start file transfer] Upon success or failure of the UUCP session, the status file must be removed before another UUCP session can be started with the above command: rm /usr/spool/uucp/STST.testhost It is also possible that a "lock" file may continue to exist if the process was aborted or did not complete execution properly. The following commands may be used to remove the "lock file before the next UUCP session is started: rm /usr/spool/locks/LCK..tty00 or rm /usr/spool/uucp/LCK..tty00 HONEYDANBER UUCP 1. MODIFY /usr/lib/uucp/Devices The Devices file contains information that describes what type of devices the system has available for use in dialing other systems, and identifies the port(s) they are connected to. It also contains information about baud rate, and may also contain instructions to the modem on how to dial, or what dialer script (or program) to use. Some examples of these entries are given below. Your system entries may appear slightly different. Use the guidelines below as a starting point. - ACU entries are for automatic dialing (using Systems entries). - DIR entries are usually associated with "direct" connections from "cu". - Modify the port number for the appropriate modem port on your system. - Use a standard dialer such as "hayes" or "hayestone" where available. - Use a custom dial script such as "tbfast" in HoneyDANBER . - Use "A\dA\dA\d" to synchronize the modem to different speeds when autobauding on outgoing calls, if necessary. - Set S50 to the appropriate speed when dialing out at low speeds, if necessary. EXAMPLE 2: /usr/lib/uucp/Devices ACU ttyxx - 2400 tb2400 ACU ttyxx - 9600 tbfast ACU ttyxx - 19200 tbfast DIR ttyxx - 19200 direct 2. MODIFY /usr/lib/uucp/Dialers The following example entries may be used in the Dialers file: tb2400 =W-, "" A\pA\pA\pT OK ATS50=3DT\T CONNECT\s2400 tbfast =W-, "" A\pA\pA\pT OK ATS50=255DT\T CONNECT\sFAST You should have no trouble dialing out at any speed. 3. MODIFY /usr/lib/uucp/Systems The only changes most systems require are to increase the baud rate from 1200 or 2400 up to 9600 or 19200. Everything else in the chat script should remain the same. Below is a typical System entry example, including the chat script: hostname Any ACU 19200 NNNNNNNNNN ogin:--ogin: Usysname ssword: XXXXXXXX NOTES: hostname = THEIR System name NNNNNNNNNN = THEIR System phone number Usysname = Your UUCP account on THEIR machine XXXXXXXX = Your UUCP passwd on THEIR machine The "chat" script is the most common point of wasted connection time and login failure. Be sure to test this entry rigorously to verify a successful login in the fastest time possible. 4. TEST UUCP UUCP can now be tested by issuing the following commands. The debugging level can be either -x4 or -x9: /usr/bin/uucp -r test.file testhost\!/test.directory [queue file transfer] /usr/lib/uucp/uucico -r1 -x4 -stesthost [start file transfer] Upon success or failure of the UUCP session, the status file must be removed before another UUCP session can be started with the above command: rm /usr/spool/uucp/.Status/testhost It is also possible that a "lock" file may continue to exist if the process was aborted or did not complete execution properly. The following commands may be used to remove the "lock file before the next UUCP session is started: rm /usr/spool/locks/LCK..tty00 or rm /usr/spool/uucp/LCK..tty00 You should now be able to run UUCP between two machines attached to your modems just as you always have with slower modems. Typical throughputs should be in the range of 10Kbps to 16K bps (1000 to 1600 cps). Enjoy the new world of of high speed UUCP "g" protocol file transfer. TCP/SLIP Serial Line Internet Protocol (SLIP) was developed and distributed for Berkeley 4.3 BSD (Berkeley Standard Distribution) systems. This program allowed the network routing code to send any IP packet through a serial port as opposed to an ether net port. The profound difference was performance. Ethernets run typically at 10 megabits per second as opposed to typical top speeds of 19.2K bps (bits per second) on asynchronous serial ports. Nevertheless, it works. TCP and IP are two cooperating methods that work together to encapsulate data for passage across a network. Just like placing a letter in an envelope, the receiver may discard the envelope after safely receiving the contents. The envelope served only to transport the contained information. Likewise, applications in a network environment become the senders and receivers of electronic letters packaged in TCP/IP envelopes. These applications, FTP (File Transfer Protocol), SMTP (Simple Mail Transfer Protocol), TELNET (virtual terminal emulation access across the network), PING (a "hello" message to any host on the net to validate its healthy presence), RLOGIN (similar to TELNET providing remote login to other host computers on the net), RCP (similar to FTP providing file transfer to other host computers on the net) and many others, all envelope their cross-net traffic inside TCP/IP envelopes. TCP's contribution to the data envelope is 20 bytes of overhead. Likewise IP contributes its own 20 bytes. SLIP prepends and appends another 2 bytes for a grand totalof 42 bytes of overhead. FTP file transfers, today, run well with TELEBIT modems achieving 12,000-14,000 bps throughput. This is true for all bulk data applications. However, a problem arises when interactive terminal emulation applications like RLOGIN or TELNET operate. When running a TELNET or RLOGIN session, that is simply typing on a screen to a host somewhere on the network, each character typed is enveloped in 42 bytes and mailed to the remote machine. When running across a 10 megabit per second ethernet (the medium this whole process was designed for) enduring that much overhead is not elegant, however, it is functional. At 9600 bps on a high-speed modem, the overhead is impeding. TELEBIT Micro-short packets potentially hold about 10 data bytes. Once the first ten bytes of a TCP/SLIP packet fill the first micro-short modem packet, the modem builds a 256 byte long packet to house the following plus or minus 32 bytes. This inefficiently stuffed packet travels the link consuming unnecessary transmission time. The action of sending packets back and forth causes the modem to thrash between micro-short and long packets and the resulting interactive TCP/SLIP performance is poor. These interactive applications currently run with about a 1.2 to 2.0 second round trip character echo delay. This interactive performance is unacceptable. Nevertheless, many TELEBIT modem users are today running SLIP. The resources available through TCP/SLIP are forcing them to accept the unacceptable. TELEBIT modems do not contain TCP/SLIP or Point-to-Point Protocol protocol support. As stated above, these protocols consist of rather large datagrams which make the use of high-speed modems a necessity. POINT-TO-POINT PROTOCOL Point-to-point circuits in the form of asynchronous and synchronous lines have long been the mainstay of data communications. Even with the growing popularity of local area networks, wide area connections are still made using various point-to-point circuits. Over time the data link levels used have settled to a few standards. However, the method use of the data link by upper level protocols, such as IP, has been largely implementation dependent. This resulted in requiring a single vendor's equipment for both ends of a point-to-point circuit. The Point-to-Point Protocol (PPP) seeks to remedy this problem by proposing a standard method of encapsulating IP datagrams, as well as other network layer protocol information, over point-to-point links. PPP also specifies the means for line and protocol operation and maintenance by providing the means for testing and configuring the line and each of the upper level protocols. PPP is designed to be easily extensible for adding new protocols and features. PHYSICAL LAYER PPP is capable of operating across virtually any DTE/DCE interface. The most common examples of interfaces are RS-232-C, EIA RS-423 and CCITT V.35. The only absolute requirement for PPP is that a duplex circuit be provided. While control signals are not required for the use of PPP, it should be recognized that they do add functionality and it is recommended that they be fully utilized when they are available from the interface. DATA LINK LAYER PPP specifies for synchronous and asynchronous circuits ISO that 3309-1979 as modified by ISO 3309:1984/PDAD1 be used. The framing specified by this document is more commonly known as HDLC and the 1984 addendum defines HDLC for asynchronous circuits. PPP describes the values to be used in the standard HDLC fields and adds a protocol field to indicate for which protocol the data is destined. There are three major types of protocols, link control, upper level protocol control, and upper level protocol data. TELEBIT MODEM CONFIGURATION FOR POINT-TO-POINT CIRCUITS Configuring a TELEBIT modem for use in a BSD4.3 TCP/SLIP, Compressed TCP/SLIP (TCP/CSLIP; BSD4.4), or Point-to-Point Protocol (PPP RFC 1134) application is merely a case of configuring the modem to behave exactly like a direct RS-232cc able connection between the two host systems in the circuit. That is, NO FLOW CONTROL! Hardware flow control (EIA or RTS/CTS) is recommended where supported by the host system. The following S-register settings should accommodate most point-to-point circuit set-ups: S-REGISTER SETTING DESCRIPTION ================================================================= S58 000 No Flow Control. S68=255 also. S58=2 For RTS/CTS. Optional. S50 XXX Modulation. S50=255 is PEP S50=6 is V.32. Optional. S66 001 Lock Interface Speed. S95 XXX MNP Error Correction or Data Compression (4/5) for V.32. Optional. S110 XXX PEP Data Compression. Optional. AUTODIALING The S104 register is used to cause the modem to go off-hook and dial one of the first two telephone numbers in the modem telephone number directory. The number dialed is dictated by the position of the A/B switch on the front of your TELEBIT modem (post-1989 models). The following example is meant to illustrate the flexibility of this feature, as well as that of modem modulation usage in the set-up of a point-to-point circuit: BANK A: AT S50=255 S52=2 S58=0 S66=1 S95=2 S104=1 S110=1 &W1 ATN0=nnnnnnn\TELEBIT_PEP_SLIP BANK B: AT S50=6 S52=2 S58=0 S66=1 S95=2 S104=1 S110=1 &W2 AT N1=nnnnnnn\TELEBIT_V.32_SLIP Where BANK A is configured to dial the telephone number stored at location N0: in the modem and establish a compressed PEP connection with the remote TCP/SLIP host up on a OFF-to-ON transition of DTR. This enables the modem to automatically dial the remote TCP/SLIP host system as soon as DTR is raised (DTR "ON") on the modem port by the execution of a SLIP attach command (slattach) on the originating TCP/SLIP system. The need for a "tip" or "cu" process in order to affect dialing is eliminated. The settings in BANK B accomplish this same task with the exception using V.32 modulation with MNP to establish the TCP/SLIP link. The telephone number in location N1: could be the same or different from that of BANK A. The A/B switch can now be used to set-up two distinct point-to-point circuits or one point-to-point circuit with the ability to use two different modulation schemes. The use of PEP or V.32 modulation allows for flexibility in the performance of the point-to point circuit in relation to the task performed and data transferred. PEP is highly recommended for use in long distance connections or low quality connections. PEP will also yield the highest throughput in the transfer of binary files or compressible bulk data files using FTP or rcp, as well as SMTP and NNTP connections. CCITT V.32 is a full duplex modulation scheme which will facilitate better interactive response during TELNET, rlogin, and rsh connections. This document is meant to take a VERY general approach to the configuration of TELEBIT modems in interactive, file transfer, and networking applications on UNIX systems. TELEBIT welcomes any questions, comments, and suggestions on this or any of our other product or configuration documents at the following U.S. Mail address, telephone number, or network account: Telebit Corporation 1315 Chesapeake Terrace Sunnyvale, CA 94089 1-800-TELEBIT UUCP: {uunet, sun, pyramid, ames, decwrl}!telebit!modem INTERNET: modems@telebit.com > >I'm using a T2500 for one year now, did a lot of peeking and poking, >wrote to Telebit tech support several times an there are still some >questions left open.. Let's begin with what I found out so far, that >will lead us to the questions. Here we go : > >------------------------------------------------------------------------------ >undocumented (or barely documented) register of the Telebit T-2500 GF7.00 >------------------------------------------------------------------------------ >S120 several functions > > Values : bitmapped ! > Default : 0 > > Bits 0-1 (register value 1 to 3) (source : tech supp) > 1 : Force PEP to Short Packets and 2 bits per carrier. > 2 : Force PEP to Long Packets and 2, 4 or 6 bits per > carrier. For fast file transfer capability, not > recommended for interactive. > 3 : Force PEP to Long Packets and 2 bits per carrier. > For fast file transfer capability, not recommended > for interactive. > "For fast file transfer capability"??? When the modem is on long-only, 2-bit-carrier mode, it runs at a maximum throughput of 700-800 cps!! Not something I would consider "fast". It's the most bulletproof mode for handling line noise, but it's not fast relative to PEP's normal capabilities. > > Bit 4 (register value 16) (source : experiments) > Bit high : V.25 Answertone prior to PEP-answertone > not sent. > Bit low : V.25 answertone prior to PEP-answertone > sent. > That bit controls the version 7 modifications to PEP for handling the echo cancellers on fiberoptic networks. There's a lot more to those mods than just the V.25 answer tone... > >S53 ???????? > > Values : 0 to 7(?) > Default : 1 > > Maybe it has something to do with the DCD line ? > The default is 0. Older Telebit modems (version 4 and earlier, version 1 for the T1000) used the S53 register to control both DCD and DSR. Modern versions use S130 to control DSR and S131 to control DCD, but they still support the old S53 register for compatibility with existing software. > >What do bits 5 to 7 of the S120 registers do ? Do they have any >function at all ? > No. > >Does anybody have a T-2500 with a working V.23 mode ? >(And if yes, what ROM Version ?) > The T2500 designed for international use does. There are different firmware versions for different countries. Firmware designed for the U.S. version (GAx.xx, GEx.xx, and GFx.xx) does not. V.23 is not a feature of the U.S. version of the modem. > >Does anybody have reliable information on ROM updates for >the modem ? (Will there be V.32bis? Will there be a working V.23 mode?) > Telebit has that information. Upgrading to V.32bis in any version of the T2500 cannot be done through a mere ROM update. As soon as a PEP/V.32bis modem becomes available, then there will be an upgrade in the form of a swap for the new modem. That's for the U.S. versions. I don't know what the plans are for the international versions of the T2500. Likely a similar deal, as long as the new modem has been approved for use in that particular country. ================================================================================ Telebit Corporation Revision 1.06 22 JULY 1992 ================================================================================ TELEBIT PEP MODEM CONSIDERATIONS FOR ADVERSE COMMUNICATION LINKS By TELEBIT CORPORATION Technical Support The Telebit modem's advanced multi-carrier design, utilizing the patented Packetized Ensemble Protocol (PEP), is ideally suited to operate over international circuits which can often cause insurmountable obstacles to standard "slow" or other high speed modems. There are several things to consider when attempting to establish a link over such a line that should help insure reliable connections with the maximum performance possible under the conditions. INTERNATIONAL CALLS When originating a call and dialing internationally, you should increase the time to wait for carrier from the default of 40 seconds, to about 80 seconds, to allow more time to dial, get a connection to the other end and then negotiate carrier. This is controlled in the modem by the S7 register, which can be set any- where up to 255 seconds as needed. Your software package may also have a parameter that controls the time to wait for carrier so be sure to set that accordingly. Leave the answering modem S7=40, because if 40 seconds has elapsed without establishing a connection, it is likely that it will fail to do so and it would be better to redial. If possible, set S50=255 to force the modem to only send PEP connect tones. This will not allow the answering modem to connect at any slow speed. It is usually good to set S110=1, (only on a TrailBlazer Plus, T2000, or T2500) so the modems can negotiate to do data compression. Do not use the data compression feature if the files have been compressed prior to transmission. If you are going to use Kermit, Xmodem or UUCP to do a file transfer, set the S111 to the appropriate value to allow the modems to negotiate for protocol support. It is recommended that you use one of the supported protocols to optimize throughput to the maximum level the telephone line will allow. Zmodem and variations might also attain good results without any protocol support, but there is no need for complex sliding window protocols with the protocol support feature in TELEBIT modems. Echo suppression equipment on long distance circuits can cause timing delays that disrupt our packet transmission. The modem can be configured to compensate for this problem if S121=1. This is a negotiated feature, which means that it is not required to set S121 on both modems, only one of the two need be set to allow us to compensate for echo suppression. Experimentation is about the only way to determine if echo supression equipment is present on the circuits. If you seem to be able to operate without setting S121, don't change it. But if you are experiencing problems with frequent long delays in data transmission, try setting this and see if there is an improvement. CELLULAR, MICROWAVE, AND SATELLITE CALLS In satellite and microwave channels, Compansion may be an obstacle to obtaining good data throughput. Compansion is the Compression and Expansion (amplification) of an analog signal over a voice or data communications link. The use of Compansion to ensure the best voice quality possible over a satellite or microwave link may cause PEP packets to be "clipped" during a data connection. Uncompanded communications channels may be available from the satellite or microwave service provider. Experimentation is the best way to determine which type of service will best suit your application. The S121, S120, and J6 S36 registers will allow for a reliable and effective connection over either of these services. In cellular communications channels Compansion may also be a factor, but the leading obstacle is usually signal strength. Due to the use of passive or active RJ-11 adapters, the modem signal strength is crucial to maintaining a reliable and effective connection. The CellBlazer product has software registers (S175) which set signal strength on the modem. Other TELEBIT modems have the ability to set signal strength via an internal gain resistor or an external (RJ-45 connector) gain resistor. The S121, S120, and J6 S36 registers, in combination with the proper signal strength adjustments, will provide a reliable and effective connection over cellular channels. The communications equipment providing the RJ-11/RJ-45 interface to the modem may also be an important factor in cellular, microwave, or satellite connections. Active RJ-11/RJ-45 adapters are highly recommended for cellular use via cellular telephones. The satellite tracking mechanisms of a ship/earth station terminal may be just as important as its signal processing and transmission capabilities. The ability to adjust signal strength for any modem interfacing unit, along with the S121, S120, and J6 S36 registers, will provide a reliable and effective communications link. DIAGNOSING AND SOLVING MODEM COMMUNICATIONS PROBLEMS Some indications that your TELEBIT modem is experiencing difficulty in communicating are: 1) Inability to connect after several attempts at "Handshaking" (the PEP connect tones) resulting in a NO CARRIER status. 2) After connection, frequent pauses during which there is no response nor data received for 10 to 30 seconds at a time. 3) Disconnection after a delay of 60 seconds with no data transmission. In many cases, depending on the types of communications link, it is possible to "fine-tune" PEP to allow for more reliable connections and maximum performance. TELEBIT Technical Support prefers to troubleshoot these situations on a case by case basis. It is therefore recommended that they be consulted prior to modifying your TELEBIT modem modulation characteristics. TELEBIT Technical Support should be able correct most, if not all, of these problems. Contact TELEBIT Technical Support at 408-734-5200 (U.S.) or 1-800-TELEBIT (U.S.) or one of the TELEBIT international offices listed in this document. Many international calls will connect without any problems, but if difficulties in connecting or maintaining connections occur, the following settings are recommended. *********************************************************************** * * * NOTE: For newer modems with Version 7 firmware (Use "ATI3" to * * find out firmware version) you MUST add 16 to ANY value of S120. * * i.e. For Level 1: AT S120=12 J6 S36=1 would be AT S120=28 J6 S36=1. * * For Level 2 use S120=18 and NOT S120=2. For Level 3 use S120=19. * * Adding 16 will disable V.25 tones that are outputted before PEP * * tones, so that the packet size then may be changed. This is for * * GF7.XX, GE7.XX, BC7.XX, HA2.10 and T1000 firmware release FA2.10. * * * * For the WorldBlazer modem the S120 command is no longer valid, * * but the *values* as described above will still pertain. The new * * command is AT~D1S500=28~D0 for no micro packets with the modem * * using either 1 through 7 bits per carrier (as shown in S71 and S73 * * when connected) or "dynamic" bits per carrier. AT~D1S500=18~D0 * * for long packet mode with dynamic bits per carrier and finally * * AT~D1S500=19~D0 for long packet mode with only 2 bits per carrier. * * * * To add tones to the front of the data packet, like J6 S36 used to * * do, use AT~D1S501=3~D0. Use ~D1S501=1 or 2~D0 when ~D1S500=28~D0. * * If you set ~D1S500=18 or 19~D0, then ~D1S501 must be either 3 or * * above. See below for more information on what to set. * ************************************************************************ The Three levels are in order of severity of line difficulties, from minor to major. Level 1: AT S120=12 J6 S36=1 (Use S120=28 for New Modems...see NOTE above) For the WorldBlazer use: AT~D1 S500=28 S501=1~D0 Generally, Level 1 will have a very minor impact on performance, both in interactive use and file transfer. It is useful, however, for achieving a degree of reliability, even when the communication lines are very good. The J6 S36 or the ~D1S501 on the WorldBlazer may incremented up to 4 in order to better survive adverse line conditions. Level 2: AT S120=2 J6 S36=2 (Use S120=18 for New Modems...see NOTE above) For the WorldBlazer use: AT~D1 S500=18 S501=3~D0 Level 2 will impact interactive performance severely while file transfers remain at close to normal performance. Level 3: AT S120=3 J6 S36=3 (Use S120=19 for New Modems...see NOTE above) For the WorldBlazer use: AT~D1 S500=19 S501=4~D0 Level 3 is a last resort setting which will severly impact interactive performance and limit file transfer speeds. Data compression, S110, S190 and S191 on the WorldBlazer, can make up some of the difference, but only if the data has not been previously compressed. The S121=1 register will enable compensation for echo cancellation on the circuit, and can be enabled at any of these levels. If a stand alone modem is in use, the special register commands should be sent to the modem and saved to Non-Volatile Memory, by sending the save command "AT&W". In situations where a mixture of local and long distance calls are being placed, it is recommended that these special settings be made in a modem initialization file or that the A/B selection switch be used. THE PEP FINE TUNING REGISTERS The S120 register is a non-documented register that governs your PEP packet size. The modem operates on three different packet sizes: Micro Packets which are sent very frequently, Small Packets which are sent a little less frequent, and Long Packets which the modem automatically switches to when a file transfer begins. Sometimes over long-distance phone lines the modem has trouble staying in Micro Packet mode and has to perform a "retrain", which you can hear by leaving your speaker on all the time with "ATM2". This is what you sometimes experience when you get long delays before you receive any data. New modems blink the PEP light when a retrain is occuring. Setting S120=28 eliminates Micro Packets and uses Small or Long Packets depending on the size of the file to be transmitted. Setting S120=18 eliminates Small Packets and only uses Long Packets. Configuring your modem to the proper settings is dependent on how bad the line quality is. The J6 S36 register adds a little tone in front of the packet being transmitted to keep the front of the PEP packet from getting "clipped off" during a long distance file transfer over adverse line conditions. Thus, if anything gets "clipped off" it will be this tone and not the data-carrying PEP packet. The more you increase the value of S36 the more tone you add to the front of the packet. Again, turn your speaker on to listen to the tones and set this register depending on how bad the line quality is. As a word of caution, J6 S36 should NOT be set above 4. This will result in a tone that is equal in size to the PEP packet and a 50% or more reduction in data throughput. The S120 and the J6 S36 are completely independent of each other. If S120 is set to a value other then default (S120=0) on one side only, the other side automatically negotiates to that value (i.e. setting S120=28 will force the other side to negotiate a value of S120=28 and the modems will NOT use Micro Packets.) On the other hand, J6 S36 is completely independent and must be set at each side when J6 S36=1 or 2 on newer modems. When J6 S36=3 or 4, tones are automatically negotiated in each direction by both modems. Sometimes it is only necessary to set one side, or whichever side has the most trouble transmitting data (answering modem is active vs. calling modem is passive). Please read your TELEBIT product reference manual for information on the S70-S76 registers and their functions. This will assist you in assessing which modem will need these registers set in accordance to its "instantaneous transmit rate" (ATS70?). Do NOT set S110=1 to enable Data Compression if the data you are transmitting has been previously compressed or is non-compressible. Data Compression on top of compression adds too much overhead that the modem has to deal with and will actually lower throughput on file transfers. UNIX In UNIX UUCP environments, it is recommended that the "chat script" in the L.sys file (Version2 UUCP) or the Dialers file (HoneyDANBER UUCP) be used to set these registers on a per site basis. These registers may also be added to "intelligent" dialers, such as the the dialTBIT dialer provided by SCO in their XENIX and UNIX systems. Here are some register entry examples: /usr/lib/uucp/Dialers (/etc/uucp/Dialers) This entry is one line: tbpepmod =W-, "" A\pA\pT OK ATS50=255S52=2S120=28J6S36=1DT\T CONNECT /usr/lib/uucp/L.sys (/etc/uucp/L.sys) This entry is one line: hostname Any cua0 19200 cua0 "" ATX0S50=255S52=2S120=28J6S36=1\r OK ATDNNNNNNNNNN\r CONNECT "" ""-\r-login: \r login: Uyoursysname ssword: XXXXXXXX /usr/lib/uucp/dialTBIT.c This section of the SCO dialTBIT.c dialer is the only one modified. The option is invoked via the dialing string in the L.sys or Systems file, with the appropriate entry to the L-devices or Devices file. LINES 204-209 [MODIFICATION]: /* * MDECHOSUP - Enable Echo Supressor Compensation * * S121=1 - Enable Echo Suppressor Compensation * S120=28 - Enable Long and Short PEP packets only * J6S36=1 - Enable calibration tone on the PEP packets */ #define MDECHOSUP "ATS120=28J6S36=1S121=1\r" /usr/lib/uucp/L.sys The "echo suppression" option is invoked by the "e" option in the following manner: hostname Any ACU 19200 NNNNNNNucpe "" \d ogin: Usys word: XXXXXX NOTES: u = UUCP protocol support enabled (S111=30) c = Data compression enabled (S110=1 ) p = PEP connection only enabled (S50=255) e = Echo suppression enabled (S121=1 ) Special registers: (S120=28) (J6S36=1)