FTP directory /ftp/index/doc/netinfo/UUNET/ at ftp.funet.fi
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`FTP directory /ftp/index/doc/netinfo/UUNET/ at ftp.funet.fi
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`Up to higher level directory
`08/11/1999 12:00AM Directory ClariNet
`08/11/1999 12:00AM Directory PrenticeHall
`08/11/1999 12:00AM Directory Services
`08/11/1999 12:00AM Directory Telebit-Info
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`ftp://ftp.funet.fi/ftp/index/doc/netinfo/UUNET/
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`FTP directory /ftp/index/doc/netinfo/UUNET/Services/ at ftp.funet.fi
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`09/14/1992 12:00AM 2,022 900
`09/14/1992 12:00AM 18,693 AlterNet.egp.ps.Z
`09/14/1992 12:00AM 52,455 AlterNet.ps.Z
`09/14/1992 12:00AM 785 access
`09/14/1992 12:00AM 159 active
`09/14/1992 12:00AM 49,565 active.Z
`09/14/1992 12:00AM 11,475 alternet
`09/14/1992 12:00AM 71,778 aw-books
`09/14/1992 12:00AM 1,600 book-offer
`05/28/1991 12:00AM 44,967 compu-dialins
`09/14/1992 12:00AM 10,966 compu-dialins.Z
`09/14/1992 12:00AM 17,419 domain-info
`09/14/1992 12:00AM 1,574 for-help
`09/14/1992 12:00AM 4,354 general-info
`09/14/1992 12:00AM 2,091 holt-books
`09/14/1992 12:00AM 1,411 index
`09/14/1992 12:00AM 1,014 info-pkg
`09/14/1992 12:00AM 11,475 ip-access
`09/14/1992 12:00AM 20,534 jw-books
`09/14/1992 12:00AM 1,098 low-volume
`09/14/1992 12:00AM 980 ls-lR.Z
`09/14/1992 12:00AM 1,893 modem-prices
`09/14/1992 12:00AM 87,293 newsgroups.Z
`09/14/1992 12:00AM 2,371 nutshell-books
`09/14/1992 12:00AM 49,417 ph-books
`09/14/1992 12:00AM 1,766 source-tapes
`09/14/1992 12:00AM 2,254 subscript-rates
`09/14/1992 12:00AM 154 sys
`09/14/1992 12:00AM 121,935 sys.Z
`09/14/1992 12:00AM 1,827 tac
`09/14/1992 12:00AM 5,169 ups-info
`09/14/1992 12:00AM 15,710 us-domain
`09/14/1992 12:00AM 253 uunet-canada
`09/14/1992 12:00AM 287 uunet-india
`09/14/1992 12:00AM 45,969 uunet-map
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`FTP directory /ftp/index/doc/netinfo/UUNET/Telebit-Info/ at ftp.funet.fi
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`Explorer.
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`03/08/1991 12:00AM 4,033 MASS.setup.Z
`08/11/1999 12:00AM Directory PRODUCTS
`03/08/1991 12:00AM 1,725 PRODUCTS.list.Z
`03/08/1991 12:00AM 2,615 SETUPS.list.Z
`03/08/1991 12:00AM 5,321 SUN.setup.Z
`03/08/1991 12:00AM 5,321 SUN3.setup.Z
`03/08/1991 12:00AM 5,053 SUN386i.setup.Z
`03/08/1991 12:00AM 5,185 SUN4.setup.Z
`03/08/1991 12:00AM 5,441 SUNSPARC.setup.Z
`03/08/1991 12:00AM 5,446 SUNSPARC_4.1.setup.Z
`03/08/1991 12:00AM 4,829 UNISYS.setup.Z
`03/08/1991 12:00AM 19,008 UNIX.setup.Z
`03/08/1991 12:00AM 4,060 UNIXPC.setup.Z
`03/08/1991 12:00AM 2,971 UUNET900.setup.Z
`03/08/1991 12:00AM 4,757 VAX.setup.Z
`03/08/1991 12:00AM 4,207 XENIX22X.setup.Z
`03/08/1991 12:00AM 936 ls-l.Z
`03/08/1991 12:00AM 918 ls-lR.Z
`03/08/1991 12:00AM 3,437 ppp.doc.Z
`03/08/1991 12:00AM 5,294 slip.doc.Z
`03/08/1991 12:00AM 5,308 tech.doc.Z
`03/08/1991 12:00AM 3,071 upgrade.doc.Z
`03/08/1991 12:00AM 1,872 warranty.doc.Z
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`ftp://ftp.funet.fi/ftp/index/doc/netinfo/UUNET/Telebit-Info/
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`FTP directory /ftp/index/doc/netinfo/UUNET/Telebit-Info/PRODUCTS/ at ftp.funet.fi
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`Explorer.
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`03/08/1991 12:00AM 3,581 CBLAZER.intro.Z
`03/08/1991 12:00AM 1,300 T1000.intro.Z
`03/08/1991 12:00AM 3,851 T2500.intro.Z
`03/08/1991 12:00AM 5,693 cellblazer.Z
`03/08/1991 12:00AM 5,579 cellblazer.pc.Z
`03/08/1991 12:00AM 5,227 t1000.Z
`03/08/1991 12:00AM 4,792 t1000.pc.Z
`03/08/1991 12:00AM 8,296 t2000.Z
`03/08/1991 12:00AM 6,157 t2500.Z
`03/08/1991 12:00AM 4,412 t9000.rm.Z
`03/08/1991 12:00AM 4,763 tb+pc.Z
`03/08/1991 12:00AM 4,762 tb+ps2.Z
`03/08/1991 12:00AM 5,158 trailblazer+.Z
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`ftp://ftp.funet.fi/ftp/index/doc/netinfo/UUNET/Telebit-Info/PRODUCTS/
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`
`========================================================================
`Telebit Corporation Revision 1.02 01 APRIL 1990
`========================================================================
` A BRIEF TECHNICAL OVERVIEW OF TELEBIT MODEMS
` By Michael Ballard, Director, Network Systems, Telebit Corp.
` Edited by C. E. Castillo, UNIX Communications Specialist, Telebit Corp.
`
`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/Cerafin E. Castillo
` Telebit Corporation
` 1315 Chesapeake Terrace
` Sunnyvale, CA 94089
` 1-800-TELEBIT
` UUCP: {ames, uunet, sun, pyramid, decwrl}!telebit!modems
` INTERNET: modems@telebit.com