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╘HE ┌═╧─┼═ ╔NTER ┴PPLICATION ╞ILE ╘RANSFER ╨ROTOCOL ├HUCK ╞ORSBERG ╧MEN ╘ECHNOLOGY ╔NC ┴ OVERVIEW OF THIS DOCUMENT IS AVAILABLE AS ┌═╧─┼═.╧╓ (IN ┌═─═╧╓.┴╥├) ╧MEN ╘ECHNOLOGY ╔NCORPORATED ╘HE ╚IGH ╥ELIABILITY ╙OFTWARE 17505-╓ ╬ORTHWEST ╙AUVIE ╔SLAND ╥OAD ╨ORTLAND ╧REGON 97231 ╓╧╔├┼: 503-621-3406 :╓╧╔├┼ ═ODEM: 503-621-3746 ╙PEED 1200,2400,19200(╘ELEBIT ╨┼╨) ├OMPUSERVE:70007,2304 ╟┼NIE:├┴╞ ╒╒├╨: ...!TEKTRONIX!REED!OMEN!CAF ┴┬╙╘╥┴├╘ ╘HE ┌═╧─┼═ FILE TRANSFER PROTOCOL PROVIDES RELIABLE FILE AND COMMAND TRANSFERS WITH COMPLETE END-TO-END DATA INTEGRITY BETWEEN APPLICATION PROGRAMS. ┌═╧─┼═'S 32-BIT ├╥├ CATCHES ERRORS THAT CONTINUE TO SNEAK INTO EVEN THE MOST ADVANCED NETWORKS. ┌═╧─┼═ RAPIDLY TRANSFERS FILES, PARTICULARLY WITH BUFFERED (ERROR CORRECTING) MODEMS, TIMESHARING SYSTEMS, SATELLITE RELAYS, AND WIDE AREA PACKET SWITCHED NETWORKS. ┌═╧─┼═ GREATLY SIMPLIFIES FILE TRANSFERS COMPARED TO ╪═╧─┼═. ╔N ADDITION TO A FRIENDLY USER INTERFACE, ┌═╧─┼═ PROVIDES ╨ERSONAL ├OMPUTER AND OTHER USERS AN EFFICIENT, ACCURATE, AND ROBUST FILE TRANSFER METHOD. ┌═╧─┼═ PROVIDES ADVANCED FILE MANAGEMENT FEATURES INCLUDING ┴UTO─OWNLOAD (┴UTOMATIC FILE ─OWNLOAD INITIATED WITHOUT USER INTERVENTION), ├RASH ╥ECOVERY, SELECTIVE FILE TRANSFERS, AND SECURITY VERIFIED COMMAND DOWNLOADING. ┌═╧─┼═ PROTOCOL FEATURES ALLOW IMPLEMENTATION ON A WIDE VARIETY OF SYSTEMS OPERATING IN A WIDE VARIETY OF ENVIRONMENTS. ┴ CHOICE OF BUFFERING AND WINDOWING MODES ALLOWS ┌═╧─┼═ TO OPERATE ON SYSTEMS THAT CANNOT SUPPORT OTHER STREAMING PROTOCOLS. ╞INELY TUNED CONTROL CHARACTER ESCAPING ALLOWS OPERATION WITH REAL WORLD NETWORKS WITHOUT ╦ERMIT'S HIGH OVERHEAD. ┴LTHOUGH ┌═╧─┼═ SOFTWARE IS MORE COMPLEX THAN UNRELIABLE ╪═╧─┼═ ROUTINES, ACTUAL ├ SOURCE CODE TO PRODUCTION PROGRAMS ALLOWS DEVELOPERS TO UPGRADE THEIR APPLICATIONS WITH EFFICIENT, RELIABLE ┌═╧─┼═ FILE TRANSFERS WITH A MINIMUM OF EFFORT. ┌═╧─┼═ IS CAREFULLY DESIGNED TO PROVIDE THESE BENEFITS USING A MINIMUM OF NEW SOFTWARE TECHNOLOGY. ┌═╧─┼═ CAN BE IMPLEMENTED ON ALL BUT THE MOST BRAIN-DAMAGED COMPUTERS. ┌═╧─┼═ WAS DEVELOPED FOR THE PUBLIC DOMAIN UNDER A ╘ELENET CONTRACT. ╘HE ┌═╧─┼═ PROTOCOL DESCRIPTIONS AND THE ╒NIX ╥┌/╙┌ PROGRAM SOURCE CODE ARE PUBLIC DOMAIN. ╬O LICENSING, TRADEMARK, OR COPYRIGHT RESTRICTIONS APPLY TO THE USE OF THE PROTOCOL, THE ╒NIX ╥┌/╙┌ SOURCE CODE AND THE ┌═╧─┼═ NAME. ├ ╧ ╬ ╘ ┼ ╬ ╘ ╙ 1. ╔╬╘┼╬─┼─ ┴╒─╔┼╬├┼....................................... 1 2. ╫╚┘ ─┼╓┼╠╧╨ ┌═╧─┼═?..................................... 1 3. ┌═╧─┼═ ╨ROTOCOL ─ESIGN ├RITERIA......................... 4 3.1 ┼ASE OF ╒SE..................................... 4 3.2 ╘HROUGHPUT...................................... 4 3.3 ╔NTEGRITY AND ╥OBUSTNESS........................ 5 3.4 ┼ASE OF ╔MPLEMENTATION.......................... 5 4. ┼╓╧╠╒╘╔╧╬ ╧╞ ┌═╧─┼═..................................... 6 5. ╥╧╙┼╘╘┴ ╙╘╧╬┼........................................... 9 6. ┌═╧─┼═ ╥┼╤╒╔╥┼═┼╬╘╙..................................... 10 6.1 ╞ILE ├ONTENTS................................... 10 7. ┌═╧─┼═ ┬┴╙╔├╙........................................... 11 7.1 ╨ACKETIZATION................................... 11 7.2 ╠INK ┼SCAPE ┼NCODING............................ 12 7.3 ╚EADER.......................................... 13 7.4 ┬INARY ─ATA ╙UBPACKETS.......................... 16 7.5 ┴╙├╔╔ ┼NCODED ─ATA ╙UBPACKET.................... 16 8. ╨╥╧╘╧├╧╠ ╘╥┴╬╙┴├╘╔╧╬ ╧╓┼╥╓╔┼╫........................... 16 8.1 ╙ESSION ╙TARTUP................................. 16 8.2 ╞ILE ╘RANSMISSION............................... 18 8.3 ╙ESSION ├LEANUP................................. 20 8.4 ╙ESSION ┴BORT ╙EQUENCE.......................... 20 9. ╙╘╥┼┴═╔╬╟ ╘┼├╚╬╔╤╒┼╙ / ┼╥╥╧╥ ╥┼├╧╓┼╥┘................... 20 9.1 ╞ULL ╙TREAMING WITH ╙AMPLING.................... 21 9.2 ╞ULL ╙TREAMING WITH ╥EVERSE ╔NTERRUPT........... 23 9.3 ╞ULL ╙TREAMING WITH ╙LIDING ╫INDOW.............. 23 9.4 ╞ULL ╙TREAMING OVER ┼RROR ╞REE ├HANNELS......... 23 9.5 ╙EGMENTED ╙TREAMING............................. 24 10. ┴╘╘┼╬╘╔╧╬ ╙┼╤╒┼╬├┼...................................... 24 11. ╞╥┴═┼ ╘┘╨┼╙............................................. 25 11.1 ┌╥╤╔╬╔╘......................................... 25 11.2 ┌╥╔╬╔╘.......................................... 25 11.3 ┌╙╔╬╔╘.......................................... 25 11.4 ┌┴├╦............................................ 26 11.5 ┌╞╔╠┼........................................... 26 11.6 ┌╙╦╔╨........................................... 28 11.7 ┌╬┴╦............................................ 28 11.8 ┌┴┬╧╥╘.......................................... 28 11.9 ┌╞╔╬............................................ 28 11.10 ┌╥╨╧╙........................................... 28 11.11 ┌─┴╘┴........................................... 29 11.12 ┌┼╧╞............................................ 29 11.13 ┌╞┼╥╥........................................... 29 11.14 ┌├╥├............................................ 29 11.15 ┌├╚┴╠╠┼╬╟┼...................................... 29 11.16 ┌├╧═╨╠.......................................... 29 11.17 ┌├┴╬............................................ 29 11.18 ┌╞╥┼┼├╬╘........................................ 29 11.19 ┌├╧══┴╬─........................................ 29 12. ╙┼╙╙╔╧╬ ╘╥┴╬╙┴├╘╔╧╬ ┼╪┴═╨╠┼╙............................ 30 12.1 ┴ SIMPLE FILE TRANSFER.......................... 30 12.2 ├HALLENGE AND ├OMMAND ─OWNLOAD.................. 31 13. ┌╞╔╠┼ ╞╥┴═┼ ╞╔╠┼ ╔╬╞╧╥═┴╘╔╧╬............................ 31 14. ╨┼╥╞╧╥═┴╬├┼ ╥┼╙╒╠╘╙..................................... 33 14.1 ├OMPATIBILITY................................... 33 14.2 ╘HROUGHPUT...................................... 33 14.3 ┼RROR ╥ECOVERY.................................. 34 15. ╨┴├╦┼╘ ╙╫╔╘├╚┼─ ╬┼╘╫╧╥╦ ├╧╬╙╔─┼╥┴╘╔╧╬╙.................. 35 16. ╨┼╥╞╧╥═┴╬├┼ ├╧═╨┴╥╔╙╧╬ ╘┴┬╠┼╙........................... 36 17. ╞╒╘╒╥┼ ┼╪╘┼╬╙╔╧╬╙....................................... 41 18. ╥┼╓╔╙╔╧╬╙............................................... 42 19. ═╧╥┼ ╔╬╞╧╥═┴╘╔╧╬........................................ 43 19.1 ╘ELE╟ODZILLA ┬ULLETIN ┬OARD..................... 43 19.2 ╒NIX ╒╒├╨ ┴CCESS................................ 43 20. ┌═╧─┼═ ╨╥╧╟╥┴═╙......................................... 44 20.1 ┴DDING ┌═╧─┼═ TO ─╧╙ ╨ROGRAMS................... 45 21. ┘═╧─┼═ ╨╥╧╟╥┴═╙......................................... 46 22. ┴├╦╬╧╫╠┼─╟═┼╬╘╙......................................... 46 23. ╥┼╠┴╘┼─ ╞╔╠┼╙........................................... 47 ╠╔╙╘ ╧╞ ╞╔╟╒╥┼╙ ╞IGURE 1. ╧RDER OF ┬YTES IN ╚EADER.......................... 13 ╞IGURE 2. 16 ┬IT ├╥├ ┬INARY ╚EADER.......................... 14 ╞IGURE 3. 32 ┬IT ├╥├ ┬INARY ╚EADER.......................... 14 ╞IGURE 4. ╚┼╪ ╚EADER........................................ 15 ╞IGURE 5. ╘RANSMISSION ╘IME ├OMPARISON...................... 37 ╠╔╙╘ ╧╞ ╘┴┬╠┼╙ ╘┴┬╠┼ 1. ╬ETWORK AND ╞LOW ├ONTROL ├OMPATIBILITY............. 36 ╘┴┬╠┼ 2. ╨ROTOCOL ╧VERHEAD ╔NFORMATION...................... 37 ╘┴┬╠┼ 3. ╠OCAL ╘IMESHARING ├OMPUTER ─OWNLOAD ╨ERFORMANCE.... 37 ╘┴┬╠┼ 4. ╞ILE ╘RANSFER ╙PEEDS............................... 38 ╘┴┬╠┼ 5. ╨ROTOCOL ├HECKLIST................................. 40 ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 1 1. ╔╬╘┼╬─┼─ ┴╒─╔┼╬├┼ ╘HIS DOCUMENT IS INTENDED FOR TELECOMMUNICATIONS MANAGERS, SYSTEMS PROGRAMMERS, AND OTHERS WHO CHOOSE AND IMPLEMENT ASYNCHRONOUS FILE TRANSFER PROTOCOLS OVER DIAL-UP NETWORKS AND RELATED ENVIRONMENTS. 2. ╫╚┘ ─┼╓┼╠╧╨ ┌═╧─┼═? ╙INCE ITS DEVELOPMENT HALF A DECADE AGO, THE ╫ARD ├HRISTENSEN MODEM PROTOCOL HAS ENABLED A WIDE VARIETY OF COMPUTER SYSTEMS TO INTERCHANGE DATA. ╘HERE IS HARDLY A COMMUNICATIONS PROGRAM THAT DOESN'T AT LEAST CLAIM TO SUPPORT THIS PROTOCOL, NOW CALLED ╪═╧─┼═. ┴DVANCES IN COMPUTING, MODEMS AND NETWORKING HAVE SPREAD THE ╪═╧─┼═ PROTOCOL FAR BEYOND THE MICRO TO MICRO ENVIRONMENT FOR WHICH IT WAS DESIGNED. ╘HESE APPLICATION HAVE EXPOSED SOME WEAKNESSES: ==> ╘HE AWKWARD USER INTERFACE IS SUITABLE FOR COMPUTER HOBBYISTS. ═ULTIPLE COMMANDS MUST BE KEYBOARDED TO TRANSFER EACH FILE. ==> ╙INCE COMMANDS MUST BE GIVEN TO BOTH PROGRAMS, SIMPLE MENU SELECTIONS ARE NOT POSSIBLE. ==> ╘HE SHORT BLOCK LENGTH CAUSES THROUGHPUT TO SUFFER WHEN USED WITH TIMESHARING SYSTEMS, PACKET SWITCHED NETWORKS, SATELLITE CIRCUITS, AND BUFFERED (ERROR CORRECTING) MODEMS. ==> ╘HE 8-BIT CHECKSUM AND UNPROTECTED SUPERVISON ALLOW UNDETECTED ERRORS AND DISRUPTED FILE TRANSFERS. ==> ╧NLY ONE FILE CAN BE SENT PER COMMAND. ╘HE FILE NAME HAS TO BE GIVEN TWICE, FIRST TO THE SENDING PROGRAM AND THEN AGAIN TO THE RECEIVING PROGRAM. ==> ╘HE TRANSMITTED FILE ACCUMULATES AS MANY AS 127 BYTES OF GARBAGE. ==> ╘HE MODIFICATION DATE AND OTHER FILE ATTRIBUTES ARE LOST. ==> ╪═╧─┼═ REQUIRES COMPLETE 8-BIT TRANSPARENCY, ALL 256 CODES. ╪═╧─┼═ WILL NOT OPERATE OVER SOME NETWORKS THAT USE ┴╙├╔╔ FLOW CONTROL OR ESCAPE CODES. ╙ETTING NETWORK TRANSPARENCY DISABLES IMPORTANT CONTROL FUNCTIONS FOR THE DURATION OF THE CALL. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 2 ┴ NUMBER OF OTHER PROTOCOLS HAVE BEEN DEVELOPED OVER THE YEARS, BUT NONE HAVE PROVEN SATISFACTORY. ==> ╠ACK OF PUBLIC-DOMAIN DOCUMENTATION AND EXAMPLE PROGRAMS HAVE KEPT PROPRIETARY PROTOCOLS SUCH AS ╥┼╠┴┘, ┬╠┴╙╘, AND OTHERS TIGHTLY BOUND TO THE FORTUNES OF THEIR SUPPLIERS. ╘HESE PROTOCOLS HAVE NOT BENEFITED FROM PUBLIC SCRUTINY OF THEIR DESIGN FEATURES. ==> ╠INK-LEVEL PROTOCOLS SUCH AS ╪.25, ╪.╨├, AND ═╬╨ DO NOT MANAGE APPLICATION-TO-APPLICATION FILE TRANSFERS. ==> ╠INK-LEVEL PROTOCOLS DO NOT ELIMINATE END-TO-END ERRORS. ╔NTERFACES BETWEEN ERROR-FREE NETWORKS ARE NOT NECESSARILY ERROR-FREE. ╙OMETIMES, ERROR-FREE NETWORKS AREN'T. ==> ╘HE ╦┼╥═╔╘ PROTOCOL WAS DEVELOPED TO ALLOW FILE TRANSFERS IN ENVIRONMENTS HOSTILE TO ╪═╧─┼═. ╘HE PERFORMANCE COMPROMISES NECESSARY TO ACCOMMODATE TRADITIONAL MAINFRAME ENVIRONMENTS LIMIT ╦ERMIT'S EFFICIENCY. ┼VEN WITH COMPLETELY TRANSPARENT CHANNELS, ╦ERMIT CONTROL CHARACTER QUOTING LIMITS THE EFFICIENCY OF BINARY FILE TRANSFERS TO ABOUT 75 PER CENT. [1] ┴ NUMBER OF SUBMODES ARE USED IN VARIOUS ╦ERMIT PROGRAMS, INCLUDING DIFFERENT METHODS OF TRANSFERRING BINARY FILES. ╘WO ╦ERMIT PROGRAMS WILL MYSTERIOUSLY FAIL TO OPERATE WITH EACH OTHER IF THE USER HAS NOT CORRECTLY SPECIFIED THESE SUBMODES. ╦ERMIT ╙LIDING ╫INDOWS ("╙UPER╦ERMIT") IMPROVES THROUGHPUT OVER NETWORKS AT THE COST OF INCREASED COMPLEXITY. ╙UPER╦ERMIT REQUIRES FULL DUPLEX COMMUNICATIONS AND THE ABILITY TO CHECK FOR THE PRESENCE OF CHARACTERS IN THE INPUT QUEUE, PRECLUDING ITS IMPLEMENTATION ON SOME OPERATING SYSTEMS. ╙UPER╦ERMIT STATE TRANSITIONS ARE ENCODED IN A SPECIAL LANGUAGE "WART" WHICH REQUIRES A ├ COMPILER. ╙UPER╦ERMIT SENDS AN ┴├╦ PACKET FOR EACH DATA PACKET OF 96 BYTES (FEWER IF CONTROL CHARACTERS ARE PRESENT). ╘HIS REDUCES THROUGHPUT ON HIGH-SPEED MODEMS, FROM 1350 TO 177 CHARACTERS PER SECOND IN ONE TEST. [1]. ╙OME ╦ERMIT PROGRAMS SUPPORT RUN-LENGTH ENCODING. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 3 ┴ NUMBER OF EXTENSIONS TO THE ╪═╧─┼═ PROTOCOL HAVE BEEN MADE TO IMPROVE PERFORMANCE AND (IN SOME CASES) THE USER INTERFACE. ╘HEY PROVIDE USEFUL IMPROVEMENTS IN SOME APPLICATIONS BUT NOT IN OTHERS. ╪═╧─┼═'S UNPROTECTED CONTROL MESSAGES COMPROMISE THEIR RELIABILITY. ├OMPLEX PROPRIETARY TECHNIQUES SUCH AS ├YBERNETIC ─ATA ╥ECOVERY (╘═) [1] IMPROVE RELIABILITY, BUT ARE NOT UNIVERSALLY AVAILABLE. ╙OME OF THE ╪═╧─┼═ MUTANT PROTOCOLS HAVE SIGNIFICANT DESIGN FLAWS OF THEIR OWN. ==> ╪═╧─┼═-╦ USES 1024 BYTE BLOCKS TO REDUCE THE OVERHEAD FROM TRANSMISSION DELAYS BY 87 PER CENT COMPARED TO ╪═╧─┼═, BUT NETWORK DELAYS STILL DEGRADE PERFORMANCE. ╙OME NETWORKS CANNOT TRANSMIT 1024 BYTE PACKETS WITHOUT FLOW CONTROL, WHICH IS DIFFICULT TO APPLY WITHOUT IMPAIRING THE PERFECT TRANSPARENCY REQUIRED BY ╪═╧─┼═. ╪═╧─┼═-╦ ADDS GARBAGE TO RECEIVED FILES. ==> ┘═╧─┼═ SENDS THE FILE NAME, FILE LENGTH, AND CREATION DATE AT THE BEGINNING OF EACH FILE, AND ALLOWS OPTIONAL 1024 BYTE BLOCKS FOR IMPROVED THROUGHPUT. ╘HE HANDLING OF FILES THAT ARE NOT A MULTIPLE OF 1024 OR 128 BYTES IS AWKWARD, ESPECIALLY IF THE FILE LENGTH IS NOT KNOWN IN ADVANCE, OR CHANGES DURING TRANSMISSION. ╘HE LARGE NUMBER OF NON-CONFORMING AND SUBSTANDARD PROGRAMS CLAIMING TO SUPPORT ┘═╧─┼═ FURTHER COMPLICATES ITS USE. ==> ┘═╧─┼═-╟ PROVIDES EFFICIENT BATCH FILE TRANSFERS, PRESERVING EXACT FILE LENGTH AND FILE MODIFICATION DATE. ┘═╧─┼═-╟ IS A MODIFICATION TO ┘═╧─┼═ WHEREIN ┴├╦S FOR DATA BLOCKS ARE NOT USED. ┘═╧─┼═-╟ IS ESSENTIALLY INSENSITIVE TO NETWORK DELAYS. ┬ECAUSE IT DOES NOT SUPPORT ERROR RECOVERY, ┘═╧─┼═-╟ MUST BE USED HARD WIRED OR WITH A RELIABLE LINK LEVEL PROTOCOL. ╙UCCESSFUL APPLICATION AT HIGH SPEED REQUIRES CAREFUL ATTENTION TO TRANSPARENT FLOW CONTROL. ╫HEN ┘═╧─┼═-╟ DETECTS A ├╥├ ERROR, DATA TRANSFERS ARE ABORTED. ┘═╧─┼═-╟ IS EASY TO IMPLEMENT BECAUSE IT CLOSELY RESEMBLES STANDARD ┘═╧─┼═. ==> ╫╪═╧─┼═, ╙┼┴╠╔╬╦, AND ═┼╟┴╠╔╬╦ HAVE APPLIED A SUBSET OF ┌═╧─┼═'S TECHNIQUES TO "├LASSIC ╪═╧─┼═" TO IMPROVE UPON THEIR SUPPLIERS' PREVIOUS OFFERINGS. ╘HEY PROVIDE GOOD PERFORMANCE UNDER IDEAL CONDITIONS. ┴NOTHER ╪═╧─┼═ "EXTENSION" IS PROTOCOL CHEATING, SUCH AS ╧MEN ╘ECHNOLOGY'S ╧╓┼╥╘╚╥╒╙╘┼╥(╘═) AND ╧╓┼╥╘╚╥╒╙╘┼╥ ╔╔(╘═). ╘HESE IMPROVE ╪═╧─┼═ THROUGHPUT UNDER SOME CONDITIONS BY COMPROMISING ERROR RECOVERY. ╘HE ┌═╧─┼═ ╨ROTOCOL CORRECTS THE WEAKNESSES DESCRIBED ABOVE WHILE MAINTAINING AS MUCH OF ╪═╧─┼═/├╥├'S SIMPLICITY AND PRIOR ART AS POSSIBLE. [1]. ╒NIQUE TO ─╙┌, ┌├╧══, ╨ROFESSIONAL-┘┴═ AND ╨OWER├OM. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 4 3. ┌═╧─┼═ ╨╥╧╘╧├╧╠ ─┼╙╔╟╬ ├╥╔╘┼╥╔┴ ╘HE DESIGN OF A FILE TRANSFER PROTOCOL IS AN ENGINEERING COMPROMISE BETWEEN CONFLICTING REQUIREMENTS: 3.1 ┼┴╙┼ ╧╞ ╒╙┼ ==> ┌═╧─┼═ ALLOWS EITHER PROGRAM TO INITIATE FILE TRANSFERS, PASSING COMMANDS AND/OR MODIFIERS TO THE OTHER PROGRAM. ==> ╞ILE NAMES NEED BE ENTERED ONLY ONCE. ==> ═ENU SELECTIONS ARE SUPPORTED. ==> ╫ILD ├ARD NAMES MAY BE USED WITH BATCH TRANSFERS. ==> ═INIMUM KEYSTROKES REQUIRED TO INITIATE TRANSFERS. ==> ┌╥╤╔╬╔╘ FRAME SENT BY SENDING PROGRAM CAN TRIGGER AUTOMATIC DOWNLOADS. ==> ┌═╧─┼═ CAN STEP DOWN TO ┘═╧─┼═ IF THE OTHER END DOES NOT SUPPORT ┌═╧─┼═. [1] 3.2 ╘╚╥╧╒╟╚╨╒╘ ┴LL FILE TRANSFER PROTOCOLS MAKE TRADEOFFS BETWEEN THROUGHPUT, RELIABILITY, UNIVERSALITY, AND COMPLEXITY ACCORDING TO THE TECHNOLOGY AND KNOWLEDGE BASE AVAILABLE TO THEIR DESIGNERS. ╔N THE DESIGN OF ┌═╧─┼═, THREE APPLICATIONS DESERVE SPECIAL ATTENTION. ==> ╬ETWORK APPLICATIONS WITH SIGNIFICANT DELAYS (RELATIVE TO CHARACTER TRANSMISSION TIME) AND LOW ERROR RATE. ==> ╘IMESHARING AND BUFFERED MODEM APPLICATIONS WITH SIGNIFICANT DELAYS AND THROUGHPUT THAT IS QUICKLY DEGRADED BY REVERSE CHANNEL TRAFFIC. ┌═╧─┼═'S ECONOMY OF REVERSE CHANNEL BANDWIDTH ALLOWS MODEMS THAT DYNAMICALLY PARTITION BANDWIDTH BETWEEN THE TWO DIRECTIONS TO OPERATE AT OPTIMAL SPEEDS. ╙PECIAL ┌═╧─┼═ FEATURES ALLOW SIMPLE, EFFICIENT IMPLEMENTATION ON A WIDE VARIETY OF TIMESHARING HOSTS. [1]. ╨ROVIDED THE TRANSMISSION MEDIUM ACCOMMODATES ╪/┘═╧─┼═. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 5 ==> ─IRECT MODEM TO MODEM COMMUNICATIONS WITH HIGH ERROR RATE. ╒NLIKE ╙LIDING ╫INDOWS ╦ERMIT, ┌═╧─┼═ IS NOT OPTIMIZED FOR OPTIMUM THROUGHPUT WHEN ERROR RATE AND DELAYS ARE BOTH HIGH. ╘HIS TRADEOFF MARKEDLY REDUCES CODE COMPLEXITY AND MEMORY REQUIREMENTS. ┌═╧─┼═ GENERALLY PROVIDES FASTER ERROR RECOVERY THAN NETWORK COMPATIBLE ╪═╧─┼═ IMPLEMENTATIONS. ╔N THE ABSENCE OF NETWORK DELAYS, RAPID ERROR RECOVERY IS POSSIBLE, MUCH FASTER THAN ═┼╟┴LINK AND NETWORK COMPATIBLE VERSIONS OF ┘═╧─┼═ AND ╪═╧─┼═. ╞ILE TRANSFERS BEGIN IMMEDIATELY REGARDLESS OF WHICH PROGRAM IS STARTED FIRST, WITHOUT THE 10-SECOND DELAY ASSOCIATED WITH ╪═╧─┼═. 3.3 ╔╬╘┼╟╥╔╘┘ ┴╬─ ╥╧┬╒╙╘╬┼╙╙ ╧NCE A ┌═╧─┼═ SESSION IS BEGUN, ALL TRANSACTIONS ARE PROTECTED WITH 16- OR 32-BIT ├╥├. [1] ├OMPLEX PROPRIETARY TECHNIQUES SUCH AS ├YBERNETIC ─ATA ╥ECOVERY (╘═) [2] ARE NOT NEEDED FOR RELIABLE TRANSFERS. ┴N OPTIONAL 32-BIT ├╥├ USED AS THE FRAME CHECK SEQUENCE IN ┴─├├╨ (┴╬╙╔ ╪3.66, ALSO KNOWN AS ╞╔╨╙ ╨╒┬ 71 AND ╞┼─-╙╘─-1003, THE ╒.╙. VERSIONS OF ├├╔╘╘'S ╪.25) IS USED WHEN AVAILABLE. ╘HE 32-BIT ├╥├ REDUCES UNDETECTED ERRORS BY AT LEAST FIVE ORDERS OF MAGNITUDE WHEN PROPERLY APPLIED (-1 PRESET, INVERSION). ┴ SECURITY CHALLENGE MECHANISM GUARDS AGAINST "╘ROJAN ╚ORSE" MESSAGES WRITTEN TO MIMIC LEGITIMATE COMMAND OR FILE DOWNLOADS. 3.4 ┼┴╙┼ ╧╞ ╔═╨╠┼═┼╬╘┴╘╔╧╬ ┌═╧─┼═ ACCOMMODATES A WIDE VARIETY OF SYSTEMS: ==> ═ICROCOMPUTERS THAT CANNOT OVERLAP DISK AND SERIAL I/O. ==> ═ICROCOMPUTERS THAT CANNOT OVERLAP SERIAL SEND AND RECEIVE. ==> ├OMPUTERS AND/OR NETWORKS REQUIRING ╪╧╬/╪╧╞╞ FLOW CONTROL. [1]. ┼XCEPT FOR THE ├┴╬-├┴╬-├┴╬-├┴╬-├┴╬ ABORT SEQUENCE WHICH REQUIRES FIVE SUCCESSIVE ├┴╬ CHARACTERS. [2]. ╒NIQUE TO ╨ROFESSIONAL-┘┴═ AND ╨OWER├OM. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 6 ==> ├OMPUTERS THAT CANNOT CHECK THE SERIAL INPUT QUEUE FOR THE PRESENCE OF DATA WITHOUT HAVING TO WAIT FOR THE DATA TO ARRIVE. ┴LTHOUGH ┌═╧─┼═ PROVIDES "HOOKS" FOR MULTIPLE "THREADS", ┌═╧─┼═ IS NOT INTENDED TO REPLACE LINK-LEVEL PROTOCOLS SUCH AS ╪.25. ┌═╧─┼═ ACCOMMODATES NETWORK AND TIMESHARING SYSTEM DELAYS BY CONTINUOUSLY TRANSMITTING DATA UNLESS THE RECEIVER INTERRUPTS THE SENDER TO REQUEST RETRANSMISSION OF GARBLED DATA. ┌═╧─┼═ IN EFFECT USES THE ENTIRE FILE AS A WINDOW. [1] ╒SING THE ENTIRE FILE AS A WINDOW SIMPLIFIES BUFFER MANAGEMENT, AVOIDING THE WINDOW-OVERRUN FAILURE MODES THAT AFFECT ═┼╟┴LINK, ╙UPER╦ERMIT, AND OTHERS. ┌═╧─┼═ PROVIDES A GENERAL PURPOSE APPLICATION TO APPLICATION FILE TRANSFER PROTOCOL WHICH MAY BE USED DIRECTLY OR WITH WITH RELIABLE LINK LEVEL PROTOCOLS SUCH AS ╪.25, ═╬╨, ╞ASTLINK, ETC. ╫HEN USED WITH ╪.25, ═╬╨, ╞ASTLINK, ETC., ┌═╧─┼═ DETECTS AND CORRECTS ERRORS IN THE INTERFACES BETWEEN ERROR-CONTROLLED MEDIA AND THE REMAINDER OF THE COMMUNICATIONS LINK. ┌═╧─┼═ WAS DEVELOPED FOR THE PUBLIC DOMAIN UNDER A ╘ELENET CONTRACT. ╘HE ┌═╧─┼═ PROTOCOL DESCRIPTIONS AND THE ╒NIX ╥┌/╙┌ PROGRAM SOURCE CODE ARE PUBLIC DOMAIN. ╬O LICENSING, TRADEMARK, OR COPYRIGHT RESTRICTIONS APPLY TO THE USE OF THE PROTOCOL, THE ╒NIX ╥┌/╙┌ SOURCE CODE OR THE ┌═╧─┼═ NAME. 4. ┼╓╧╠╒╘╔╧╬ ╧╞ ┌═╧─┼═ ╔N EARLY 1986, ╘ELENET FUNDED A PROJECT TO DEVELOP AN IMPROVED PUBLIC- DOMAIN APPLICATION-TO-APPLICATION FILE TRANSFER PROTOCOL. ╘HIS PROTOCOL WOULD ALLEVIATE THE THROUGHPUT PROBLEMS NETWORK CUSTOMERS WERE EXPERIENCING WITH ╪═╧─┼═ AND ╦ERMIT FILE TRANSFERS. ╔N THE BEGINNING, WE THOUGHT A FEW MODIFICATIONS TO ╪═╧─┼═ WOULD ALLOW HIGH PERFORMANCE OVER PACKET-SWITCHED NETWORKS WHILE PRESERVING ╪═╧─┼═'S SIMPLICITY. ╘HE INITIAL CONCEPT WOULD ADD A BLOCK NUMBER TO THE ┴├╦ AND ╬┴╦ CHARACTERS USED BY ╪═╧─┼═. ╘HE RESULTANT PROTOCOL WOULD ALLOW THE SENDER TO SEND MORE THAN ONE BLOCK BEFORE WAITING FOR A RESPONSE. [1]. ╙TREAMING STRATEGIES ARE DISCUSSED IN COMING CHAPTERS. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 7 ┬UT HOW TO ADD THE BLOCK NUMBER TO ╪═╧─┼═'S ┴├╦ AND ╬┴╦? ╫╪═╧─┼═, ╙┼┴LINK, ═┼╟┴LINK AND SOME OTHER PROTOCOLS ADD BINARY BYTE(S) TO INDICATE THE BLOCK NUMBER. ╨URE BINARY WAS UNSUITABLE FOR ┌═╧─┼═ BECAUSE BINARY CODE COMBINATIONS WON'T PASS BIDIRECTIONALLY THROUGH SOME MODEMS, NETWORKS AND OPERATING SYSTEMS. ╧THER OPERATING SYSTEMS MAY NOT BE ABLE TO RECOGNIZE SOMETHING COMING BACK [1] UNLESS A BREAK SIGNAL OR A SYSTEM DEPENDENT CODE OR SEQUENCE IS PRESENT. ┬Y THE TIME ALL THIS AND OTHER PROBLEMS WITH THE SIMPLE ┴├╦/╬┴╦ SEQUENCES MENTIONED ABOVE WERE CORRECTED, ╪═╧─┼═'S SIMPLE ┴├╦ AND ╬┴├╦ CHARACTERS HAD EVOLVED INTO A REAL PACKET. ╘HE ╞ROG WAS RIVETING. ═ANAGING THE WINDOW [2] WAS ANOTHER PROBLEM. ┼XPERIENCE GAINED IN DEBUGGING ╘HE ╙OURCE'S ╙UPER╦ERMIT PROTOCOL INDICATED A WINDOW SIZE OF ABOUT 1000 CHARACTERS WAS NEEDED AT 1200 BPS. ╚IGH SPEED MODEMS REQUIRE A WINDOW OF 20000 OR MORE CHARACTERS FOR FULL THROUGHPUT. ═UCH OF THE ╙UPER╦ERMIT'S INEFFICIENCY, COMPLEXITY AND DEBUGGING TIME CENTERED AROUND ITS RING BUFFERING AND WINDOW MANAGEMENT. ╘HERE HAD TO BE A BETTER WAY TO GET THE JOB DONE. ┴ SORE POINT WITH ╪═╧─┼═ AND ITS PROGENY IS ERROR RECOVERY. ═ORE TO THE POINT, HOW CAN THE RECEIVER DETERMINE WHETHER THE SENDER HAS RESPONDED, OR IS READY TO RESPOND, TO A RETRANSMISSION REQUEST? ╪═╧─┼═ ATTACKS THE PROBLEM BY THROWING AWAY CHARACTERS UNTIL A CERTAIN PERIOD OF SILENCE. ╘OO SHORT A TIME ALLOWS A SPURIOUS PAUSE IN OUTPUT (NETWORK OR TIMESHARING CONGESTION) TO MASQUERADE AS ERROR RECOVERY. ╘OO LONG A TIMEOUT DEVASTATES THROUGHPUT, AND ALLOWS A NOISY LINE TO LOCK UP THE PROTOCOL. ╙UPER╦ERMIT SOLVES THE PROBLEM WITH A DISTINCT START-OF-PACKET CHARACTER (╙╧╚). ╫╪═╧─┼═ AND ┌═╧─┼═ USE UNIQUE CHARACTER SEQUENCES TO DELINEATE THE START OF FRAMES. ╙┼┴LINK AND ═┼╟┴LINK DO NOT ADDRESS THIS PROBLEM. ┴ FURTHER ERROR-RECOVERY PROBLEM ARISES IN STREAMING PROTOCOLS. ╚OW DOES THE RECEIVER KNOW WHEN (OR IF) THE SENDER HAS RECOGNIZED ITS ERROR SIGNAL? ╔S THE NEXT PACKET THE CORRECT RESPONSE TO THE ERROR SIGNAL? ╔S IT SOMETHING LEFT OVER "IN THE QUEUE"? ╧R IS THIS NEW SUBPACKET ONE OF MANY THAT WILL HAVE TO BE DISCARDED BECAUSE THE SENDER DID NOT RECEIVE THE ERROR SIGNAL? ╚OW LONG SHOULD THIS CONTINUE BEFORE SENDING ANOTHER ERROR SIGNAL? ╚OW CAN THE PROTOCOL PREVENT THIS FROM DEGENERATING INTO AN ARGUMENT ABOUT MIXED SIGNALS? [1]. ╫ITHOUT STOPPING FOR A RESPONSE. [2]. ╘HE ╫╔╬─╧╫ IS THE DATA IN TRANSIT BETWEEN SENDER AND RECEIVER. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 8 ╙UPER╦ERMIT USES SELECTIVE RETRANSMISSION, SO IT CAN ACCEPT ANY GOOD PACKET IT RECEIVES. ┼ACH TIME THE ╙UPER╦ERMIT RECEIVER GETS A DATA PACKET, IT MUST DECIDE WHICH OUTSTANDING PACKET (IF ANY) IT "WANTS MOST" TO RECEIVE, AND ASKS FOR THAT ONE. ╔N PRACTICE, COMPLEX SOFTWARE "HACKS" ARE NEEDED TO ATTAIN ACCEPTABLE ROBUSTNESS. [1] ╞OR ┌═╧─┼═, WE DECIDED TO FORGO THE COMPLEXITY OF ╙UPER╦ERMIT'S PACKET ASSEMBLY SCHEME AND ITS ASSOCIATED BUFFER MANAGEMENT LOGIC AND MEMORY REQUIREMENTS. ┴NOTHER SORE POINT WITH ╪═╧─┼═ AND ╫╪═╧─┼═ IS THE GARBAGE ADDED TO FILES. ╘HIS WAS ACCEPTABLE WITH OLD ├╨/═ FILES WHICH HAD NO EXACT LENGTH, BUT NOT WITH MODERN SYSTEMS SUCH AS ─╧╙ AND ╒NIX. ┘═╧─┼═ USES FILE LENGTH INFORMATION TRANSMITTED IN THE HEADER BLOCK TO TRIM THE OUTPUT FILE, BUT THIS CAUSES DATA LOSS WHEN TRANSFERRING FILES THAT GROW DURING A TRANSFER. ╔N SOME CASES, THE FILE LENGTH MAY BE UNKNOWN, AS WHEN DATA IS OBTAINED FROM A PROCESS. ╓ARIABLE-LENGTH DATA SUBPACKETS SOLVE BOTH OF THESE PROBLEMS. ╙INCE SOME CHARACTERS HAD TO BE ESCAPED ANYWAY, THERE WASN'T ANY POINT WASTING BYTES TO FILL OUT A FIXED PACKET LENGTH OR TO SPECIFY A VARIABLE PACKET LENGTH. ╔N ┌═╧─┼═, THE LENGTH OF DATA SUBPACKETS IS DENOTED BY ENDING EACH SUBPACKET WITH AN ESCAPE SEQUENCE SIMILAR TO ┬╔╙┘╬├ AND ╚─╠├. ╘HE END RESULT IS A ┌═╧─┼═ HEADER CONTAINING A "FRAME TYPE", FOUR BYTES OF SUPERVISORY INFORMATION, AND ITS OWN ├╥├. ─ATA FRAMES CONSIST OF A HEADER FOLLOWED BY ONE OR MORE DATA SUBPACKETS. ╔N THE ABSENCE OF TRANSMISSION ERRORS, AN ENTIRE FILE CAN BE SENT IN ONE DATA FRAME. ╙INCE THE SENDING SYSTEM MAY BE SENSITIVE TO NUMEROUS CONTROL CHARACTERS OR STRIP PARITY IN THE REVERSE DATA PATH, ALL OF THE HEADERS SENT BY THE RECEIVER ARE SENT IN HEX. ┴ COMMON LOWER-LEVEL ROUTINE RECEIVES ALL HEADERS, ALLOWING THE MAIN PROGRAM LOGIC TO DEAL WITH HEADERS AND DATA SUBPACKETS AS OBJECTS. ╫ITH EQUIVALENT BINARY (EFFICIENT) AND HEX (APPLICATION FRIENDLY) FRAMES, THE SENDING PROGRAM CAN SEND AN "INVITATION TO RECEIVE" SEQUENCE TO ACTIVATE THE RECEIVER WITHOUT CRASHING THE REMOTE APPLICATION WITH UNEXPECTED CONTROL CHARACTERS. [1]. ╞OR EXAMPLE, WHEN ╙UPER╦ERMIT ENCOUNTERS CERTAIN ERRORS, THE ╫╬─┼╙╥ FUNCTION IS CALLED TO DETERMINE THE NEXT BLOCK TO REQUEST. ┴ BURST OF ERRORS GENERATES SEVERAL WASTEFUL REQUESTS TO RETRANSMIT THE SAME BLOCK. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 9 ╟OING "BACK TO SCRATCH" IN THE PROTOCOL DESIGN PRESENTS AN OPPORTUNITY TO STEAL GOOD IDEAS FROM MANY SOURCES AND TO ADD A FEW NEW ONES. ╞ROM ╦ERMIT AND ╒╒├╨ COMES THE CONCEPT OF AN INITIAL DIALOG TO EXCHANGE SYSTEM PARAMETERS. ┌═╧─┼═ GENERALIZES ├OMPUSERVE ┬ ╨ROTOCOL'S HOST-CONTROLLED TRANSFERS TO SINGLE-COMMAND ┴UTO─OWNLOAD AND COMMAND DOWNLOADING. ┴ ╙ECURITY ├HALLENGE DISCOURAGES PASSWORD HACKERS AND ╘ROJAN ╚ORSE AUTHORS FROM ABUSING ┌═╧─┼═'S POWER. ╫E WERE ALSO KEEN TO THE PAIN AND $UFFERING OF LEGIONS OF TELECOMMUNICATORS WHOSE FILE TRANSFERS HAVE BEEN RUINED BY COMMUNICATIONS AND TIMESHARING FAULTS. ┌═╧─┼═'S FILE TRANSFER RECOVERY AND ADVANCED FILE MANAGEMENT ARE DEDICATED TO THESE KINDRED COMRADES. ┴FTER ┌═╧─┼═ HAD BEEN OPERATIONAL A SHORT TIME, ┼ARL ╚ALL POINTED OUT THE OBVIOUS: ┌═╧─┼═'S USER-FRIENDLY ┴UTO─OWNLOAD WAS ALMOST USELESS IF THE USER MUST ASSIGN TRANSFER OPTIONS TO EACH OF THE SENDING AND RECEIVING PROGRAMS. ╬OW, TRANSFER OPTIONS MAY BE SPECIFIED TO/BY THE SENDING PROGRAM, WHICH PASSES THEM TO THE RECEIVING PROGRAM IN THE ┌╞╔╠┼ HEADER. 5. ╥╧╙┼╘╘┴ ╙╘╧╬┼ ╚ERE ARE SOME DEFINITIONS WHICH REFLECT CURRENT VERNACULAR IN THE COMPUTER MEDIA. ╘HE ATTEMPT HERE IS IDENTIFY THE FILE TRANSFER PROTOCOL RATHER THAN SPECIFIC PROGRAMS. ╞╥┴═┼ ┴ ┌═╧─┼═ FRAME CONSISTS OF A HEADER AND ZERO OR MORE DATA SUBPACKETS. ╪═╧─┼═ ╥EFERS TO THE ORIGINAL 1977 FILE TRANSFER ETIQUETTE INTRODUCED BY ╫ARD ├HRISTENSEN'S ═╧─┼═2 PROGRAM. ╔T'S ALSO CALLED THE ═╧─┼═ OR ═╧─┼═2 PROTOCOL. ╙OME WHO ARE UNAWARE OF ═╧─┼═7'S UNUSUAL BATCH FILE MODE CALL IT ═╧─┼═7. ╧THER ALIASES INCLUDE "├╨/═ ╒SERS'S ╟ROUP" AND "╘┼╥═ ╔╔ ╞╘╨ 3". ╘HIS PROTOCOL IS SUPPORTED BY MOST COMMUNICATIONS PROGRAMS BECAUSE IT IS EASY TO IMPLEMENT. ╪═╧─┼═/├╥├ ╥EPLACES ╪═╧─┼═'S ONE-BYTE CHECKSUM WITH A TWO-BYTE ├YCLICAL ╥EDUNDANCY ├HECK (├╥├-16), IMPROVING ERROR DETECTION. ╪═╧─┼═-1╦ ╥EFERS TO ╪═╧─┼═-├╥├ WITH OPTIONAL 1024-BYTE BLOCKS. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 10 ┘═╧─┼═ ╥EFERS TO THE ╪═╧─┼═/├╥├ PROTOCOL WITH BATCH TRANSMISSION AND OPTIONAL 1024 BYTE BLOCKS AS DESCRIBED IN ┘═╧─┼═.─╧├. [1] 6. ┌═╧─┼═ ╥┼╤╒╔╥┼═┼╬╘╙ ┌═╧─┼═ REQUIRES AN 8-BIT TRANSFER MEDIUM. [2] ┌═╧─┼═ ESCAPES NETWORK CONTROL CHARACTERS TO ALLOW OPERATION WITH PACKET SWITCHED NETWORKS. ╔N GENERAL, ┌═╧─┼═ OPERATES OVER ANY PATH THAT SUPPORTS ╪═╧─┼═, AND OVER MANY THAT DON'T. ╘O SUPPORT FULL STREAMING, [3] THE TRANSMISSION PATH SHOULD EITHER ASSERT FLOW CONTROL OR PASS FULL SPEED TRANSMISSION WITHOUT LOSS OF DATA. ╧THERWISE THE ┌═╧─┼═ SENDER MUST MANAGE THE WINDOW SIZE. 6.1 ╞╔╠┼ ├╧╬╘┼╬╘╙ 6.1.1 ┬╔╬┴╥┘ ╞╔╠┼╙ ┌═╧─┼═ PER SYSTEMS, TEXT FILES MUST MEET MINIMUM REQUIREMENTS IF THEY ARE TO BE READABLE ON A WIDE VARIETY OF SYSTEMS AND ENVIRONMENTS. ╘EXT LINES CONSIST OF PRINTING ┴╙├╔╔ CHARACTERS, SPACES, TABS, AND BACKSPACES. 6.1.2.1 ┴╙├╔╔ ┼╬─-╧╞-╠╔╬┼ ╘HE ┴╙├╔╔ CODE DEFINITION ALLOWS TEXT LINES TERMINATED BY A ├╥/╠╞ (013,012) SEQUENCE, OR BY A ╬╠ (012) CHARACTER. ╠INES LOGICALLY TERMINATED BY A LONE ├╥ (013) ARE NOT ┴╙├╔╔ TEXT. [1]. ┴VAILABLE ON ╘ELE╟ODZILLA AS PART OF ┘┌═╧─┼═.┌╧╧. [2]. ╘HE ┌═╧─┼═ DESIGN ALLOWS ENCODED PACKETS FOR LESS TRANSPARENT MEDIA. [3]. ╫ITH ╪╧╞╞ AND ╪╧╬, OR OUT-OF-BAND FLOW CONTROL SUCH AS ╪.25 OR ├╘╙. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 11 ┴ ├╥ (013) WITHOUT A LINEFEED IMPLIES OVERPRINTING, AND IS NOT ACCEPTABLE AS A LOGICAL LINE SEPARATOR. ╧VERPRINTED LINES SHOULD PRINT ALL IMPORTANT CHARACTERS IN THE LAST PASS TO ALLOW ├╥╘ DISPLAYS TO DISPLAY MEANINGFUL TEXT. ╧VERSTRUCK CHARACTERS MAY BE GENERATED BY BACKSPACING OR BY OVERPRINTING THE LINE WITH ├╥ (013) NOT FOLLOWED BY ╠╞. ╧VERSTRUCK CHARACTERS GENERATED WITH BACKSPACES SHOULD BE SENT WITH THE MOST IMPORTANT CHARACTER LAST TO ACCOMMODATE ├╥╘ DISPLAYS THAT CANNOT OVERSTRIKE. ╘HE SENDING PROGRAM MAY USE THE ┌├╬╠ BIT TO FORCE THE RECEIVING PROGRAM TO CONVERT THE RECEIVED END-OF-LINE TO ITS LOCAL END-OF-LINE CONVENTION. [1] 7. ┌═╧─┼═ ┬┴╙╔├╙ 7.1 ╨┴├╦┼╘╔┌┴╘╔╧╬ ┌═╧─┼═ FRAMES DIFFER SOMEWHAT FROM ╪═╧─┼═ BLOCKS. ╪═╧─┼═ BLOCKS ARE NOT USED FOR THE FOLLOWING REASONS: ==> ┬LOCK NUMBERS ARE LIMITED TO 256 ==> ╬O PROVISION FOR VARIABLE LENGTH BLOCKS ==> ╠INE HITS CORRUPT PROTOCOL SIGNALS, CAUSING FAILED FILE TRANSFERS. ╔N PARTICULAR, MODEM ERRORS SOMETIMES GENERATE FALSE BLOCK NUMBERS, FALSE ┼╧╘S AND FALSE ┴├╦S. ╞ALSE ┴├╦S ARE THE MOST TROUBLESOME AS THEY CAUSE THE SENDER TO LOSE SYNCHRONIZATION WITH THE RECEIVER. ╙TATE-OF-THE-ART PROGRAMS SUCH AS ╨ROFESSIONAL-┘┴═ AND ┌├╧══ OVERCOME SOME OF THESE WEAKNESSES WITH CLEVER PROPRIETARY CODE, BUT A STRONGER PROTOCOL IS DESIRED. ==> ╔T IS DIFFICULT TO DETERMINE THE BEGINNING AND ENDS OF ╪═╧─┼═ BLOCKS WHEN LINE HITS CAUSE A LOSS OF SYNCHRONIZATION. ╘HIS PRECLUDES RAPID ERROR RECOVERY. [1]. ╞ILES THAT HAVE BEEN TRANSLATED IN SUCH A WAY AS TO MODIFY THEIR LENGTH CANNOT BE UPDATED WITH THE ┌├╥┼├╧╓ ├ONVERSION ╧PTION. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 12 7.2 ╠╔╬╦ ┼╙├┴╨┼ ┼╬├╧─╔╬╟ ┌═╧─┼═ ACHIEVES DATA TRANSPARENCY BY EXTENDING THE 8-BIT CHARACTER SET (256 CODES) WITH ESCAPE SEQUENCES BASED ON THE ┌═╧─┼═ DATA LINK ESCAPE CHARACTER ┌─╠┼. [1] ╠INK ESCAPE CODING PERMITS VARIABLE-LENGTH DATA SUBPACKETS WITHOUT THE OVERHEAD OF A SEPARATE BYTE COUNT. ╔T ALLOWS THE BEGINNING OF FRAMES TO BE DETECTED WITHOUT SPECIAL TIMING TECHNIQUES, FACILITATING RAPID ERROR RECOVERY. ╠INK ESCAPE CODING DOES ADD SOME OVERHEAD. ╘HE WORST CASE, A FILE CONSISTING ENTIRELY OF ESCAPED CHARACTERS, WOULD INCUR A 50% OVERHEAD. ╘HE ┌─╠┼ CHARACTER IS SPECIAL. ┌─╠┼ REPRESENTS A CONTROL SEQUENCE OF SOME SORT. ╔F A ┌─╠┼ CHARACTER APPEARS IN BINARY DATA, IT IS PREFIXED WITH ┌─╠┼, THEN SENT AS ┌─╠┼┼. ╘HE VALUE FOR ┌─╠┼ IS OCTAL 030 (┴╙├╔╔ ├┴╬). ╘HIS PARTICULAR VALUE WAS CHOSEN TO ALLOW A STRING OF 5 CONSECUTIVE ├┴╬ CHARACTERS TO ABORT A ┌═╧─┼═ SESSION, COMPATIBLE WITH ┘═╧─┼═ SESSION ABORT. ╙INCE ├┴╬ IS NOT USED IN NORMAL TERMINAL OPERATIONS, INTERACTIVE APPLICATIONS AND COMMUNICATIONS PROGRAMS CAN MONITOR THE DATA FLOW FOR ┌─╠┼. ╘HE FOLLOWING CHARACTERS CAN BE SCANNED TO DETECT THE ┌╥╤╔╬╔╘ HEADER, THE INVITATION TO AUTOMATICALLY DOWNLOAD COMMANDS OR FILES. ╥ECEIPT OF FIVE SUCCESSIVE ├┴╬ CHARACTERS WILL ABORT A ┌═╧─┼═ SESSION. ┼IGHT ├┴╬ CHARACTERS ARE SENT. ╘HE RECEIVING PROGRAM DECODES ANY SEQUENCE OF ┌─╠┼ FOLLOWED BY A BYTE WITH BIT 6 SET AND BIT 5 RESET (UPPER CASE LETTER, EITHER PARITY) TO THE EQUIVALENT CONTROL CHARACTER BY INVERTING BIT 6. ╘HIS ALLOWS THE TRANSMITTER TO ESCAPE ANY CONTROL CHARACTER THAT CANNOT BE SENT BY THE COMMUNICATIONS MEDIUM. ╔N ADDITION, THE RECEIVER RECOGNIZES ESCAPES FOR 0177 AND 0377 SHOULD THESE CHARACTERS NEED TO BE ESCAPED. ┌═╧─┼═ SOFTWARE ESCAPES ┌─╠┼, 020, 021, 023, 0220, 0221, AND 0223. ╔F PRECEDED BY 0100 OR 0300 (@), 015 AND 0215 ARE ALSO ESCAPED TO PROTECT THE ╘ELENET COMMAND ESCAPE ├╥-@-├╥. ╘HE RECEIVER IGNORES 021, 023, 0221, AND 0223 CHARACTERS IN THE DATA STREAM. [1]. ╘HIS AND OTHER CONSTANTS ARE DEFINED IN THE ┌═╧─┼═.╚ INCLUDE FILE. ╨LEASE NOTE THAT CONSTANTS WITH A LEADING '0' ARE OCTAL CONSTANTS IN ├. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 13 ╘HE ┌═╧─┼═ ROUTINES IN ┌═.├ ACCEPT AN OPTION TO ESCAPE ALL CONTROL CHARACTERS, TO ALLOW OPERATION WITH LESS TRANSPARENT NETWORKS. ╘HIS OPTION CAN BE GIVEN TO EITHER THE SENDING OR RECEIVING PROGRAM. 7.3 ╚┼┴─┼╥ ┴LL ┌═╧─┼═ FRAMES BEGIN WITH A HEADER WHICH MAY BE SENT IN BINARY OR ╚┼╪ FORM. ┌═╧─┼═ USES A SINGLE ROUTINE TO RECOGNIZE BINARY AND HEX HEADERS. ┼ITHER FORM OF THE HEADER CONTAINS THE SAME RAW INFORMATION: ==> ┴ TYPE BYTE [1] [2] ==> ╞OUR BYTES OF DATA INDICATING FLAGS AND/OR NUMERIC QUANTITIES DEPENDING ON THE FRAME TYPE ╞IGURE 1. ╧RDER OF ┬YTES IN ╚EADER ╘┘╨┼:FRAME TYPE ╞0: ╞LAGS LEAST SIGNIFICANT BYTE ╨0: FILE ╨OSITION LEAST SIGNIFICANT ╨3: FILE ╨OSITION MOST SIGNIFICANT ╘┘╨┼ ╞3 ╞2 ╞1 ╞0 ------------------- ╘┘╨┼ ╨0 ╨1 ╨2 ╨3 7.3.1 16-┬╔╘ ├╥├ ┬╔╬┴╥┘ ╚┼┴─┼╥ ┴ BINARY HEADER IS SENT BY THE SENDING PROGRAM TO THE RECEIVING PROGRAM. ┌─╠┼ ENCODING ACCOMMODATES ╪╧╬/╪╧╞╞ FLOW CONTROL. ┴ BINARY HEADER BEGINS WITH THE SEQUENCE ┌╨┴─, ┌─╠┼, ┌┬╔╬. ╘HE FRAME TYPE BYTE IS ┌─╠┼-ENCODED. ╘HE FOUR POSITION/FLAGS BYTES ARE ┌─╠┼-ENCODED. [1]. ╘HE FRAME TYPES ARE CARDINAL NUMBERS BEGINNING WITH ZERO TO MINIMIZE STATE TRANSITION TABLE MEMORY REQUIREMENTS. [2]. ╞UTURE EXTENSIONS TO ┌═╧─┼═ MAY USE THE HIGH-ORDER BITS OF THE TYPE BYTE TO INDICATE THREAD SELECTION. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 14 ┴ TWO-BYTE ├╥├ OF THE FRAME TYPE AND POSITION/FLAG BYTES IS ┌─╠┼-ENCODED. ┌ERO OR MORE BINARY DATA SUBPACKETS WITH 16-BIT ├╥├ WILL FOLLOW DEPENDING ON THE FRAME TYPE. ╘HE FUNCTION ┌╙┬╚─╥ TRANSMITS A BINARY HEADER. ╘HE FUNCTION ┌╟┼╘╚─╥ RECEIVES A BINARY OR HEX HEADER. ╞IGURE 2. 16-┬╔╘ ├╥├ ┬╔╬┴╥┘ ╚┼┴─┼╥ * ┌─╠┼ ┴ ╘┘╨┼ ╞3/╨0 ╞2/╨1 ╞1/╨2 ╞0/╨3 ├╥├-1 ├╥├-2 7.3.2 32-┬╔╘ ├╥├ ┬╔╬┴╥┘ ╚┼┴─┼╥ ┴ "32-BIT ├╥├" ┬INARY HEADER IS SIMILAR TO A ┬INARY ╚EADER, EXCEPT THE ┌┬╔╬ (┴) CHARACTER IS REPLACED BY A ┌┬╔╬32 (├) CHARACTER, AND FOUR CHARACTERS OF ├╥├ ARE SENT. ┌ERO OR MORE BINARY DATA SUBPACKETS WITH 32-BIT ├╥├ WILL FOLLOW DEPENDING ON THE FRAME TYPE. ╘HE COMMON VARIABLE ╘╪╞├╙32 MAY BE SET ╘╥╒┼ FOR 32-BIT ├╥├ IF THE RECEIVER INDICATES THE CAPABILITY WITH THE ├┴╬╞├32 BIT. ╘HE ┌╟┼╘╚─╥, ┌╙─┴╘┴ ┴╬─ ┌╥─┴╘┴ FUNCTIONS AUTOMATICALLY ADJUST TO THE TYPE OF ╞RAME ├HECK ╙EQUENCE BEING USED. ╞IGURE 3. 32-┬╔╘ ├╥├ ┬╔╬┴╥┘ ╚┼┴─┼╥ * ┌─╠┼ ├ ╘┘╨┼ ╞3/╨0 ╞2/╨1 ╞1/╨2 ╞0/╨3 ├╥├-1 ├╥├-2 ├╥├-3 ├╥├-4 7.3.3 ╚┼╪ ╚┼┴─┼╥ ╘HE RECEIVER SENDS RESPONSES IN HEX HEADERS. ╘HE SENDER ALSO USES HEX HEADERS WHEN THEY ARE NOT FOLLOWED BY BINARY DATA SUBPACKETS. ╚EX ENCODING PROTECTS THE REVERSE CHANNEL FROM RANDOM CONTROL CHARACTERS. ╘HE HEX HEADER RECEIVING ROUTINE IGNORES PARITY. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 15 ╒SE OF ╦ERMIT-STYLE ENCODING FOR CONTROL AND PARITIED CHARACTERS WAS CONSIDERED AND REJECTED BECAUSE OF INCREASED POSSIBILITY OF INTERACTING WITH SOME TIMESHARING SYSTEMS' LINE-EDIT FUNCTIONS. ╒SE OF ╚┼╪ HEADERS FROM THE RECEIVING PROGRAM ALLOWS CONTROL CHARACTERS TO BE USED TO INTERRUPT THE SENDER WHEN ERRORS ARE DETECTED. ┴ ╚┼╪ HEADER MAY BE USED IN PLACE OF A BINARY HEADER WHEREVER CONVENIENT. ╔F A DATA PACKET FOLLOWS A ╚┼╪ HEADER, IT IS PROTECTED WITH ├╥├-16. ┴ HEX HEADER BEGINS WITH THE SEQUENCE ┌╨┴─, ┌╨┴─, ┌─╠┼, ┌╚┼╪. ╘HE ┌╟┼╘╚─╥ ROUTINE SYNCHRONIZES WITH THE ┌╨┴─-┌─╠┼ SEQUENCE. ╘HE EXTRA ┌╨┴─ CHARACTER ALLOWS THE SENDING PROGRAM TO DETECT AN ASYNCHRONOUS HEADER (INDICATING AN ERROR CONDITION) AND THEN CALL ┌╟┼╘╚─╥ TO RECEIVE THE HEADER. ╘HE TYPE BYTE, THE FOUR POSITION/FLAG BYTES, AND THE 16-BIT ├╥├ THEREOF ARE SENT IN HEX USING THE CHARACTER SET 01234567890┴┬├─┼╞. ╒PPER-CASE HEX DIGITS ARE NOT ALLOWED; THEY FALSELY TRIGGER ╪═╧─┼═ AND ┘═╧─┼═ PROGRAMS. ╙INCE THIS FORM OF HEX ENCODING DETECTS MANY PATTERNS OF ERRORS, ESPECIALLY MISSING CHARACTERS, A HEX HEADER WITH 32-BIT ├╥├ HAS NOT BEEN DEFINED. ┴ CARRIAGE RETURN AND LINE FEED ARE SENT WITH ╚┼╪ HEADERS. ╘HE RECEIVE ROUTINE EXPECTS TO SEE AT LEAST ONE OF THESE CHARACTERS, TWO IF THE FIRST IS ├╥. ╘HE ├╥/╠╞ AIDS DEBUGGING FROM PRINTOUTS, AND HELPS OVERCOME CERTAIN OPERATING-SYSTEM-RELATED PROBLEMS. ┴N ╪╧╬ CHARACTER IS APPENDED TO ALL ╚┼╪ PACKETS EXCEPT ┌┴├╦ AND ┌╞╔╬. ╘HE ╪╧╬ RELEASES THE SENDER FROM SPURIOUS ╪╧╞╞ FLOW CONTROL CHARACTERS GENERATED BY LINE NOISE, A COMMON OCCURRENCE. ╪╧╬ IS NOT SENT AFTER ┌┴├╦ HEADERS TO PROTECT FLOW CONTROL IN STREAMING SITUATIONS. ╪╧╬ IS NOT SENT AFTER A ┌╞╔╬ HEADER TO ALLOW CLEAN SESSION CLEANUP. ┌ERO OR MORE DATA SUBPACKETS WILL FOLLOW DEPENDING ON THE FRAME TYPE. ╘HE FUNCTION ┌╙╚╚─╥ SENDS A HEX HEADER. ╞IGURE 4. ╚┼╪ ╚EADER * * ┌─╠┼ ┬ ╘┘╨┼ ╞3/╨0 ╞2/╨1 ╞1/╨2 ╞0/╨3 ├╥├-1 ├╥├-2 ├╥ ╠╞ ╪╧╬ (╘┘╨┼, ╞3...╞0, ├╥├-1, AND ├╥├-2 ARE EACH SENT AS TWO HEX DIGITS.) ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 16 7.4 ┬╔╬┴╥┘ ─┴╘┴ ╙╒┬╨┴├╦┼╘╙ ┬INARY DATA SUBPACKETS IMMEDIATELY FOLLOW THE ASSOCIATED BINARY HEADER PACKET. ┴ BINARY DATA PACKET CONTAINS 0 TO 1024 BYTES OF DATA. ╥ECOMMENDED LENGTH VALUES ARE 256 BYTES BELOW 2400 BPS, 512 AT 2400 BPS, AND 1024 ABOVE 4800 BPS OR WHEN THE DATA LINK IS KNOWN TO BE RELATIVELY ERROR-FREE. [1] ╬O PADDING IS USED WITH BINARY DATA SUBPACKETS. ╘HE DATA BYTES ARE ┌─╠┼-ENCODED AND TRANSMITTED. ┴ ┌─╠┼ AND FRAME-END ARE THEN SENT, FOLLOWED BY TWO OR FOUR ┌─╠┼ ENCODED ├╥├ BYTES. ╘HE ├╥├ ACCUMULATES THE DATA BYTES AND FRAME-END. ╘HE FUNCTION ┌╙─┴╘┴ SENDS A DATA SUBPACKET. ╘HE FUNCTION ┌╥─┴╘┴ RECEIVES A DATA SUBPACKET. 7.5 ┴╙├╔╔-┼╬├╧─┼─ ─┴╘┴ ╙╒┬╨┴├╦┼╘ ╘HE FORMAT OF ┴╙├╔╔-┼NCODED DATA SUBPACKETS IS NOT CURRENTLY SPECIFIED. ╘HESE COULD BE USED FOR SERVER COMMANDS, OR MAIN TRANSFERS IN 7-BIT ENVIRONMENTS. 8. ╨╥╧╘╧├╧╠ ╘╥┴╬╙┴├╘╔╧╬ ╧╓┼╥╓╔┼╫ ┴S WITH THE ╪═╧─┼═ RECOMMENDATION, ┌═╧─┼═ TIMING IS RECEIVER-DRIVEN. ╘HE TRANSMITTER SHOULD NOT TIME OUT AT ALL, EXCEPT TO ABORT THE PROGRAM IF NO HEADERS ARE RECEIVED FOR AN EXTENDED PERIOD OF TIME, SAY ONE MINUTE. [2] 8.1 ╙┼╙╙╔╧╬ ╙╘┴╥╘╒╨ ╘O START A ┌═╧─┼═ FILE TRANSFER SESSION, THE SENDING PROGRAM IS CALLED WITH THE NAMES OF THE DESIRED FILE(S) AND OPTION(S). [1]. ╙TRATEGIES FOR ADJUSTING THE SUBPACKET LENGTH FOR OPTIMAL RESULTS BASED ON REAL-TIME ERROR RATES ARE STILL EVOLVING. ╙HORTER SUBPACKETS SPEED ERROR DETECTION BUT INCREASE PROTOCOL OVERHEAD SLIGHTLY. [2]. ╙PECIAL CONSIDERATIONS APPLY WHEN SENDING COMMANDS. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 17 ╘HE SENDING PROGRAM MAY SEND THE STRING "╥┌/╥" TO INVOKE THE RECEIVING PROGRAM FROM A POSSIBLE COMMAND MODE. ╘HE "╥┌" FOLLOWED BY CARRIAGE RETURN ACTIVATES A ┌═╧─┼═ RECEIVE PROGRAM OR COMMAND IF IT WERE NOT ALREADY ACTIVE. ╘HE SENDER MAY THEN DISPLAY A MESSAGE INTENDED FOR HUMAN CONSUMPTION, SUCH AS A LIST OF THE FILES REQUESTED, ETC. ╘HEN THE SENDER MAY SEND A ┌╥╤╔╬╔╘ HEADER. ╘HE ┌╥╤╔╬╔╘ HEADER CAUSES A PREVIOUSLY STARTED RECEIVE PROGRAM TO SEND ITS ┌╥╔╬╔╘ HEADER WITHOUT DELAY. ╔N AN INTERACTIVE OR CONVERSATIONAL MODE, THE RECEIVING APPLICATION MAY MONITOR THE DATA STREAM FOR ┌─╠┼. ╘HE FOLLOWING CHARACTERS MAY BE SCANNED FOR ┬00 INDICATING A ┌╥╤╔╬╔╘ HEADER, A COMMAND TO DOWNLOAD A COMMAND OR DATA. ╘HE SENDING PROGRAM AWAITS A COMMAND FROM THE RECEIVING PROGRAM TO START FILE TRANSFERS. ╔F A "├", "╟", OR ╬┴╦ IS RECEIVED, AN ╪═╧─┼═ OR ┘═╧─┼═ FILE TRANSFER IS INDICATED, AND FILE TRANSFER(S) USE THE ┘═╧─┼═ PROTOCOL. ╬OTE: ╫ITH ┌═╧─┼═ AND ┘═╧─┼═, THE SENDING PROGRAM PROVIDES THE FILE NAME, BUT NOT WITH ╪═╧─┼═. ╔N CASE OF GARBLED DATA, THE SENDING PROGRAM CAN REPEAT THE INVITATION-TO-RECEIVE A NUMBER OF TIMES UNTIL A SESSION STARTS. ╫HEN THE ┌═╧─┼═ RECEIVE PROGRAM STARTS, IT IMMEDIATELY SENDS A ┌╥╔╬╔╘ HEADER TO INITIATE ┌═╧─┼═ FILE TRANSFERS, OR A ┌├╚┴╠╠┼╬╟┼ HEADER TO VERIFY THE SENDING PROGRAM. ╘HE RECEIVE PROGRAM RESENDS ITS HEADER AT RESPONSE TIME (DEFAULT 10 SECOND) INTERVALS FOR A SUITABLE PERIOD OF TIME (40 SECONDS TOTAL) BEFORE FALLING BACK TO ┘═╧─┼═ PROTOCOL. ╔F THE RECEIVING PROGRAM RECEIVES A ┌╥╤╔╬╔╘ HEADER, IT RESENDS THE ┌╥╔╬╔╘ HEADER. ╔F THE SENDING PROGRAM RECEIVES THE ┌├╚┴╠╠┼╬╟┼ HEADER, IT PLACES THE DATA IN ┌╨0...┌╨3 IN AN ANSWERING ┌┴├╦ HEADER. ╔F THE RECEIVING PROGRAM RECEIVES A ┌╥╔╬╔╘ HEADER, IT IS AN ECHO INDICATING THAT THE SENDING PROGRAM IS NOT OPERATIONAL. ┼VENTUALLY THE SENDING PROGRAM CORRECTLY RECEIVES THE ┌╥╔╬╔╘ HEADER. ╘HE SENDER MAY THEN SEND AN OPTIONAL ┌╙╔╬╔╘ FRAME TO DEFINE THE RECEIVING PROGRAM'S ┴╘╘╬ SEQUENCE, OR TO SPECIFY COMPLETE CONTROL CHARACTER ESCAPING. [1] [1]. ╔F THE RECEIVER SPECIFIES THE SAME OR HIGHER LEVEL OF ESCAPING, THE ┌╙╔╬╔╘ FRAME NEED NOT BE SENT UNLESS AN ┴╘╘╬ SEQUENCE IS NEEDED. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 18 ╔F THE ┌╙╔╬╔╘ HEADER SPECIFIES ┼╙├├╘╠ OR ┼╙├8, A ╚┼╪ HEADER IS USED, AND THE RECEIVER ACTIVATES THE SPECIFIED ┼╙├ MODES BEFORE READING THE FOLLOWING DATA SUBPACKET. ╘HE RECEIVER SENDS A ┌┴├╦ HEADER IN RESPONSE, OPTIONALLY CONTAINING THE SERIAL NUMBER OF THE RECEIVING PROGRAM, OR ZERO. 8.2 ╞╔╠┼ ╘╥┴╬╙═╔╙╙╔╧╬ ╘HE SENDER THEN SENDS A ┌╞╔╠┼ HEADER WITH ┌═╧─┼═ ├ONVERSION, ═ANAGEMENT, AND ╘RANSPORT OPTIONS [1] FOLLOWED BY A ┌├╥├╫ DATA SUBPACKET CONTAINING THE FILE NAME, FILE LENGTH, MODIFICATION DATE, AND OTHER INFORMATION IDENTICAL TO THAT USED BY ┘═╧─┼═ ┬ATCH. ╘HE RECEIVER EXAMINES THE FILE NAME, LENGTH, AND DATE INFORMATION PROVIDED BY THE SENDER IN THE CONTEXT OF THE SPECIFIED TRANSFER OPTIONS, THE CURRENT STATE OF ITS FILE SYSTEM(S), AND LOCAL SECURITY REQUIREMENTS. ╘HE RECEIVING PROGRAM SHOULD INSURE THE PATHNAME AND OPTIONS ARE COMPATIBLE WITH ITS OPERATING ENVIRONMENT AND LOCAL SECURITY REQUIREMENTS. ╘HE RECEIVER MAY RESPOND WITH A ┌╙╦╔╨ HEADER, WHICH MAKES THE SENDER PROCEED TO THE NEXT FILE (IF ANY) IN THE BATCH. ╔F THE RECEIVER HAS A FILE WITH THE SAME NAME AND LENGTH, IT MAY RESPOND WITH A ┌├╥├ HEADER, WHICH REQUIRES THE SENDER TO PERFORM A 32-BIT ├╥├ ON THE FILE AND TRANSMIT THE COMPLEMENT OF THE ├╥├ IN A ┌├╥├ HEADER. [2] ╘HE RECEIVER USES THIS INFORMATION TO DETERMINE WHETHER TO ACCEPT THE FILE OR SKIP IT. ╘HIS SEQUENCE IS TRIGGERED BY THE ┌═├╥├ ═ANAGEMENT ╧PTION. ┴ ┌╥╨╧╙ HEADER FROM THE RECEIVER INITIATES TRANSMISSION OF THE FILE DATA STARTING AT THE OFFSET IN THE FILE SPECIFIED IN THE ┌╥╨╧╙ HEADER. ╬ORMALLY THE RECEIVER SPECIFIES THE DATA TRANSFER TO BEGIN AT OFFSET ZERO IN THE FILE. [1]. ╙EE BELOW, UNDER ┌╞╔╠┼ HEADER TYPE. [2]. ╘HE ├╥├ IS INITIALIZED TO 0XFF. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 19 ╘HE RECEIVER MAY START THE TRANSFER FURTHER DOWN IN THE FILE. ╘HIS ALLOWS A FILE TRANSFER INTERRUPTED BY A LOSS OF CARRIER OR SYSTEM CRASH TO BE COMPLETED ON THE NEXT CONNECTION WITHOUT REQUIRING THE ENTIRE FILE TO BE RETRANSMITTED. [1] ╔F DOWNLOADING A FILE FROM A TIMESHARING SYSTEM THAT BECOMES SLUGGISH, THE TRANSFER CAN BE INTERRUPTED AND RESUMED LATER WITH NO LOSS OF DATA. ╘HE SENDER SENDS A ┌─┴╘┴ BINARY HEADER (WITH FILE POSITION) FOLLOWED BY ONE OR MORE DATA SUBPACKETS. ╘HE RECEIVER COMPARES THE FILE POSITION IN THE ┌─┴╘┴ HEADER WITH THE NUMBER OF CHARACTERS SUCCESSFULLY RECEIVED TO THE FILE. ╔F THEY DO NOT AGREE, A ┌╥╨╧╙ ERROR RESPONSE IS GENERATED TO FORCE THE SENDER TO THE RIGHT POSITION WITHIN THE FILE. [2] ┴ DATA SUBPACKET TERMINATED BY ┌├╥├╟ AND ├╥├ DOES NOT ELICIT A RESPONSE UNLESS AN ERROR IS DETECTED; MORE DATA SUBPACKET(S) FOLLOW IMMEDIATELY. ┌├╥├╤ DATA SUBPACKETS EXPECT A ┌┴├╦ RESPONSE WITH THE RECEIVER'S FILE OFFSET IF NO ERROR, OTHERWISE A ┌╥╨╧╙ RESPONSE WITH THE LAST GOOD FILE OFFSET. ┴NOTHER DATA SUBPACKET CONTINUES IMMEDIATELY. ┌├╥├╤ SUBPACKETS ARE NOT USED IF THE RECEIVER DOES NOT INDICATE ╞─╪ ABILITY WITH THE ├┴╬╞─╪ BIT. ┌├╥├╫ DATA SUBPACKETS EXPECT A RESPONSE BEFORE THE NEXT FRAME IS SENT. ╔F THE RECEIVER DOES NOT INDICATE OVERLAPPED ╔/╧ CAPABILITY WITH THE ├┴╬╧╓╔╧ BIT, OR SETS A BUFFER SIZE, THE SENDER USES THE ┌├╥├╫ TO ALLOW THE RECEIVER TO WRITE ITS BUFFER BEFORE SENDING MORE DATA. ┴ ZERO-LENGTH DATA FRAME MAY BE USED AS AN IDLE SUBPACKET TO PREVENT THE RECEIVER FROM TIMING OUT IN CASE DATA IS NOT IMMEDIATELY AVAILABLE TO THE SENDER. ╔N THE ABSENCE OF FATAL ERROR, THE SENDER EVENTUALLY ENCOUNTERS END-OF-FILE. ╔F THE END-OF-FILE IS ENCOUNTERED WITHIN A FRAME, THE FRAME IS CLOSED WITH A ┌├╥├┼ DATA SUBPACKET WHICH DOES NOT ELICIT A RESPONSE EXCEPT IN CASE OF ERROR. [1]. ╘HIS DOES NOT APPLY TO FILES THAT HAVE BEEN TRANSLATED. [2]. ╔F THE ┌═╙╨┴╥╙ OPTION IS USED, THE RECEIVER INSTEAD SEEKS TO THE POSITION GIVEN IN THE ┌─┴╘┴ HEADER. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 20 ╘HE SENDER SENDS A ┌┼╧╞ HEADER WITH THE FILE ENDING OFFSET EQUAL TO THE NUMBER OF CHARACTERS IN THE FILE. ╘HE RECEIVER COMPARES THIS NUMBER WITH THE NUMBER OF CHARACTERS RECEIVED. ╔F THE RECEIVER HAS RECEIVED ALL OF THE FILE, IT CLOSES THE FILE. ╔F THE FILE CLOSE WAS SATISFACTORY, THE RECEIVER RESPONDS WITH ┌╥╔╬╔╘. ╔F THE RECEIVER HAS NOT RECEIVED ALL THE BYTES OF THE FILE, THE RECEIVER IGNORES THE ┌┼╧╞ BECAUSE A NEW ┌─┴╘┴ IS COMING. ╔F THE RECEIVER CANNOT PROPERLY CLOSE THE FILE, A ┌╞┼╥╥ HEADER IS SENT. ┴FTER ALL FILES ARE PROCESSED, ANY FURTHER PROTOCOL ERRORS SHOULD NOT PREVENT THE SENDING PROGRAM FROM RETURNING WITH A SUCCESS STATUS. 8.3 ╙┼╙╙╔╧╬ ├╠┼┴╬╒╨ ╘HE SENDER CLOSES THE SESSION WITH A ┌╞╔╬ HEADER. ╘HE RECEIVER ACKNOWLEDGES THIS WITH ITS OWN ┌╞╔╬ HEADER. ╫HEN THE SENDER RECEIVES THE ACKNOWLEDGING HEADER, IT SENDS TWO CHARACTERS, "╧╧" (╧VER AND ╧UT) AND EXITS TO THE OPERATING SYSTEM OR APPLICATION THAT INVOKED IT. ╘HE RECEIVER WAITS BRIEFLY FOR THE "╧" CHARACTERS, THEN EXITS WHETHER THEY WERE RECEIVED OR NOT. 8.4 ╙┼╙╙╔╧╬ ┴┬╧╥╘ ╙┼╤╒┼╬├┼ ╔F THE RECEIVER IS RECEIVING DATA IN STREAMING MODE, THE ┴╘╘╬ SEQUENCE IS EXECUTED TO INTERRUPT DATA TRANSMISSION BEFORE THE ├┴╬├┼╠ SEQUENCE IS SENT. ╘HE ├┴╬├┼╠ SEQUENCE CONSISTS OF EIGHT ├┴╬ CHARACTERS AND TEN BACKSPACE CHARACTERS. ┌═╧─┼═ ONLY REQUIRES FIVE ├┴╬├┼╠ CHARACTERS, THE OTHER THREE ARE "INSURANCE". ╘HE TRAILING BACKSPACE CHARACTERS ATTEMPT TO ERASE THE EFFECTS OF THE ├┴╬ CHARACTERS IF THEY ARE RECEIVED BY A COMMAND INTERPRETER. STATIC CHAR CANISTR[] = │24,24,24,24,24,24,24,24,8,8,8,8,8,8,8,8,8,8,0½; 9. ╙╘╥┼┴═╔╬╟ ╘┼├╚╬╔╤╒┼╙ / ┼╥╥╧╥ ╥┼├╧╓┼╥┘ ╔T IS A FACT OF LIFE THAT NO SINGLE METHOD OF STREAMING IS APPLICABLE TO A MAJORITY OF TODAY'S COMPUTING AND TELECOMMUNICATIONS ENVIRONMENTS. ┌═╧─┼═ PROVIDES SEVERAL DATA STREAMING METHODS SELECTED ACCORDING TO THE LIMITATIONS OF THE SENDING ENVIRONMENT, RECEIVING ENVIRONMENT, AND TRANSMISSION CHANNEL(S). ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 21 9.1 ╞╒╠╠ ╙╘╥┼┴═╔╬╟ ╫╔╘╚ ╙┴═╨╠╔╬╟ ╔F THE RECEIVER CAN OVERLAP SERIAL ╔/╧ WITH DISK ╔/╧, AND IF THE SENDER CAN SAMPLE THE REVERSE CHANNEL FOR THE PRESENCE OF DATA WITHOUT HAVING TO WAIT, FULL STREAMING CAN BE USED WITH NO ┴╘╘╬ SEQUENCE REQUIRED. ╘HE SENDER BEGINS DATA TRANSMISSION WITH A ┌─┴╘┴ HEADER AND CONTINUOUS ┌├╥├╟ DATA SUBPACKETS. ╫HEN THE RECEIVER DETECTS AN ERROR, IT EXECUTES THE ┴╘╘╬ SEQUENCE AND THEN SENDS A ┌╥╨╧╙ HEADER WITH THE CORRECT POSITION WITHIN THE FILE. ┴T THE END OF EACH TRANSMITTED DATA SUBPACKET, THE SENDER CHECKS FOR THE PRESENCE OF AN ERROR HEADER FROM THE RECEIVER. ╘O DO THIS, THE SENDER SAMPLES THE REVERSE DATA STREAM FOR THE PRESENCE OF EITHER A ┌╨┴─ OR ├┴╬ CHARACTER. [1] ╞LOW CONTROL CHARACTERS (IF PRESENT) ARE ACTED UPON. ╧THER CHARACTERS (INDICATING LINE NOISE) INCREMENT A COUNTER WHICH IS RESET WHENEVER THE SENDER WAITS FOR A HEADER FROM THE RECEIVER. ╔F THE COUNTER OVERFLOWS, THE SENDER SENDS THE NEXT DATA SUBPACKET AS ┌├╥├╫, AND WAITS FOR A RESPONSE. ┌╨┴─ INDICATES SOME SORT OF ERROR HEADER FROM THE RECEIVER. ┴ ├┴╬ SUGGESTS THE USER IS ATTEMPTING TO "STOP THE BUBBLE MACHINE" BY KEYBOARDING ├┴╬ CHARACTERS. ╔F ONE OF THESE CHARACTERS IS SEEN, AN EMPTY ┌├╥├┼ DATA SUBPACKET IS SENT. ╬ORMALLY, THE RECEIVER WILL HAVE SENT AN ┌╥╨╧╙ OR OTHER ERROR HEADER, WHICH WILL FORCE THE SENDER TO RESUME TRANSMISSION AT A DIFFERENT ADDRESS, OR TAKE OTHER ACTION. ╔N THE UNLIKELY EVENT THE ┌╨┴─ OR ├┴╬ CHARACTER WAS SPURIOUS, THE RECEIVER WILL TIME OUT AND SEND A ┌╥╨╧╙ HEADER. [2] ╘HEN THE RECEIVER'S RESPONSE HEADER IS READ AND ACTED UPON. [3] ┴ ┌╥╨╧╙ HEADER RESETS THE SENDER'S FILE OFFSET TO THE CORRECT POSITION. ╔F POSSIBLE, THE SENDER SHOULD PURGE ITS OUTPUT BUFFERS AND/OR NETWORKS OF ALL UNPROCESSED OUTPUT DATA, TO MINIMIZE THE AMOUNT OF UNWANTED DATA THE RECEIVER MUST DISCARD BEFORE RECEIVING DATA STARTING AT THE CORRECT FILE OFFSET. ╘HE NEXT TRANSMITTED DATA FRAME SHOULD BE A ┌├╥├╫ FRAME FOLLOWED BY A WAIT TO GUARANTEE COMPLETE FLUSHING OF THE NETWORK'S MEMORY. [1]. ╘HE CALL TO ╥─├╚╦() IN ╙┌.├ PERFORMS THIS FUNCTION. [2]. ╘HE OBVIOUS CHOICE OF ┌├╥├╫ PACKET, WHICH WOULD TRIGGER AN ┌┴├╦ FROM THE RECEIVER, IS NOT USED BECAUSE MULTIPLE IN-TRANSIT FRAMES COULD RESULT IF THE CHANNEL HAS A LONG PROPAGATION DELAY. [3]. ╘HE CALL TO ╟┼╘╔╬╙┘╬├() IN ╙┌.├ PERFORMS THIS FUNCTION. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 22 ╔F THE RECEIVER GETS A ┌┴├╦ HEADER WITH AN ADDRESS THAT DISAGREES WITH THE SENDER ADDRESS, IT IS IGNORED, AND THE SENDER WAITS FOR ANOTHER HEADER. ┴ ┌╞╔╬, ┌┴┬╧╥╘, OR TIMEOUT TERMINATES THE SESSION; A ┌╙╦╔╨ TERMINATES THE PROCESSING OF THIS FILE. ╘HE REVERSE CHANNEL IS THEN SAMPLED FOR THE PRESENCE OF ANOTHER HEADER FROM THE RECEIVER. [1] ╔F ONE IS DETECTED, THE ╟┼╘╔╬╙┘╬├() FUNCTION IS AGAIN CALLED TO READ ANOTHER ERROR HEADER. ╧THERWISE, TRANSMISSION RESUMES AT THE (POSSIBLY RESET) FILE OFFSET WITH A ┌─┴╘┴ HEADER FOLLOWED BY DATA SUBPACKETS. 9.1.1 ╫╔╬─╧╫ ═┴╬┴╟┼═┼╬╘ ╫HEN SENDING DATA THROUGH A NETWORK, SOME NODES OF THE NETWORK STORE DATA WHILE IT IS TRANSFERRED TO THE RECEIVER. ╙EVEN THOUSAND BYTES AND MORE OF TRANSIENT STORAGE HAVE BEEN OBSERVED. ╙UCH A LARGE AMOUNT OF STORAGE CAUSES THE TRANSMITTER TO "GET AHEAD" OF THE RECEIVER. ╘HIS CAN BE FATAL WITH ═┼╟┴LINK AND OTHER PROTOCOLS THAT DEPEND ON TIMELY NOTIFICATION OF ERRORS FROM THE RECEIVER. ╘HIS CONDITION IS NOT FATAL WITH ┌═╧─┼═, BUT IT DOES SLOW ERROR RECOVERY. ╘O MANAGE THE WINDOW SIZE, THE SENDING PROGRAM USES ┌├╥├╤ DATA SUBPACKETS TO TRIGGER ┌┴├╦ HEADERS FROM THE RECEIVER. ╘HE RETURNING ┌┴├╦ HEADERS INFORM THE SENDER OF THE RECEIVER'S PROGRESS. ╫HEN THE WINDOW SIZE (CURRENT TRANSMITTER FILE OFFSET - LAST REPORTED RECEIVER FILE OFFSET) EXCEEDS A SPECIFIED VALUE, THE SENDER WAITS FOR A ┌┴├╦ [2] PACKET WITH A RECEIVER FILE OFFSET THAT REDUCES THE WINDOW SIZE. ╒NIX ╙┌ VERSIONS BEGINNING WITH ═AY 9 1987 CONTROL THE WINDOW SIZE WITH THE "-┌W ╬" OPTION, WHERE ╬ IS THE MAXIMUM WINDOW SIZE. ╨RO-┘┴═, ┌├╧══ AND ─╙┌ VERSIONS BEGINNING WITH ═AY 9 1987 CONTROL THE WINDOW SIZE WITH "┌═╧─┼═ ╨╫╬". ╘HIS IS COMPATIBLE WITH PREVIOUS VERSIONS OF THESE PROGRAMS. [3] [1]. ╔F SAMPLING IS POSSIBLE. [2]. ┌╥╨╧╙ AND OTHER ERROR PACKETS ARE HANDLED NORMALLY. [3]. ╫HEN USED WITH MODEMS OR NETWORKS THAT SIMULTANEOUSLY ASSERT FLOW CONTROL WITH ╪╧╬ AND ╪╧╞╞ CHARACTERS AND PASS ╪╧╬ CHARACTERS THAT VIOLATE FLOW CONTROL, THE RECEIVING PROGRAM SHOULD HAVE A REVISION DATE OF ═AY 9 OR LATER. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 23 9.2 ╞╒╠╠ ╙╘╥┼┴═╔╬╟ ╫╔╘╚ ╥┼╓┼╥╙┼ ╔╬╘┼╥╥╒╨╘ ╘HE ABOVE METHOD CANNOT BE USED IF THE REVERSE DATA STREAM CANNOT BE SAMPLED WITHOUT ENTERING AN ╔/╧ WAIT. ┴N ALTERNATE METHOD IS TO INSTRUCT THE RECEIVER TO INTERRUPT THE SENDING PROGRAM WHEN AN ERROR IS DETECTED. ╘HE RECEIVER CAN INTERRUPT THE SENDER WITH A CONTROL CHARACTER, BREAK SIGNAL, OR COMBINATION THEREOF, AS SPECIFIED IN THE ┴╘╘╬ SEQUENCE. ┴FTER EXECUTING THE ┴╘╘╬ SEQUENCE, THE RECEIVER SENDS A HEX ┌╥╨╧╙ HEADER TO FORCE THE SENDER TO RESEND THE LOST DATA. ╫HEN THE SENDING PROGRAM RESPONDS TO THIS INTERRUPT, IT READS A ╚┼╪ HEADER (NORMALLY ┌╥╨╧╙) FROM THE RECEIVER AND TAKES THE ACTION DESCRIBED IN THE PREVIOUS SECTION. ╘HE ╒NIX ╙┌.├ PROGRAM USES A ╙┼╘╩═╨/╠╧╬╟╩═╨ CALL TO CATCH THE INTERRUPT GENERATED BY THE ┴╘╘╬ SEQUENCE. ├ATCHING THE INTERRUPT ACTIVATES THE ╟┼╘╔╬╙┘╬├() FUNCTION TO READ THE RECEIVER'S ERROR HEADER AND TAKE APPROPRIATE ACTION. ╫HEN COMPILED FOR STANDARD ╙┘╙╘┼═ ╔╔╔/╓ ╒NIX, ╙┌.├ USES AN ┴╘╘╬ SEQUENCE OF ├TRL-├ FOLLOWED BY A 1 SECOND PAUSE TO INTERRUPT THE SENDER, THEN GIVE THE SENDER (╒NIX) TIME TO PREPARE FOR THE RECEIVER'S ERROR HEADER. 9.3 ╞╒╠╠ ╙╘╥┼┴═╔╬╟ ╫╔╘╚ ╙╠╔─╔╬╟ ╫╔╬─╧╫ ╔F NONE OF THE ABOVE METHODS IS APPLICABLE, HOPE IS NOT YET LOST. ╔F THE SENDER CAN BUFFER RESPONSES FROM THE RECEIVER, THE SENDER CAN USE ┌├╥├╤ DATA SUBPACKETS TO GET ┴├╦S FROM THE RECEIVER WITHOUT INTERRUPTING THE TRANSMISSION OF DATA. ┴FTER A SUFFICIENT NUMBER OF ┌├╥├╤ DATA SUBPACKETS HAVE BEEN SENT, THE SENDER CAN READ ONE OF THE HEADERS THAT SHOULD HAVE ARRIVED IN ITS RECEIVE-INTERRUPT BUFFER. ┴ PROBLEM WITH THIS METHOD IS THE POSSIBILITY OF WASTING AN EXCESSIVE AMOUNT OF TIME RESPONDING TO THE RECEIVER'S ERROR HEADER. ╔T MAY BE POSSIBLE TO PROGRAM THE RECEIVER'S ┴╘╘╬ SEQUENCE TO FLUSH THE SENDER'S INTERRUPT BUFFER BEFORE SENDING THE ┌╥╨╧╙ HEADER. 9.4 ╞╒╠╠ ╙╘╥┼┴═╔╬╟ ╧╓┼╥ ┼╥╥╧╥-╞╥┼┼ ├╚┴╬╬┼╠╙ ╞ILE TRANSFER PROTOCOLS PREDICATED ON THE EXISTENCE OF AN ERROR-FREE END-TO-END COMMUNICATIONS CHANNEL HAVE BEEN PROPOSED FROM TIME TO TIME. ╙UCH CHANNELS HAVE PROVEN TO BE MORE READILY AVAILABLE IN THEORY THAN IN ACTUALITY. ╘HE FREQUENCY OF UNDETECTED ERRORS INCREASES WHEN MODEM SCRAMBLERS HAVE MORE BITS THAN THE ERROR-DETECTING ├╥├. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 24 ┴ ┌═╧─┼═ SENDER ASSUMING AN ERROR-FREE CHANNEL WITH END-TO-END FLOW CONTROL CAN SEND THE ENTIRE FILE IN ONE FRAME WITHOUT ANY CHECKING OF THE REVERSE STREAM. ╔F THIS CHANNEL IS COMPLETELY TRANSPARENT, ONLY ┌─╠┼ NEED BE ESCAPED. ╘HE RESULTING PROTOCOL OVERHEAD FOR AVERAGE LONG FILES IS LESS THAN ONE PERCENT. [1] 9.5 ╙┼╟═┼╬╘┼─ ╙╘╥┼┴═╔╬╟ ╔F THE RECEIVER CANNOT OVERLAP SERIAL AND DISK ╔/╧, IT USES THE ┌╥╔╬╔╘ FRAME TO SPECIFY A BUFFER LENGTH WHICH THE SENDER WILL NOT OVERFLOW. ╘HE SENDING PROGRAM SENDS A ┌├╥├╫ DATA SUBPACKET AND WAITS FOR A ┌┴├╦ HEADER BEFORE SENDING THE NEXT SEGMENT OF THE FILE. ╔F THE SENDING PROGRAM SUPPORTS REVERSE DATA STREAM SAMPLING OR INTERRUPT, ERROR RECOVERY WILL BE FASTER (ON AVERAGE) THAN A PROTOCOL (SUCH AS ┘═╧─┼═) THAT SENDS LARGE BLOCKS. ┴ SUFFICIENTLY LARGE RECEIVING BUFFER ALLOWS THROUGHPUT TO CLOSELY APPROACH THAT OF FULL STREAMING. ╞OR EXAMPLE, 16╦┬ SEGMENTED STREAMING ADDS ABOUT 3 PERCENT TO FULL STREAMING ┌═╧─┼═ FILE TRANSFER TIMES WHEN THE ROUND TRIP DELAY IS FIVE SECONDS. 10. ┴╘╘┼╬╘╔╧╬ ╙┼╤╒┼╬├┼ ╘HE RECEIVING PROGRAM SENDS THE ┴╘╘╬ SEQUENCE WHENEVER IT DETECTS AN ERROR AND NEEDS TO INTERRUPT THE SENDING PROGRAM. ╘HE DEFAULT ┴╘╘╬ STRING VALUE IS EMPTY (NO ┴╘╘╬ SEQUENCE). ╘HE RECEIVING PROGRAM RESETS ┴╘╘╬ TO THE EMPTY DEFAULT BEFORE EACH TRANSFER SESSION. ╘HE SENDER SPECIFIES THE ┴╘╘╬ SEQUENCE IN ITS OPTIONAL ┌╙╔╬╔╘ FRAME. ╘HE ┴╘╘╬ STRING IS TERMINATED WITH A NULL. ╘WO META-CHARACTERS PERFORM SPECIAL FUNCTIONS: ==> /335 (OCTAL) ╙END A BREAK SIGNAL ==> /336 (OCTAL) ╨AUSE ONE SECOND [1]. ╧NE IN 256 FOR ESCAPING ┌─╠┼, ABOUT TWO (FOUR IF 32-BIT ├╥├ IS USED) IN 1024 FOR DATA SUBPACKET ├╥├'S. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 25 11. ╞╥┴═┼ ╘┘╨┼╙ ╘HE NUMERIC VALUES FOR THE VALUES SHOWN IN BOLDFACE ARE GIVEN IN ┌═╧─┼═.╚. ╒NUSED BITS AND UNUSED BYTES IN THE HEADER (┌╨0...┌╨3) ARE SET TO ZERO. 11.1 ┌╥╤╔╬╔╘ ╙ENT BY THE SENDING PROGRAM, TO TRIGGER THE RECEIVING PROGRAM TO SEND ITS ┌╥╔╬╔╘ HEADER. ╘HIS AVOIDS THE AGGRAVATING STARTUP DELAY ASSOCIATED WITH ╪═╧─┼═ AND ╦ERMIT TRANSFERS. ╘HE SENDING PROGRAM MAY REPEAT THE RECEIVE INVITATION (INCLUDING ┌╥╤╔╬╔╘) IF A RESPONSE IS NOT OBTAINED AT FIRST. ┌╞0 CONTAINS ┌├╧══┴╬─ IF THE PROGRAM IS ATTEMPTING TO SEND A COMMAND, ZERO OTHERWISE. 11.2 ┌╥╔╬╔╘ ╙ENT BY THE RECEIVING PROGRAM. ┌╞0 AND ┌╞1 CONTAIN THE BITWISE-╧╥ OF THE RECEIVER CAPABILITY FLAGS: #DEFINE ├┴╬├╥┘ 8 /* ╥ECEIVER CAN DECRYPT */ #DEFINE ├┴╬╞─╪ 01 /* ╥ECEIVER CAN SEND AND RECEIVE TRUE ╞─╪ */ #DEFINE ├┴╬╧╓╔╧ 02 /* ╥ECEIVER CAN RECEIVE DATA DURING DISK ╔/╧ */ #DEFINE ├┴╬┬╥╦ 04 /* ╥ECEIVER CAN SEND A BREAK SIGNAL */ #DEFINE ├┴╬├╥┘ 010 /* ╥ECEIVER CAN DECRYPT */ #DEFINE ├┴╬╠┌╫ 020 /* ╥ECEIVER CAN UNCOMPRESS */ #DEFINE ├┴╬╞├32 040 /* ╥ECEIVER CAN USE 32-BIT ╞RAME ├HECK */ #DEFINE ┼╙├├╘╠ 0100 /* ╥ECEIVER EXPECTS ├╘╠ CHARS TO BE ESCAPED */ #DEFINE ┼╙├8 0200 /* ╥ECEIVER EXPECTS 8TH BIT TO BE ESCAPED */ ┌╨0 AND ┌╨1 CONTAIN THE SIZE OF THE RECEIVER'S BUFFER IN BYTES, OR ZERO IF NONSTOP ╔/╧ IS ALLOWED. 11.3 ┌╙╔╬╔╘ ╘HE ╙ENDER SENDS FLAGS FOLLOWED BY A BINARY DATA SUBPACKET TERMINATED WITH ┌├╥├╫. /* ┬IT ═ASKS FOR ┌╙╔╬╔╘ FLAGS BYTE ┌╞0 */ #DEFINE ╘┼╙├├╘╠ 0100 /* ╘RANSMITTER EXPECTS ├╘╠ CHARS TO BE ESCAPED*/ #DEFINE ╘┼╙├8 0200 /* ╘RANSMITTER EXPECTS 8TH BIT TO BE ESCAPED ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 26 ╘HE DATA SUBPACKET CONTAINS THE NULL-TERMINATED ┴╘╘╬ SEQUENCE, MAXIMUM LENGTH 32 BYTES INCLUDING THE TERMINATING NULL. 11.4 ┌┴├╦ ┴CKNOWLEDGMENT TO A ┌╙╔╬╔╘ FRAME, ┌├╚┴╠╠┼╬╟┼ HEADER, ┌├╥├╤ OR ┌├╥├╫ DATA SUBPACKET. ┌╨0 TO ┌╨3 CONTAIN FILE OFFSET. ╘HE RESPONSE TO ┌├╚┴╠╠┼╬╟┼ CONTAINS THE SAME 32-BIT NUMBER RECEIVED IN THE ┌├╚┴╠╠┼╬╟┼ HEADER. 11.5 ┌╞╔╠┼ ╘HIS FRAME DENOTES THE BEGINNING OF A FILE TRANSMISSION ATTEMPT. ┌╞0, ┌╞1, AND ┌╞2 MAY CONTAIN OPTIONS. ┴ VALUE OF ZERO IN EACH OF THESE BYTES IMPLIES NO SPECIAL TREATMENT. ╧PTIONS SPECIFIED TO THE RECEIVER OVERRIDE OPTIONS SPECIFIED TO THE SENDER WITH THE EXCEPTION OF ┌├┬╔╬ WHICH OVERRIDES ANY OTHER ├ONVERSION ╧PTION GIVEN TO THE SENDER OR RECEIVER. 11.5.1 ┌╞00 ├╧╬╓┼╥╙╔╧╬ ╧╨╘╔╧╬ ╔F THE RECEIVER DOES NOT RECOGNIZE THE ├ONVERSION ╧PTION, AN APPLICATION-DEPENDENT DEFAULT CONVERSION MAY APPLY. ┌├┬╔╬ "┬INARY" TRANSFER - INHIBIT CONVERSION UNCONDITIONALLY. ┌├╬╠ ├ONVERT RECEIVED END-OF-LINE TO LOCAL END-OF-LINE CONVENTION. ╘HE SUPPORTED END-OF-LINE CONVENTIONS ARE ├╥/╠╞ (MOST ┴╙├╔╔ BASED OPERATING SYSTEMS EXCEPT ╒NIX AND ═ACINTOSH), AND ╬╠ (╒NIX). ┼ITHER OF THESE TWO END-OF-LINE CONVENTIONS MEET THE PERMISSIBLE ┴╙├╔╔ DEFINITIONS FOR ├ARRIAGE ╥ETURN AND ╠INE ╞EED/╬EW ╠INE. ╬EITHER THE ┴╙├╔╔ CODE NOR ┌═╧─┼═ ┌├╬╠ ENCOMPASS LINES SEPARATED ONLY BY CARRIAGE RETURNS. ╧THER PROCESSING APPROPRIATE TO ┴╙├╔╔ TEXT FILES AND THE LOCAL OPERATING SYSTEM MAY ALSO BE APPLIED BY THE RECEIVER. [1] ┌├╥┼├╧╓ ╥ECOVER/╥ESUME INTERRUPTED FILE TRANSFER. ┌├╥┼╓╧╓ IS ALSO USEFUL FOR UPDATING A REMOTE COPY OF A FILE THAT GROWS WITHOUT RESENDING OF OLD DATA. ╔F THE DESTINATION FILE EXISTS AND IS NO LONGER THAN THE SOURCE, APPEND TO THE DESTINATION FILE AND START TRANSFER AT THE OFFSET CORRESPONDING TO THE RECEIVER'S END-OF-FILE. ╘HIS OPTION DOES NOT APPLY IF THE SOURCE FILE IS SHORTER. ╞ILES THAT HAVE BEEN CONVERTED (E.G., ┌├╬╠) OR SUBJECT TO A SINGLE ENDED ╘RANSPORT ╧PTION CANNOT HAVE THEIR TRANSFERS RECOVERED. [1]. ╞ILTERING ╥╒┬╧╒╘, ╬╒╠╠, ├TRL-┌, ETC. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 27 11.5.2 ┌╞1 ═┴╬┴╟┼═┼╬╘ ╧╨╘╔╧╬ ╔F THE RECEIVER DOES NOT RECOGNIZE THE ═ANAGEMENT ╧PTION, THE FILE SHOULD BE TRANSFERRED NORMALLY. ╘HE ┌═╙╦╬╧╠╧├ BIT INSTRUCTS THE RECEIVER TO BYPASS THE CURRENT FILE IF THE RECEIVER DOES NOT HAVE A FILE WITH THE SAME NAME. ╞IVE BITS (DEFINED BY ┌══┴╙╦) DEFINE THE FOLLOWING SET OF MUTUALLY EXCLUSIVE MANAGEMENT OPTIONS. ┌═╬┼╫╠ ╘RANSFER FILE IF DESTINATION FILE ABSENT. ╧THERWISE, TRANSFER FILE OVERWRITING DESTINATION IF THE SOURCE FILE IS NEWER OR LONGER. ┌═├╥├ ├OMPARE THE SOURCE AND DESTINATION FILES. ╘RANSFER IF FILE LENGTHS OR FILE POLYNOMIALS DIFFER. ┌═┴╨╬─ ┴PPEND SOURCE FILE CONTENTS TO THE END OF THE EXISTING DESTINATION FILE (IF ANY). ┌═├╠╧┬ ╥EPLACE EXISTING DESTINATION FILE (IF ANY). ┌═─╔╞╞ ╘RANSFER FILE IF DESTINATION FILE ABSENT. ╧THERWISE, TRANSFER FILE OVERWRITING DESTINATION IF FILES HAVE DIFFERENT LENGTHS OR DATES. ┌═╨╥╧╘ ╨ROTECT DESTINATION FILE BY TRANSFERRING FILE ONLY IF THE DESTINATION FILE IS ABSENT. ┌═╬┼╫ ╘RANSFER FILE IF DESTINATION FILE ABSENT. ╧THERWISE, TRANSFER FILE OVERWRITING DESTINATION IF THE SOURCE FILE IS NEWER. 11.5.3 ┌╞2 ╘╥┴╬╙╨╧╥╘ ╧╨╘╔╧╬ ╔F THE RECEIVER DOES NOT IMPLEMENT THE PARTICULAR TRANSPORT OPTION, THE FILE IS COPIED WITHOUT CONVERSION FOR LATER PROCESSING. ┌╘╠┌╫ ╠EMPEL-┌EV-╫ELCH ├OMPRESSION. ╘RANSMITTED DATA WILL BE IDENTICAL TO THAT PRODUCED BY ├╧═╨╥┼╙╙ 4.0 OPERATING ON A COMPUTER WITH ╓┴╪ BYTE ORDERING, USING 12-BIT ENCODING. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 28 ┌╘├╥┘╨╘ ┼NCRYPTION. ┴N INITIAL NULL-TERMINATED STRING IDENTIFIES THE KEY. ─ETAILS TO BE DETERMINED. ┌╘╥╠┼ ╥UN-╠ENGTH ENCODING. ─ETAILS TO BE DETERMINED. ┴ ┌├╥├╫ DATA SUBPACKET FOLLOWS WITH FILE NAME, FILE LENGTH, MODIFICATION DATE, AND OTHER INFORMATION DESCRIBED IN A LATER CHAPTER. 11.5.4 ┌╞3 ┼╪╘┼╬─┼─ ╧╨╘╔╧╬╙ ╘HE ┼XTENDED ╧PTIONS ARE BIT-ENCODED. ┌╘╙╨┴╥╙ ╙PECIAL PROCESSING FOR SPARSE FILES, OR SENDER-MANAGED SELECTIVE RETRANSMISSION. ┼ACH FILE SEGMENT IS TRANSMITTED AS A SEPARATE FRAME, WHERE THE FRAMES ARE NOT NECESSARILY CONTIGUOUS. ╘HE SENDER SHOULD END EACH SEGMENT WITH A ┌├╥├╫ DATA SUBPACKET AND PROCESS THE EXPECTED ┌┴├╦ TO INSURE NO DATA IS LOST. ┌╘╙╨┴╥╙ CANNOT BE USED WITH ┌├╬╠. 11.6 ┌╙╦╔╨ ╙ENT BY THE RECEIVER IN RESPONSE TO ┌╞╔╠┼, MAKES THE SENDER SKIP TO THE NEXT FILE. 11.7 ┌╬┴╦ ╔NDICATES LAST HEADER WAS GARBLED. (╙EE ALSO ┌╥╨╧╙). 11.8 ┌┴┬╧╥╘ ╙ENT BY RECEIVER TO TERMINATE BATCH FILE TRANSFERS WHEN REQUESTED BY THE USER. ╙ENDER RESPONDS WITH A ┌╞╔╬ SEQUENCE. [1] 11.9 ┌╞╔╬ ╙ENT BY SENDING PROGRAM TO TERMINATE A ┌═╧─┼═ SESSION. ╥ECEIVER RESPONDS WITH ITS OWN ┌╞╔╬. 11.10 ┌╥╨╧╙ ╙ENT BY RECEIVER TO FORCE FILE TRANSFER TO RESUME AT FILE OFFSET GIVEN IN ┌╨0...┌╨3. [1]. ╧R ┌├╧═╨╠ IN CASE OF SERVER MODE. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 29 11.11 ┌─┴╘┴ ┌╨0...┌╨3 CONTAIN FILE OFFSET. ╧NE OR MORE DATA SUBPACKETS FOLLOW. 11.12 ┌┼╧╞ ╙ENDER REPORTS END-OF-FILE. ┌╨0...┌╨3 CONTAIN THE ENDING FILE OFFSET. 11.13 ┌╞┼╥╥ ┼RROR IN READING OR WRITING FILE, PROTOCOL EQUIVALENT TO ┌┴┬╧╥╘. 11.14 ┌├╥├ ╥EQUEST (RECEIVER) AND RESPONSE (SENDER) FOR FILE POLYNOMIAL. ┌╨0...┌╨3 CONTAIN FILE POLYNOMIAL. 11.15 ┌├╚┴╠╠┼╬╟┼ ╥EQUEST SENDER TO ECHO A RANDOM NUMBER IN ┌╨0...┌╨3 IN A ┌┴├╦ FRAME. ╙ENT BY THE RECEIVING PROGRAM TO THE SENDING PROGRAM TO VERIFY THAT IT IS CONNECTED TO AN OPERATING PROGRAM, AND WAS NOT ACTIVATED BY SPURIOUS DATA OR A ╘ROJAN ╚ORSE MESSAGE. 11.16 ┌├╧═╨╠ ╥EQUEST NOW COMPLETED. 11.17 ┌├┴╬ ╘HIS IS A PSEUDO FRAME TYPE RETURNED BY ╟┼╘╚─╥() IN RESPONSE TO A ╙ESSION ┴BORT SEQUENCE. 11.18 ┌╞╥┼┼├╬╘ ╙ENDING PROGRAM REQUESTS A ┌┴├╦ FRAME WITH ┌╨0...┌╨3 CONTAINING THE NUMBER OF FREE BYTES ON THE CURRENT FILE SYSTEM. ┴ VALUE OF ZERO REPRESENTS AN INDEFINITE AMOUNT OF FREE SPACE. 11.19 ┌├╧══┴╬─ ┌├╧══┴╬─ IS SENT IN A BINARY FRAME. ┌╞00 CONTAINS 00 OR ┌├┴├╦1 (SEE BELOW). ┴ ┌├╥├╫ DATA SUBPACKET FOLLOWS, WITH THE ┴╙├╔╔ TEXT COMMAND STRING TERMINATED WITH A ╬╒╠╠ CHARACTER. ╔F THE COMMAND IS INTENDED TO BE EXECUTED BY THE OPERATING SYSTEM HOSTING THE RECEIVING PROGRAM (E.G., "SHELL ESCAPE"), IT MUST HAVE "!" AS THE FIRST CHARACTER. ╧THERWISE THE COMMAND IS MEANT TO BE EXECUTED BY THE APPLICATION PROGRAM WHICH RECEIVES THE COMMAND. ╔F THE RECEIVER DETECTS AN ILLEGAL OR BADLY FORMED COMMAND, THE RECEIVER IMMEDIATELY RESPONDS WITH A ┌├╧═╨╠ HEADER WITH AN ERROR CODE IN ┌╨0...┌╨3. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 30 ╔F ┌╞0 CONTAINED ┌├┴├╦1, THE RECEIVER IMMEDIATELY RESPONDS WITH A ┌├╧═╨╠ HEADER WITH ZERO STATUS. ╧THERWISE, THE RECEIVER RESPONDS WITH A ┌├╧═╨╠ HEADER WHEN THE OPERATION IS COMPLETED. ╘HE EXIT STATUS OF THE COMPLETED COMMAND IS STORED IN ┌╨0...┌╨3. ┴ ZERO EXIT STATUS IMPLIES NOMINAL COMPLETION OF THE COMMAND. ╔F THE COMMAND CAUSES A FILE TO BE TRANSMITTED, THE COMMAND SENDER WILL SEE A ┌╥╤╔╬╔╘ FRAME FROM THE OTHER COMPUTER ATTEMPTING TO SEND DATA. ╘HE SENDER EXAMINES ┌╞0 OF THE RECEIVED ┌╥╤╔╬╔╘ HEADER TO VERIFY IT IS NOT AN ECHO OF ITS OWN ┌╥╤╔╬╔╘ HEADER. ╔T IS ILLEGAL FOR THE SENDING PROGRAM TO COMMAND THE RECEIVING PROGRAM TO SEND A COMMAND. ╔F THE RECEIVER PROGRAM DOES NOT IMPLEMENT COMMAND DOWNLOADING, IT MAY DISPLAY THE COMMAND TO THE STANDARD ERROR OUTPUT, THEN RETURN A ┌├╧═╨╠ HEADER. 12. ╙┼╙╙╔╧╬ ╘╥┴╬╙┴├╘╔╧╬ ┼╪┴═╨╠┼╙ 12.1 ┴ ╙╔═╨╠┼ ╞╔╠┼ ╘╥┴╬╙╞┼╥ ┴ SIMPLE TRANSACTION, ONE FILE, NO ERRORS, NO ├╚┴╠╠┼╬╟┼, OVERLAPPED ╔/╧: ╙ENDER ╥ECEIVER "RZ/R" ┌╥╤╔╬╔╘(0) ┌╥╔╬╔╘ ┌╞╔╠┼ ┌╥╨╧╙ ┌─┴╘┴ DATA ... ┌┼╧╞ ┌╥╔╬╔╘ ┌╞╔╬ ┌╞╔╬ ╧╧ ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 31 12.2 ├╚┴╠╠┼╬╟┼ ┴╬─ ├╧══┴╬─ ─╧╫╬╠╧┴─ ╙ENDER ╥ECEIVER "RZ/R" ┌╥╤╔╬╔╘(┌├╧══┴╬─) ┌├╚┴╠╠┼╬╟┼(RANDOM-NUMBER) ┌┴├╦(SAME-NUMBER) ┌╥╔╬╔╘ ┌├╧══┴╬─, ┌─┴╘┴ (╨ERFORMS ├OMMAND) ┌├╧═╨╠ ┌╞╔╬ ┌╞╔╬ ╧╧ 13. ┌╞╔╠┼ ╞╥┴═┼ ╞╔╠┼ ╔╬╞╧╥═┴╘╔╧╬ ┌═╧─┼═ SENDS THE SAME FILE INFORMATION WITH THE ┌╞╔╠┼ FRAME DATA THAT ┘═╧─┼═ ┬ATCH SENDS IN ITS BLOCK ZERO. ╘HE PATHNAME (FILE NAME) FIELD IS MANDATORY. ╨┴╘╚╬┴═┼ ╘HE PATHNAME (CONVENTIONALLY, THE FILE NAME) IS SENT AS A NULL-TERMINATED ┴╙├╔╔ STRING. ╘HIS IS THE FILENAME FORMAT USED BY THE HANDLE-ORIENTED ═╙-─╧╙(╘═) FUNCTIONS AND ├ LIBRARY ╞╧╨┼╬ FUNCTIONS. ┴N ASSEMBLY LANGUAGE EXAMPLE FOLLOWS: ─┬ 'FOO.BAR',0 ╬O SPACES ARE INCLUDED IN THE PATHNAME. ╬ORMALLY ONLY THE FILE NAME STEM (NO DIRECTORY PREFIX) IS TRANSMITTED UNLESS THE SENDER HAS SELECTED ┘┴═'S '╞' OPTION TO SEND THE FULL ABSOLUTE OR RELATIVE PATHNAME. ╘HE SOURCE DRIVE DESIGNATOR (┴:, ┬:, ETC.) USUALLY IS NOT SENT. ╞╔╠┼╬┴═┼ ├╧╬╙╔─┼╥┴╘╔╧╬╙ ==> ╞ILE NAMES SHOULD BE TRANSLATED TO LOWER CASE UNLESS THE SENDING SYSTEM SUPPORTS UPPER/LOWER CASE FILE NAMES. ╘HIS IS A CONVENIENCE FOR USERS OF SYSTEMS (SUCH AS ╒NIX) WHICH STORE FILENAMES IN UPPER AND LOWER CASE. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 32 ==> ╘HE RECEIVER SHOULD ACCOMMODATE FILE NAMES IN LOWER AND UPPER CASE. ==> ╫HEN TRANSMITTING FILES BETWEEN DIFFERENT OPERATING SYSTEMS, FILE NAMES MUST BE ACCEPTABLE TO BOTH THE SENDER AND RECEIVING OPERATING SYSTEMS. ╔F NOT, TRANSFORMATIONS SHOULD BE APPLIED TO MAKE THE FILE NAMES ACCEPTABLE. ╔F THE TRANSFORMATIONS ARE UNSUCCESSFUL, A NEW FILE NAME MAY BE INVENTED BY THE RECEIVING PROGRAM. ╔F DIRECTORIES ARE INCLUDED, THEY ARE DELIMITED BY '/' ; I.E., "SUBDIR/FOO" IS ACCEPTABLE, "SUBDIR FOO" IS NOT. ╠┼╬╟╘╚ ╘HE FILE LENGTH AND EACH OF THE SUCCEEDING FIELDS ARE OPTIONAL. [1] ╘HE LENGTH FIELD IS STORED AS A DECIMAL STRING COUNTING THE NUMBER OF DATA BYTES IN THE FILE. ╘HE ┌═╧─┼═ RECEIVER USES THE FILE LENGTH AS AN ESTIMATE ONLY. ╔T MAY BE USED TO DISPLAY AN ESTIMATE OF THE TRANSMISSION TIME, AND MAY BE COMPARED WITH THE AMOUNT OF FREE DISK SPACE. ╘HE ACTUAL LENGTH OF THE RECEIVED FILE IS DETERMINED BY THE DATA TRANSFER. ┴ FILE MAY GROW AFTER TRANSMISSION COMMENCES, AND ALL THE DATA WILL BE SENT. ═╧─╔╞╔├┴╘╔╧╬ ─┴╘┼ ┴ SINGLE SPACE SEPARATES THE MODIFICATION DATE FROM THE FILE LENGTH. ╘HE MODIFICATION DATE IS OPTIONAL, AND THE FILENAME AND LENGTH MAY BE SENT WITHOUT REQUIRING THE MODIFICATION DATE TO BE SENT. ╘HE MODIFICATION DATE IS SENT AS AN OCTAL NUMBER GIVING THE TIME THE CONTENTS OF THE FILE WERE LAST CHANGED MEASURED IN SECONDS FROM ╩AN 1 1970 ├OORDINATED ╒NIVERSAL ╘IME (╒╘├). ┴ DATE OF ZERO IMPLIES THE MODIFICATION DATE IS UNKNOWN AND SHOULD BE LEFT AS THE DATE THE FILE IS RECEIVED. ╘HIS STANDARD FORMAT WAS CHOSEN TO ELIMINATE AMBIGUITIES ARISING FROM TRANSFERS BETWEEN DIFFERENT TIME ZONES. ╞╔╠┼ ═╧─┼ ┴ SINGLE SPACE SEPARATES THE FILE MODE FROM THE MODIFICATION DATE. ╘HE FILE MODE IS STORED AS AN OCTAL STRING. ╒NLESS THE FILE ORIGINATED FROM A ╒NIX SYSTEM, THE FILE MODE IS SET TO ZERO. ╥┌(1) CHECKS THE FILE MODE FOR THE 0X8000 BIT WHICH INDICATES A ╒NIX TYPE REGULAR FILE. ╞ILES WITH THE 0X8000 BIT SET ARE ASSUMED TO HAVE BEEN SENT FROM ANOTHER ╒NIX (OR SIMILAR) SYSTEM WHICH USES THE SAME FILE CONVENTIONS. ╙UCH FILES ARE NOT TRANSLATED IN ANY WAY. [1]. ╞IELDS MAY NOT BE SKIPPED. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 33 ╙┼╥╔┴╠ ╬╒═┬┼╥ ┴ SINGLE SPACE SEPARATES THE SERIAL NUMBER FROM THE FILE MODE. ╘HE SERIAL NUMBER OF THE TRANSMITTING PROGRAM IS STORED AS AN OCTAL STRING. ╨ROGRAMS WHICH DO NOT HAVE A SERIAL NUMBER SHOULD OMIT THIS FIELD, OR SET IT TO ZERO. ╘HE RECEIVER'S USE OF THIS FIELD IS OPTIONAL. ╬╒═┬┼╥ ╧╞ ╞╔╠┼╙ ╥┼═┴╔╬╔╬╟ ╔F THE NUMBER OF FILES REMAINING IS SENT, A SINGLE SPACE SEPARATES THIS FIELD FROM THE PREVIOUS FIELD. ╘HIS FIELD IS CODED AS A DECIMAL NUMBER, AND INCLUDES THE CURRENT FILE. ╘HIS FIELD IS AN ESTIMATE, AND INCORRECT VALUES MUST NOT BE ALLOWED TO CAUSE LOSS OF DATA. ╘HE RECEIVER'S USE OF THIS FIELD IS OPTIONAL. ╬╒═┬┼╥ ╧╞ ┬┘╘┼╙ ╥┼═┴╔╬╔╬╟ ╔F THE NUMBER OF BYTES REMAINING IS SENT, A SINGLE SPACE SEPARATES THIS FIELD FROM THE PREVIOUS FIELD. ╘HIS FIELD IS CODED AS A DECIMAL NUMBER, AND INCLUDES THE CURRENT FILE. ╘HIS FIELD IS AN ESTIMATE, AND INCORRECT VALUES MUST NOT BE ALLOWED TO CAUSE LOSS OF DATA. ╘HE RECEIVER'S USE OF THIS FIELD IS OPTIONAL. ╘HE FILE INFORMATION IS TERMINATED BY A NULL. ╔F ONLY THE PATHNAME IS SENT, THE PATHNAME IS TERMINATED WITH TWO NULLS. ╘HE LENGTH OF THE FILE INFORMATION SUBPACKET, INCLUDING THE TRAILING NULL, MUST NOT EXCEED 1024 BYTES; A TYPICAL LENGTH IS LESS THAN 64 BYTES. 14. ╨┼╥╞╧╥═┴╬├┼ ╥┼╙╒╠╘╙ 14.1 ├╧═╨┴╘╔┬╔╠╔╘┘ ┼XTENSIVE TESTING HAS DEMONSTRATED ┌═╧─┼═ TO BE COMPATIBLE WITH SATELLITE LINKS, PACKET SWITCHED NETWORKS, MICROCOMPUTERS, MINICOMPUTERS, REGULAR AND ERROR-CORRECTING BUFFERED MODEMS AT 75 TO 19200 BPS. ┌═╧─┼═'S ECONOMY OF REVERSE CHANNEL BANDWIDTH ALLOWS MODEMS THAT DYNAMICALLY PARTITION BANDWIDTH BETWEEN THE TWO DIRECTIONS TO OPERATE AT OPTIMAL SPEEDS. 14.2 ╘╚╥╧╒╟╚╨╒╘ ┬ETWEEN TWO SINGLE-TASK ╨├-╪╘ COMPUTERS SENDING A PROGRAM IMAGE ON AN IN-HOUSE ╘ELENET LINK, ╙UPER╦ERMIT PROVIDED 72 CH/SEC THROUGHPUT AT 1200 BAUD. ┘═╧─┼═-╦ YIELDED 85 CHARS/SEC, AND ┌═╧─┼═ PROVIDED 113 CHARS/SEC. ╪═╧─┼═ WAS NOT MEASURED, BUT WOULD HAVE BEEN MUCH SLOWER BASED ON OBSERVED NETWORK PROPAGATION DELAYS. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 34 ╥ECENT TESTS DOWNLOADING LARGE BINARY FILES TO AN ╔┬═ ╨├ (4.7 M╚Z ╓20) RUNNING ┘┴═╦ 16.30 WITH TABLE-DRIVEN 32-BIT ├╥├ CALCULATION YIELDED A THROUGHPUT OF 1870 CPS ON A 19200 BPS DIRECT CONNECTION. ╘ESTS WITH ╘┼╠┼┬╔╘ ╘RAIL┬LAZER MODEMS HAVE SHOWN TRANSFER RATES APPROACHING 1400 CHARACTERS PER SECOND FOR LONG FILES. ╫HEN FILES ARE COMPRESSED, EFFECTIVE TRANSFER RATES OF 2000 CHARACTERS PER SECOND ARE POSSIBLE. 14.3 ┼╥╥╧╥ ╥┼├╧╓┼╥┘ ╙OME TESTS OF ┌═╧─┼═ PROTOCOL ERROR-RECOVERY PERFORMANCE HAVE BEEN MADE. ┴ ╨├-┴╘ WITH ╙├╧ ╙┘╙ ╓ ╪ENIX OR ─╧╙ 3.1 WAS CONNECTED TO A ╨├ WITH ─╧╙ 2.1 EITHER DIRECTLY AT 9600 BPS OR WITH UNBUFFERED DIAL-UP 1200 BPS MODEMS. ╘HE ┌═╧─┼═ SOFTWARE WAS CONFIGURED TO USE 1024-BYTE DATA SUBPACKET LENGTHS ABOVE 2400 BPS, 256 OTHERWISE. ┬ECAUSE NO TIME DELAYS ARE NECESSARY IN NORMAL FILE TRANSFERS, PER-FILE NEGOTIATIONS ARE MUCH FASTER THAN WITH ┘═╧─┼═, THE ONLY OBSERVED DELAY BEING THE TIME REQUIRED BY THE PROGRAM(S) TO UPDATE LOGGING FILES. ─URING A FILE TRANSFER, A SHORT LINE HIT SEEN BY THE RECEIVER USUALLY INDUCES A ├╥├ ERROR. ╘HE INTERRUPT SEQUENCE IS USUALLY SEEN BY THE SENDER BEFORE THE NEXT DATA SUBPACKET IS COMPLETELY SENT, AND THE RESULTANT LOSS OF DATA THROUGHPUT AVERAGES ABOUT HALF A DATA SUBPACKET PER LINE HIT. ┴T 1200 BPS THIS IS WOULD BE ABOUT .75 SECOND LOST PER HIT. ┴T 10-5 ERROR RATE, THIS WOULD DEGRADE THROUGHPUT BY ABOUT 9 PER CENT. ╘HE THROUGHPUT DEGRADATION INCREASES WITH INCREASING CHANNEL DELAY, AS MORE DATA SUBPACKETS IN TRANSIT THROUGH THE CHANNEL ARE DISCARDED WHEN AN ERROR IS DETECTED. ┴ LONGER NOISE BURST THAT AFFECTS BOTH THE RECEIVER AND THE SENDER'S RECEPTION OF THE INTERRUPT SEQUENCE USUALLY CAUSES THE SENDER TO REMAIN SILENT UNTIL THE RECEIVER TIMES OUT IN 10 SECONDS. ╔F THE ROUND TRIP CHANNEL DELAY EXCEEDS THE RECEIVER'S 10 SECOND TIMEOUT, RECOVERY FROM THIS TYPE OF ERROR MAY BECOME DIFFICULT. ╬OISE AFFECTING ONLY THE SENDER IS USUALLY IGNORED, WITH ONE COMMON EXCEPTION. ╙PURIOUS ╪╧╞╞ CHARACTERS GENERATED BY NOISE STOP THE SENDER UNTIL THE RECEIVER TIMES OUT AND SENDS AN INTERRUPT SEQUENCE WHICH CONCLUDES WITH AN ╪╧╬. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 35 ╔N SUMMATION, ┌═╧─┼═ PERFORMANCE IN THE PRESENCE OF ERRORS RESEMBLES THAT OF ╪.╨├ AND ╙UPER╦ERMIT. ╙HORT BURSTS CAUSE MINIMAL DATA RETRANSMISSION. ╠ONG BURSTS (SUCH AS PULSE DIALING NOISES) OFTEN REQUIRE A TIMEOUT ERROR TO RESTORE THE FLOW OF DATA. 15. ╨┴├╦┼╘ ╙╫╔╘├╚┼─ ╬┼╘╫╧╥╦ ├╧╬╙╔─┼╥┴╘╔╧╬╙ ╞LOW CONTROL IS NECESSARY FOR PRINTING MESSAGES AND DIRECTORIES, AND FOR STREAMING FILE TRANSFER PROTOCOLS. ┴ NON-TRANSPARENT FLOW CONTROL IS INCOMPATIBLE WITH ╪═╧─┼═ AND ┘═╧─┼═ TRANSFERS. ╪═╧─┼═ AND ┘═╧─┼═ PROTOCOLS REQUIRE COMPLETE TRANSPARENCY OF ALL 256 8-BIT CODES TO OPERATE PROPERLY. ╘HE "BEST" FLOW CONTROL (WHEN ╪.25 OR HARDWARE ├╘╙ IS UNAVAILABLE) WOULD NOT "EAT" ANY CHARACTERS AT ALL. ╫HEN THE ╨┴─'S BUFFER ALMOST FILLS UP, AN ╪╧╞╞ SHOULD BE EMITTED. ╫HEN THE BUFFER IS NO LONGER NEARLY FULL, SEND AN ╪╧╬. ╧THERWISE, THE NETWORK SHOULD NEITHER GENERATE NOR EAT ╪╧╬ OR ╪╧╞╞ CONTROL CHARACTERS. ╧N ╘ELENET, THIS CAN BE MET BY SETTING ├├╔╘ ╪3 5:1 AND 12:0 AT BOTH ENDS OF THE NETWORK. ╞OR BEST THROUGHPUT, PARAMETER 64 (ADVANCE ┴├╦) SHOULD BE SET TO SOMETHING LIKE 4. ╨ACKETS SHOULD BE FORWARDED WHEN THE PACKET IS A FULL 128 BYTES, OR AFTER A MODERATE DELAY (3:0, 4:10, 6:0). ╫ITH ╨├-╨URSUIT, IT IS SUFFICIENT TO SET PARAMETER 5 TO 1 AT BOTH ENDS AFTER ONE IS CONNECTED TO THE REMOTE MODEM. <┼╬╘┼╥> @ <┼╬╘┼╥> SET 5:1 <┼╬╘┼╥> RST? 5:1 <┼╬╘┼╥> CONT <┼╬╘┼╥> ╒NFORTUNATELY, MANY ╨┴─S DO NOT ACCEPT THE "RST?" COMMAND. ╞OR ┘═╧─┼═, ╨┴─ BUFFERING SHOULD GUARANTEE THAT A MINIMUM OF 1040 CHARACTERS CAN BE SENT IN A BURST WITHOUT LOSS OF DATA OR GENERATION OF FLOW CONTROL CHARACTERS. ╞AILURE TO PROVIDE THIS BUFFERING WILL GENERATE EXCESSIVE RETRIES WITH ┘═╧─┼═. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 36 ╘┴┬╠┼ 1. ╬ETWORK AND ╞LOW ├ONTROL ├OMPATIBILITY ╔╬╘┼╥- ╫╪ ╙╒╨┼╥ ├╧╬╬┼├╘╔╓╔╘┘ ┴├╘╔╓┼ ╪═╧─┼═ ═╧─┼═ ╦┼╥═╔╘ ┌═╧─┼═ ─IRECT ├ONNECT ┘┼╙ ┘┼╙ ┘┼╙ ┘┼╙ ┘┼╙ ╬ETWORK, NO ╞├ ╬╧ ┘┼╙ [4] [6] ┘┼╙ [1] ╬ET, TRANSPARENT ╞├ ┘┼╙ ┘┼╙ ┘┼╙ ┘┼╙ ┘┼╙ ╬ET, NON-TRANS. ╞├ ┘┼╙ ╬╧ ╬╧ [5] ┘┼╙ ┘┼╙ ╬ETWORK, 7 BIT ┘┼╙ ╬╧ ╬╧ ┘┼╙ [2] ┘┼╙ [3] [1] ┌═╧─┼═ CAN OPTIMIZE WINDOW SIZE OR BURST LENGTH FOR FASTEST TRANSFERS. [2] ╨ARITY BITS MUST BE ENCODED, SLOWING BINARY TRANSFERS. [3] ╬ATURAL PROTOCOL EXTENSION POSSIBLE FOR ENCODING DATA TO 7 BITS. [4] ╙MALL ╫╪═╧─┼═ WINDOW SIZE MAY MAY ALLOW OPERATION. [5] ╙OME FLOW CONTROL CODES ARE NOT ESCAPED IN ╫╪═╧─┼═. [6] ╦ERMIT WINDOW SIZE MUST BE REDUCED TO AVOID BUFFER OVERRUN. 16. ╨┼╥╞╧╥═┴╬├┼ ├╧═╨┴╥╔╙╧╬ ╘┴┬╠┼╙ "╥OUND ╘RIP ─ELAY ╘IME" INCLUDES THE TIME FOR THE LAST BYTE IN A PACKET TO PROPAGATE THROUGH THE OPERATING SYSTEMS AND NETWORK TO THE RECEIVER, PLUS THE TIME FOR THE RECEIVER'S RESPONSE TO THAT PACKET TO PROPAGATE BACK TO THE SENDER. ╘HE FIGURES SHOWN BELOW ARE CALCULATED FOR ROUND TRIP DELAY TIMES OF 40 MILLISECONDS AND 5 SECONDS. ╙HIFT REGISTERS IN THE TWO COMPUTERS AND A PAIR OF 212 MODEMS GENERATE A ROUND TRIP DELAY TIME ON THE ORDER OF 40 MILLISECONDS. ╧PERATION WITH BUSY TIMESHARING COMPUTERS AND NETWORKS CAN EASILY GENERATE ROUND TRIP DELAYS OF FIVE SECONDS. ┬ECAUSE THE ROUND TRIP DELAYS CAUSE VISIBLE INTERRUPTIONS OF DATA TRANSFER WHEN USING ╪═╧─┼═ PROTOCOL, THE SUBJECTIVE EFFECT OF THESE DELAYS IS GREATLY EXAGGERATED, ESPECIALLY WHEN THE USER IS PAYING FOR CONNECT TIME. ┴ 102400-BYTE BINARY FILE WITH RANDOMLY DISTRIBUTED CODES IS SENT AT 1200 BPS 8 DATA BITS, 1 STOP BIT. ╘HE CALCULATIONS ASSUME NO TRANSMISSION ERRORS. ╞OR EACH OF THE PROTOCOLS, ONLY THE PER-FILE FUNCTIONS ARE CONSIDERED. ╨ROCESSOR AND ╔/╧ OVERHEAD ARE NOT INCLUDED. ┘═-╦ REFERS TO ┘═╧─┼═ WITH 1024-BYTE DATA PACKETS. ┘═-╟ REFERS TO THE ┘═╧─┼═ "╟" OPTION. ┌═╧─┼═ USES 256-BYTE DATA SUBPACKETS FOR THIS EXAMPLE. ╙UPER╦ERMIT USES MAXIMUM STANDARD PACKET SIZE, 8-BIT TRANSPARENT TRANSMISSION, NO RUN-LENGTH COMPRESSION. ╘HE 4-BLOCK ╫╪═╧─┼═ WINDOW IS TOO SMALL TO SPAN THE 5-SECOND DELAY IN THIS EXAMPLE; THE RESULTING THOUGHPUT DEGRADATION IS IGNORED. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 37 ╞OR COMPARISON, A STRAIGHT "DUMP" OF THE FILE CONTENTS WITH NO FILE MANAGEMENT OR ERROR CHECKING TAKES 853 SECONDS. ╘┴┬╠┼ 2. ╨ROTOCOL ╧VERHEAD ╔NFORMATION (102400-BYTE BINARY FILE, 5 ╙ECOND ╥OUND ╘RIP) ╨ROTOCOL ╪═╧─┼═ ┘═-╦ ┘═-╟ ┌═╧─┼═ ╙╦ERMIT ╫╪═╧─┼═ ╨ROTOCOL ╥OUND ╘RIPS 804 104 5 5 5 4 ╘RIP ╘IME AT 40MS 32S 4S 0 0 0 0 ╘RIP ╘IME AT 5S 4020S 520S 25S 25S 25 20 ╧VERHEAD ├HARACTERS 4803 603 503 3600 38280 8000 ╠INE ╘URNAROUNDS 1602 204 5 5 2560 1602 ╘RANSFER ╘IME AT 0S 893S 858S 857S 883S 1172S 916S ╘RANSFER ╘IME AT 40MS 925S 862S 857S 883S 1172S 916S ╘RANSFER ╘IME AT 5S 5766S 1378S 882S 918S 1197S 936S ╞╔╟╒╥┼ 5. ╘RANSMISSION ╘IME ├OMPARISON (102400-BYTE BINARY FILE, 5 ╙ECOND ╥OUND ╘RIP) ╪═╧─┼═ ************************************************** ┘═╧─┼═-╦ ************ ╙UPER╦ERMIT ********** (╙LIDING ╫INDOWS) ┌═╧─┼═ 16KB ******* ╙EGMENTED ╙TREAMING ┌═╧─┼═ ******* ╞ULL ╙TREAMING ┘═╧─┼═-╟ ******* ╘┴┬╠┼ 3. ╠OCAL ╘IMESHARING ├OMPUTER ─OWNLOAD ╨ERFORMANCE ├OMMAND ╨ROTOCOL ╘IME/╚─ ╘IME/╞─ ╘HROUGHPUT ┼FFICIENCY KERMIT -X ╦ERMIT 1:49 2:03 327 34% SZ -╪A PHONES.T ╪═╧─┼═ 1:20 1:44 343 36% SZ -A PHONES.T ┌═╧─┼═ :39 :48 915 95% ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 38 ╘IMES WERE MEASURED DOWNLOADING A 35721-CHARACTER TEXT FILE AT 9600 BPS, FROM ╙ANTA ├RUZ ╙YS╓ 2.1.2 ╪ENIX ON A 9 M╚Z ╔┬═ ╨├-┴╘ TO ─╧╙ 2.1 ON AN ╔┬═ ╨├. ╪ENIX WAS IN MULTI-USER MODE BUT OTHERWISE IDLE. ╘RANSFER TIMES TO ╨├ HARD DISK AND FLOPPY DISK DESTINATIONS ARE SHOWN. ├-╦ERMIT 4.2 (030) USED SERVER MODE AND FILE COMPRESSION, SENDING TO ╨RO-┘┴═ 15.52 USING ZERO DELAY AND A "GET PHONES.T" COMMAND. ├ROSSTALK ╪╓╔ 3.6 USED ╪═╧─┼═ 8-BIT CHECKSUM (├╥├ NOT AVAILABLE) AND AN "┼╙├ RX PHONES.T" COMMAND. ╘HE ├ROSSTALK TIME DOES NOT INCLUDE THE TIME NEEDED TO ENTER THE EXTRA COMMANDS NOT NEEDED BY ╦ERMIT AND ┌═╧─┼═. ╨ROFESSIONAL-┘┴═ USED ┌═╧─┼═ ┴UTO─OWNLOAD. ┌═╧─┼═ TIMES INCLUDED A SECURITY CHALLENGE TO THE SENDING PROGRAM. ╘┴┬╠┼ 4. ╞ILE ╘RANSFER ╙PEEDS ╨╥╧╘ ╞╔╠┼ ┬┘╘┼╙ ┬╨╙ ├╚/╙┼├ ╬╧╘┼╙ ╪ JANCOL.C 18237 2400 53 ╘YMNET ╨╘╠ 5/3/87 ╪ SOURCE.XXX 6143 2400 56 ╙OURCE/╘ELENET ╨╘╠ ╪ JANCOL.C 18237 2400 64 ╘YMNET ╨╘╠ ┬ JANCOL.C 18237 1200 87 ─ATA╨AC (604-687-7144) ╪╬ TSRMAKER.ARC 25088 1200 94 ╟┼NIE ╨╘╠ ┬/OVTH EMAIBM.ARC 51200 1200 101 ├╔╙ ╨╘╠ ═╬╨ ╒╒├╨ 74 FILES, EACH >7000 1200 102 ┴VERAGE FOR ╓ARIOUS CALLERS ┌═ JANCOL.C 18237 1200 112 ─ATA╨AC (604-687-7144) ╪/OVTH EMAIBM.ARC 51200 1200 114 ├╔╙ ╨╘╠ ═╬╨ ┌═ EMAIBM.ARC 51200 1200 114 ├╔╙ ╨╘╠ ═╬╨ ┬ JANCOL.C 18237 2400 124 ╘YMNET ╨╘╠ ┬ ┘╔0515.87 9081 2400 157 ├╔╙ ╨╘╠ NODE 5/29/87 ╙╦ SOURCE.XXX 6143 2400 170 ╙OURCE/╘ELENET ╨╘╠ 5/29/87 ┌═ JANCOL.C 18237 2400 221 ╘YMNET ╨╘╠ UPL/DL ┬/OVTH DESTRO.GIF 33613 2400 223 ├╔╙/╨╘╠ ╠┼╓┼╠ 5 9-12-87 ┌═ JANCOL.C 18237 2400 224 ╘YMNET ╨╘╠ ┌═ JANCOL.C 18237 2400 226/218 ╘ELE╟ODZILLA UPL ┌═ JANCOL.C 18237 2400 226 ╘YMNET ╨╘╠ 5/3/87 ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 39 ╨╥╧╘ ╞╔╠┼ ┬┘╘┼╙ ┬╨╙ ├╚/╙┼├ ╬╧╘┼╙ ┌═ ZMODEM.OV 35855 2400 227 ├╔╙ ╨╘╠ NODE ├ JANCOL.C 18237 2400 229 ╘YMNET ╨╘╠ 5/3/87 ┌═ JANCOL.C 18237 2400 229/221 ╘ELE╟ODZILLA ┌═ ZMODEM.OV 35855 2400 229 ├╔╙ ╨╘╠ NODE UPL ┌═ JANCOL.C 18237 2400 232 ├╔╙ ╨╘╠ NODE ┌═ MBOX 473104 9600 948/942 ╘ELE╟ODZILLA UPL ┌═ ZMODEM.ARC 318826 14K 1357/1345 ╘ELE╟ODZILLA ┌═ MBOX 473104 14K 1367/1356 ╘ELE╟ODZILLA UPL ┌═ C2.DOC 218823 38K 3473 ╪ENIX 386 ╘OOLKIT UPLOAD ┌═ MBOX 511893 38K 3860 386 ╪ENIX 2.2 ┬ETA # ┌═ C.DOC 218823 57K 5611 ** ┴┬┬╥┼╓╔┴╘╔╧╬╙: ┬ = ├OMPUSERVE ┬ ╨ROTOCOL ┬/OVTH = ├╔╙ ┬ WITH ╧MEN ╘ECHNOLOGY ╧VER╘HRUSTER(╘═) ├ = ├APTURE ─├2/─├4 (NO PROTOCOL) ╦ = ╦ERMIT ═╬╨ = ═ICROCOM ═╬╨ ERROR CORRECTING ╙╪/1200 MODEM ╨╘╠ = ╨ORTLAND ╧REGON NETWORK NODE ╙╦ = ╙LIDING ╫INDOW ╦ERMIT (╙UPER╦ERMIT) W=15 ╪ = ╪═╧─┼═ ╪╬ = ╪═╧─┼═ PROTOCOL IMPLEMENTED IN NETWORK MODES ╪/OVTH = ╪═╧─┼═, ╧MEN ╘ECHNOLOGY ╧VER╘HRUSTER(╘═) ┌═ = ┌═╧─┼═ ╘K = ╪ENIX 386 ╘OOLKIT, RZ COMPILED -═3, DUMB SERIAL PORT ** = ┴╘ ├LONE RAMDISK TO 386 RAMDISK, OR EITHER RAMDISK TO NUL # = ╧N THE FLY FORMAT TRANSLATION ╬╠ TO ├╥/╠╞ ╘IMES ARE FOR DOWNLOADS UNLESS NOTED. ╫HERE TWO SPEEDS ARE NOTED, THE FASTER SPEED IS REPORTED BY THE RECEIVER BECAUSE ITS TRANSFER TIME CALCULATION EXCLUDES THE SECURITY CHECK AND TRANSACTION LOG FILE PROCESSING. ╘HE ╘ELE╟ODZILLA COMPUTER IS A 4.77 ═╚┌ ╔┬═ ╨├ WITH A 10 ═┬ HARD DISK. ╘HE 386 COMPUTER USES AN ╔NTEL MOTHERBOARD AT 18 ═╚┌ 1WS. ╘HE ┴╘ ├LONE (╤╔├) RUNS AT 8 ═╚┌ 0WS. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 40 ╘┴┬╠┼ 5. ╨ROTOCOL ├HECKLIST ╔╘┼═ ╪═╧─┼═ ╫╪═╧─┼═ ┘═─═-╦ ┘═─═-╦ ┌═╧─┼═ ╙╦ERMIT ╔╬ ╙┼╥╓╔├┼ 1977 1986 1982 1985 1986 1985 ╒SER FEATURES ╒SER ╞RIENDLY ╔/╞ - - - - ┘┼╙ - ├OMMANDS/BATCH 2*╬ 2*╬ 2 2 1 1 [1] ├OMMANDS/FILE 2 2 0 0 0 0 ├OMMAND ─OWNLOAD - - - - ┘┼╙ ┘┼╙ [6] ═ENU ├OMPATIBLE - - - - ┘┼╙ - ╘RANSFER ╥ECOVERY - - - - ┘┼╙ - ╞ILE ═ANAGEMENT - - - - ┘┼╙ - ╙ECURITY ├HECK - - - - ┘┼╙ - ┘═╧─┼═ ╞ALLBACK ┘┼╙ ┘┼╙ ┘┼╙ ┘┼╙ ┘┼╙ - ********************************************************************** ├╧═╨┴╘╔┬╔╠╔╘┘ ╪═╧─┼═ ╫╪═╧─┼═ ┘═─═-╦ ┘═─═-╦ ┌═╧─┼═ ╙╦ERMIT ─YNAMIC ╞ILES ┘┼╙ ┘┼╙ FAIL FAIL ┘┼╙ ┘┼╙ ╨ACKET ╙╫ ╬┼╘╙ - ┘┼╙ - - ┘┼╙ ┘┼╙ 7-BIT ╨╙ ╬┼╘╙ - - - - [8] ┘┼╙ ╧LD ═AINFRAMES - - - - [8] ┘┼╙ ├╨/═-80 ┘┼╙ ┘┼╙ ┘┼╙ - ┘┼╙[9] - ********************************************************************** ┴╘╘╥╔┬╒╘┼╙ ╪═╧─┼═ ╫╪═╧─┼═ ┘═─═-╦ ┘═─═-╦ ┌═╧─┼═ ╙╦ERMIT ╥ELIABILITY [5] FAIR POOR FAIR[5] NONE ┬┼╙╘ ╚╔╟╚ ╙TREAMING - ┘┼╙ - ┘┼╙ ┘┼╙ ┘┼╙ ╧VERHEAD [2] 7% 7% 1% 1% 1% 30% ╞AITHFUL ╪FERS - - ┘┼╙ ┘┼╙ ┘┼╙ ┘┼╙ ╨RESERVE ─ATE - - ┘┼╙ ┘┼╙ ┘┼╙ - ********************************************************************** ├╧═╨╠┼╪╔╘┘ ╪═╧─┼═ ╫╪═╧─┼═ ┘═─═-╦ ┘═─═-╦ ┌═╧─┼═ ╙╦ERMIT ╬O-╫AIT ╙AMPLE - ╥┼╤─ - - OPT ╥┼╤─ ╥ING ┬UFFERS - ╥┼╤─ - - OPT ╥┼╤─ ╪═╧─┼═ ╙IMILAR ┘┼╙ ╠╧╫ ╚╔╟╚ ╚╔╟╚ ╠╧╫ ╬╧╬┼ ├OMPLEXITY ╠╧╫[5] ═┼─ ╠╧╫[5] ╠╧╫ ═┼─ ╚╔╟╚ ********************************************************************** ┼╪╘┼╬╙╔╧╬╙ ╪═╧─┼═ ╫╪═╧─┼═ ┘═─═-╦ ┘═─═-╦ ┌═╧─┼═ ╙╦ERMIT ╙ERVER ╧PERATION - - - - ┘┼╙[4] ┘┼╙ ═ULTIPLE ╘HREADS - - - - FUTURE - ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 41 ╬╧╘┼╙: [1] ╙ERVER MODE OR ╧MEN ╘ECHNOLOGY ╦ERMIT ┴UTO─OWNLOAD [2] ├HARACTER COUNT, BINARY FILE, TRANSPARENT CHANNEL [3] 32-BIT MATH NEEDED FOR ACCURATE TRANSFER (NO GARBAGE ADDED) [4] ┴UTO─OWNLOAD OPERATION [5] ├YBERNETIC ─ATA ╥ECOVERY(╘═) IMPROVES ╪═╧─┼═ AND ┘═╧─┼═ RELIABILITY WITH COMPLEX PROPRIETARY LOGIC. [6] ╙ERVER COMMANDS ONLY [7] ╬O PROVISION FOR TRANSFERS ACROSS TIME ZONES [8] ╞UTURE ENHANCEMENT PROVIDED FOR [9] ╫ITH ╙EGMENTED ╙TREAMING ╫╪═╧─┼═: ╪═╧─┼═ DERIVATIVE PROTOCOL WITH DATA ENCODING AND WINDOWING 17. ╞╒╘╒╥┼ ┼╪╘┼╬╙╔╧╬╙ ╞UTURE EXTENSIONS INCLUDE: ==> ├OMPATIBILITY WITH 7-BIT NETWORKS ==> ╙ERVER/╠INK ╠EVEL OPERATION: ┴N ┼╬─-╘╧-┼╬─ ERROR-CORRECTED PROGRAM-TO-PROGRAM SESSION IS REQUIRED FOR FINANCIAL AND OTHER SENSITIVE APPLICATIONS. ==> ═ULTIPLE INDEPENDENT THREADS ==> ┼NCRYPTION ==> ├OMPRESSION ==> ╞ILE ├OMPARISON ==> ╙ELECTIVE TRANSFER WITHIN A FILE (E.G., MODIFIED SEGMENTS OF A DATABASE FILE) ==> ╙ELECTIVE ╥ETRANSMISSION FOR ERROR CORRECTION ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 42 18. ╥┼╓╔╙╔╧╬╙ 10-27-87 ╧PTIONAL FIELDS ADDED FOR NUMBER OF FILES REMAINING TO BE SENT AND TOTAL NUMBER OF BYTES REMAINING TO BE SENT. 07-31-87 ╘HE RECEIVER SHOULD IGNORE A ┌┼╧╞ WITH AN OFFSET THAT DOES NOT MATCH THE CURRENT FILE LENGTH. ╘HE PREVIOUS ACTION OF RESPONDING WITH ┌╥╨╧╙ CAUSED TRANSFERS TO FAIL IF A ├╥├ ERROR OCCURRED IMMEDIATELY BEFORE END-OF-FILE, BECAUSE TWO RETRANSMISSION REQUESTS WERE BEING SENT FOR EACH ERROR. ╘HIS HAS BEEN OBSERVED UNDER EXCEPTIONAL CONDITIONS, SUCH AS DATA TRANSMISSION AT SPEEDS GREATER THAN THE RECEIVING COMPUTER'S INTERRUPT RESPONSE CAPABILITY OR GROSS MISAPPLICATION OF FLOW CONTROL. ─ISCUSSION OF THE ╘X BACKCHANNEL GARBAGE COUNT AND ┌├╥├╫ AFTER ERROR ┌╥╨╧╙ WAS ADDED. ═ANY REVISIONS FOR CLARITY. 07-09-87 ├ORRECTED ╪═╧─┼═'S DEVELOPMENT DATE, INCORRECTLY STATED AS 1979 INSTEAD OF THE ACTUAL ┴UGUST 1977. ═ORE PERFORMANCE DATA WAS ADDED. 05-30-87 ┴DDED ┌═╬┼╫ AND ┌═╙╦╬╧╠╧├ 05-14-87 ╫INDOW MANAGEMENT, ┌┴├╦ ┌╙╚╚─╥ ╪╧╬ REMOVED, CONTROL-CHARACTER ON. 03-15-87 32-BIT ├╥├ ADDED. 12-19-86 ┌ERO-╠ENGTH ┌├╥├╫ DATA SUBPACKET SENT IN RESPONSE TO ┌╨┴─ OR ┌─┼╠┼ DETECTED ON REVERSE CHANNEL HAS BEEN CHANGED TO ┌├╥├┼. ╘HE REVERSE CHANNEL IS NOW CHECKED FOR ACTIVITY BEFORE SENDING EACH ┌─┴╘┴ HEADER. 11-08-86 ═INOR CHANGES FOR CLARITY. 10-02-86 ┌├╬╠ DEFINITION EXPANDED. 09-11-86 ┌═╨╥╧╘ FILE MANAGEMENT OPTION ADDED. 08-20-86 ═ORE PERFORMANCE DATA INCLUDED. 08-04-86 ┴╙├╔╔ ─╠┼ (├TRL-╨, 020) NOW ESCAPED; COMPATIBLE WITH PREVIOUS VERSIONS. ═ORE DOCUMENT REVISIONS FOR CLARITY. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 43 07-15-86 ╘HIS DOCUMENT WAS EXTENSIVELY EDITED TO IMPROVE CLARITY AND CORRECT SMALL ERRORS. ╘HE DEFINITION OF THE ┌═╬┼╫ MANAGEMENT OPTION WAS MODIFIED, AND THE ┌═─╔╞╞ MANAGEMENT OPTION WAS ADDED. ╘HE CANCEL SEQUENCE WAS CHANGED FROM TWO TO FIVE ├┴╬ CHARACTERS AFTER SPURIOUS TWO-CHARACTER CANCEL SEQUENCES WERE DETECTED. 19. ═╧╥┼ ╔╬╞╧╥═┴╘╔╧╬ ╨LEASE CONTACT ╧MEN ╘ECHNOLOGY FOR TROFF SOURCE FILES AND TYPESET COPIES OF THIS DOCUMENT. 19.1 ╘┼╠┼╟╧─┌╔╠╠┴ ┬╒╠╠┼╘╔╬ ┬╧┴╥─ ═ORE INFORMATION MAY BE OBTAINED BY CALLING THE ╘ELE╟ODZILLA BULLETIN BOARD AT 503-621-3746. ╘ELE╟ODZILLA SUPPORTS 19200 (╘ELEBIT ╨┼╨), 2400 AND 1200 BPS CALLERS WITH AUTOMATIC SPEED RECOGNITION. ╥ELEVANT FILES INCLUDE ┘┌═╧─┼═.┌╧╧, ┘┴═─┼═╧.┌╧╧, ┘┴═╚┼╠╨.┌╧╧, ┌├╧══┼╪┼.┴╥├, ┌├╧══─╧├.┴╥├, ┌├╧══╚╠╨.┴╥├, AND ┘═╧─┼═.─╤├. ╒SEFUL COMMANDS FOR ╘ELE╟ODZILLA INCLUDE "MENU", "DIR", "SX FILE (╪═╧─┼═)", "KERMIT SB FILE ...", AND "SZ FILE ...". 19.2 ╒╬╔╪ ╒╒├╨ ┴├├┼╙╙ ╒╒├╨ SITES CAN OBTAIN THE CURRENT VERSION OF THIS FILE WITH ╒╒├╨ OMEN!/U/CAF/PUBLIC/ZMODEM.DOC /TMP┴ CONTINUALLY UPDATED LIST OF AVAILABLE FILES IS STORED IN /USR/SPOOL/╒╒├╨PUBLIC/╞╔╠┼╙. ╒╒├╨OMEN!▒╒╒├╨/╞╔╠┼╙ /USR/SPOOL/╒╒├╨PUBLIC ╘HE FOLLOWING ╠.SYS LINE ALLOWS ╒╒├╨ TO CALL SITE "OMEN" VIA ╧MEN'S BULLETIN BOARD SYSTEM "╘ELE╟ODZILLA". ╘ELE╟ODZILLA IS AN INSTANCE OF ╧MEN ╘ECHNOLOGY'S ╨ROFESSIONAL-┘┴═ IN HOST OPERATION, ACTING AS A BULLETIN BOARD AND FRONT-ENDING A ╪ENIX SYSTEM. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 44 ╔N RESPONSE TO ╘ELE╟ODZILLA'S "╬AME ╨LEASE:" (E:--E:), "UUCICO" GIVES THE ╨RO-┘┴═ "LINK" COMMAND AS A USER NAME. ╘ELEGODZILLA THEN ASKS FOR A LINK PASSWORD (D:). ╘HE PASSWORD (╟IZNOID) CONTROLS ACCESS TO THE ╪ENIX SYSTEM CONNECTED TO THE ╔┬═ ╨├'S OTHER SERIAL PORT. ├OMMUNICATIONS BETWEEN ╨RO-┘┴═ AND ╪ENIX USE 9600 BPS; ┘┴═ CONVERTS THIS TO THE CALLER'S SPEED. ╞INALLY, THE CALLING "UUCICO" SEES THE ╪ENIX "╠OGIN:" MESSAGE (N:--N:), AND LOGS IN AS "╒╒├╨". ╬O PASSWORD IS USED FOR THE ╒╒├╨ ACCOUNT. OMEN ┴NY ┴├╒ 2400 1-503-621-3746 E:--E: LINK D: ╟IZNOID N:--N: ╒╒├╨ 20. ┌═╧─┼═ ╨╥╧╟╥┴═╙ ┴ COPY OF THIS DOCUMENT, A DEMONSTRATION VERSION OF ╨ROFESSIONAL-┘┴═, A FLASH-UP TREE-STRUCTURED HELP FILE AND PROCESSOR, ARE AVAILABLE IN ┘┌═╧─┼═.┌╧╧ ON ╘ELE╟ODZILLA AND OTHER BULLETIN BOARDS. ╘HIS FILE MUST BE UNPACKED WITH ╠╧╧┌.┼╪┼, ALSO AVAILABLE ON ╘ELE╟ODZILLA. ┘┌═╧─┼═.┌╧╧ MAY BE DISTRIBUTED PROVIDED NONE OF THE FILES ARE DELETED OR MODIFIED WITHOUT THE WRITTEN CONSENT OF ╧MEN ╘ECHNOLOGY. ╘ELE╟ODZILLA AND OTHER BULLETIN BOARDS ALSO FEATURE ┌├╧══, A SHAREWARE COMMUNICATIONS PROGRAM. ┌├╧══ INCLUDES ╧MEN ╘ECHNOLOGY'S ╘URBO╠EARN(╘═) ╙CRIPT ╫RITER, ┌═╧─┼═, ╧MEN'S HIGHLY ACCLAIMED ╪═╧─┼═ AND ┘═╧─┼═ PROTOCOL SUPPORT, ╙LIDING ╫INDOWS ╦ERMIT, SEVERAL TRADITIONAL PROTOCOLS, A POWERFUL SCRIPT LANGUAGE, AND THE MOST ACCURATE ╓╘100/102 EMULATION AVAILABLE IN A USER-SUPPORTED PROGRAM. ╘HE ┌├╧══ FILES INCLUDE: ==> ┌├╧══┼╪┼.┴╥├ ┼XECUTABLE FILES AND BEGINNER'S TELEPHONE DIRECTORY ==> ┌├╧══─╧├.┴╥├ "╒NIVERSAL ╠INE ╨RINTER ┼DITION" ═ANUAL ==> ┌├╧══╚╠╨.┴╥├ ╘REE-STRUCTURED ╞LASH-UP HELP PROCESSOR AND DATABASE ╙OURCE CODE AND MANUAL PAGES FOR THE ╒NIX/╪ENIX ╥┌ AND ╙┌ PROGRAMS ARE AVAILABLE ON ╘ELE╟ODZILLA IN ╥┌╙┌.┌╧╧. ╘HIS ┌╧╧ ARCHIVE MAY BE UNPACKED WITH ╠╧╧┌.┼╪┼, ALSO AVAILABLE ON ╘ELE╟ODZILLA. ═OST ╒NIX-LIKE SYSTEMS ARE SUPPORTED, INCLUDING ╓7, ╙YS ╔╔╔, 4.X ┬╙─, ╙┘╙ ╓, ╔DRIS, ├OHERENT, AND ╥EGULUS. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 45 ╥┌╙┌.┌╧╧ INCLUDES A ┌├╧══/╨RO-┘┴═/╨OWER├OM SCRIPT ┌╒╨╠.╘ TO UPLOAD THE SMALL (178 LINES) ┘═╧─┼═ BOOTSTRAP PROGRAM ═╔╬╔╥┬.├ WITHOUT A FILE TRANSFER PROTOCOL. ═╔╬╔╥┬ USES THE ╒NIX ╙╘╘┘(1) PROGRAM TO SET THE REQUIRED RAW ╘╘┘ MODES, AND COMPILES WITHOUT SPECIAL FLAGS ON VIRTUALLY ALL ╒NIX AND ╪ENIX SYSTEMS. ┌╒╨╠.╘ DIRECTS THE ╒NIX SYSTEM TO COMPILE ═╔╬╔╥┬, THEN USES IT AS A BOOTSTRAP TO UPLOAD THE ╥┌/╙┌ SOURCE AND MANUAL FILES. ╘HE ╨├-─╧╙ ╧╨╒╙ AND ╬╧├╚┴╬╟┼ BULLETIN BOARDS SUPPORT ┌═╧─┼═. ╔NTEGRATED ┌═╧─┼═ SUPPORT FOR THE ├╧╠╠╔┼ BULLETIN BOARD PROGRAM IS PLANNED. ┴ NUMBER OF OTHER BULLETIN BOARD PROGRAMS SUPPORT ┌═╧─┼═ WITH EXTERNAL MODULES (─╙┌, ETC.). ╘HE ╨├-─╧╙ ╘ELECONFERENCING SYSTEM ╔╬-╙┘╬├╚ USES ┌═╧─┼═. ╘HE ╠┴╬ MODEM-SHARING PROGRAM ╠╔╬┼ ╨╠╒╙ HAS ANNOUNCED ┌═╧─┼═ SUPPORT. ╧THER ╨├-─╧╙ COMMUNICATIONS PROGRAMS WITH ┌═╧─┼═ SUPPORT MODULES INCLUDE ╤═╧─┼═ AND ┬╧┘┴╬. ═ANY PROGRAMS ARE ADDING DIRECT ┌═╧─┼═ SUPPORT, INCLUDING ├ROSSTALK ═ARK ╔╓, ╘ELIX 3.0, AND (EXPECTED) ╨ROCOMM AND ╤MODEM. ╘HE ┌═─═ COMMUNICATIONS PROGRAM BY ╩WAHAR ┬AMMI RUNS ON ┴TARI ╙╘ MACHINES. ╘HE ONLINE!!!! PROGRAM FOR THE ┴MIGA SUPPORTS ┌═╧─┼═. ╘HE ├OMPUSERVE ╔NFORMATION ╙ERVICE HAS PORTED THE ╒NIX ╥┌/╙┌ ┌═╧─┼═ PROGRAMS TO ─┼├ ╙┘╙╘┼═ 20 ASSEMBLER. 20.1 ┴──╔╬╟ ┌═╧─┼═ ╘╧ ─╧╙ ╨╥╧╟╥┴═╙ ─╙┌ IS A SMALL PROGRAM THAT SUPPORTS ╪═╧─┼═, ┘═╧─┼═, AND ┌═╧─┼═ FILE TRANSFERS. ─╙┌ IS DESIGNED TO BE CALLED FROM A BULLETIN BOARD PROGRAM OR ANOTHER COMMUNICATIONS PROGRAM. ╔T MAY BE CALLED ┴╙─╙┌ ╨╧╥╘ 2 ╙┌ ╞╔╠┼1 ╞╔╠┼2 TO SEND FILES, OR AS ─╙┌ ╨╧╥╘ 2 ╥┌╘╧ RECEIVE ZERO OR MORE FILE(S), OR AS ─╙┌ ╨╧╥╘ 2 ╥┌ ╞╔╠┼┴ ╞╔╠┼┬ TO RECEIVE TWO FILES, THE FIRST TO ╞╔╠┼┴ AND THE SECOND (IF SENT) TO ╞╔╠┼┬. ╘HIS FORM OF ─╙┌ MAY BE USED TO CONTROL THE PATHNAME OF INCOMING FILE(S). ╔N THIS EXAMPLE, IF THE SENDING PROGRAM ATTEMPTED TO SEND A THIRD FILE, THE TRANSFER WOULD BE TERMINATED. ─╙┌ USES ─╧╙ STDOUT FOR MESSAGES (NO DIRECT ├╥╘ ACCESS), ACQUIRES THE ├╧══ PORT VECTORS WITH STANDARD ─╧╙ CALLS, AND RESTORES THE ├╧══ PORT'S INTERRUPT VECTOR AND REGISTERS UPON EXIT. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 46 ╞URTHER INFORMATION ON ─╙┌ MAY BE FOUND IN ─╙┌.─╧├ AND THE ┌├╧══ OR ╨RO-┘┴═ USER MANUALS. 21. ┘═╧─┼═ ╨╥╧╟╥┴═╙ ╘HE ╒NIX ╥┌/╙┌ PROGRAMS SUPPORT ┘═╧─┼═ AS WELL AS ┌═╧─┼═. ═OST ╒NIX-LIKE SYSTEMS ARE SUPPORTED, INCLUDING ╓7, ╙YS ╔╔╔, 4.2 ┬╙─, ╙┘╙ ╓, ╔DRIS, ├OHERENT, AND ╥EGULUS. ┴ VERSION FOR ╓┴╪-╓═╙ IS AVAILABLE IN ╓╥┬╙┬.╙╚╤, IN THE SAME DIRECTORY. ╔RV ╚OFF HAS ADDED 1K PACKETS AND ┘═╧─┼═ TRANSFERS TO THE ╦═─ AND ╔═╨ SERIES PROGRAMS, WHICH REPLACE THE ╪═╧─┼═ AND ═╧─┼═7/═─═7XX SERIES RESPECTIVELY. ╧VERLAYS ARE AVAILABLE FOR A WIDE VARIETY OF ├╨/═ SYSTEMS. ═ANY OTHER PROGRAMS, INCLUDING ═┼╪-╨╠╒╙ AND ├ROSSTALK ═ARK ╔╓ ALSO SUPPORT SOME OF ┘═╧─┼═'S FEATURES. ╤UESTIONS ABOUT ┘═╧─┼═, THE ╨ROFESSIONAL-┘┴═ COMMUNICATIONS PROGRAM, AND REQUESTS FOR EVALUATION COPIES MAY BE DIRECTED TO: ├HUCK ╞ORSBERG ╧MEN ╘ECHNOLOGY ╔NC 17505-╓ ╙AUVIE ╔SLAND ╥OAD ╨ORTLAND ╧REGON 97231 ╓╧╔├┼: 503-621-3406 ═ODEM (╘ELE╟ODZILLA): 503-621-3746 ╒SENET: ...!TEKTRONIX!REED!OMEN!CAF ├OMPUSERVE: 70007,2304 ╙OURCE: ╘├┼022 22. ┴├╦╬╧╫╠┼─╟═┼╬╘╙ ┌═╧─┼═ WAS DEVELOPED FOR THE PUBLIC DOMAIN UNDER A ╘ELENET CONTRACT. ╘HE ┌═╧─┼═ PROTOCOL DESCRIPTIONS AND THE ╒NIX ╥┌/╙┌ PROGRAM SOURCE CODE ARE PUBLIC-DOMAIN. ╬O LICENSING, TRADEMARK, OR COPYRIGHT RESTRICTIONS APPLY TO THE USE OF THE PROTOCOL, THE ╒NIX ╥┌/╙┌ SOURCE CODE AND THE ┌═╧─┼═ NAME. ┼NCOURAGEMENT AND SUGGESTIONS BY ╘HOMAS ┬UCK, ╫ARD ├HRISTENSEN, ┼ARL ╚ALL, ╔RV ╚OFF, ╙TUART ═ATHISON, AND ╩OHN ╫ALES, ARE GRATEFULLY ACKNOWLEDGED. 32-BIT ├╥├ CODE COURTESY ╟ARY ╙. ┬ROWN. ┌═╧─┼═ ╨ROTOCOL ─OCUMENTATION ╨AGE 47 23. ╥┼╠┴╘┼─ ╞╔╠┼╙ ╘HE FOLLOWING FILES MAY BE USEFUL WHILE STUDYING THIS DOCUMENT: ┘═╧─┼═.─╧├.........─ESCRIBES THE ╪═╧─┼═, ╪═╧─┼═-1K, AND ┘═╧─┼═ BATCH FILE TRANSFER PROTOCOLS. ╘HIS FILE IS AVAILABLE ON ╘ELE╟ODZILLA'S ┘═╧─┼═.─╤├. ┌═╧─┼═.╚...........─EFINITIONS FOR ┌═╧─┼═ MANIFEST CONSTANTS. ╥┌.├, ╙┌.├, ╥┬╙┬.├ ╒NIX SOURCE CODE FOR OPERATING ┌═╧─┼═ PROGRAMS. ╥┌.1, ╙┌.1.........═ANUAL PAGES FOR ╥┌ AND ╙┌ (╘ROFF SOURCES). ┌═.├...............╧PERATING-SYSTEM-INDEPENDENT LOW-LEVEL ┌═╧─┼═ SUBROUTINES. ═╔╬╔╥┬.├...........┴ ┘═╧─┼═ BOOTSTRAP PROGRAM, 178 LINES. ╥┌╙┌.┌╧╧,╥┌╙┌.┴╥├..├ONTAIN THE ├ SOURCE CODE AND MANUAL PAGES LISTED ABOVE, PLUS A ┌├╧══ SCRIPT TO UPLOAD ═╔╬╔╥┬.├ TO A ╒NIX OR ╪ENIX SYSTEM, COMPILE IT, AND USE THE PROGRAM TO UPLOAD THE ┌═╧─┼═ SOURCE FILES WITH ERROR CHECKING. ─╙┌.┌╧╧,─╙┌.┴╥├....├ONTAINS ─╙┌.├╧═, A SHAREWARE ╪/┘/┌═╧─┼═ SUBPROGRAM, ─┼╙╤ VIEW "PIF" FILES FOR BACKGROUND OPERATION IN MINIMUM MEMORY, AND ─╙┌.─╧├. ┌├╧══*.┴╥├.........┴RCHIVE FILES FOR ┌├╧══, A POWERFUL SHAREWARE COMMUNICATIONS PROGRAM. - = [ ┼ N D ╧ F ╘ E X T ] = -