309:. The binary form of the SYN byte has the property that no rotation of the byte is equal to the original. This allows the receiver to find the beginning of a frame by searching the received bit stream for the SYN pattern. When this is found, tentative byte synchronization has been achieved. If the next character is also a SYN, character synchronization has been achieved. The receiver then searches for a character that can start a frame. Characters outside of this set are described as "leading graphics". They are sometimes used to identify the sender of a frame. Long messages have SYN bytes inserted approximately every second to maintain synchronization. These are ignored by the receiver.
361:
data framing provides an unrestricted alphabet of 64, 128 or 256 characters. In transparent mode block framing characters such as ETB, ETX, and SYN are preceded by a DLE character to indicate their control significance (The DLE character itself is represented by the sequence DLE DLE). This technique
385:
Error recovery is by retransmission of the corrupted frame. Since Bisync data packets are not serial-numbered, it's considered possible for a data frame to go missing without the receiver realizing it. Therefore, alternating ACK0s and ACK1s are deployed; if the transmitter receives the wrong ACK, it
421:
operation, and full-duplex (4-wire) can be used in many circumstances to improve performance by eliminating the turn-around time, at the added expense of 4-wire installation and support. In typical full-duplex, data packets are transmitted along one wire pair while the acknowledgements are returned
446:
terminals which are attached via analog bridges to the same communication line. This is accomplished by sending a message consisting only of an ENQ character addressed to each device in turn. The selected station then transmits a message to the master or reply with EOT to indicate that it has no
438:
to determine the master station. In this case one device can transmit ENQ to bid for control. The other device can reply ACK0 to accept the bid and prepare to receive, or NAK or WABT to refuse. In some cases connection of a terminal to multiple hosts is possible via the dial telephone network.
354:
Normal data frames do not allow certain characters to appear in the data. These are the block ending characters: ETB, ETX and ENQ and the ITB and SYN characters. The number of unique characters that can be transmitted is therefore limited to 59 for
Transcode, 123 for USASCII, or 251 for EBCDIC.
336:
characters are required following a line turn-around—NAK, EOT, ENQ, ACK0, ACK1. If the transmission ends with EOT or ETX the pad follows the BCC. This pad is either all '1' bits or alternating '0' and '1' bits. The next transmission begins with a pad character which can be either of the
344:
containing control information can precede data in a frame. The content of the heading is not defined by the protocol but is defined for each specific device. The heading, if present, is preceded by an SOH (start of heading) character and followed by an STX (start of text).
324:(CRC). A data frame may contain an intermediate check sum preceded by an ITB character. This ability to include intermediate check sums in a long data frame allows a considerable improvement of the error detection probability. USASCII characters are also transmitted using
547:(HASP) uses Bisync half-duplex hardware in conjunction with its own link control protocol to provide full-duplex multi-datastream communication between a small computer and a mainframe running HASP. In Bisync terms, this is
400:(2-wire). In this environment, packets or frames of transmission are strictly unidirectional, necessitating 'turn-around' for even the simplest purposes, such as acknowledgments. Turn-around involves
378:
The link control protocol is similar to STR. The designers attempted to protect against simple transmission errors. The protocol requires that every message be acknowledged (ACK0/ACK1) or
382:(NAK), so transmission of small packets has high transmission overhead. The protocol can recover from a corrupted data frame, a lost data frame, and a lost acknowledgment.
46:(STR) protocol used with second generation computers. The intent was that common link management rules could be used with three different character encodings for messages.
471:. The RJE terminals support a limited number of data formats: punched card images in and out and print line images to the terminal. Some non-IBM hardware vendors such as
298:(even/odd affirmative acknowledgement) are encoded as two characters—DLE '70'x, and DLE / for EBCDIC, DLE 0 and DLE 1 for USASCII, DLE - and DLE T for Transcode.
910:
876:
363:
88:(PPP), etc. each have different framing schemes but only one frame format exists within a specific protocol. Bisync has five different framing formats.
386:
can assume a data packet (or an ACK) went missing. A potential flaw is that corruption of ACK0 into ACK1 could result in duplication of a data frame.
805:
536:
used BSC protocol for communication between
Regional Center and Institution (bank) server over leased line. In a mid-1990 BSC was replaced by the
642:
81:
61:
with 256 characters looked forward. Transcode disappeared very quickly but the EBCDIC and USASCII dialects of Bisync continued in use.
684:
475:
used Bisync for other purposes such as tape-to-tape transmission. A programmer can easily emulate an RJE terminal or other device.
636:
Other computer vendors offered their own variety of byte-oriented protocols similar to Bisync. Some widely used protocols include
351:
data normally follows the heading, begun by the STX, and terminated by ETX (end of text) or ETB (end transmission block).
856:
544:
529:, together with connecting networks in other geographic areas, used Bisync to connect 3000 computer systems at its peak.
431:
710:
612:
880:
562:
data and control packets. As of 2012, several vendors encapsulate Bisync transmissions within TCP/IP data streams.
493:
72:
Bisync differs from protocols that succeeded it in the complexity of message framing. Later protocols use a single
574:(SNA) which allows construction of a network with multiple hosts and multiple programs using telecommunications.
937:
379:
50:
637:
317:
732:
571:
442:
Multi-drop is part of the initial Bisync protocol. A master station, normally a computer, can sequentially
43:
896:
758:
418:
397:
64:
At one time Bisync was the most widely used communications protocol and is still in limited use in 2013.
663:
478:
IBM offered assembler language macros to provide programming support. During the System/360 era, these
932:
321:
85:
507:
558:
networks tolerated a connection scheme where transparent Bisync data frames encapsulated HDLC
647:
73:
414:
In a 2-wire environment, this causes a noticeable round-trip delay and reduces performance.
472:
8:
778:
543:
Some important systems use Bisync data framing with a different link control protocol.
456:
579:
912:
General
Information - Binary Synchronous Communications, third edition, October 1970
519:
460:
390:
515:
455:
The original purpose of Bisync was for batch communications between a System/360
501:
480:
877:"Bisync DLC Character Codes in Communications Trace on OS/400 or i5/OS System"
860:
926:
831:
600:
35:
367:
582:
are later protocols which, like SNA, provide more than mere link control.
492:(Queued Telecommunications Access Method) – which was later replaced by
522:
platforms used Bisync line control to communicate with remote devices.
325:
39:
898:
General
Information - Binary Synchronous Communications, first edition
837:
590:
A large number of devices use the Bisync protocol, some of these are:
812:
316:(block check character or BCC). For USASCII, this is a one character
313:
306:
711:"Binary Synchronous and Asynchronous Communications (Bisync/Async)"
624:
618:
606:
594:
468:
464:
302:(wait before transmit) was encoded as DLE ", DLE ?, or DLE W.
320:(LRC); for Transcode and EBCDIC, the check sum is a two character
526:
58:
312:
A normal block ending character (ETB or ETX) is followed by a
806:
Detailed discussion of Bisync link control by
Charles A Wilde
533:
54:
575:
559:
555:
537:
511:
497:
489:
485:
77:
31:
760:
General
Information - Binary Synchronous Communications
685:"Terrestrial to Satellite Switching Creates Options"
500:(Virtual Telecommunications Access Method) with the
924:
389:Error protection for ACK0 and ACK1 is weak. The
38:, announced in 1967 after the introduction of
776:
570:Bisync began to be displaced in the 1970s by
488:(Basic Telecommunications Access Method) and
643:Digital Data Communications Message Protocol
82:Digital Data Communications Message Protocol
908:
894:
874:
756:
393:between the two messages is only two bits.
305:All frame formats begin with at least two
434:. Point-to-point lines can optionally use
832:Bisync & STR programming for IBM 1130
733:"Binary Synchronous Communications (BSC)"
597:Display Terminal Subsystem control units.
76:for all messages sent by the protocol.
857:"What is Bisync? A Short History Lesson"
842:Telecom Corner Technical Reference Site
828:A detailed description of the protocol.
682:
631:
404:the reversal of transmission direction,
925:
777:Peterson, Larry; Davie, Bruce (2012).
750:
780:Computer Networks: A Systems Approach
16:IBM mainframe communications protocol
859:. Serengeti Systems. Archived from
730:
683:Scuilli, Joseph A. (Oct 26, 1981).
545:Houston Automatic Spooling Priority
285:Intermediate block check character
13:
799:
518:(display unit control system) and
53:looked backward to older systems;
14:
949:
708:
514:and third-party software such as
494:Telecommunications Access Method
34:character-oriented, half-duplex
20:Binary Synchronous Communication
844:. TBI/WebNet, Inc. October 2004
838:"Data Communications Protocols"
817:Connectivity Knowledge Platform
525:The academic computing network
450:
373:
770:
724:
702:
676:
565:
1:
669:
638:Digital Equipment Corporation
318:longitudinal redundancy check
572:Systems Network Architecture
92:BSC Link Control Characters
44:synchronous transmit-receive
7:
657:
603:Data Transmission Terminal.
463:(RJE) terminal such as the
459:and another mainframe or a
425:
10:
954:
664:Asynchronous communication
585:
183:End of transmission block
67:
330:for additional checking.
251:Negative acknowledgement
652:Poll and Select Protocol
57:with 128 characters and
508:Teleprocessing monitors
496:(TCAM). IBM introduced
430:Much Bisync traffic is
407:quiescing of line echo,
380:negatively acknowledged
322:cyclic redundancy check
86:Point-to-Point Protocol
627:Programmable Terminal.
417:Some datasets support
938:IBM computer hardware
648:Burroughs Corporation
613:IBM HASP workstations
609:Transmission Control.
632:Comparable protocols
473:Mohawk Data Sciences
217:End of transmission
42:. It replaced the
549:conversational mode
93:
532:Financial network
447:data to transmit.
366:, by analogy with
364:character stuffing
91:
909:IBM Corporation.
895:IBM Corporation.
875:IBM Corporation.
757:IBM Corporation.
621:Computing System.
580:Internet Protocol
422:along the other.
362:became known as
289:
288:
268:Data link escape
149:Start of heading
132:Synchronous idle
945:
919:
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905:
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891:
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879:. Archived from
871:
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706:
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699:
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695:
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540:infrastructure.
461:Remote Job Entry
396:The protocol is
391:Hamming distance
337:above or a SYN.
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800:Further reading
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933:Link protocols
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510:such as IBM's
481:access methods
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166:Start of text
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74:framing scheme
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883:on 2013-01-26
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813:"Bisync, BSC"
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689:Computerworld
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112:(hexadecimal)
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36:link protocol
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29:
25:
21:
911:
897:
885:. Retrieved
881:the original
865:. Retrieved
861:the original
846:. Retrieved
841:
821:. Retrieved
816:
785:. Retrieved
779:
772:
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740:. Retrieved
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714:. Retrieved
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692:. Retrieved
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651:
641:
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569:
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451:Applications
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374:Link control
368:bit stuffing
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348:
347:
341:
340:An optional
339:
333:
332:
326:
311:
304:
299:
295:
291:
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200:End of text
115:Description
71:
63:
48:
27:
23:
19:
18:
737:IT Glossary
566:Disposition
554:Some early
516:Remote DUCS
419:full-duplex
398:half-duplex
359:Transparent
927:Categories
887:2012-06-07
867:2006-07-06
848:2006-07-06
823:2006-07-06
808:(new link)
787:August 17,
783:. Elsevier
670:References
534:S.W.I.F.T.
502:System/370
436:contention
410:resyncing.
327:odd parity
40:System/360
819:. Made IT
731:Gartner.
457:mainframe
314:check sum
307:SYN bytes
110:Transcode
84:(DDCMP),
51:Transcode
658:See also
625:IBM 2922
619:IBM 1130
607:IBM 2703
601:IBM 2780
595:IBM 3270
578:and the
469:IBM 3780
465:IBM 2780
426:Topology
234:Enquiry
49:Six-bit
30:) is an
742:Oct 23,
716:Oct 23,
709:Cisco.
694:Aug 27,
586:Devices
342:heading
282:1D (US)
279:1F (US)
105:USASCII
68:Framing
55:USASCII
646:, and
527:Bitnet
100:EBCDIC
59:EBCDIC
28:Bisync
916:(PDF)
902:(PDF)
764:(PDF)
520:Westi
484:were
789:2023
744:2013
718:2013
696:2012
576:X.25
560:LAPB
556:X.25
538:X.25
512:CICS
498:VTAM
490:QTAM
486:BTAM
444:poll
349:Text
300:WABT
296:ACK1
294:and
292:ACK0
97:Char
78:HDLC
650:'s
640:'s
467:or
334:Pad
273:ITB
256:DLE
239:NAK
222:ENQ
205:EOT
188:ETX
171:ETB
154:STX
137:SOH
120:SYN
32:IBM
26:or
24:BSC
929::
840:.
815:.
735:.
687:.
654:.
551:.
504:.
370:.
276:1F
265:1F
262:10
259:10
248:3D
245:15
242:3D
231:2D
228:05
225:2D
214:1E
211:04
208:37
197:2E
194:03
191:03
180:0F
177:17
174:26
163:0A
160:02
157:02
146:00
143:01
140:01
129:3A
126:16
123:32
80:,
918:.
904:.
890:.
870:.
851:.
826:.
791:.
766:.
746:.
720:.
698:.
615:.
22:(
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