1106:, are primarily used for link management, although a few are used to transfer user data. They exchange session management and control information between connected devices, and some U-frames contain an information field, used for system management information or user data. The first 2 bits (11) mean it is a U-frame. The five type bits (2 before P/F bit and 3 bit after P/F bit) can create 32 different types of U-frame. In a few cases, the same encoding is used for different things as a command and a response.
36:
1400:. This is the mode that a secondary station is in before it is initialized by the primary, or when it is explicitly disconnected. In this mode, the secondary responds to almost every frame other than a mode set command with a "Disconnected mode" response. The purpose of this mode is to allow the primary to reliably detect a secondary being powered off or otherwise reset.
465:", has the value 0x7D (bit sequence '10111110', as RS-232 transmits least-significant bit first). If either of these two octets appears in the transmitted data, an escape octet is sent, followed by the original data octet with bit 5 inverted. For example, the byte 0x7E would be transmitted as 0x7D 0x5E ("10111110 01111010"). Other reserved octet values (such as
1742:
Unnumbered frames are identified by the low two bits being 1. With the P/F flag, that leaves 5 bits as a frame type. Even though fewer than 32 values are in use, some types have different meanings depending on the direction they are sent: as a command or as a response. The relationship between the
958:
When operating as a combined station, it is important to maintain the distinction between P and F bits, because there may be two checkpoint cycles operating simultaneously. A P bit arriving in a command from the remote station is not in response to our P bit; only an F bit arriving in a response is.
3793:
The SM command (an ISO/IEC 13239 addition) is a generic "set mode" command which includes an information field (in the same ISO 8885 format as XID) specifying parameters. This allows parameter values (like 15- and 31-bit sequence numbers) and parameters like window sizes and maximum frame sizes not
1372:(NRM) is an unbalanced configuration in which only the primary terminal may initiate data transfer. The secondary terminals transmit data only in response to commands from the primary terminal. The primary terminal polls each secondary terminal to give it an opportunity to transmit any data it has.
918:
Poll/Final is a single bit with two names. It is called Poll when part of a command (set by the primary station to obtain a response from a secondary station), and Final when part of a response (set by the secondary station to indicate a response or the end of transmission). In all other cases, the
3797:
The FRMR response contains a description of the unacceptable frame, in a standardized format. The first 1 or 2 bytes are a copy of the rejected control field, the next 1 or 2 contain the secondary's current send and receive sequence numbers, and the following 4 or 5 bits are error flags indicating
554:
computed over the
Address, Control, and Information fields. It provides a means by which the receiver can detect errors that may have been induced during the transmission of the frame, such as lost bits, flipped bits, and extraneous bits. However, given that the algorithms used to calculate the FCS
926:
that is passed back and forth between the stations. Only one token should exist at a time. The secondary only sends a Final when it has received a Poll from the primary. The primary only sends a Poll when it has received a Final back from the secondary, or after a timeout indicating that the bit
643:
which can act as both a primary and a secondary. Unfortunately, this mode of operation has some implementation subtleties. While the most common frames sent do not care whether they are in a command or response frame, some essential ones do (notably most unnumbered frames, and any frame with the
373:
The receiving device knows that this is being done, and after seeing five 1-bits in a row, a following 0-bit is stripped out of the received data. If instead the sixth bit is 1, this is either a flag (if the seventh bit is 0), or an error (if the seventh bit is 1). In the latter case, the frame
1214:
respond, even though it has not received the poll bit. This is rarely used in HDLC, but was used in the original IBM SDLC as a substitute for the lack of asynchronous response mode; where the communication channel could handle simultaneous responses, the primary would periodically send UP to the
967:
Both I and S frames contain a receive sequence number N(R). N(R) provides a positive acknowledgement for the receipt of I-frames from the other side of the link. Its value is always the first frame not yet received; it acknowledges that all frames with N(S) values up to N(R)−1 (modulo 8 or modulo
953:
scheme that is required to implement HDLC; all other variants (such as the REJ S-frame) are optional and only serve to increase efficiency. Whenever a station receives a P/F bit, it may assume that any frames that it sent before it last transmitted the P/F bit and not yet acknowledged will never
1331:
This command was defined in SDLC for debugging. It had a 1-byte payload which specified a non-standard test mode for the secondary. Even numbers disabled the mode, while odd numbers enabled it. A payload of 0 disabled all test modes. The secondary normally acknowledged a configure command by
1014:
The first (least significant) 2 bits mean it is an S-frame. All S frames include a P/F bit and a receive sequence number as described above. Except for the interpretation of the P/F field, there is no difference between a command S frame and a response S frame; when P/F is 0, the two forms are
1228:
The FRMR response contains a description of the unacceptable frame, in a standardized format. The first 1 or 2 bytes are a copy of the rejected control field, the next 1 or 2 contain the secondary's current send and receive sequence numbers (and a flag indicating that the frame was a response,
1338:
This response was defined in SDLC to indicate a communications failure. A secondary which received no frames at all for a long time would begin sending a stream of beacon responses, allowing a unidirectional fault to be located. Note that ISO/IEC 13239 assigns UIH the same encoding as
647:
This means that the address field is not optional, even on point-to-point links where it is not needed to disambiguate the peer being talked to. Some HDLC variants extend the address field to include both source and destination addresses, or an explicit command/response bit.
1378:(ARM) is an unbalanced configuration in which secondary terminals may transmit without permission from the primary terminal. However, there is still a distinguished primary terminal which retains responsibility for line initialization, error recovery, and logical disconnect.
1263:
The RSET command causes a secondary to reset its receive sequence number so the next expected frame is sequence number 0. This is a possible alternative to sending a new mode set command, which resets both sequence numbers. It is acknowledged with UA, like a mode set
1209:
This command solicits a response from the secondary. With the poll bit set, it acts like any other poll frame, without the acknowledgement that must be included in I or S frame. With the poll bit clear, it has a special meaning in normal response mode: the secondary
192:
Originally, HDLC was used in multi-device networks, where one device acted as the master and others as slaves, through modes like Normal
Response Mode (NRM) and Asynchronous Response Mode (ARM). These modes are now rarely used. Currently, HDLC is primarily employed in
1125:
When the secondary is disconnected (the default state on power-up), it sends this generic response to any poll (command frame with the poll flag set) except an acceptable mode setting command. It may alternatively give a FRMR response to an unacceptable mode set
994:
The least significant bit (first transmitted) defines the frame type. 0 means an I-frame. Except for the interpretation of the P/F field, there is no difference between a command I frame and a response I frame; when P/F is 0, the two forms are exactly equivalent.
1229:
applicable only in balanced mode), and the following 4 or 5 bits are error flags indicating the reason for the rejection. The secondary repeats the same FRMR response to every poll until the error is cleared by a mode set command or RSET. The error flags are:
1202:
This frame (command or response), a ISO/IEC 13239 addition and rarely used, is like UI but also excludes CRC protection. Only a configurable-length prefix ("header") of the frame is covered by the CRC polynomial; errors in the rest of the frame are not
472:
The "abort sequence" 0x7D 0x7E ends a packet with an incomplete byte-stuff sequence, forcing the receiver to detect an error. This can be used to abort packet transmission with no chance the partial packet will be interpreted as valid by the receiver.
632:
links. While retaining the primary/secondary distinction, it allows the secondary to transmit at any time. Thus, there must be some other mechanism to ensure that multiple secondaries do not try to transmit at the same time (or only one secondary).
600:) permission to speak in turn. Because all communication is either to or from the primary terminal, frames include only one address, that of the secondary terminal; the primary terminal is not assigned an address. There is a distinction between
1282:
defined one format for the information field, in which the most significant bit of the first byte is clear (0), but HDLC implementations normally implement the variant defined in ISO 8885, which has the most significant bit of the first byte set
1118:. Briefly, there are two non-operational modes (initialization mode and disconnected mode) and three operational modes (normal response, asynchronous response, and asynchronous balanced modes) with 3-bit or 7-bit (extended) sequence numbers.
389:. If there are too many 1-bits in a row, the receiver can lose count. Bit-stuffing provides a minimum of one transition per six bit times during transmission of data, and one transition per seven bit times during transmission of a flag.
931:
In NRM, possession of the poll token also grants the addressed secondary permission to transmit. The secondary sets the F-bit in its last response frame to give up permission to transmit. (It is equivalent to the word "Over" in radio
1241:
Z: the frame included an invalid receive sequence number N(R), one which is not between the previously received value and the highest sequence number transmitted. (This error cannot be cleared by receiving RSET, but can be cleared by
240:
The HDLC specification does not specify the full semantics of the frame fields. This allows other fully compliant standards to be derived from it, and derivatives have since appeared in innumerable standards. It was adopted into the
1010:
The S-frame control field includes a leading "10" indicating that it is an S-frame. This is followed by a 2-bit type, a poll/final bit, and a 3-bit sequence number. (Or a 4-bit padding field followed by a 7-bit sequence number.)
1151:
Generic mode set, new in ISO/IEC 13239, using an information field to select parameters. ISO/IEC 13239 added many additional options to HDLC, including 15- and 31-bit sequence numbers, which can only be selected with this
392:
When no frames are being transmitted on a simplex or full-duplex synchronous link, a frame delimiter is continuously transmitted on the link. This generates one of two continuous waveforms, depending on the initial state:
351:, and encoding the data to ensure that the flag sequence is never seen inside a frame. Each frame begins and ends with a frame delimiter. A frame delimiter at the end of a frame may also mark the start of the next frame.
1249:
V: the frame included an invalid send sequence number N(S), greater than the last number acknowledged plus the transmit window size. This error is only possible if a transmit window size smaller than the maximum has been
188:
HDLC ensures reliable data transfer, allowing one device to understand data sent by another. It can operate with or without a continuous connection between devices, making it versatile for various network configurations.
1277:
An XID command includes an information field specifying the primary's capabilities; the secondary responds with an XID response specifying its capabilities. This is normally done before sending a mode set command.
644:
P/F bit set), and the address field of a received frame must be examined to determine whether it contains a command (the address received is ours) or a response (the address received is that of the other terminal).
555:
are such that the probability of certain types of transmission errors going undetected increases with the length of the data being checked for errors, the FCS can implicitly limit the practical size of the frame.
346:
links. Those links have no mechanism to mark the beginning or end of a frame, so the beginning and end of each frame has to be identified. This is done by using a unique sequence of bits as a frame delimiter, or
3775:
A UIH frame (an ISO/IEC 13239 addition) is like a UI frame, but additionally applies the frame check sequence only to a specified-length prefix of the frame; transmission errors after this prefix are not
3783:
defined one format, but the variant defined in ISO 8885 is more commonly used. A primary advertises its capabilities with an XID command, and a secondary returns its own capabilities in an XID response.
1138:
Place the secondary in the specified mode, with 3-bit sequence numbers (1-byte control field). The secondary acknowledges with UA. If the secondary does not implement the mode, it responds with DM or
406:
For half-duplex or multi-drop communication, where several transmitters share a line, a receiver on the line will see continuous idling 1-bits in the inter-frame period when no transmitter is active.
608:
sent by a secondary to the primary, but this is not reflected in the encoding; commands and responses are indistinguishable except for the difference in the direction in which they are transmitted.
1003:
Supervisory Frames, or 'S-frames', are used for flow and error control whenever piggybacking is impossible or inappropriate, such as when a station does not have data to send. S-frames in HDLC
979:
This is incremented for successive I-frames, modulo 8 or modulo 128. Depending on the number of bits in the sequence number, up to 7 or 127 I-frames may be awaiting acknowledgment at any time.
562:
packet to the sender, or send nothing. After either receiving a negative acknowledge packet or timing out waiting for a positive acknowledge packet, the sender can retransmit the failed frame.
991:, transport user data from the network layer. In addition they also include flow and error control information piggybacked on data. The sub-fields in the control field define these functions.
403:
The HDLC specification allows the 0-bit at the end of a frame delimiter to be shared with the start of the next frame delimiter, i.e. "011111101111110". Some hardware does not support this.
1384:(ABM) is a balanced configuration in which either station may initialize, supervise, recover from errors, and send frames at any time. There is no master/slave relationship. The DTE (
398:
381:
encoded, so that a 0-bit is transmitted as a change in the signal on the line, and a 1-bit is sent as no change. Thus, each 0 bit provides an opportunity for a receiving
1164:
This response requests the primary to send a DISC command. The primary should do so promptly, but may delay long enough to ensure all pending frames are acknowledged.
366:
Because a flag sequence consists of six consecutive 1-bits, other data is coded to ensure that it never contains more than five 1-bits in a row. This is done by
558:
If the receiver's calculation of the FCS does not match that of the sender's, indicating that the frame contains errors, the receiver can either send a negative
3768:
The UI, UIH, XID, TEST frames contain a payload, and can be used as both commands and responses. The SM command and FRMR response also contain a payload.
939:
In ARM and ABM, the P bit forces a response. In these modes, the secondary need not wait for a poll to transmit, so the final bit may be included in the
671:, are used for flow and error control whenever piggybacking is impossible or inappropriate, such as when a station does not have data to send. S-frames
1440:
The HDLC module on the other end transmits (UA) frame when the request is accepted. If the request is rejected it sends (DM) disconnect mode frame.
682:, are used for various miscellaneous purposes, including link management. Some U-frames contain an information field, depending on the type.
377:
This bit-stuffing serves a second purpose, that of ensuring a sufficient number of signal transitions. On synchronous links, the data is
3941:(4th ed.). 482, F.I.E., Patparganj, Delhi 110 092: Dorling Kindersley(India)Pvt. Ltd., licenses of Pearson Education in South Asia.
1303:
1158:
This command causes the secondary to acknowledge with UA and disconnect (enter disconnected mode). Any unacknowledged frames are lost.
792:
There are also extended (two-byte) forms of I and S frames. Again, the least significant bit (rightmost in this table) is sent first.
17:
1253:
The error flags are normally padded with 0 bits to an 8-bit boundary, but HDLC permits frames which are not a multiple of a byte long.
1180:
This requests the primary to send SIM and initialize the secondary. It sent in lieu of DM if the secondary requires initialization.
971:
N(R) operates the same way whether it is part of a command or response. A combined station only has one sequence number space.
4076:
3925:
226:
4081:
4061:
664:, transport user data from the network layer. They can also include flow and error control information piggybacked on data.
185:. Developed by the International Organization for Standardization (ISO), it is defined in the standard ISO/IEC 13239:2002.
622:
communication links, as long as the primary is aware that it may not transmit when it has permitted a secondary to do so.
194:
1196:
This frame (command or response) communicates user data, but without acknowledgement or retransmission in case of error.
4027:
ISO 3309:1984 Information
Processing Systems—Data Communication—High Level Data Link Control Procedures—Frame Structure
1389:
618:, because it has the primary give the secondaries permission to transmit one at a time. It also allows operation over
370:: any time that five consecutive 1-bits appear in the transmitted data, the data is paused and a 0-bit is transmitted.
946:
If no response is received to a P bit in a reasonable period of time, the primary station times out and sends P again.
3946:
3904:
343:
79:
1132:
This is the secondary's response to an acceptable mode set command, indicating that it is now in the requested mode.
61:
1007:
have information fields, although some HDLC-derived protocols use information fields for "multi-selective reject".
532:
Note that the end flag of one frame may be (but does not have to be) the beginning (start) flag of the next frame.
339:
3772:
A UI frame contains user information, but unlike an I frame it is neither acknowledged nor retransmitted if lost.
4037:
ISO 4335:1984 Data
Communication—High Level Data Link Control Procedures—Consolidation of Elements of Procedures
1170:
This rarely-implemented command is used to perform some secondary-specific initialization, such as downloading
46:
535:
Data is usually sent in multiples of 8 bits, but only some variants require this; others theoretically permit
4086:
4071:
3878:
3864:
3813:
1425:
Initialization can be requested by either side. When the primary sends one of the six mode-set commands, it:
585:
581:
218:
150:
3850:
1315:
The "nonreserved" commands and responses are guaranteed by the HDLC standard to be available for other uses.
432:
Bit stuffing is not needed to ensure an adequate number of transitions, as start and stop bits provide that,
3962:
3780:
1279:
222:
202:
53:
4014:
3787:
1290:
4019:
1036:
A secondary terminal can use this with the F-bit set to respond to a poll if it has no data to send.
570:
536:
3790:
command for debugging purposes. The payload of the TEST command is returned in the TEST response.
4066:
3818:
3808:
1385:
300:
57:
1308:
There are several U frames which are not part of HDLC, but defined in other related standards.
569:, and the FCS could readily be computed by simple, fast circuitry or software. More effective
174:
98:
4036:
4026:
1145:
Place the secondary in the specified mode, with 7-bit sequence numbers (2-byte control field).
1071:
Sent in response to an observed sequence number gap; e.g. after seeing I1/I2/I3/I5, send REJ4.
1027:
Indicate that the sender is ready to receive more data (cancels the effect of a previous RNR).
326:
uses low-level HDLC framing techniques but adds a protocol field to the standard HDLC header.
559:
1235:
X: the frame type is not understood with a non-empty information field, but one was present.
1033:
A primary station can send this with the P-bit set to solicit data from a secondary station.
543:
409:
HDLC transmits bytes of data with the least significant bit first (not to be confused with
296:
592:. The original "normal response mode" is a primary-secondary mode where the computer (or
8:
1293:
for debugging purposes. The payload of the TEST command is returned in the TEST response.
615:
1238:
Y: the frame included an information field that is larger than the secondary can accept.
968:
128) have been received and indicates the N(S) of the next frame it expects to receive.
3956:
3915:
1174:. What happens in initialization mode is not otherwise specified in the HDLC standard.
436:
378:
354:
On both synchronous and asynchronous links, the flag sequence is binary "01111110", or
198:
178:
439:
encoded for transmission, rather than NRZI encoded, the encoded waveform is different,
4040:
4030:
3942:
3921:
3900:
565:
The FCS was implemented because many early communication links had a relatively high
386:
304:
1392:) are treated as equals. The initiator for Asynchronous Balanced Mode sends an SABM.
4001:
3981:
1450:
1093:
Optional to generate; a working implementation may use only RR, or only RR and REJ.
462:
182:
588:) was originally designed to connect one computer with multiple peripherals via a
3936:
933:
566:
162:
289:
ISO/IEC 13239:2002, the current standard, replaced all of these specifications.
1055:
Can be used like RR with F bit set to respond to a poll if the station is busy.
1052:
Can be used like RR with P bit set to solicit the status of a secondary station
449:; it is not necessary to worry about the bit pattern straddling multiple bytes.
3895:
Friend, George E.; Fike, John L.; Baker, H. Charles; Bellamy, John C. (1988).
1355:, which consists of one primary terminal, and one or more secondary terminals.
4055:
923:
589:
454:
453:
Instead asynchronous framing uses "control-octet transparency", also called "
442:
RS-232 sends bits in groups of 8, making adding single bits very awkward, and
410:
1751:(request disconnect) response seems clear enough, but the reason for making
367:
4046:
1049:
Acknowledge some packets but request no more be sent until further notice.
1030:
Send this packet if you need to send a packet but have no I frame to send.
629:
619:
458:
425:
355:
258:
3995:
576:
374:
receive procedure is aborted, to be restarted when a flag is next seen.
1322:
1232:
W: the frame type (control field) is not understood or not implemented.
457:" or "octet stuffing". The frame boundary octet is 01111110, (0x7E in
428:, synchronous-style bit stuffing is inappropriate for several reasons:
335:
323:
293:
250:
4006:
3986:
299:
protocol, and it is the basis for the framing mechanism used with the
547:
315:
157:
1466:
64:. Statements consisting only of original research should be removed.
3794:
expressible by the standard six mode-set commands to be negotiated.
1171:
466:
397:
308:
1189:
These frames may be used as part of normal information transfer.
445:
For the same reason, it is only necessary to specially code flag
413:
order, which refers to byte ordering within a multi-byte field).
1084:
Bit value = 11 (0x0c to match above table type field bit order)
1065:
Bit value = 10 (0x08 to match above table type field bit order)
1046:
Bit value = 01 (0x04 to match above table type field bit order)
1024:
Bit value = 00 (0x00 to match above table type field bit order)
481:
The contents of an HDLC frame are shown in the following table:
1074:
Optional to generate; a working implementation may use only RR.
551:
422:
1304:
Synchronous Data Link
Control § SLDC features not in HDLC
974:
421:
When using asynchronous serial communication such as standard
303:
on synchronous lines, as used by many servers to connect to a
1463:
656:
Three fundamental types of HDLC frames may be distinguished:
382:
319:
234:
3899:(2nd ed.). Indianapolis: Howard W. Sams & Company.
3920:(7th ed.). Upper Saddle River: Pearson/Prentice Hall.
266:
262:
254:
246:
242:
230:
4015:
3779:
The XID frame is used to exchange terminal capabilities.
2106:
Initialize link control function in the addressed station
614:
allows the secondary-to-primary link to be shared without
1516:
1434:
Specifies whether 3 or 7 bit sequence numbers are in use.
1412:
Commands: I, RR, RNR, DISC, and one of SNRM, SARM or SABM
214:
2277:
Acknowledge acceptance of one of the set-mode commands.
1348:
Link configurations can be categorized as being either:
205:, using a mode called Asynchronous Balanced Mode (ABM).
1506:
Data Link Test
Commands & Responses are: ADD – TEST
1428:
Signals the other side that initialization is requested
1403:
272:
The original ISO standards for HDLC are the following:
3894:
3837:
1068:
Requests immediate retransmission starting with N(R).
577:
Types of stations (computers) and data transfer modes
314:
A similar version is used as the control channel for
962:
124:
1215:
broadcast address to collect any pending responses.
1142:
Set ... mode extended (SNRME, SARME, SABME) command
2555:Exchange identical information fields for testing
1503:For Mode Reset (ABM only) Commands are: ADD – RSET
1469:For Information Commands & Responses: ADD – Ul
1443:
651:
221:protocol, which is the layer 2 protocol for IBM's
4053:
573:schemes are now widely used by other protocols.
225:(SNA). It was extended and standardized by the
1087:Requests retransmission of only the frame N(R).
469:) can be escaped in the same way if necessary.
282:ISO 6159-1980 – Unbalanced Classes of Procedure
177:used for transmitting data between devices in
3978:PPP in a Real-time Oriented HDLC-like Framing
3578:
3344:
3196:
3079:
1297:
285:ISO 6256-1981 – Balanced Classes of Procedure
3934:
1408:The minimal set required for operation are:
691:The general format of the control field is:
975:N(S), the sequence number of the sent frame
358:0x7E, but the details are quite different.
1509:Request Disconnect. Responses are ADD – RD
1177:Request initialization mode (RIM) response
1078:
1040:
233:named their essentially identical version
4005:
3985:
3913:
949:The P/F bit is at the heart of the basic
80:Learn how and when to remove this message
4020:HDLC packet format and other information
1115:
604:sent by the primary to a secondary, and
1361:, which consists of two peer terminals.
1184:
1135:Set ... mode (SNRM, SARM, SABM) command
982:
954:arrive, and so should be retransmitted.
416:
14:
4054:
3745:
3741:
1343:
361:
229:as LAP (Link Access Procedure), while
2593:Report receipt of unacceptable frame
1167:Set initialization mode (SIM) command
1018:
998:
279:ISO 4335-1979 – Elements of Procedure
3760:
3756:
3752:
2517:Used to Request/Report capabilities
2438:Used to solicit control information
1737:
1517:HDLC command and response repertoire
1404:HDLC Command and response repertoire
1396:An additional link configuration is
1129:Unnumbered acknowledge (UA) response
29:
1419:
1415:Responses: I, RR, RNR, UA, DM, FRMR
1365:The three link configurations are:
1114:The various modes are described in
1090:Not supported by all HDLC variants.
24:
2952:HDLC U frames, by binary encoding
2189:Terminate logical link connection
1390:data circuit-terminating equipment
25:
4098:
3970:
3897:Understanding Data Communications
3879:"X.25 frame types - Martin Baker"
3865:"X.25 frame types - Martin Baker"
3851:"X.25 frame types - Martin Baker"
1755:command numerically equal to the
1431:Specifies the mode, NRM, ABM, ARM
1268:
1219:
963:N(R), the receive sequence number
628:is an HDLC addition for use over
344:asynchronous serial communication
292:HDLC was the inspiration for the
3917:Data and Computer Communications
1312:Nonreserved (NR0, NR1, NR2, NR3)
1161:Request disconnect (RD) response
686:
539:on other than 8-bit boundaries.
396:
34:
2315:Responder in disconnected mode
1974:Set asynchronous balanced mode
1892:Set asynchronous response mode
1444:Functional extensions (options)
1122:Disconnected mode (DM) response
1109:
1059:
652:HDLC operations and frame types
385:to synchronize its clock via a
276:ISO 3309-1979 – Frame Structure
3871:
3857:
3843:
3830:
1679:Retransmit starting with N(R)
1611:Ready to receive I-frame N(R)
1325:logical link control standard.
322:multichannel telephone lines.
13:
1:
3935:S. Tanenbaum, Andrew (2005).
3888:
3814:Serial Line Internet Protocol
3798:the reason for the rejection.
2192:Future I and S frames return
1747:(disconnect) command and the
1318:Ack connectionless (AC0, AC1)
1274:Exchange identification (XID)
796:Extended HDLC control fields
582:Synchronous Data Link Control
4077:Telecommunications standards
3781:Systems Network Architecture
2932:
2914:
2891:
2873:
2850:
2832:
2809:
2791:
2768:
2750:
2727:
2709:
2686:
2668:
2645:
2627:
2604:
2589:
2566:
2551:
2528:
2513:
2490:
2472:
2449:
2434:
2411:
2393:
2370:
2352:
2329:
2311:
2288:
2273:
2250:
2229:
2206:
2185:
2162:
2140:
2135:Request initialization mode
2117:
2102:
2079:
2061:
2038:
2020:
1997:
1979:
1956:
1938:
1915:
1897:
1874:
1856:
1833:
1815:
1280:Systems Network Architecture
1225:Frame reject (FRMR) response
1206:Unnumbered poll (UP) command
476:
223:Systems Network Architecture
171:High-Level Data Link Control
93:High-Level Data Link Control
7:
4082:Telecommunication protocols
4062:Computer network technology
3914:Stallings, William (2004).
3802:
3786:The TEST frame is simply a
1289:A TEST command is simply a
1193:Unnumbered information (UI)
1097:
134:; 45 years ago
60:the claims made and adding
10:
4103:
3729:
2965:
2827:Ack connectionless, seq 1
2786:Ack connectionless, seq 0
2268:Unnumbered acknowledgment
2027:Use 7 bit sequence number
1986:Use 3 bit sequence number
1945:Use 7 bit sequence number
1904:Use 3 bit sequence number
1863:Use 7 bit sequence number
1822:Use 3 bit sequence number
1382:Asynchronous Balanced Mode
1376:Asynchronous Response Mode
1301:
1298:Defined in other standards
1199:UI with header check (UIH)
1116:§ Link configurations
913:
637:Asynchronous balanced mode
626:Asynchronous response mode
329:
208:
195:point-to-point connections
18:Asynchronous Balanced Mode
3724:
3721:
3718:
3715:
3712:
3709:
3706:
3703:
3700:
3605:
3520:
3462:
3254:
3137:
3052:
2973:
2970:
2967:
2962:
2959:
2956:
2839:IEEE 802.2 LLC extension
2798:IEEE 802.2 LLC extension
2592:
2554:
2516:
2479:Resets N(R) but not N(S)
2437:
2276:
2105:
1810:Set normal response mode
1778:
1775:
1772:
1767:
1764:
1715:
1710:Negative Acknowledgement
1681:
1676:Negative Acknowledgement
1647:
1642:Positive Acknowledgement
1613:
1608:Positive Acknowledgement
1590:
1584:
1540:
1537:
1534:
1529:
1526:
1523:
1321:These are defined in the
1155:Disconnect (DISC) command
951:checkpoint retransmission
897:
877:
864:
862:
854:
776:
770:
756:
748:
735:
727:
596:) gives each peripheral (
156:
146:
128:
120:
112:
104:
97:
3997:PPP in HDLC-like Framing
3961:: CS1 maint: location (
3824:
2508:Exchange identification
2097:Set initialization mode
1704:Selective Reject (SREJ)
1636:Receive Not Ready (RNR)
1494:Delete Response I Frames
1458:Responses: ADD – XID, RD
943:response after the poll.
675:have information fields.
571:forward error correction
338:can be transmitted over
269:protocol stack as LAPD.
3819:Self-synchronizing code
3809:Point-to-Point Protocol
2347:Unnumbered information
1497:Delete Command I Frames
1386:data terminal equipment
1332:echoing it in response.
1079:Selective Reject (SREJ)
1041:Receive Not Ready (RNR)
987:Information frames, or
667:Supervisory frames, or
660:Information frames, or
461:notation). A "control
27:Communications protocol
3749:ISO/IEC 13239 addition
2144:Initialization needed
1102:Unnumbered frames, or
678:Unnumbered frames, or
639:adds the concept of a
175:communication protocol
99:Communication protocol
2388:UI with header check
1759:response is obscure.
1713:Retransmit only N(R)
1645:Not ready to receive
1335:Beacon (BCN) response
1302:Further information:
1148:Set mode (SM) command
922:The bit is used as a
4087:Networking standards
4072:Logical link control
2757:For application use
2716:For application use
2675:For application use
2634:For application use
2397:Unacknowledged data
2356:Unacknowledged data
1478:Responses: ADD – RIM
1370:Normal Response Mode
1260:Reset (RSET) command
1185:Information transfer
1015:exactly equivalent.
983:I-Frames (user data)
880:Receive sequence no.
857:Receive sequence no.
751:Receive sequence no.
730:Receive sequence no.
695:HDLC control fields
612:Normal response mode
544:frame check sequence
435:Because the data is
417:Asynchronous framing
307:, most commonly the
2953:
2868:Configure for test
2224:Request disconnect
2024:Set mode; extended
1942:Set mode; extended
1860:Set mode; extended
1602:Receive Ready (RR)
1580:User exchange data
1491:Extended Addressing
1475:Commands: ADD – SIM
1472:For Initialization
1455:Commands: ADD – XID
1344:Link configurations
797:
696:
516:Variable length, 8×
362:Synchronous framing
94:
4047:ISO/IEC 13239:2002
3838:Friend et al. 1988
2951:
2476:Used for recovery
2318:Mode set required
2065:Set mode, generic
1500:Extended Numbering
1486:Commands: ADD – UP
1483:For Group Polling
1019:Receive Ready (RR)
999:S-frames (control)
795:
694:
598:secondary terminal
546:(FCS) is a 16-bit
261:protocol stack as
245:protocol stack as
203:network interfaces
197:, such as between
92:
45:possibly contains
3938:Computer Networks
3927:978-0-13-100681-2
3738:
3737:
2949:
2948:
2921:Was part of SDLC
2918:Not part of HDLC
2880:Was part of SDLC
2877:Not part of HDLC
2836:Not part of HDLC
2795:Not part of HDLC
2754:Not standardized
2713:Not standardized
2672:Not standardized
2631:Not standardized
2400:New in ISO 13239
2233:Solicitation for
2068:New in ISO 13239
1738:Unnumbered frames
1735:
1734:
1451:Switched Circuits
1398:Disconnected mode
911:
910:
907:Extended S-frame
873:Extended I-frame
867:Send sequence no.
790:
789:
738:Send sequence no.
641:combined terminal
530:
529:
387:phase-locked loop
213:HDLC is based on
179:telecommunication
168:
167:
90:
89:
82:
47:original research
16:(Redirected from
4094:
4011:
4009:
3991:
3989:
3966:
3960:
3952:
3931:
3910:
3883:
3882:
3875:
3869:
3868:
3861:
3855:
3854:
3847:
3841:
3834:
3764:Not part of HDLC
3763:
3759:
3755:
3748:
3744:
2954:
2950:
2429:Unnumbered poll
2306:Disconnect mode
1762:
1761:
1599:Supervisory (S)
1521:
1520:
1420:Basic operations
1328:Configure (CFGR)
798:
794:
697:
693:
594:primary terminal
484:
483:
400:
142:
140:
135:
95:
91:
85:
78:
74:
71:
65:
62:inline citations
38:
37:
30:
21:
4102:
4101:
4097:
4096:
4095:
4093:
4092:
4091:
4052:
4051:
3994:
3976:
3973:
3954:
3953:
3949:
3928:
3907:
3891:
3886:
3877:
3876:
3872:
3863:
3862:
3858:
3849:
3848:
3844:
3835:
3831:
3827:
3805:
1779:C-Field Format
1769:
1740:
1572:Information(I)
1541:C-Field Format
1531:
1519:
1446:
1422:
1406:
1346:
1306:
1300:
1271:
1222:
1187:
1112:
1100:
1081:
1062:
1043:
1021:
1001:
985:
977:
965:
934:voice procedure
927:has been lost.
916:
879:
866:
856:
750:
737:
729:
689:
654:
579:
537:data alignments
510:8 or more bits
479:
419:
364:
332:
211:
163:Data link layer
138:
136:
133:
86:
75:
69:
66:
51:
39:
35:
28:
23:
22:
15:
12:
11:
5:
4100:
4090:
4089:
4084:
4079:
4074:
4069:
4067:Link protocols
4064:
4050:
4049:
4044:
4034:
4024:
4022:
4017:
4012:
3992:
3972:
3971:External links
3969:
3968:
3967:
3947:
3932:
3926:
3911:
3905:
3890:
3887:
3885:
3884:
3870:
3856:
3842:
3840:, p. 191)
3828:
3826:
3823:
3822:
3821:
3816:
3811:
3804:
3801:
3800:
3799:
3795:
3791:
3784:
3777:
3773:
3766:
3765:
3750:
3736:
3735:
3732:
3730:
3727:
3726:
3723:
3720:
3717:
3714:
3711:
3708:
3705:
3702:
3699:
3696:
3694:
3691:
3688:
3685:
3682:
3679:
3676:
3673:
3669:
3668:
3666:
3663:
3660:
3657:
3654:
3651:
3648:
3645:
3642:
3639:
3636:
3633:
3630:
3627:
3624:
3621:
3618:
3615:
3612:
3608:
3607:
3604:
3601:
3598:
3595:
3592:
3589:
3586:
3583:
3580:
3577:
3574:
3571:
3568:
3565:
3562:
3559:
3556:
3552:
3551:
3549:
3546:
3543:
3540:
3537:
3534:
3531:
3528:
3525:
3522:
3519:
3516:
3513:
3510:
3507:
3504:
3501:
3498:
3494:
3493:
3491:
3488:
3485:
3482:
3479:
3476:
3473:
3470:
3467:
3464:
3461:
3458:
3455:
3452:
3449:
3446:
3443:
3440:
3436:
3435:
3433:
3430:
3427:
3424:
3421:
3418:
3415:
3412:
3409:
3406:
3403:
3401:
3398:
3395:
3392:
3389:
3386:
3383:
3380:
3376:
3375:
3373:
3370:
3367:
3364:
3361:
3358:
3355:
3352:
3349:
3346:
3343:
3340:
3337:
3334:
3331:
3328:
3325:
3322:
3318:
3317:
3314:
3311:
3308:
3305:
3302:
3299:
3296:
3293:
3290:
3287:
3285:
3282:
3279:
3276:
3273:
3270:
3267:
3264:
3261:
3257:
3256:
3253:
3250:
3247:
3244:
3241:
3238:
3235:
3232:
3229:
3227:
3224:
3221:
3218:
3215:
3212:
3209:
3206:
3203:
3199:
3198:
3195:
3192:
3189:
3186:
3183:
3180:
3177:
3174:
3171:
3168:
3165:
3162:
3159:
3156:
3153:
3150:
3147:
3144:
3140:
3139:
3136:
3133:
3130:
3127:
3124:
3121:
3118:
3115:
3112:
3110:
3107:
3104:
3101:
3098:
3095:
3092:
3089:
3086:
3082:
3081:
3078:
3075:
3072:
3069:
3066:
3063:
3060:
3057:
3054:
3051:
3048:
3045:
3042:
3039:
3036:
3033:
3030:
3026:
3025:
3022:
3019:
3016:
3013:
3010:
3007:
3004:
3001:
2998:
2995:
2992:
2989:
2986:
2983:
2980:
2976:
2975:
2972:
2969:
2968:C-Field Format
2966:
2964:
2961:
2958:
2957:C-Field Format
2947:
2946:
2943:
2940:
2937:
2934:
2931:
2928:
2925:
2922:
2919:
2916:
2913:
2906:
2905:
2902:
2899:
2896:
2893:
2890:
2887:
2884:
2881:
2878:
2875:
2872:
2865:
2864:
2861:
2858:
2855:
2852:
2849:
2846:
2843:
2840:
2837:
2834:
2831:
2824:
2823:
2820:
2817:
2814:
2811:
2808:
2805:
2802:
2799:
2796:
2793:
2790:
2783:
2782:
2779:
2776:
2773:
2770:
2767:
2764:
2761:
2758:
2755:
2752:
2749:
2745:Nonreserved 3
2742:
2741:
2738:
2735:
2732:
2729:
2726:
2723:
2720:
2717:
2714:
2711:
2708:
2704:Nonreserved 2
2701:
2700:
2697:
2694:
2691:
2688:
2685:
2682:
2679:
2676:
2673:
2670:
2667:
2663:Nonreserved 1
2660:
2659:
2656:
2653:
2650:
2647:
2644:
2641:
2638:
2635:
2632:
2629:
2626:
2622:Nonreserved 0
2619:
2618:
2615:
2612:
2609:
2606:
2603:
2600:
2597:
2594:
2591:
2588:
2581:
2580:
2577:
2574:
2571:
2568:
2565:
2562:
2559:
2556:
2553:
2550:
2543:
2542:
2539:
2536:
2533:
2530:
2527:
2524:
2521:
2518:
2515:
2512:
2505:
2504:
2501:
2498:
2495:
2492:
2489:
2486:
2483:
2480:
2477:
2474:
2471:
2464:
2463:
2460:
2457:
2454:
2451:
2448:
2445:
2442:
2439:
2436:
2433:
2426:
2425:
2422:
2419:
2416:
2413:
2410:
2407:
2404:
2401:
2398:
2395:
2392:
2385:
2384:
2381:
2378:
2375:
2372:
2369:
2366:
2363:
2360:
2359:Has a payload
2357:
2354:
2351:
2344:
2343:
2340:
2337:
2334:
2331:
2328:
2325:
2322:
2319:
2316:
2313:
2310:
2303:
2302:
2299:
2296:
2293:
2290:
2287:
2284:
2281:
2278:
2275:
2272:
2265:
2264:
2261:
2258:
2255:
2252:
2249:
2246:
2243:
2240:
2238:
2231:
2228:
2221:
2220:
2217:
2214:
2211:
2208:
2205:
2202:
2199:
2196:
2190:
2187:
2184:
2177:
2176:
2173:
2170:
2167:
2164:
2161:
2158:
2155:
2152:
2145:
2142:
2139:
2132:
2131:
2128:
2125:
2122:
2119:
2116:
2113:
2110:
2107:
2104:
2101:
2094:
2093:
2090:
2087:
2084:
2081:
2078:
2075:
2072:
2069:
2066:
2063:
2060:
2053:
2052:
2049:
2046:
2043:
2040:
2037:
2034:
2031:
2028:
2025:
2022:
2019:
2015:SABM extended
2012:
2011:
2008:
2005:
2002:
1999:
1996:
1993:
1990:
1987:
1984:
1981:
1978:
1971:
1970:
1967:
1964:
1961:
1958:
1955:
1952:
1949:
1946:
1943:
1940:
1937:
1933:SARM extended
1930:
1929:
1926:
1923:
1920:
1917:
1914:
1911:
1908:
1905:
1902:
1899:
1896:
1889:
1888:
1885:
1882:
1879:
1876:
1873:
1870:
1867:
1864:
1861:
1858:
1855:
1851:SNRM extended
1848:
1847:
1844:
1841:
1838:
1835:
1832:
1829:
1826:
1823:
1820:
1817:
1814:
1807:
1806:
1803:
1800:
1797:
1794:
1791:
1788:
1785:
1781:
1780:
1777:
1774:
1771:
1766:
1739:
1736:
1733:
1732:
1729:
1726:
1723:
1720:
1717:
1714:
1711:
1708:
1705:
1702:
1699:
1698:
1695:
1692:
1689:
1686:
1683:
1680:
1677:
1674:
1671:
1668:
1665:
1664:
1661:
1658:
1655:
1652:
1649:
1646:
1643:
1640:
1637:
1634:
1631:
1630:
1627:
1624:
1621:
1618:
1615:
1612:
1609:
1606:
1603:
1600:
1596:
1595:
1592:
1589:
1586:
1583:
1581:
1578:
1575:
1573:
1569:
1568:
1565:
1562:
1559:
1556:
1553:
1550:
1547:
1543:
1542:
1539:
1536:
1533:
1528:
1525:
1524:Type Of Frame
1518:
1515:
1514:
1513:
1510:
1507:
1504:
1501:
1498:
1495:
1492:
1489:
1488:
1487:
1481:
1480:
1479:
1476:
1470:
1467:
1464:
1461:
1460:
1459:
1456:
1445:
1442:
1438:
1437:
1436:
1435:
1432:
1429:
1421:
1418:
1417:
1416:
1413:
1405:
1402:
1394:
1393:
1379:
1373:
1363:
1362:
1356:
1345:
1342:
1341:
1340:
1336:
1333:
1329:
1326:
1319:
1316:
1313:
1299:
1296:
1295:
1294:
1287:
1284:
1275:
1270:
1269:Peer discovery
1267:
1266:
1265:
1261:
1257:
1256:
1255:
1254:
1251:
1247:
1239:
1236:
1233:
1226:
1221:
1220:Error Recovery
1218:
1217:
1216:
1207:
1204:
1200:
1197:
1194:
1186:
1183:
1182:
1181:
1178:
1175:
1168:
1165:
1162:
1159:
1156:
1153:
1149:
1146:
1143:
1140:
1136:
1133:
1130:
1127:
1123:
1111:
1108:
1099:
1096:
1095:
1094:
1091:
1088:
1085:
1080:
1077:
1076:
1075:
1072:
1069:
1066:
1061:
1058:
1057:
1056:
1053:
1050:
1047:
1042:
1039:
1038:
1037:
1034:
1031:
1028:
1025:
1020:
1017:
1000:
997:
984:
981:
976:
973:
964:
961:
956:
955:
947:
944:
937:
919:bit is clear.
915:
912:
909:
908:
905:
902:
899:
896:
893:
890:
887:
884:
881:
875:
874:
871:
868:
863:
861:
858:
852:
851:
849:
846:
843:
840:
837:
834:
831:
828:
825:
823:
820:
817:
814:
811:
808:
805:
802:
788:
787:
784:
781:
778:
775:
772:
768:
767:
764:
761:
758:
755:
752:
746:
745:
742:
739:
734:
731:
725:
724:
722:
719:
716:
713:
710:
707:
704:
701:
688:
685:
684:
683:
676:
665:
653:
650:
578:
575:
567:bit error rate
528:
527:
524:
523:16 or 32 bits
521:
514:
511:
508:
504:
503:
500:
497:
494:
491:
488:
478:
475:
451:
450:
443:
440:
433:
418:
415:
363:
360:
331:
328:
287:
286:
283:
280:
277:
210:
207:
166:
165:
160:
154:
153:
148:
144:
143:
130:
126:
125:
122:
118:
117:
114:
110:
109:
106:
102:
101:
88:
87:
42:
40:
33:
26:
9:
6:
4:
3:
2:
4099:
4088:
4085:
4083:
4080:
4078:
4075:
4073:
4070:
4068:
4065:
4063:
4060:
4059:
4057:
4048:
4045:
4042:
4038:
4035:
4032:
4028:
4025:
4023:
4021:
4018:
4016:
4013:
4008:
4003:
3999:
3998:
3993:
3988:
3983:
3979:
3975:
3974:
3964:
3958:
3950:
3948:81-7758-165-1
3944:
3940:
3939:
3933:
3929:
3923:
3919:
3918:
3912:
3908:
3906:0-672-27270-9
3902:
3898:
3893:
3892:
3880:
3874:
3866:
3860:
3852:
3846:
3839:
3833:
3829:
3820:
3817:
3815:
3812:
3810:
3807:
3806:
3796:
3792:
3789:
3785:
3782:
3778:
3774:
3771:
3770:
3769:
3762:
3758:
3754:
3751:
3747:
3743:
3740:
3739:
3733:
3731:
3728:
3697:
3695:
3692:
3689:
3686:
3683:
3680:
3677:
3674:
3671:
3670:
3667:
3664:
3661:
3658:
3655:
3652:
3649:
3646:
3643:
3640:
3637:
3634:
3631:
3628:
3625:
3622:
3619:
3616:
3613:
3610:
3609:
3602:
3599:
3596:
3593:
3590:
3587:
3584:
3581:
3575:
3572:
3569:
3566:
3563:
3560:
3557:
3554:
3553:
3550:
3547:
3544:
3541:
3538:
3535:
3532:
3529:
3526:
3523:
3517:
3514:
3511:
3508:
3505:
3502:
3499:
3496:
3495:
3492:
3489:
3486:
3483:
3480:
3477:
3474:
3471:
3468:
3465:
3459:
3456:
3453:
3450:
3447:
3444:
3441:
3438:
3437:
3434:
3431:
3428:
3425:
3422:
3419:
3416:
3413:
3410:
3407:
3404:
3402:
3399:
3396:
3393:
3390:
3387:
3384:
3381:
3378:
3377:
3374:
3371:
3368:
3365:
3362:
3359:
3356:
3353:
3350:
3347:
3341:
3338:
3335:
3332:
3329:
3326:
3323:
3320:
3319:
3315:
3312:
3309:
3306:
3303:
3300:
3297:
3294:
3291:
3288:
3286:
3283:
3280:
3277:
3274:
3271:
3268:
3265:
3262:
3259:
3258:
3251:
3248:
3245:
3242:
3239:
3236:
3233:
3230:
3228:
3225:
3222:
3219:
3216:
3213:
3210:
3207:
3204:
3201:
3200:
3193:
3190:
3187:
3184:
3181:
3178:
3175:
3172:
3169:
3166:
3163:
3160:
3157:
3154:
3151:
3148:
3145:
3142:
3141:
3134:
3131:
3128:
3125:
3122:
3119:
3116:
3113:
3111:
3108:
3105:
3102:
3099:
3096:
3093:
3090:
3087:
3084:
3083:
3076:
3073:
3070:
3067:
3064:
3061:
3058:
3055:
3049:
3046:
3043:
3040:
3037:
3034:
3031:
3028:
3027:
3023:
3020:
3017:
3014:
3011:
3008:
3005:
3002:
2999:
2996:
2993:
2990:
2987:
2984:
2981:
2978:
2977:
2955:
2944:
2941:
2938:
2935:
2929:
2926:
2923:
2920:
2917:
2912:
2908:
2907:
2903:
2900:
2897:
2894:
2888:
2885:
2882:
2879:
2876:
2871:
2867:
2866:
2862:
2859:
2856:
2853:
2847:
2844:
2841:
2838:
2835:
2830:
2826:
2825:
2821:
2818:
2815:
2812:
2806:
2803:
2800:
2797:
2794:
2789:
2785:
2784:
2780:
2777:
2774:
2771:
2765:
2762:
2759:
2756:
2753:
2748:
2744:
2743:
2739:
2736:
2733:
2730:
2724:
2721:
2718:
2715:
2712:
2707:
2703:
2702:
2698:
2695:
2692:
2689:
2683:
2680:
2677:
2674:
2671:
2666:
2662:
2661:
2657:
2654:
2651:
2648:
2642:
2639:
2636:
2633:
2630:
2625:
2621:
2620:
2616:
2613:
2610:
2607:
2601:
2598:
2595:
2587:
2584:Frame reject
2583:
2582:
2578:
2575:
2572:
2569:
2563:
2560:
2557:
2549:
2545:
2544:
2540:
2537:
2534:
2531:
2525:
2522:
2519:
2511:
2507:
2506:
2502:
2499:
2496:
2493:
2487:
2484:
2481:
2478:
2475:
2470:
2466:
2465:
2461:
2458:
2455:
2452:
2446:
2443:
2440:
2432:
2428:
2427:
2423:
2420:
2417:
2414:
2408:
2405:
2402:
2399:
2396:
2391:
2387:
2386:
2382:
2379:
2376:
2373:
2367:
2364:
2361:
2358:
2355:
2350:
2346:
2345:
2341:
2338:
2335:
2332:
2326:
2323:
2320:
2317:
2314:
2309:
2305:
2304:
2300:
2297:
2294:
2291:
2285:
2282:
2279:
2271:
2267:
2266:
2262:
2259:
2256:
2253:
2247:
2244:
2241:
2239:
2236:
2232:
2227:
2223:
2222:
2218:
2215:
2212:
2209:
2203:
2200:
2197:
2195:
2191:
2188:
2183:
2179:
2178:
2174:
2171:
2168:
2165:
2159:
2156:
2153:
2150:
2146:
2143:
2138:
2134:
2133:
2129:
2126:
2123:
2120:
2114:
2111:
2108:
2100:
2096:
2095:
2091:
2088:
2085:
2082:
2076:
2073:
2070:
2067:
2064:
2059:
2055:
2054:
2050:
2047:
2044:
2041:
2035:
2032:
2029:
2026:
2023:
2018:
2014:
2013:
2009:
2006:
2003:
2000:
1994:
1991:
1988:
1985:
1982:
1977:
1973:
1972:
1968:
1965:
1962:
1959:
1953:
1950:
1947:
1944:
1941:
1936:
1932:
1931:
1927:
1924:
1921:
1918:
1912:
1909:
1906:
1903:
1900:
1895:
1891:
1890:
1886:
1883:
1880:
1877:
1871:
1868:
1865:
1862:
1859:
1854:
1850:
1849:
1845:
1842:
1839:
1836:
1830:
1827:
1824:
1821:
1818:
1813:
1809:
1808:
1804:
1801:
1798:
1795:
1792:
1789:
1786:
1783:
1782:
1763:
1760:
1758:
1754:
1750:
1746:
1730:
1727:
1724:
1721:
1718:
1712:
1709:
1706:
1703:
1701:
1700:
1696:
1693:
1690:
1687:
1684:
1678:
1675:
1672:
1670:Reject (REJ)
1669:
1667:
1666:
1662:
1659:
1656:
1653:
1650:
1644:
1641:
1638:
1635:
1633:
1632:
1628:
1625:
1622:
1619:
1616:
1610:
1607:
1604:
1601:
1598:
1597:
1593:
1587:
1582:
1579:
1576:
1574:
1571:
1570:
1566:
1563:
1560:
1557:
1554:
1551:
1548:
1545:
1544:
1522:
1511:
1508:
1505:
1502:
1499:
1496:
1493:
1490:
1485:
1484:
1482:
1477:
1474:
1473:
1471:
1468:
1465:
1462:
1457:
1454:
1453:
1452:
1448:
1447:
1441:
1433:
1430:
1427:
1426:
1424:
1423:
1414:
1411:
1410:
1409:
1401:
1399:
1391:
1387:
1383:
1380:
1377:
1374:
1371:
1368:
1367:
1366:
1360:
1357:
1354:
1351:
1350:
1349:
1337:
1334:
1330:
1327:
1324:
1320:
1317:
1314:
1311:
1310:
1309:
1305:
1292:
1288:
1285:
1281:
1276:
1273:
1272:
1262:
1259:
1258:
1252:
1248:
1245:
1240:
1237:
1234:
1231:
1230:
1227:
1224:
1223:
1213:
1208:
1205:
1201:
1198:
1195:
1192:
1191:
1190:
1179:
1176:
1173:
1169:
1166:
1163:
1160:
1157:
1154:
1150:
1147:
1144:
1141:
1137:
1134:
1131:
1128:
1124:
1121:
1120:
1119:
1117:
1107:
1105:
1092:
1089:
1086:
1083:
1082:
1073:
1070:
1067:
1064:
1063:
1054:
1051:
1048:
1045:
1044:
1035:
1032:
1029:
1026:
1023:
1022:
1016:
1012:
1008:
1006:
996:
992:
990:
980:
972:
969:
960:
952:
948:
945:
942:
938:
935:
930:
929:
928:
925:
920:
906:
903:
900:
894:
891:
888:
885:
882:
876:
872:
869:
859:
853:
850:
847:
844:
841:
838:
835:
832:
829:
826:
824:
821:
818:
815:
812:
809:
806:
803:
800:
799:
793:
785:
782:
779:
773:
769:
765:
762:
759:
753:
747:
743:
740:
732:
726:
723:
720:
717:
714:
711:
708:
705:
702:
699:
698:
692:
687:Control field
681:
677:
674:
670:
666:
663:
659:
658:
657:
649:
645:
642:
638:
634:
631:
627:
623:
621:
617:
613:
609:
607:
603:
599:
595:
591:
590:multidrop bus
587:
583:
574:
572:
568:
563:
561:
556:
553:
549:
545:
540:
538:
533:
525:
522:
519:
515:
513:8 or 16 bits
512:
509:
506:
505:
501:
498:
495:
492:
489:
486:
485:
482:
474:
470:
468:
464:
460:
456:
455:byte stuffing
448:
444:
441:
438:
434:
431:
430:
429:
427:
424:
414:
412:
411:little-endian
407:
404:
401:
399:
394:
390:
388:
384:
380:
375:
371:
369:
359:
357:
352:
350:
345:
341:
337:
327:
325:
321:
317:
312:
310:
306:
302:
298:
295:
290:
284:
281:
278:
275:
274:
273:
270:
268:
265:and into the
264:
260:
256:
252:
248:
244:
238:
236:
232:
228:
224:
220:
216:
206:
204:
200:
196:
190:
186:
184:
180:
176:
172:
164:
161:
159:
155:
152:
149:
145:
131:
127:
123:
119:
115:
111:
107:
103:
100:
96:
84:
81:
73:
63:
59:
55:
49:
48:
43:This article
41:
32:
31:
19:
3996:
3977:
3937:
3916:
3896:
3873:
3859:
3845:
3832:
3767:
3761:
3757:
3753:
3746:
3742:
2910:
2869:
2828:
2787:
2746:
2705:
2664:
2623:
2585:
2547:
2509:
2468:
2430:
2389:
2348:
2307:
2269:
2234:
2225:
2193:
2181:
2148:
2147:Request for
2136:
2098:
2057:
2016:
1975:
1934:
1893:
1852:
1811:
1773:Description
1756:
1752:
1748:
1744:
1741:
1535:Description
1439:
1407:
1397:
1395:
1381:
1375:
1369:
1364:
1358:
1352:
1347:
1307:
1291:ping command
1243:
1211:
1188:
1113:
1110:Mode setting
1103:
1101:
1060:Reject (REJ)
1013:
1009:
1004:
1002:
993:
988:
986:
978:
970:
966:
957:
950:
940:
921:
917:
791:
690:
679:
672:
668:
661:
655:
646:
640:
636:
635:
625:
624:
611:
610:
605:
601:
597:
593:
580:
564:
557:
550:or a 32-bit
541:
534:
531:
517:
496:Information
480:
471:
463:escape octet
452:
446:
426:serial ports
420:
408:
405:
402:
395:
391:
376:
372:
368:bit stuffing
365:
353:
348:
333:
313:
291:
288:
271:
253:protocol as
239:
212:
191:
187:
173:(HDLC) is a
170:
169:
129:Introduction
121:Developer(s)
116:Data framing
105:Abbreviation
76:
67:
44:
2180:Disconnect
1388:) and DCE (
1250:negotiated.
630:full-duplex
620:half-duplex
560:acknowledge
467:XON or XOFF
459:hexadecimal
356:hexadecimal
340:synchronous
259:Frame Relay
257:, into the
249:, into the
4056:Categories
3889:References
1512:32-bit FCS
1353:Unbalanced
1323:IEEE 802.2
616:contention
324:Cisco HDLC
294:IEEE 802.2
183:networking
70:March 2019
54:improve it
4010:. STD 51.
3957:cite book
3776:detected.
3579:(unused)
3345:(unused)
3197:(unused)
3080:(unused)
2974:Response
2963:Response
2056:Set Mode
1983:Set mode
1901:Set mode
1819:Set mode
1770:Response
1532:Response
1203:detected.
606:responses
548:CRC-CCITT
477:Structure
318:(E1) and
316:E-carrier
158:OSI layer
58:verifying
4041:archived
4031:archived
3803:See also
3521:NR0–NR3
3255:AC0–AC1
2237:Command
2151:command
1768:Command/
1530:Command/
1359:Balanced
1264:command.
1172:firmware
1152:command.
1126:command.
1104:U-frames
1098:U-Frames
989:I-frames
786:U-frame
766:S-frame
744:I-frame
680:U-frames
669:S-frames
662:I-frames
602:commands
493:Control
490:Address
309:Internet
147:Based on
2971:Command
2960:Command
2909:Beacon
1244:sending
914:P/F bit
526:8 bits
507:8 bits
330:Framing
209:History
199:routers
137: (
113:Purpose
52:Please
4004:
3984:
3945:
3924:
3903:
2467:Reset
1246:RSET.)
1005:do not
673:do not
552:CRC-32
423:RS-232
336:frames
3825:Notes
3698:FRMR
3665:SABME
3490:SNRME
3463:TEST
3432:SARME
3138:CFGR
2546:Test
2017:SABME
1935:SARME
1853:SNRME
1776:Info
1765:Name
1538:Info
1527:Name
1139:FRMR.
941:first
924:token
520:bits
502:Flag
487:Flag
447:bytes
383:modem
334:HDLC
320:SONET
235:ADCCP
4007:1662
3987:2687
3963:link
3943:ISBN
3922:ISBN
3901:ISBN
3788:ping
3734:BCN
3725:UIH
3638:RIM
3606:XID
3548:SABM
3372:RSET
3313:SARM
3167:DISC
3109:SNRM
2874:C/R
2870:CFGR
2833:C/R
2792:C/R
2751:C/R
2710:C/R
2669:C/R
2628:C/R
2586:FRMR
2552:C/R
2548:TEST
2514:C/R
2469:RSET
2394:C/R
2353:C/R
2235:DISC
2182:DISC
1976:SABM
1894:SARM
1812:SNRM
1753:SARM
1745:DISC
1716:N(R)
1707:C/R
1682:N(R)
1673:C/R
1648:N(R)
1639:C/R
1614:N(R)
1605:C/R
1591:N(S)
1585:N(R)
1577:C/R
1449:For
1339:BCN.
1286:TEST
1283:(1).
898:type
878:N(R)
865:N(S)
855:N(R)
777:type
771:type
757:type
749:N(R)
736:N(S)
728:N(R)
586:SDLC
542:The
499:FCS
379:NRZI
349:flag
267:ISDN
263:LAPF
255:LAPM
251:V.42
247:LAPB
243:X.25
231:ANSI
219:SDLC
181:and
151:SDLC
139:1979
132:1979
108:HDLC
4002:RFC
3982:RFC
3713:P/F
3684:P/F
3653:P/F
3635:SIM
3623:P/F
3594:P/F
3567:P/F
3536:P/F
3509:P/F
3478:P/F
3451:P/F
3420:P/F
3405:UA
3391:P/F
3360:P/F
3333:P/F
3316:DM
3301:P/F
3272:P/F
3243:P/F
3214:P/F
3185:P/F
3170:RD
3155:P/F
3126:P/F
3097:P/F
3068:P/F
3053:UI
3041:P/F
2911:BCN
2892:P/F
2851:P/F
2829:AC1
2810:P/F
2788:AC0
2769:P/F
2747:NR3
2728:P/F
2706:NR2
2687:P/F
2665:NR1
2646:P/F
2624:NR0
2567:P/F
2529:P/F
2510:XID
2412:P/F
2390:UIH
2371:P/F
2149:SIM
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