122:. The original variable length message is thus represented as a concatenation of a variable number of sub-blocks. While in standard ARQ the message as a whole is either acknowledged (ACKed) or negatively acknowledged (NAKed), in ARQ with selective transmission the ACK response would additionally carry a bit flag indicating the identity of each sub-block successfully received. In ARQ with selective retransmission of sub-divided messages each retransmission diminishes in length, needing to only contain the sub-blocks that were linked.
126:
messages have increased difficulty delivering longer messages, as each repeat is the full length. Selective re-transmission applied to variable length messages completely eliminates the difficulty in delivering longer messages, as successfully delivered sub-blocks are retained after each transmission, and the number of outstanding sub-blocks in following transmissions diminishes. Selective Repeat is implemented in UDP transmission.
110:−1) to avoid miscommunication in all cases of packets being dropped. To understand this, consider the case when all ACKs are destroyed. If the receiving window is larger than half the maximum sequence number, some, possibly even all, of the packets that are present after timeouts are duplicates that are not recognized as such. The sender moves its window for every packet that is acknowledged.
49:. The receiver may selectively reject a single frame, which may be retransmitted alone; this contrasts with other forms of ARQ, which must send every frame from that point again. The receiver accepts out-of-order frames and buffers them. The sender individually retransmits frames that have timed out.
125:
In most channel models with variable length messages, the probability of error-free reception diminishes in inverse proportion with increasing message length. In other words, it's easier to receive a short message than a longer message. Therefore, standard ARQ techniques involving variable length
117:
it works somewhat differently. In non-continuous channels where messages may be variable in length, standard ARQ or Hybrid ARQ protocols may treat the message as a single unit. Alternately selective retransmission may be employed in conjunction with the basic ARQ mechanism where the message is
44:
Selective Repeat is part of the automatic repeat request (ARQ). With selective repeat, the sender sends a number of frames specified by a window size even without the need to wait for individual ACK from the receiver as in
389:
must be less than half the total number of sequence numbers (if they are numbered from zero to the maximum value of the sequence number space) to avoid ambiguity in detecting duplicate packets and dropped
95:. The receiver continues to fill its receiving window with the subsequent frames, replying each time with an ACK containing the sequence number of the earliest missing
57:
It may be used as a protocol for the delivery and acknowledgement of message units, or it may be used as a protocol for the delivery of subdivided message sub-units.
106:
The size of the sending and receiving windows must be equal, and half the maximum sequence number (assuming that sequence numbers are numbered from 0 to
459:
Profile for High
Frequency (HF) Radio Data Communication uses selective repeat ARQ, with a maximum window size of 128 protocol-data units (PDUs).
91:(ACK) it sends. If a frame from the sender does not reach the receiver, the sender continues to send subsequent frames until it has emptied its
419:
87:
The receiver process keeps track of the sequence number of the earliest frame it has not received, and sends that number with every
703:
209:
Accept the packet from the buffer and send it to a higher layer Remove packet Rn from the buffer
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88:
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to sub-divide messages into smaller units, to increase the probability that each one is received correctly.
483:
437:
29:
652:
Comroe, R.; D. Costello (July 1984). "ARQ schemes for data transmission in mobile radio systems".
81:
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should be bounded by the receiver’s capacity to process and buffer out-of-order packets.
103:, it re-sends the frame number given by the ACKs, and then continues where it left off.
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first subdivided into sub-blocks (typically of fixed length) in a process called
444:), uses Selective Repeat ARQ to ensure reliable transmission over noisy media.
673:
636:
692:
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468:
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standard, which provides a way to create a high-speed (up to 1 Gigabit/s)
134:
These examples assume an infinite number of sequence and request numbers.
456:
96:
65:
615:
Weldon, E. (March 1982). "An
Improved Selective-Repeat ARQ Strategy".
32:(ARQ) protocol used to manage sequence numbers and retransmissions in
598:. 3rd International Conference on Digital Satellite Communications.
80:
frames sent after an initial error; this is the general case of the
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The sender must not transmit faster than the receiver can handle.
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There are a few things to keep in mind when choosing a value for
600:
265: := empty Repeat the following steps forever:
418:, which does not provide guaranteed delivery of packets; with
426:
190:Accept the packet and send it to a higher layer
84:
with both transmit and receive window sizes greater than 1.
445:
429:
594:
Lockitt, J. A.; Gatfield, A. G.; Dobyns, T. R. (1975).
593:
175: := empty Do the following forever:
76:, the receiving process will continue to accept and
64:, the sending process continues to send a number of
393:Considering the constraints in (1) and (2), choose
333:Store the transmitted packet in the buffer
512:
397:to be as large as possible to maximize throughput.
651:
414:to ensure reliable transmission of data over the
99:. Once the sender has sent all the frames in its
690:
654:IEEE Journal on Selected Areas in Communications
539:
16:Data transmission and error correction protocol
160: := buffer to store out-of-order packets
113:When used as the protocol for the delivery of
60:When used as the protocol for the delivery of
362:
506:
504:
420:Selective Acknowledgement (SACK) extension
533:
239:Ignore packet Send a Request for
542:Computer Networking: A Top-Down Approach
501:
422:, it may also use Selective Repeat ARQ.
691:
614:
221:the packet received is error-free and
179:the packet received is error-free and
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617:IEEE Transactions on Communications
564:
269:you receive a request number where
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587:
14:
715:
540:Kurose, James F.; Keith W. Ross.
72:even after a frame loss. Unlike
704:Error detection and correction
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232:Buffer the packet at position
28:is a specific instance of the
1:
596:A Selective Repeat ARQ system
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408:Transmission Control Protocol
317:no packet is in transmission
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436:using existing home wiring (
7:
462:
401:
10:
720:
52:
39:
674:10.1109/JSAC.1984.1146084
637:10.1109/TCOM.1982.1095497
375:in Selective Repeat ARQ:
148: := sequence number
484:Automatic repeat request
363:Choosing a window size (
321:Transmit a packet where
144: := request number
30:automatic repeat request
152: := sequence base
82:sliding window protocol
34:reliable communications
474:Reliable Data Transfer
156: := sequence max
511:Tanenbaum, Andrew S.
140: := window size
699:Logical link control
602:. pp. 189–195.
302:Remove packets with
26:Selective Reject ARQ
22:Selective Repeat ARQ
666:1984IJSAC...2..472C
629:1982ITCom..30..480W
608:1975dsc..conf..189L
489:Computer networking
479:Pipeline (software)
450:packet segmentation
120:packet segmentation
115:subdivided messages
440:, phone lines and
434:Local area network
410:uses a variant of
356:Retransmit packet
515:Computer Networks
416:Internet Protocol
352:timeout occurred
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565:Marbach, Peter.
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519:(4th ed.).
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390:acknowledgments.
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457:STANAG 5066
438:power lines
78:acknowledge
70:window size
693:Categories
575:August 24,
495:References
341:in buffer
283: := (
130:Pseudocode
645:0090-6778
310:from the
298: :=
257: :=
213: :=
194: :=
164:receiver
682:22759443
463:See also
448:employs
402:Examples
335:for each
261:+ 1
244:function
162:function
62:messages
662:Bibcode
625:Bibcode
604:Bibcode
348:packet
337:packet
246:sender
219:else if
205:exists
53:Concept
40:Summary
680:
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312:buffer
263:buffer
203:buffer
173:buffer
158:buffer
101:window
93:window
66:frames
678:S2CID
570:(PDF)
427:ITU-T
329:<
306:<
273:>
225:>
200:while
97:frame
641:ISSN
577:2013
546:ISBN
521:ISBN
455:The
446:G.hn
430:G.hn
425:The
406:The
354:then
319:then
291:) +
278:then
237:else
230:then
188:then
670:doi
633:doi
24:or
695::
676:.
668:.
656:.
639:.
631:.
621:30
619:.
544:.
503:^
358:Sn
350:Sn
346:if
343:do
339:Sn
331:Sm
327:Sn
325:≤
323:Sb
315:if
308:Rn
304:Sn
300:Rn
296:Sb
293:Rn
289:Sb
287:−
285:Sm
281:Sm
275:Sb
271:Rn
267:if
255:Sm
251:Sb
248:is
241:Rn
234:Sn
227:Rn
223:Sn
215:Rn
211:Rn
207:do
196:Rn
192:Rn
185:Rn
183:=
181:Sn
177:if
169:Rn
166:is
154:Sm
150:Sb
146:Sn
142:Rn
36:.
684:.
672::
664::
658:2
647:.
635::
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395:N
387:N
381:N
373:N
367:)
365:N
259:N
138:N
108:n
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