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Bounded re-transmission protocol in Software Integration data matrix barcodes in Software Bounded re-transmission protocol bar code for visual C#




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Bounded re-transmission protocol using barcode development for none control to generate, create none image in none applications.barcode generator c# digit We nally introduce an even none none t that modi es the activation pointer w. This event will receive a full explanation in the next re nement: SND_time_out_current when s_st = working w = FALSE then w := TRUE end. QR Code Safty 6.7.3 Synchronization of th e events In this re nement, the events are synchronized according to Fig.

6.3, where the new events are written in italic. These new events are inserted in the previous synchronization diagram, Fig.

6.2. Events SND_failure, RCV_failure, and SND_time_out_current are presently spontaneous .

They will receive more explanations in the next re nement.. init SND_snd_current_data SND_snd_last_data RCV_rcv_current_data RCV_success SND_rcv_current_ack SND_success SND_failure SND_time_out_current RCV_failure Fig. 6.3. Synchronization of the events in the fourth re nement 6.8 Fifth re nement 6.8 Fifth re nement 6.8.

1 T none none he state In this re nement, we introduce the unreliability of the channels.This is done by rst adding three activation bits: db, ab, and v. At most one of these bits, together with w already introduced in previous re nements, is equal to TRUE; this is expressed in invariants inv5_1 to inv5_6.

The use of the activation bits is illustrated in Fig. 6.4:.

inv5_1: w = TRUE db = FAL SE inv5_2: w = TRUE ab = FALSE variables: ...

db ab v inv5_3: w = TRUE v = FALSE inv5_4: db = TRUE ab = FALSE inv5_5: db = TRUE v = FALSE inv5_6: ab = TRUE v = FALSE. db SND_snd w SND_rcv Data channel ab Acknowledgment channel Fig. 6.4. The activation bits RCV_rcv v RCV_snd We introduce an additional boolean variable, l, which denotes the last item indicator. It is sent by the sender to the receiver (together with d and s). When equal to TRUE,.

Bounded re-transmission protocol this bit indicates that the sent item is the last one (invariants inv5_7 and inv5_8): inv5_7: db = TRUE r = s l = FALSE r + 1 < n inv5_8: db = TRUE r = s l = TRUE r + 1 = n. variables: . . . l Finally, we introduce a con stant M AX and a variable c. Constant M AX denotes the maximum number of re-tries and variable c denotes the current number of re-tries. In invariant inv3_10, it is explained that when c exceeds M AX, then the sender fails: axm3_1: M AX N.

constants:. ... M AX inv3_9: variables: ... c c 0 .. M AX + 1 inv3_10: c = M AX + 1 s_st = f ailure 6.8.2 The events The initia l event is extended in a straightforward fashion.

Event brp is not modi ed in this re nement: init r := 0 g := r_st := working s_st := working s := 0 d : D w := TRUE db := FALSE ab := FALSE v := FALSE l := FALSE c := 0. brp when r = working s = working then skip end 6.8 Fifth re nement The following events are mo none none di ed as indicated by the underlined actions. We split now abstract event SND_snd_data into two events according to the sending of the last data or not. The activation bit, db, of the data channel is set to TRUE: SND_snd_current_data re nes SND_snd_data when s_st = working w = TRUE s+1<n then d := f (s + 1) w := FALSE db := TRUE l := FALSE end SND_snd_last_data re nes SND_snd_data when s_st = working w = TRUE s+1=n then d := f (s + 1) w := FALSE db := TRUE l := TRUE end.

In the next two receiver ev ents, the abstract cheating guards r + 1 < n and r + 1 = n have disappeared. They have been replaced by guards l = FALSE and l = TRUE, respectively. Invariants inv3_11 and inv3_12 de ned below ensure guard strengthening.

The receiver activation bit v is set to TRUE: RCV_success when r_st = working db = TRUE r=s l = TRUE then r_st := success r := r + 1 h := h {r + 1 d} db := FALSE v := TRUE end. RCV_rcv_current_data when r none for none _st = working db = TRUE r=s l = FALSE then r := r + 1 h := h {r + 1 d} db := FALSE v := TRUE end. The next two events are new . Event RCV_rcv_retry corresponds to the receiver receiving a re-try. The receiver detects this by the fact that its own pointer r is di erent.

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