Impact of unauthorised access on the time performance of

Unauthorised access by malicious users, who have not registered and obtained authorised access information, can affect the network performance, resulting in a delay in the overall communication process for the other CUs. This delay resulted from the failure of successful authentication by the dedicated server, which makes the CCC busy for others waiting for the contention process to launch ITA frames. Therefore, both throughput rate and total successful communication time include authentication, and exchanging both control information and data, that is affected

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by malicious users, since they contribute to the communication process with other valid CUs. In the unauthorised access scenario, it has been assumed that malicious user usually communicates with a valid CU, and we do not consider the situation of 2 malicious users communicating with one another. Two different cases, which have different numbers of invalid users involved in the communication over the CCC by transmitting ITA frames for initiating communication with other CUs, are considered to investigate their influence on the network’s performance. Therefore, the first case includes only 1 invalid user in the communication process, while 6 malicious users are considered in the second case.

5.4.4.1. Communication time in DSMCRN with unauthorised

access

Figure 5-14 shows the successful communication time for 20 users over both control and data channels in five different runs, consisting of 4, 8, 12, 16 and 20 users, in which the case of 1 malicious user on the 4th run is considered. Generally, the increase in each run occurs due to the increase in participating CUs in the communication process, which arises when exchanging both the control and data frames phases. However, it is evident that the increase in the communication time affected the 4th run, in which 7 out of 8 pairs of CUs successfully completed their communication processes over both the CCC and data channel, the difference is obvious compared to the same run in case showing no malicious users involvement in the communication of the DSMCRN, as shown previously in Figure 5-5. This is because of the detection mechanism of unauthorised access by a malicious user who transmits the ITA and fails to be authenticated by the server after receiving the RTA. Therefore, the receiver is updated by the status of the sender to halt the process of communication with that particular user. This process requires time over the control channel, and affects other legitimate users from using the CCC channel and transmitting their ITA frames.

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Figure ‎5-14: Communication time for 20 pairs of users, including 1 malicious user in DSMCRN

Figure 5-15 shows the communication time for 20 users over both the control and data channels in five different runs, consisting of 4, 8, 12, 16 and 20 users; in which the cases of 1, 2 and 3 malicious users in the 3rd, 4th and 5th runs are considered respectively. Although, the communication time increases in each run, due to the increase in the number of CUs participating in the communication process, it experienced a different increase pattern in the 3rd, 4th and 5th runs, where the malicious users participated in the communication process. This creates a delay resulting from unsuccessful authentication processes, leading to termination of the communication before the control information can be exchanged with the malicious users. For example, the first run indicate 4 CUs successfully communicating with each other and requiring time equal to 0.5*106 µsecs, while the second run involves 8 CUs that are successfully authenticated and exchange their data in 1*106µsecs.

In contrast, in the third run, only 10 valid users out of 12 successfully completed their communication over both the control and data channels, since 1 malicious attempt to make unauthorised access was detected by the server, resulting in stopping the communication process. Thus, the total time for the run requires 1.4*106µsecs, including the detection process. Therefore, 139003.61µsecs refers to the detection time over the control channel for the 6th pair of users, which includes 1 malicious and 1 valid CU user.

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However, the 4th run, which involves 16 users in the communication, only 12 valid CUs communicated and exchanged their data successfully, since 2 malicious users were detected and banned from continuous communication with other valid users. Therefore, the total communication time, including the detection process, was 1.75*106µsecs. Regarding the last run, in which 20 users were communicating, only 14 CUs successfully exchanged data and three invalid users (senders) were banned from the communication process as soon as the recipients CUs were updated because of failed authentication. Thus, 2.15*106µsecs is the time required to successfully complete the communication time for the last run.

Figure ‎5-15: Communication time for 20 pair of users include 4 malicious users in DSMCRN

5.4.4.2. Throughput in DSMCRN with unauthorised access

Figure 5-16 shows the throughput rate for 20 users in five different runs, consisting of 4, 8, 12, 16 and 20 users, in which the case of 1 malicious users being present in the 4th run is considered. Despite the successful messages delivery rate increasing significantly for the 1st, 2nd, 3rd and 5th runs, due to the number of successful data exchanges among the intended destinations, there was a slight increase noted in the throughput rate of the 4th run, because only 14 out of 16 users successfully exchanged their data over the selected data channels. This decreased the message delivery rate, especially when the detection time over the control channel involved and has direct influence on the throughput compared to

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the same run in case showing no malicious users involvement in the communication of DSMCRN in Figure 5-12.

Figure ‎5-16: Throughput for 20 pair of users include 1 malicious user in DSMCRN

However, Figure 5-17 shows the throughput rate for 20 users in five different runs, consisting of 4, 8, 12, 16 and 20 users, in which the cases of 1, 2 and 3 malicious users in the 3rd, 4th and 5th runs respectively are considered. The figure shows a significant increase in the throughput rate for both the 1st and 2nd runs, due to the quantity of successful data exchanged over the SLDCHs in each run. However, the increasing pattern did not remain same in the others runs, which all have less successful message delivery rate compared to the same runs in the situation showing no malicious user’s involvement in the DSMCRN. This is because of the malicious users’ detection, which results in terminating the communication process before the control and data exchanged. Subsequently the throughput rate decreased since there was no data exchange with unauthorised users. Thus, only 5 pairs out of 6 in the 3rd run, 6 pairs out of 8 in the 4th run and 7 pairs out of 10 in the final run which the CUs complete the data exchange successfully.

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Figure ‎5-17: Throughput for 20 pair of users include 4 malicious users in DSMCRN

To summarise the impact of unauthorised access by malicious users, both communication time and throughput can be affected by unauthorised access. Although, the detection process requires a time to proceed, which affects the entire network by increasing communication time, there is no data exchanged with the detected malicious users and resulting in a decrease of the message delivery rate.