Session Arrival Rate

The main function of an AC protocol is to manage the offered load, and therefore this study highlights one of the most important aspects of FAAC protocol performance. Table 3-8 lists the studied loads. Ideally, FAAC protocol rejects all sessions that would degrade the throughput of previously-admitted sessions and therefore there should be no significant drop in the achieved QoS. However, non-predictable overhead, in the form of AdReq and RtRq packets, can still degrade the QoS after session admission. Furthermore, the simple cs-range=2 hops model might not encompass all cs-neighbours, and therefore some QoS degradation is possible as the load increases. Each of the studied protocols is now discussed in turn.

3.6.2.1 Session A dm ission R atio

Figure 3-17 shows the session admission ratio of DSR is higher than any other admission control protocol. Actually in DSR there is no mechanism to check the resources before getting the session admission into the network. FAAC protocol admission ratio is lower than DSR and CACP protocol due to thorough checking of resources, as the main contribution of our protocol is to uphold the throughput requirements of the session till completion. The admission ratio of both protocols FAAC and CACP decreases as the number of sessions (load) increases in the network. The session admission request uses the capacity of the network before acceptance or rejection, because FAAC and CACP protocols check the resources for each admission request. Network load have no effect on DSR admission ratio.

0.9 _FAAC

CACP DSR

0.4

^ 0.1

Sessions per source

0.9 FAAC 0.7 CACP -D SR U 0.5 ^ 0.1

Sessions per source

Figure 3-17 Session Admission Ratio Figure 3-18 Session Completion Ratio

3.6.2.2 Session C om pletion R atio

DSR performs better in lower network load because there is less congestion, but as the load increases, the session completion ratio drops. The FAAC protocol maintains almost high completion ratio at lower as well as higher network load. This is due to the careful admission of sessions and considering the effect of new sessions over previously admitted sessions.

CACP protocol also does not uphold throughput and drops the data sessions. Figure 3-18 shows a significant percentage of CACP sessions dropping even at lowest load. This is partly because CACP does not consider the increase in collision rate that occurs upon session admission. The dropped sessions releases the network capacity and allows new sessions to be admitted to use the newly available capacity. The session pausing mechanism in CACP also drops the SCR.

3.6.2.3 P ack et Loss R atio

Packet Loss Ratio is an opposite of Packet Delivery Ratio (PDR). Figure 3-19 presents high packet loss ratio of DSR protocol due to admitting all requesting sessions into the network. The PLR of DSR increases from 6.2% to 45.7% as the traffic load increases in the network.

Design and Evaluation o f Flow Aware Admission Control TFAAC) protocol 63

PLR of CACP is low as compared to DSR but high as compared to FAAC. PLR of CACP changes from 3.1% to 8.26% when number of sessions per source increases from 5 to 40. Relatively low PLR of CACP due to the reason that CACP pauses the session readily and does not admit all admission requesting sessions.

FAAC protocol has lowest PLR at different network loads because of careful and thorough admission control. There is no session pausing mechanism in FAAC protocol because session pausing increases average end-to-end delay and as a result PLR increase. The ultimate purpose of FAAC protocol is to uphold the guaranteed throughput of the data session. PLR of FAAC protocol changes from 0.8% to 5.1%, when number of sessions per source increase from 5 to 40. 0.5 0.6 0.5 0.4 0.4 FAAC CACP DSR FAAC .CACP DSR 0.3 0.3 0.2 _0.2 0.1 0.1 40

S essions per source Sessions per source

Figure 3-19 Packet Loss Ratio Figure 3-20 Average End-to-End Delay

3.6.2.4 T h e A verage end-to-end delay

Figure 3-20 represents the average end-to-end delay of data packets. Average end-to-end delay includes different types of delays; including buffer delay, queuing delay, re-transmission and propagation delay. In DSR, average end-to-end delay increases with increasing number of sessions due to increasing collision rate and PLR. Session pausing mechanism in CACP also contributes to longer end-to-end delays other than collision and PLR. FAAC protocol maintains low average end-to-end delay due to thorough admission control, low PLR and absence of sessions pausing mechanism. The higher number of sessions in the network increases the collision rate. CACP faces more collision and as a result link failure occurs more frequently. The route failure causes the protocol to re-initiate the route discovery for the data session. All these control overheads increases average end-to-end delay of the CACP.

3.6.2.5 T he A ggregate th ro u g h p u t

Throughput is the average successful reception of data at application layer and is usually measured in bits per second. Figure 3-21 shows the aggregate throughput of the FAAC, DSR and CACP protocols. The aggregate throughputs of all the studied protocols increase when the

sessions per source increase from 5 to 25. FAAC protocol maintains high aggregate throughput in low as well as in high traffic load. CACP performs better than DSR at higher traffic rate. At low traffic load such as 5 sessions per source, DSR performs better than CACP because there is no congestion at that time in the network and enough resources are available for all data traffic sessions.

3.6.2.6 U seful A ggregate th ro u g h p u t

The useful aggregate throughput parameter explains the efficiency o f the protocols as shown in Figure 3-22. This metric is like the aggregate throughput, except that it is multiplied by the session completion ratio. It indicates the fraction of the throughput that is useful in terms of allowing an application data session to be completed while upholding its throughput requirements.

800 a 600

M400

3 200

Sessions per source

Figure 3-21 Aggregate Throughput

FAAC CACP

10 15 20 25 30 35 40