Asynchronous Transfer Mode and Download Response Time

INTRODUCTION Asynchronous Transfer Mode (ATM) is a connection-oriented, packet-switched technology. The packets that are switched in an ATM network are of a fixed length, 53 bytes, and are called cells. The cell size has a particular effect on carrying voice traffic effectively. The ATM Adaptation Layer (AAL) sits between ATM and the variable-length packet protocols that might use ATM, such as IP. ATM provides QoS capabilities through its five service classes: CBR, VBR-rt, VBR-nrt, ABR, and UBR. With CBR (constant bit rate), sources transmit stream traffic at a fixed rate. CBR is well-suited for voice traffic that usually requires circuit switching. Therefore, CBR is very important to telephone companies. UBR, unspecified bit rate, is ATM’s best- effort service. IMPLEMENTATION

SIMULATION

Question 1:

Analyze the result we obtained regarding the voice Packet Delay Variation time. Obtain the graphs that compare the Voice packet end-to-end delay, the Email download response time, and the FTP download response time for both scenarios. Comment on the results

Figure 1.1: Email- Download Response Time

Graph shows the UBR performance is greater compare to CBR for Email download response time. Both graph shows unstable simulation but remain between 0.175 to 0.0125 for CBR and UBR.

Figure 1.2: FTP- Download Response Time

From the graph above, CBR performance is lower compare to UBR for FTP download response time. Both graph stable constant in the same area which is 0.4 to 0.5 from 2m to 10m.

Figure 1.3: Voice- Packet End-to-End Delay

From the graph above, as CBR is well suited for voice traffic that usually requires circuit switching, we can see the CBR simulation is constant and the performance is greater compare to UBR. For the UBR graph we can see UBR simulation unstable at 0.0150 to 0.0125. CBR is very important to telephone