Virtual vpn in the cloud

VM Failure Ratio 
According to the NFV Service Quality Metrics document by ETSI [43], VM Failure 
Rate is the ratio of VM instances delivered to the VNF customer. It is defined as the ratio of 
total failed attempts to launch VM to the total number of successful attempts. Over the 30 
iterations calculated, the numbers of successful attempts recorded of VM instantiation were 
30 and the failed attempts were recorded to be zero. Thus the average value for VM Failure 
Rate is measured to be 
zero.
Average 
0 
•
Service operational time 
According to the NFV Service Quality Metrics document by ETSI [43], VM service 
start up time/operational time is the time elapsed for VM provisioning and time required for 
setting up the VPN tunnel. The values measured for setting up the VPN tunnel were recoded 
to be 2 seconds. Thus the total operational time including VM start up time and VPN service 
start up time was measured to be 23.4+2.4 
≈
25.8 seconds. The average value of VPN 
service start up time has been tabulated below. 
Average 
2.4 
≈
2 seconds 
Half-length 95% Confidence Interval 
0.18 

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32 
6
 
A
NALYSIS AND 
D
ISCUSSIONS
 
6.1
 
Requirements to offer VPN as a VNF 
A comparative study on different architectures reviewed in the previous sections 
give a detailed analysis on the different designs stating the pros and cons of each, enabling 
cloud users to determine the best suited. Comparative analysis on the different modes of 
operation including the tunnel and transport mode has also been studied, stating each of its 
advantages and disadvantages for better efficiency and suitability. Various key distribution 
mechanisms have also been reviewed for enhancing security mechanism in the cloud, 
concentrating on pre-shared keys for this research to avoid IPSec complexities [15].
Being a VNF, VPNaaS could be included in complex service chains that can be 
automatically managed and configured to provide sophisticated virtualized services. Among 
the high level requirements stated by the NFV document proposed by ETSI [44], including 
portability, performance, elasticity, resilience, security, service continuity and so on, 
following are the requirements identified to provision VPN as an VNF: