Virtual vpn in the cloud

Figure 2: Site-to-site VPN architecture 
3.3.1
 
Site-to-site VPNs 
In Site-to-site VPNs the hosts/clients/users operating across the VPN tunnel do not 
require separate installation of VPN client software on each, sending or receiving of TCP/IP 
traffic is enabled across the VPN gateways. The gateway at one end is responsible for 
encapsulating, encrypting and authenticating outbound traffic, sending it to the peer VPN 
gateway at the other end across the public infrastructure to the target site. The VPN peer at 
the other end, detaches the IP header, decrypts the data and forwards the data packets to the 
target host in its private network. 
The most commonly deployed secure protocol used in setting up site-to-site 
VPNs is IPSec protocol [23]. VPNs are largely deployed using IPSec protocol because of its 
ability to enhance productivity and communication thus increasing network flexibility. 
 
Advantage: 
Site-to-site VPNs offer greater scalability and flexibility because only the 
gateway VPN needs to support IPSec functionality and hence the installation and 
management costs across deployed gateways is minimal. Also it offloads the processing 
overhead from individual systems to the gateway router thus freeing up memory 
consumption and processing speed. 
 
Disadvantage: 
However, the processing overheads managed by the gateway routers increase 
CPU utilization thus degrading user performance in terms of communication speed.

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Figure 3: Remote Access VPN architecture 
3.3.2
 
Remote Access VPNs 
Remote Access VPNs, every host must have VPN client software. Whenever the 
host tries to send traffic to the protected network, the VPN client software encapsulates and 
encrypts the data before sending it over the public infrastructure to the target VPN gateway. 
Upon reception, the VPN gateway behaves in the same way as the site-to-site peer 
decrypting and detaching of the IP header before forwarding it to its private subnet. 
Remote access VPN protocols are more varied. The Point-to-Point tunneling protocol 
(PPPTP), layer 2 tunneling protocol (L2TP), SSL/TLS, IPSec are all used to deliver Remote 
access VPNs.