Abstract: “Internet communication is largely based on TCP/IP protocols. The main design of TCP/IP is for trusted peers to communicate. IP Packets have no inherent security, and therefore it is relatively easy to forge the addresses of IP packets, modify the contents of IP packets, replay old packets, and inspect the contents of IP packets in transit. In this paper, we discuss how Internet Protocol Security (IPSec) is used for secured and encrypted communication between Internet hosts. IPSec is described as an end-to-end security scheme operating in the Internet Layer of the Internet Protocol Suite[1]. According to Kent et al., it can be used in protecting data flows between a pair of hosts (host-to-host), between a pair of security gateways (network-to-network), or between a security gateway and a host (network-to-host). To discussthe use of IPSec in an TCP/IP based network, we chose Virtual Private Network (VPN) as the application in describing how IPSec provides the platform for secure and encr”

Keywords: TCP/IP Security, IPSec, VPN, IKE, IKE2, AH, SA, ESP