It is used to secure IPv4 traffic.
Internet Protocol Security (IPsec) is a protocol suite for secure Internet Protocol (IP) communications by authenticating and encrypting each IP packet of a communication session. IPsec is most commonly used to secure IPv4 traffic. IPsec protocols were originally defined in RFC 1825 through RFC 1829, which were published in 1995. In 1998, these documents were superseded by RFC 2401 and RFC 2412 with a few incompatible engineering details, although they were conceptually identical. Internet Protocol security (IPsec) uses cryptographic security services to protect communications over Internet Protocol (IP) networks. IPsec supports network-level peer authentication, data origin authentication, data integrity, data confidentiality (encryption), and replay protection. IPsec is most commonly used to secure IPv4 traffic. IPsec protocols were originally defined in RFC 1825 through RFC 1829, which were published in 1995. In 1998, these documents were superseded by RFC 2401 and RFC 2412 with a few incompatible engineering details, although they were conceptually identical. Layer 2 Tunneling Protocol (L2TP) is a protocol used to tunnel data communications traffic between two sites over the Internet. L2TP is often used in tandem with IPSec (which acts as a security layer) to secure the transfer of L2TP data packets over the Internet. Protocols. There are a number of VPN protocols in use that secure the transport of data traffic over a public network infrastructure. Each protocol varies slightly in the way that data is kept secure. IP security (IPSec) is used to secure communications over the Internet. IPSec traffic can use either transport mode or tunneling to encrypt data traffic in a VPN Normally this Internet Protocol Security or IPSec is a system that is applied in the VPN. This Virtual Private Network is a process to increase the security of internet by hiding the ip address and also hiding the original identity. But most of the VPN use this Ipsec. Because it can in any remote device by just installing a client software. IPSec works on the IP security. It is normally used when there is any need to communicate others via net. IPsec is officially standardised by the Internet Engineering Task Force (IETF) in a series of Request for Comments documents addressing various components and extensions. It specifies the spelling of the protocol name to be IPsec. IPsec is most commonly used to secure IPv4 traffic. IPsec protocols were originally defined in RFC 1825 through RFC 1829, which were published in 1995. In 1998, these documents were superseded by RFC 2401 and RFC 2412 with a few incompatible engineering details, although they were conceptually identical. IPSec tunnel mode is not designed to be used for virtual private network (VPN) remote access. The Windows® 2000 Server operating system simplifies deployment and management of network security with Windows 2000 IP Security, a robust implementation of IP Security (IPSec).  IPsec is an end-to-end security scheme operating in the Internet Layer of the Internet Protocol Suite, while some other Internet security systems in widespread use, such as Transport Layer Security (TLS) and Secure Shell (SSH), operate in the upper layers at the Application layer. IPsec is most commonly used to secure IPv4 traffic. IPsec protocols were originally defined in RFC 1825 through RFC 1829, which were published in 1995. In 1998, these documents were superseded by RFC 2401 and RFC 2412 with a few incompatible engineering details, although they were conceptually identical. IPsec (Internet Protocol Security) is a set of protocols and standards intended to provide security for information sent over the Internet. Specifically, IPsec was created to provide the following sorts of protection for Internet traffic: 1  Encryption to ensure data confidentiality. Although IU has mostly implemented IPsec in VPN service, it is designed to be used more generally, and is built into the IPv6 standard for general use. Because of this, any modern operating system that can use the IPv6 protocol will have IPsec capabilities. IPsec is an extension to the IP protocol which provides security to the IP and the upper-layer protocols. It was first developed for the new IPv6 standard and then “backported” to IPv4. The IPsec architecture is described in the RFC2401. The following few paragraphs will give you a short introduction into IPsec. To derive this HMAC the IPsec protocols use hash algorithms like MD5 and SHA to calculate a hash based on a secret key and the contents of the IP datagram. This HMAC is then included in the IPsec protocol header and the receiver of the packet can check the HMAC if it has access to the secret key.
https://en.wikipedia.org/wiki/IPsec https://en.wikipedia.org/wiki/IPsec http://whatismyipaddress.com/vpn http://www.bestvpnserver.com/what-is-ipsec-and-why-use-ipsec-vpn/ https://en.wikipedia.org/wiki/IPsec https://msdn.microsoft.com/en-us/library/bb742429.aspx https://en.wikipedia.org/wiki/IPsec https://kb.iu.edu/d/bbhw http://www.ipsec-howto.org/x202.html
what is ipsec used for