What is IPSec

What is an IPSec and how exactly does it work?

What is IPSec?

IPSec (Internet Protocol Security) consists of a number of different security protocols. It was developed to ensure that data packets sent over an IP network are neither seen by nor accessible to third parties. IPSec offers a high level of security for an Internet protocol. The encryption is used to guarantee confidentiality and for authentication.

Why is IPSec so popular?

Thanks to its two-pronged approach, IPSec is one of the safest ways to encrypt data. It also has the great advantage of working at the network level while systems like SSL work at the application level. SSL security systems require changes to individual applications, but IPSec only requires changes to the operating system.

How exactly does IPSec work?

Most other security protocols operate at the application layer of network communication. A big advantage of IPSec is that because it works at the network level rather than the application level, it can encrypt an entire IP packet. This is done with two mechanisms:

Authentication Header (AH) - Each package is assigned a digital signature, which protects your network and your data from interference by third parties. This means that the content of a data packet cannot be changed without noticing it, and it also enables the identity check between the two ends of a connection.

Encapsulating Security Payload (ESP) - While the AH prevents the manipulation of a packet, the ESP ensures that the information in the packet is encrypted and cannot be read. An ESP header, trailer and authentication block are used to encrypt the entire payload of a packet.

Technical details

  • Compatible with Windows 7+, Windows Server 2008, Cisco routers, MacOS and iOS devices.
  • Supports compatible versions for Linux and other operating systems.
  • Primary protocol is Internet Key Exchange (IKE)
  • Uses Internet Security Association and Key Management Protocol (ISAKMP) as defined in IETF RFC 2408 to negotiate VPN service.

How does IPSec work alongside the VPN protocols?

IPSec is used in conjunction with other VPN protocols to provide a fast and secure service. There are two main options:

L2TP / IPSec

L2TP (Layer 2 Tunnel Protocol) is a tunnel protocol that has been programmed into most operating systems and VPN-capable devices. On its own, it doesn't offer any encryption. However, when combined with IPSec, it becomes the ideal tool for a VPN. L2TP / IPSec offers high speeds and extremely high security for data packets. AES ciphers are generally used for encryption.

IKEv2 / IPSec

IKEv2 (Internet Key Exchange Version 2) was jointly developed by Microsoft and Cisco and is supported by Windows 7+, iOS and Blackberry. Open source versions for Linux have also been developed. Like L2TP, it is a tunnel protocol that can be used as a VPN when used with IPSec. The main selling points are response speed and flexibility: IKEv2 automatically re-establishes the connection after a brief signal loss and thanks to the MOBIKE protocol, changes in the network can be processed without any problems.

What are the pros and cons of IPSec?

Like all security systems, IPSec has its own advantages and disadvantages. Here are some of them:


  • Since IPSec works at the network level, changes only need to be made to the operating system and not to individual applications.
  • IPSec is completely invisible during operation and is therefore the ideal choice for a VPN.
  • The use of AH and ESP guarantees the highest level of security and data protection.


  • IPSec is more complicated than alternative security protocols and more difficult to configure.
  • Secure public keys are required for IPSec. If your key is compromised or you have poor key management problems can arise.
  • When transmitting small packets, IPSec can be an inefficient method of encrypting data.


Despite its complexity, IPSec is fast becoming the preferred protocol for a VPN. By combining various security and encryption functions, the highest level of data protection can be guaranteed. Over time, IPSec seems to be increasingly establishing itself as the industry standard for VPN security.

Tim has been writing content and copy for a living for over 4 years and has been involved in VPN, Internet privacy and cybersecurity for more than 2 years. He likes to keep up to date with the latest online privacy news and helps people find new ways to protect their rights online.