What is the IPSec protocol and how does it work?

by Amrita Mitra | Mar 2, 2017 | CCNP, CompTIA, Data Breaches and Prevention, Encryption, End Point Protection, Network Security, Privacy, Security Fundamentals, VPN

from it.

IPSec

These two protocols can also be implemented together.

Mode of Operation of IPSec Protocol

There are two specific modes of operations defined for IPSec :

Transport mode
Tunnel mode

The selection of modes determines what specific parts of the IP datagram are protected and how the headers are arranged.

Transport Mode: When IPSec is used in transport mode, the IPSec header is applied only on the IP payload and not on the IP header. AH and ESP headers appear between the original IP header and the IP payload. This mode encrypts the data part of each packet and leaves the header intact.

Tunnel Mode: In this mode, the entire IP datagram is encrypted and encapsulated within another IP datagram. Here, the IPSec headers appear in front of the original IP header, and the new IP header is added in front of the IPSec header.

And when two devices communicate with each other, they must share a public key to send and receive information securely. To ensure that, a protocol known as the Internet Security Association and Key Management Protocol/Oakley (ISAKMP/Oakley) is used.

How does the IPSec protocol work?

IPSec provides security over a network and is widely used in VPNs. Its operation can be broken down into five steps:

Step 1: ‘Interesting traffic’ initiates the IPSec traffic.
Step 2: Internet Key Exchange or IKE Phase 1
Step 3: IKE Phase 2
Step 4: Data transfer
Step 5: IPSec tunnel termination

Let’s look into the details of what these steps are.

Step 1: In this step, ‘interesting traffic’ initiates the IPSec process. What type of traffic is deemed interesting depends on the VPN’s security policy. Often, access lists are used for this purpose. The permit statement of the policy means the traffic should be encrypted. And deny statement …

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