IPsec - Internet Protocol Security
===================================

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      **What is IPsec (Inside VPN)?**

         IPsec (Internet Protocol Security) is a suite of protocols that provides encryption, authentication, and integrity for IP traffic.
         When used inside a VPN, IPsec works with tunneling protocols (like L2TP or IKEv2) to create secure, encrypted tunnels over public networks.
         Think of it as a secure tunnel that wraps and protects all your data as it travels across the internet.

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      **Why is IPsec important inside VPN?**

         * **Data Confidentiality** – Encrypts entire IP packets to prevent unauthorized access.
         * **Data Integrity** – Ensures that tunneled data hasn’t been altered during transit.
         * **Authentication** – Verifies the identity of both VPN endpoints.
         * **Tunnel Protection** – Secures the entire communication path between networks or users.
         * **Mobility & NAT Support** – Works well with mobile users and NAT traversal.

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      **How IPsec works inside VPN (in simple steps):**

         * **Tunnel Setup** – A VPN tunnel is established using a tunneling protocol (e.g., L2TP or IKEv2).
         * **Negotiation** – IPsec negotiates encryption/authentication parameters using IKE.
         * **Authentication** – Endpoints authenticate using pre-shared keys or certificates.
         * **Encryption & Integrity** – The entire IP packet is encrypted and signed.
         * **Transmission & Decryption** – Encrypted packets are sent through the tunnel and decrypted at the other end.

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      **Where is IPsec used?**

         * **Site-to-Site VPNs** – Securely connects branch offices over the internet.
         * **Remote Access VPNs** – Allows users to securely access internal networks from anywhere.
         * **Cloud Connectivity** – Secures traffic between on-prem and cloud environments.
         * **Geo-Restriction Bypass** – Enables access to region-restricted content securely.
         * **BYOD Security** – Protects enterprise data on employee-owned devices.

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      **Which OSI Layer does this protocol belong to?**

         * IPsec secures entire IP packets, regardless of the application or transport protocol.
         * It operates below the transport layer (TCP/UDP) and above the data link layer, making it part of the **Network Layer (Layer 3)**.
         * This allows IPsec to secure all traffic within the VPN tunnel, not just specific applications.

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        Topics in this section,

                * :ref:`Learnings in this section <IPsec_step1>`

                * :ref:`Terminology <IPsec_step2>`

                * :ref:`Version Info <IPsec_step3>`

                * :ref:`IPsec Version&RFC Details <IPsec_step5>`

                * :ref:`IPsec Basic Setup on Ubuntu using IPv4 <IPsec_step20>`

                * :ref:`IPsec Basic Setup on Ubuntu using IPv6 <IPsec_step21>`

                * :ref:`IPsec Protocol Packet Details <IPsec_step6>`

                * :ref:`IPsec Usecases <IPsec_step7>`

                * :ref:`IPsec Basic Features <IPsec_step8>`
                    
                * :ref:`IPsec Feature : Encryption <IPsec_step9>` 

                * :ref:`IPsec Feature : Authentication <IPsec_step10>`

                * :ref:`IPsec Feature : Integrity Checking <IPsec_step11>`  

                * :ref:`IPsec Feature : Tunneling and Transport Modes <IPsec_step12>`  

                * :ref:`IPsec Feature : Key Exchange (IKE/IKEv2) <IPsec_step13>`

                * :ref:`IPsec Feature : Security Associations (SAs) <IPsec_step14>`

                * :ref:`IPsec Feature : Protocol Support (ESP & AH) <IPsec_step15>`   

                * :ref:`IPsec Feature : NAT Traversal <IPsec_step16>` 

                * :ref:`IPsec Feature : Replay Protection <IPsec_step17>` 

                * :ref:`IPsec Feature : Flexible Algorithm Support <IPsec_step18>` 

                * :ref:`Reference links <IPsec_step19>`


.. _IPsec_step1:

.. tab-set::

    .. tab-item:: Learnings in this section

        * In this section, you are going to learn

.. _IPsec_step2:

.. tab-set::

    .. tab-item:: Terminology
        
       * Terminology


.. _IPsec_step3:

.. tab-set::

    .. tab-item:: Version Info
    
         * Version Info


.. _IPsec_step5:

.. tab-set::

    .. tab-item:: IPsec Version&RFC Details

        
         .. csv-table:: 
               :file: ./IPsec/IPsec_Version&RFC_Details.csv
               :widths: 10,10,10,30
               :header-rows: 1

.. _IPsec_step20:

.. tab-set::

    .. tab-item:: IPsec Basic Setup on Ubuntu using IPv4

      **Setup**



.. _IPsec_step21:

.. tab-set::

   .. tab-item:: IPsec Basic Setup on Ubuntu using IPv6
       
    **Setup**



.. _IPsec_step6:

.. tab-set::

    .. tab-item:: IPsec Protocol Packet Details
       
         **Tunnel Mode with AH**

         .. csv-table:: 
                :file: ./IPsec/IPsec_packetdetails1.csv
                :widths: 10,20,30,10
                :header-rows: 1

         **Tunnel Mode with ESP**

         .. csv-table::
                :file: ./IPsec/IPsec_packetdetails2.csv
                :widths: 10,20,30,10
                :header-rows: 1
        
.. _IPsec_step7:

.. tab-set::

    .. tab-item:: IPsec Usecases
        
        
         .. csv-table:: 
               :file: ./IPsec/IPsec_Use_Cases.csv
               :widths: 10,20,30
               :header-rows: 1

.. _IPsec_step8:

.. tab-set::

    .. tab-item:: IPsec Basic Features
    
         
         .. csv-table:: 
                  :file: ./IPsec/IPsec_Basic_Features.csv
                  :widths: 10,10,30
                  :header-rows: 1

.. _IPsec_step9:

.. tab-set::

    .. tab-item:: IPsec Feature : Encryption

          **Encryption - Testcases**

          .. csv-table:: 
                 :file: ./IPsec/IPsec_Feature1_Encryption_TestCases.csv
                 :widths: 10,10,30,20
                 :header-rows: 1


   
.. _IPsec_step10:

.. tab-set::

    .. tab-item:: IPsec Feature : Authentication

         **Authentication - Testcases**

         .. csv-table:: 
                :file: ./IPsec/IPsec_Feature2_Authentication_TestCases.csv
                :widths: 10,10,30,20
                :header-rows: 1


.. _IPsec_step11:

.. tab-set::

    .. tab-item:: IPsec Feature : Integrity Checking

        **Integrity Checking - Testcases**

        .. csv-table:: 
                 :file: ./IPsec/IPsec_Feature3_Integrity_Checking_TestCases.csv
                 :widths: 10,10,30,20
                 :header-rows: 1


.. _IPsec_step12:

.. tab-set::

    .. tab-item:: IPsec Feature : Tunneling and Transport Modes

          **Tunneling and Transport Modes - Testcases**

          .. csv-table:: 
                :file: ./IPsec/IPsec_Feature4_Tunneling_and_Transport_Modes_TestCases.csv
                :widths: 10,10,30,20
                :header-rows: 1



.. _IPsec_step13:

.. tab-set::

    .. tab-item:: IPsec Feature : Key Exchange (IKE/IKEv2)

         **Key Exchange (IKE/IKEv2) - Testcases**

         .. csv-table:: 
                 :file: ./IPsec/IPsec_Feature5_Key_Exchange(IKE_IKEv2)_TestCases.csv
                 :widths: 10,10,30,20
                 :header-rows: 1


 
.. _IPsec_step14:

.. tab-set::

    .. tab-item:: IPsec Feature : Security Associations (SAs)

         **Security Associations (SAs) - Testcases**

         .. csv-table:: 
                  :file: ./IPsec/IPsec_Feature6_Security_Associations(SAs)_TestCases.csv
                  :widths: 10,10,30,20
                  :header-rows: 1


.. _IPsec_step15:

.. tab-set::

    .. tab-item:: IPsec Feature : Protocol Support (ESP & AH)
   
          **Protocol Support (ESP & AH) - Testcases**

          .. csv-table:: 
                 :file: ./IPsec/IPsec_Feature7_Protocol_Support(ESP&AH)_TestCases.csv
                 :widths: 10,10,30,20
                 :header-rows: 1


.. _IPsec_step16:

.. tab-set::

    .. tab-item:: IPsec Feature : NAT Traversal

         **NAT Traversal - Testcases**

         .. csv-table:: 
                 :file: ./IPsec/IPsec_Feature8_NAT_Traversal_TestCases.csv
                 :widths: 10,10,30,20
                 :header-rows: 1


.. _IPsec_step17:

.. tab-set::

    .. tab-item:: IPsec Feature : Replay Protection

        **Replay Protection - Testcases**

        .. csv-table::
                :file: ./IPsec/IPsec_Feature9_Replay_Protection_TestCases.csv
                :widths: 10,10,30,20
                :header-rows: 1


.. _IPsec_step18:

.. tab-set::

    .. tab-item:: IPsec Feature : Flexible Algorithm Support

        **Flexible Algorithm Support - Testcases**

        .. csv-table::
                :file: ./IPsec/IPsec_Feature10_Flexible_Algorithm_Support_TestCases.csv
                :widths: 10,10,30,20
                :header-rows: 1


.. _IPsec_step19:

.. tab-set::

    .. tab-item:: Reference links
     
       * Reference links