Mar 30, 2012 · UDP Encapsulated Process for Software Engines Transport Mode and Tunnel Mode ESP Encapsulation After the IPsec packet is encrypted by a hardware accelerator or a software crypto engine, a UDP header and a non-IKE marker (which is 8 bytes in length) are inserted between the original IP header and ESP header.
RFC 3948 UDP Encapsulation of IPsec ESP Packets January 2005 3.Encapsulation and Decapsulation Procedures 3.1.Auxiliary Procedures 3.1.1.Tunnel Mode Decapsulation NAT Procedure When a tunnel mode has been used to transmit packets (see [RFC3715], section 3, criteria "Mode support" and "Telecommuter scenario"), the inner IP header can contain addresses that are not suitable for the current network. The response was that forced UDP encapsulation is only available with the VPN 3000 concentrator. So, on connections from the VPN client to a PIX only the automatic mode is implemented. The alternative in cases where ESP is blocked is to use NAT to (indirectly) enable UDP encapsulation. UDP (User Datagram Protocol) is faster than TCP (Transmission Control Protocol). The Application layer message is encapsulated at the Transport layer . If the protocol used at the Transport Layer is TCP (Transmission Control Protocol) , the data packet is known as " TCP Segment ". NAT-T (NAT traversal or UDP encapsulation) makes sure that IPsec VPN connections stay open when traffic goes through gateways or devices that use NAT. When an IP packet passes through a network address translator device, it is changed in a way that is not compatible with IPsec. UDP encapsulation solves this problem. In practice, UDP encapsulation is used only on ESP packets. A NAT or NAPT can modify the unencrypted IP and UDP headers of a UDP-encapsulated ESP packet without breaking ESP authentication and without being stymied by ESP encryption.
if this UDP encapsulation in not done then the ESP packet will be dropped and data will not flow. well my question is : the ESP packet starts after 9 th packet of quick mode. but the NAT-T is detected and changes the port from udp 500 to 4500 on 5th packet. why is this done on 5th packet, is there any particular reason to do this in 5th packet.
Encapsulation prevents from accessing accidentally, but not intentionally. The private attributes and methods are not really hidden, they’re renamed adding _Car” in the beginning of their name. The method can actually be called using redcar._Car__updateSoftware() Private variables. Class with private variables UDP encapsulation may also be forced, even if no NAT situation is detected, by using the forceencaps and encap options in ipsec.conf and swanctl.conf, respectively. If enabled, the daemon will send a fake NAT_DETECTION_SOURCE_IP notify payload so it looks to the peer as if there is a NAT situation. Generic UDP Encapsulation (Internet-Draft, 2020) Internet Area WG T. Herbert Internet-Draft Quantonium Intended status: Standard track L. Yong Expires April 28, 2020 Independent O. Zia Microsoft October 26, 2019 Generic UDP Encapsulation draft-ietf-intarea-gue-09 Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.
This GRE-in-UDP encapsulation allows the UDP source port field to be used as an entropy field. This may be used for load-balancing of GRE traffic in transit networks using existing Equal-Cost Multipath (ECMP) mechanisms.
if this UDP encapsulation in not done then the ESP packet will be dropped and data will not flow. well my question is : the ESP packet starts after 9 th packet of quick mode. but the NAT-T is detected and changes the port from udp 500 to 4500 on 5th packet. why is this done on 5th packet, is there any particular reason to do this in 5th packet. Encapsulation prevents from accessing accidentally, but not intentionally. The private attributes and methods are not really hidden, they’re renamed adding _Car” in the beginning of their name. The method can actually be called using redcar._Car__updateSoftware() Private variables. Class with private variables UDP encapsulation may also be forced, even if no NAT situation is detected, by using the forceencaps and encap options in ipsec.conf and swanctl.conf, respectively. If enabled, the daemon will send a fake NAT_DETECTION_SOURCE_IP notify payload so it looks to the peer as if there is a NAT situation. Generic UDP Encapsulation (Internet-Draft, 2020) Internet Area WG T. Herbert Internet-Draft Quantonium Intended status: Standard track L. Yong Expires April 28, 2020 Independent O. Zia Microsoft October 26, 2019 Generic UDP Encapsulation draft-ietf-intarea-gue-09 Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.