The main purpose of phase 1 is to establish a secure connection and authenticate peers. Internet Key Exchange (IKE) is the protocol used to set up a secure authenticated communication between peers NAT Traversal is used to overcome NAT, since ESP doesn’t support NAT, the technology adds a fake UDP port 4500 header on each IPsec packet
Data Integrity – via hashing (method that guarantees the data was not changed).
IPsec (IP Security) – is a secure network protocol suite that is used for authentication and encryption over the Internet Protocol (3rd Layer of the OSI model). There are different ways how these functions can be done, but we are going to be exploring IPsec. A session key is generated, which is used for encryption and decryption of the traffic.Peers agree on what protocols will be used for encryption, what subnets will be used etc.Peers have to authenticate each other to make sure the encrypted traffic is sent to a proper destination.There are main stages how VPN session is being established. When you are setting up client-to-site connection, you define an encryption domain on one side, and define clients that will have access to these encryption domains. If we are connecting a remote user to access corporate resources, that type of connection is called client-to-siteĭevices that are performing encryption and decryption are called peers.Īn administrator defines an Encryption domain (hosts, networks and other objects that have to go to the VPN tunnel). If we are connecting a whole site to another site, that type of connection is called site-to-site. VPN connection is also private, thus the traffic should be encrypted. VPN (Virtual Private Network) – is a logical connection designed to interconnect networks that are physically not in the same location. Therefore, in today’s post I want to discuss the following topics
CHECK POINT VPN UDP ISSUES SOFTWARE
I have been working as a Technical Support for Check Point Software Technologies in a VPN team. I want to share some of my expertise that might be helpful. While this document focuses on Check Point feature implementation for VPN, more general information can be found at RFC 4459 (and RFC 2923).My name is Evgenii, and I have been working with networking products for years. The peer Security Gateway reassembles the ESP packets and decrypts them while the inner packet is intact.įragmentation and reassembly are considered to cause CPU and bandwidth overhead. Therefore, when the Security Gateway receives a packet from an internal Host, which fits the MTU of the external interface, but would exceed that MTU upon encryption, the Security Gateway encapsulates it and fragments the big outer ESP packet in order to fit into the external interface's MTU. However, in practice, the external interface will usually be a regular Ethernet interface supporting up to 1500 bytes MTU (sometimes even less, e.g., PPPoE on the Security Gateway, or on the next hop router). If the link of the external interface of a Security Gateway - on which the encapsulated packets will be transmitted - would have MTU large enough to compensate for the encapsulation overhead, then the encapsulated big packets will be forwarded, and there would be no fragmentation issues. MTU on the path may be lower (due to the tunnel overhead), than what is configured on their local interfaces (usually client and server will have Ethernet interface with MTU of 1500 bytes). The issue occurs when the server or the client send relatively big packets as they are not aware of the MTU on the path. When tunneling IP packets, there is an inherent MTU and fragmentation issue.
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