The A refers to the certification on theâ¦ Airframe structure, to work on the wings, structure of the Frame or assemblies such as air vents for repairs. The P stands for Power Plant, The Certification repair for an Engine of a craft which also includes the hydraulic system.
Protocols. There are a number of VPN protocols in use that secure the transport of data traffic over a public network infrastructure. Each protocol varies slightly in the way that data is kept secure. IP security (IPSec) is used to secure communications over the Internet. IPSec traffic can use either transport mode or tunneling to encrypt data traffic in a VPN.
In tunnel mode, an IPSec header (AH or ESP header) is inserted between the IP header and the upper layer protocol. Between AH and ESP, ESP is most commonly used in IPSec VPN Tunnel configuration.The packet diagram below illustrates IPSec Tunnel mode with ESP header : ESP is identified in the New IP header with an IP protocol ID of 50.The packet diagram below illustrates IPSec Tunnel mode with AH header :The AH can be applied alone or together with the ESP, when IPSec is in tunnel mode. AHâs job is to protect the entire packet.PSec transport mode is usually used when another tunneling protocol (like GRE) is used to first encapsulate the IP data packet, then IPSec is used to protect the GRE tunnel packets. IPSec protects the GRE tunnel traffic in transport mode.