| Cisco Encryption Technology (CET) encrypts network data through IPSec or Cisco proprietary mechanisms. Network encryption is provided at the IP packet level, meaning that only IP packets can be directly encrypted. If you want to encrypt a network protocol other than IP, then you must encapsulate the protocol within an IP packet. When encrypted, individual IP packets can be detected during transmission, but the IP packet contents, or the payload, cannot be read. Specifically, the IP header and upper-layer protocol headers, such as TCP or UDP, are not encrypted, but all payload data within packet will be encrypted.