r to implement in interactive multimedia applications even though both encryption and decryption introduce latency. The H.323 standards family specifies security and encryption with the H.235 standard. IPSec (IP Security) is a framework of open standards that eases interoperable establishment of secure private communications over networks. IPSec does this by establishing a virtual private network (VPN). A VPN session is one in which packets are encrypted before leaving the sender's system in such a way as to make them illegible until the desired recipient unencrypts them. IPSec is a security standard that operates at the network or packet-processing layer, rather than at the application layer as does approaches such as SSL (Secure Sockets Layer). IPSec is a standard for implementing virtual private networks between networks or between users and networks. IPSec requires installation of a client, but no other significant changes to an individual user's computers. IPSec defines Transport Mode and Tunnel Mode. Transport Mode protects only the (TCP, UDP, or ICMP) payload. Tunnel Mode Protects both the payload and the IP header. The elements of IPSec include the Authentication Header (AH), for source authentication, and Encapsulating Security Payload (ESP), for both source authentication and data encryption. Associated information is placed into the packet in a header that immediately follows the IP packet header. IPSec, in itself, does not provide security association, key distribution, or key management. It orchestrates multiple other protocols such as Internet Key Exchange (IKE, RFC 2409) which, in turn, relies upon ISAKMP for security association and key management and Oakley for key exchange (Oakley is based upon Diffie-Hellman key agreement protocol). IPSec can also be used in conjunction with a variety of encryption algorithms, including AES. Intent to standardize upon a cipher that will remain secure for the foreseeable future, NIST selected the Advanced Encryption Standard (based on the Rijndael algorithm, inv