Ip address of the peer encryption algorithm protocol

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IP address of the peer; encryption algorithm; protocol format (AH or ESP); and security parameter index (SPI), a unique number assigned to each SA and used to manage multiple SAs. Once negotiated, each peer stores the SA parameters locally in a SA database (SAD). The SA is unidirectional, meaning a separate SA is needed for each inbound and outbound connection and bidirectional traffic therefore requires two SAs. IPSec Protocols: AH and ESP AH (Authentication Header) is a format protocol defined in RFC 2402 that provides data authentication, integrity, and nonrepudiation but does not provide data confidentiality. AH adds security to the communication stream by encrypting nonvolatile fields of the IP header and creating a message digest value at origination that can be re-created and compared at the destination. The message digest value is created through the application of a one-way hash of the IP header and data portion of the packet. After that message digest value is created, an encrypted AH header is inserted between the original IP header and data portion of the packet. The encrypted AH header includes the message digest value and authentication information for the packet. The IP packet is then sent to the IPSec peer. The IPSec peer hashes the IP header and data portion of the packet to create a message digest value and compares it to the hash value in the AH header that it has decrypted. If the message digest values match, it ensures that the packet has not been modified in transit. If a packet is determined to have been modified in transit, it is
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