Dell PowerConnect Brocade 300 Fabric OS Administrator's Guide v7.1.0 - Page 233

Management interface security 7 FIGURE 16 Endpoint-to-gateway tunnel configuration RoadWarrior configuration In endpoint-to-endpoint security, packets are encrypted and decrypted by the host which produces or consumes the traffic. In the gateway-to-gateway example, a router on the network encrypts and decrypts the packets on behalf of the hosts on a protected network. A combination of the two is referred to as a RoadWarrior configuration where a host on the Internet requires access to a network through a security gateway that is protecting the network. IP sec protocols IP sec ensures confidentiality, integrity, and authentication using the following protocols: • Authentication Header (AH) • Encapsulating Security Payload (ESP) IP sec protocols protect IP datagram integrity using hash message authentication codes (HMAC). Using hash algorithms with the contents of the IP datagram and a secret key, the IP sec protocols generate this HMAC and add it to the protocol header. The receiver must have access to the secret key in order to decode the hash. IP sec protocols use a sliding window to assist in flow control, The IP sec protocols also use this sliding window to provide protection against replay attacks in which an attacker attempts a denial of service attack by replaying an old sequence of packets. IP sec protocols assign a sequence number to each packet. The recipient accepts each packet only if its sequence number is within the window. It discards older packets. Security associations A security association (SA) is the collection of security parameters and authenticated keys that are negotiated between IP sec peers to protect the IP datagram. A security association database (SADB) is used to store these SAs. Information in these SAs-IP addresses, secret keys, algorithms, and so on-is used by peers to encapsulate and decapsulate the IP sec packets An IP sec security association is a construct that specifies security properties that are recognized by communicating hosts. The properties of the SA are the security protocol (AH or ESP), destination IP address, and Security Parameter Index (SPI) number. SPI is an arbitrary 32-bit value contained in IP sec protocol headers (AH or ESP) and an IP sec SA is unidirectional. Because most communication is peer-to-peer or client-to-server, two SAs must be present to secure traffic in both directions. An SA specifies the IP sec protocol (AH or ESP), the algorithms used for encryption and authentication, and the expiration definitions used in security associations of the traffic. IKE uses Fabric OS Administrator's Guide 233 53-1002745-02