... standardas far as IP level security is concerned, the paper describesthe IPsec architecture including its defined security formatsand the related key management procedures. Finally, com-mon IPsec applications ... knownas the Security Association Database (SAD). An entry inthe SAD (i.e., a security association) is uniquely identifiedby a triple consisting of a Security Parameter Index (SPI),an IP Destination ... 8 IP PACKET FROM H1 TO FW1 IP header (src=H1,dst=H2,Protocol=TCP)TCP payloadAH-PROTECTED IP PACKET FROM FW1 TO FW2 IP tunnel header (src=FW1, dst=FW2, Protocol=AH)AH header (Next header =IP) IP...