References

http://www.vpnc.org/vpn-standards.html

http://en.wikipedia.org/wiki/IPsec

http://www.networksorcery.com/enp/protocol/ah.htm

http://www.networksorcery.com/enp/protocol/esp.htm

http://www.cisco.com/go/ipsec

http://en.wikipedia.org/wiki/Public_key_infrastructure

http://searchsecurity.techtarget.com/sDefinition/0,,sid14_gci214299,00.html

http://www.cisco.com/en/US/products/ps6635/products_white_paper0900aecd8034bd59.shtml

http://www.cisco.com/en/US/netsol/ns340/ns394/ns171/ns142/networking_solutions_sub_solution_home.html

http://www.cisco.com/en/US/products/sw/iosswrel/ps5207/products_feature_guide09186a008041faef.html

http://www.cisco.com/go/easyvpn

http://www.cisco.com/en/US/netsol/ns340/ns394/ns171/ns125/networking_solutions_sub_solution_home.html

http://www.cisco.com/en/US/products/ps6659/products_ios_protocol_option_home.html

http://www.cisco.com/en/US/products/ps6635/products_data_sheet09186a00801541d5.html

http://www.cisco.com/en/US/netsol/ns340/ns394/ns171/ns142/netbr09186a00801f0a72.html

http://www.cisco.com/en/US/tech/tk583/tk372/technologies_white_paper0900aecd8029d629.shtml

http://www.cisco.com/en/US/products/ps6635/products_white_paper0900aecd803645b5.shtml