CompTIA Security+ Guide to Network Security Fundamentals (with CertBlaster Printed Access Card) https://www.amazon.com/dp/1305093917/ref=cm_sw_r_cp_apa_i_82SrDb2Y6HMZY
http://www.amazon.com/CompTIA-Security-Guide-Network-Fundamentals/dp/1305093917
Page 6, second bullet from bottom.