Between two end PCs in a WAN or between a user and a server in the internet, there lies a vast list of equipment such as switchers, routers, firewalls, IDSs, etc., all working 24 hours a day, seven days a week and following various disparate technologies such as Ethernet, WLAN, E1-T1, DSL, SDH, FDDI, ATM, etc.; and, all aimed at ensuring that the end systems or users send and receive their required data without any loss, disruption or hassle.