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Figure 1: from, accessed 8 February 2007. Figure 2: based on Stallings, W., SNMP, SNMPv2, SNMPv3, and RMON 1 and 2, 3rd edition, May 2001, Addison Wesley; Figures 7 and 8: based on Schneier, B. (1996) Applied Cryptography, 2nd edition, John Wiley & Sons; Figure 9: based on King, T. and Newson, D. (1999) Data Network Engineering, Kluwer; Figure 10: based on Stallings, W (1995) Cryptography and Network Security, Prentice Hall.

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