SNMPv1 : Five operations/PDU: GET-RESPONSE, GET-NEXT, GET-request, SET, TRAP. Security: Community based. (No authentication no privacy) SNMP Community strings are not encrypted(clear-text) in v1 & v2c. Community string will be easily identified by packet sniffer. SNMPv2c : Two new operations/PDU – GET-BULK(efficient retrieval of multiple OIDs), informs (trap + ACK mech.), plus 64-bit object support. Security: Community based. (No authentication no privacy) SNMP Community strings are not encrypted(clear-text) in v1 & v2c. Community string will be easily identified by packet sniffer. SNMP v3: PDUs: Includes all the v1&v2c pdu's. Security: New architecture including security functionality; authentication (SHA, MD5), privacy (encryption - DES, 3DES, AES). Uses Authentication(MD5 or SHA). Encryption using CBC-DES(Adds DES 56-Bit Encryption in Addition to Authentication Based on DES-56).