Since its introduction in 1988, the Simple Network Management Protocol (SNMP) has become the de facto network management protocol on TCP/IP-based networks. The IETF created SNMP to allow remote management of IP-based devices using a standardized set of operations. It is now widely supported by servers, printers, hubs, switches, modems, UPS systems, and, of course, Cisco routers.
The SNMP set of standards defines much more than a communication protocol used for management traffic. The standards also define how management data should be accessed and stored, as well as the entire distributed framework of SNMP agents and servers. The IETF has officially recognized SNMP as a fully standard part of the IP protocol suite. The original SNMP definition is documented in RFC 1157.
In 1993, SNMP Version 2 (SNMPv2) was created to address a number of functional deficiencies that were apparent in the original protocol. The added and improved features included better error handling, larger data counters (64-bit), improved efficiency (get-bulk transfers), confirmed event notifications (informs), and, most notably, security enhancements. Unfortunately, SNMPv2 did not become widely accepted because the IETF was unable to come to a consensus on the SNMP security features.
So a revised edition of SNMPv2 was released in 1996. It is discussed in RFCs 1905, 1906, and 1907 and included all of the proposed enhancements, except for the security facility. The IETF refers to this new version as SNMPv2c, ...