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Simple Network Management Protocol

SNMP describes the Structure of network Management Information (SMI) in network devices, and the protocols for accessing (and possibly modifying) such information. In the most common scenario, SNMP is used to monitor network devices (usually, but not always, routers).
 
The key concept in SNMP is the Management Information Base, or MIB. The MIB is formally described using the Abstract Syntax Notation-1 (ASN.1) specification language, and defines all of the information which a nettwork manager would like to measure in the network device.
 
ASN.1 is used to define what the data items are. A companion standard defines a set of Basic Encoding Rules (BER)[1] which detail how an ASN.1 data entity is encoded for transmission across a network service. Note that for our purposes, ASN.1 is a Read-Only Language -- you will not be required to write ASN.1 specifications, but you will be expected to understand (approximately, at least) definitions given in ASN.1.
 
The use of ASN.1 illustrates an interesting aspect of the history of the Internet. It was adopted in the 1980s when it was widely believed that the OSI protocols would eventually replace the TCP/IP protocol set -- that the Internet would eventually be replaced by a global OSI-based network. ASN.1 was developed by the OSI standards groups, and the designers of SNMP wanted their protocol to survive the anticipated migration to OSI. In the end, it never happened, and the use of ASN.1 is simply an interesting historical artifact. Nevertheless, we have to deal with it...
 
[1] In some ASN.1 applications (X.509 certificates in particular), a somewhat "tightened" set of Distinguished Encoding Rules are used, but SNMP uses the original BER, and so shall we! BTW: ASN.1 and BER are International Standards, defined in ISO/IEC 8824:1987 and ISO/IEC 8825:1987
Lecture 21: Network Management #1 Copyright © 2005 P.Scott, La Trobe University Bendigo.


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