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Table Of Contents  The TCP/IP Guide
 9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)
      9  TCP/IP Network Configuration and Management Protocols (BOOTP, DHCP, SNMP and RMON)
           9  TCP/IP Network Management Framework and Protocols (SNMP and RMON)
                9  TCP/IP Simple Network Management Protocol (SNMP) Protocol
                     9  SNMP Protocol Operations

Previous Topic/Section
SNMP Protocol Information Notification Using Trap(v2) and InformRequest Messages
Previous Page
Pages in Current Topic/Section
12
3
Next Page
SNMP Protocol Messaging and Message Formats
Next Topic/Section

SNMP Protocol Security Issues and Methods
(Page 3 of 3)

SNMPv2/v3 Security Methods

During the “evolution” of SNMPv2 variants, and eventually the creation of SNMPv3, several new security models were created to improve upon SNMPv1's security:

  • Party-Based Security Model: This was the security model for the original SNMPv2 standard, now called SNMPv2p. A logical entity called a party is defined for communication that specifies a particular authentication protocol and a privacy (encryption) protocol. The information is used to verify that a particular request is authentic, and to ensure that the sender and receiver agree on how to encrypt and decrypt data.

  • User-Based Security Model (USM): This was developed in the SNMPv2u variant and used in SNMPv2* (SNMPv2 asterisk); it eventually was adopted in SNMPv3. The idea here is to move away from tying security to the machines and instead use more traditional security based on access rights of a user of a machine. A variety of authentication and encryption protocols can be used to ensure access rights are respected and to protect message privacy. The method relies on time stamps, clock synchronization and other techniques to protect against certain types of attacks.

  • View-Based Access Control Model (VACM): VACM is part of SNMPv3, and defines a method where more fine control can be placed on access to objects on a device. A view specifies a particular set of MIB objects that can be accessed by a particular group in a particular context. By controlling these views an administrator can manage what information is accessed by whom.

These descriptions are “grossly simplified”, to say the least. Security is probably the most complicated subtopic in networking, and describing these methods in detail would require dozens and dozens of topics. You can refer to the relevant standards if you want more information, though unless you are well-read on security topics, you will likely not be able to make heads or tails out of what is written in them.

Use of SNMP Security Methods

Party-based security pretty much died with SNMPv2p; USM and VACM are part of SNMPv3 and provide enhanced security for those who need it (though again, it's interesting to note how many networks continue to use SNMPv1, security warts and all.) SNMPv3 took another important security-related step in redefining the SNMP architecture to seamlessly support multiple security models. This enables different implementations to choose the security model that is best for them. USM is the default model in SNMPv3.

 


Previous Topic/Section
SNMP Protocol Information Notification Using Trap(v2) and InformRequest Messages
Previous Page
Pages in Current Topic/Section
12
3
Next Page
SNMP Protocol Messaging and Message Formats
Next Topic/Section

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Version 3.0 - Version Date: September 20, 2005

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