Simple Network Management Protocol

Simple Network Management Protocol (SNMP) is a UDP-based network protocol. It is used mostly in network management systems to monitor network-attached devices for conditions that warrant administrative attention. SNMP is a component of the Internet Protocol Suite as defined by the Internet Engineering Task Force (IETF). It consists of a set of standards for network management, including an application layer protocol, a database schema, and a set of data objects

Control and supervision of modern networks can quickly become a challenging task, especially when handling heterogeneous network topologies. The Interpeak SNMP Agent resolves this by providing a uniform management interface using the industry-standard SNMP protocol.

The SNMP Protocol

Simple Network Management Protocol (SNMP) is one of the standard operations and maintenance protocols for the Internet. SNMP has been a key technology that enabled the Internet's phenomenal growth. This page provides information about this protocol, ranging from beginner's FAQs to the latest industry standard - SNMPv3. 

SNMP

SNMP standards are defined in a series of documents, called request for comments or RFCs, proposed by the Internet Engineering Task Force (IETF). A list of RFCs for SNMPv1, SNMPv2, and SNMPv3 is available. Please note that the IETF has changed the recommended status of SNMPv1 and SNMPv2c to historic. The IETF now recommends using SNMPv3 for internet management.

SNMPv3

SNMPv3 with Security and Administration
Information on SNMP Research's implementations, as well as general SNMPv3 information.
Advanced Protocol Operations
SNMP Research's initiative for product evolution, protocol enhancement, and to align with future industry standards.
Extended Security Options
SNMP Research products beginning with release 16.1 (domestic) support the Triple DES Privacy Protocol and the Advanced Encryption Standard (AES) Privacy Protocol for SNMPv3 privacy.
XML-Based Internet Management
Discover how SNMP Research has been developing solutions to incorporate the Extensible Markup Language (XML) into standards-based network management.

SNMP FAQ

SNMP FAQ (part 1) from comp.protocols.snmp
Beginner to advanced information about SNMP.
SNMP FAQ (part 2) from comp.protocols.snmp
Beginner to advanced information about SNMP.

SNMP Research Activities

The SNMP Research and IETF Activities Web page contains presentations on the Evolution of SNMP (EOS) and on the Status of Internet Management, as well as information about SNMPCONF activities.
Presentations from IM2001 and NANOG 22.

Requests for Comments (RFCs)

List of RFCs from the IETF (Internet Engineering Task Force).

SNMP & Network Web Sites

IETF: The Internet Engineering Task Force posts information on its groups, activities, and current happenings with the status of Internet network management.
Get the IEEE 802™ Program. The IEEE Standards Association and the IEEE 802 Plenary offer the "Get IEEE 802" pilot program, which grants public access to view and download individual electronic (PDF) IEEE Local and Metropolitan Area Network (IEEE 802) standards at no charge.
mibDepot is an online SNMP MIB reference site. A powerful search engine lets you search quickly for any MIB object or SNMP trap. This site includes MIBs from many vendors.
The Simple Times is a quarterly newsletter devoted to the "promotion of the Simple Network Management Protocol. " Each Issue contains technical articles, featured columns, standards, summaries, and a list of Internet resources.
The Simple Web is a Web site created and maintained by the SNMP group at the University of Twente in Holland. This page contains pointers to many sources of information about SNMP and management.
SNMP World is a Web site created and maintained by a group of Network Management Engineers. This page offers information about SNMP and network management.

SNMP Print Literature

Books About SNMP provides a list of books about SNMP technology and enterprise management using SNMP.

SNMP Mailing List

PSINet SNMP mailing list: snmp-request@lists.psi.com.

SNMP Testing Tools

Gambit Communications provides SNMP Agent simulation software.
InterWorking Labs provides a full line of test suite software products.
SimpleSoft provides SNMP agent simulation and automated agent testing software.

Proxy Agent Concepts

Proxy Agent Concepts provides information sheets.

Since its creation in 1988 as a short-term solution to manage elements in the growing Internet and other attached networks, SNMP has achieved widespread acceptance. SNMP was derived from its predecessor SGMP (Simple Gateway Management Protocol) and was intended to be replaced by a solution based on the CMIS/CMIP (Common Management Information Service/Protocol) architecture. This long-term solution, however, never received the widespread acceptance of SNMP.

SNMP is based on the manager/agent model consisting of an SNMP manager, an SNMP agent, a database of management information, managed SNMP devices and the network protocol. The SNMP manager provides the interface between the human network manager and the management system. The SNMP agent provides the interface between the manager and the physical device(s) being managed (see the illustration above).

SNMP is based on the manager/agent model of a network management architecture.

The SNMP manager and agent use an SNMP Management Information Base (MIB) and a relatively small set of commands to exchange information. The SNMP MIB is organized in a tree structure with individual variables, such as point status or description, being represented as leaves on the branches. A long numeric tag or object identifier (OID) is used to distinguish each variable uniquely in the MIB and in SNMP messages.

SNMP uses five basic messages (GET, GET-NEXT, GET-RESPONSE, SET, and TRAP) to communicate between the SNMP manager and the SNMP agent. The GET and GET-NEXT messages allow the manager to request information for a specific variable.

The agent, upon receiving a GET or GET-NEXT message, will issue a GET-RESPONSE message to the SNMP manager with either the information requested or an error indication as to why the request cannot be processed. A SET message allows the SNMP manager to request a change be made to the value of a specific variable in the case of an alarm remote that will operate a relay. The SNMP agent will then respond with a GET-RESPONSE message indicating the change has been made or an error indication as to why the change cannot be made. The SNMP TRAP message allows the agent to spontaneously inform the SNMP manager of an "important" event.

As you can see, most of the messages (GET, GET-NEXT, and SET) are only issued by the SNMP manager. Because the TRAP message is the only message capable of being initiated by an SNMP agent, it is the message used by DPS Remote Telemetry Units (RTUs) to report alarms. This notifies the SNMP manager as soon as an alarm condition occurs, instead of waiting for the SNMP manager to ask.

The small number of commands used is only one of the reasons SNMP is "simple." The other simplifying factor is the SNMP protocol's reliance on an unsupervised or connectionless communication link. This simplicity has led directly to the widespread use of SNMP, specifically in the Internet Network Management Framework. Within this framework, it is considered "robust" because of the independence of the SNMP managers from the agents, e.g. if an SNMP agent fails, the SNMP manager will continue to function, or vice versa. The unsupervised communication link does however create some interesting issues for network alarm monitoring we will discuss more thoroughly in a later issue of our SNMP tutorial.

Each SNMP element manages specific objects with each object having specific characteristics. Each object / characteristic has a unique object identifier (OID) consisting of numbers separated by decimal points (i.e., 1.3.6.1.4.1.2682.1). These object identifiers naturally form a tree as shown below. The MIB associates each OID with a readable label (i.e., dpsRTUAState) and various other parameters related to the object. The MIB then serves as a data dictionary or code book that is used to assemble and interpret SNMP messages.

The branch of the MIB object identifier tree.

When an SNMP manager wants to know the value of an object / characteristic, such as the state of an alarm point, the system name, or the element uptime, it will assemble a GET packet that includes the OID for each object / characteristic of interest. The element receives the request and looks up each OID in its code book (MIB). If the OID is found (the object is managed by the element), a response packet is assembled and sent with the current value of the object / characteristic included. If the OID is not found, a special error response is sent that identifies the unmanaged object.

When an element sends a TRAP packet, it can include OID and value information (bindings) to clarify the event. DPS remote units send a comprehensive set of bindings with each TRAP to maintain traditional telemetry event visibility. Well-designed SNMP managers can use the bindings to correlate and manage the events. SNMP managers will also generally display the readable labels to facilitate user understanding and decision-making.

SNMP is a standard protocol that has wide acceptance in the industry and is flexible enough to describe almost anything. Because of these advantages, many network managers have come to believe that SNMP should be used for all network monitoring applications.

SNMP certainly has its place in an effective telecom network management solution, but this doesn't mean that any off-the-shelf SNMP manager can provide adequate visibility and control of your network.

The typical off-the-shelf SNMP manager is not designed for displaying and processing telemetry data for effective network monitoring, especially for the kind of real-world monitoring tasks network managers most need performed. These capabilities can be added to an SNMP manager, but it usually requires substantial custom software development.