IMG 1010 - Overview of SNMP

Description:

SNMP (Simple Network Management Protocol) was designed as the standard language to be used by all computers on a network. The SNMP protocol is used by network management systems to communicate with network elements to monitor and control different aspects of the equipment. For SNMP to function in a network there needs to be at least two elements: The SNMP Manager and the SNMP Agent. See descriptions below:

In an SNMP operation, network information is exchanged through messages sent between the Manager and Agent. The Manager uses messages to request operations to be performed on the SNMP agent. The messages sent are GetRequest, GetNextRequest, SetRequest, and GetBulk. The SNMP Agent responds with a GetResponse message. If a specific condition or event occurs the SNMP Agent sends a Trap message to the Manager for viewing. Below are descriptions of messages sent between the Manager and Agent

Each message sent between the SNMP Agent and the SNMP Manager makes reference to a specific object. For example, requesting span status is requesting the status of the object which is a span. These objects have an address or number associated with them. The number is referred to as an OID (Object Identifier). A series of OIDs in a specific area are considered the MIB (Management Information Base). Below is a description of what a MIB is. For more information on how a MIB is identified, see the Topic

An IMG does not support company specific or Enterprise MIBS 

SNMP Basic Information and Definitions

Notable Terms:

NMS: A Network Management Station is a console that monitors and controls SNMP Agents by executing SNMP Manager Applications. To perform NMS functions, high-performance workstation computers that have fast CPUs and extensive disk space are used. A managed network requires at least one NMS workstation to perform SNMP operations.

Enterprise MIB: A proprietary MIB developed by a private company. Users of the MIB will have to design their managers around it. The IMG does not support proprietary MIBS

Entity MIB: A well-defined MIB laid out in RFCs. Users of this MIB will likely already have software in place to handle it.

Get: A type of SNMP message sent from a manager to an agent which requests to know the value of a particular variable on the agent.

NMS: Network Management System. A collection of applications used to monitor and maintain a network. An SNMP manager would be an example of one such application.

Notify: A message sent from an SNMP agent (server) to the set of SNMP managers (clients) that have registered to receive it. The agent expects an acknowledgement from the manager. If it does not receive the acknowledgement within the specified interval, it will resend a number of times.

Community String: The most basic form of SNMP security is the Community String. SNMP Community Strings are like passwords for network elements. Generally, there is one community string which is used for read-only access to an SNMP Agent. The default value for this community string is often "public". Using this community string like a password, the NMS (Network Management System) can retrieve data from network elements. Less often, there is also a read-write community string. The default value for this is often "private". Using this community string, the NMS can actually change MIB variables on a network element.

Object Identifier (OID): An Object Identifier is the identification value of an object that is defined in a MIB. Object identifiers are arranged in a hierarchical tree structure that is compliant with Internet standard and that consists of roots and branches. An object identifier is written as a sequence of sub-identifiers, starting with the tree root, in dotted decimal notation. For example, the IMG branch of the MIB naming tree is expressed as 1.3.6.1.4.1.2754.2.1. (Cantata IMG)/ 1.3.6.1.4.1.3028.6.1.3 (Dialogic)This identifies the IMG and would be the identifier for enterprise MIBS. For more information on OID values see http://www.alvestrand.no/objectid/top.html

SNMP Message Format

Each SNMP message contains the following:

• Version Number

• Community Name (password)

• One or more SNMP PDU's (Protocol Data Units or SNMP messages) 

An SNMP message also contains the following: (All messages other than traps)

• request id

• error status

• error index

• list of OIDs and values

A Trap (alarm) contains the following:

• enterprise

• generic trap id

• specific trap id

• time stamp

• list of OIDs and values

SNMP Diagram of Basic Implementation

The diagram below shows a basic SNMP Implementation, in which there is a packet-switched network that is monitored and maintained by a network administrator. The portal into the network is through an NMS - network management station (or network management system). The NMS is a collection of applications which fall into the following broad categories:

• Configuration management

• Performance management

• Accounting

• Fault management

• Security
  
  

  Open

  

SNMP Implementation on  the IMG

Version:

SNMPv2c: SNMPv2 with community-based security allows for configuration of an agent for authentication, encryption, data access, and trap management. To utilize the SNMPv2c features, one must have an SNMP Manager Application loaded on a PC which supports SNMPv2c. SNMPv2c will monitor DS1, DS3 and Ethernet Interfaces using industry standards MIBs

Get and Trap Commands:

• Can query MIB-II statistics via the "GET" message

• Can direct MIB-II traps to an SNMP Manager

• Can set up the MIB-II variables (Geographic Location, etc) 

IMG Supports:

• Supports (4) SNMP Managers per GCEMS

• Can manage network resources consumed by SNMP by limiting the number of traps. This will limit the amount of packets sent.

• Supports industry standard MIBs. For a list of MIBs supported see link IMG 1010 - Supported MIBs.

• For a list of supported Traps see link IMG 1010 - Supported Traps

Restrictions:

• The IMG does not support the "SET" command in SNMP. Any "SET" commands can be accomplished through the GCEMS ClientView GUI.

• The IMG does not support provisioning with SNMP

• The IMG cannot act as a proxy

• The IMG does not support Proprietary or Enterprise MIBs

Miscellaneous Information:

• The OID for the IMG 1010 is 1.3.6.1.4.1.2754.2.1 (Cantata)

• The OID for the IMG 1004 is 1.3.6.1.4.1.2754.2.3 (Cantata)

• The OID for the IMG 1010 is 1.3.6.1.4.1.3028.6.1.3 (Dialogic)

• The OID for the IMG 1004 is 1.3.6.1.4.1.3028.6.1.5 (Dialogic)

Related Topics:

IMG 1010 - Supported MIBs

IMG 1010 - Supported Traps

IMG 1010 - Configuring SNMP

IMG 1010 - SNMP Agent

IMG 1010 - SNMP Managers

IMG 1010 - SNMP Manager