SNMP

Used for acquiring the status and usage of nodes, links, and services over time.

Used for obtaining:

Used for estimating, characterizing, and predicting:

Data flow performance.
- Packet losses and (by indirect inference) delay/jitter at nodes.
- Allows to obtain information about current and future service performance.
Nodes performance.
- Memory/CPU usage, number of processes, etc...
- Allows to detect points of failure, service degradation nodes, and unstable nodes.
Network link usage.
- Ingress/egress bytes and packet counts.
- Allows to perform optimizations in terms of routing (load balancing), link upgrade, and introduction of redundancy.
Data/flow routing.
- At Layer 2, Layer 3, and MPLS levels.
- Allows to understand how data flows and how may react to disruptive events.

Basic Components

An SNMP-managed network consists of three key components:

A network node that contains an SNMP agent.
Collect and store management information and make this information available using SNMP.
Can be routers and access servers, switches and bridges, hubs, computer hosts, or printers.

Executes applications that monitor and control managed devices.
Provide the bulk of the processing and memory resources required for network management.
One or more NMSs must exist on any managed network.

In SNMPv3 get operations are performed using authentication and encryption.

SNMP provides the following five basic operations:

Request sent by the NMS to the agent to retrieve one or more values from the agent.

Request sent by the NMS to retrieve the value of the next OID in the tree.

Request sent by the NMS to the agent to set one or more values of the agent.

Response sent by the agent to the NMS.

Unsolicited response sent by the agent to notify the NMS of the events that occurred.

An SNMP MIB module is a specification of management information on a device.

The SMI represents the MIB database structure in a tree form with conceptual tables, where each managed resource is represented by an object.

Object Identifiers (OIDs) uniquely identify or name MIB variables in the tree.

An ordered sequence of non-negative integers written left to right, containing at least two elements.
For easier human interaction, string-valued names also identify the OIDs.
- MIB-II (object ID 1.3.6.1.2.1).
- Cisco private MIB (object ID 1.3.6.1.4.1.9).

The MIB tree is extensible with new standard MIB modules or by experimental and private branches.

Vendors can define their own private branches to include instances of their own products.

To nominate all possible objects (protocols, data, etc.) it is used an ISO Object Identifier (OID) tree:

Management Information Base (MIB): set of managed objects, used to define information from equipment, and created by the manufacturer.

Example: UDP module.

Interface characteristics, configurations, status, and stats:

Nodes management information (description, general information, CPU/memory status, etc...):

SNMPv2-SMI and ENTITY-MIB.
Vendor specific: CISCO-SMI, JUNIPER-SMI, etc...
Cisco extra: CISCO-PROCESS-MIB, CISCO-FLASH-MIB, CISCO-ENVMON-MIB, CISCO-IMAGE-MIB, etc...

Node routing and traffic engineering: