Today, SNMP is the most popular protocol for managing diverse commercial internetworks, as well as those used in universities and research organizations. SNMP-related standardization activity continues even as vendors develop and release state-of-the-art, SNMP-based management applications. SNMP is a relatively simple protocol, yet its feature set is sufficiently powerful to handle the difficult problems presented when trying to manage todays heterogeneous networks.
Introduction to SNMP
Until the early-to-mid 1990s, the management method used for these two devices depended upon SNMP-compatible management platforms offered by the hardware vendors. They provided remote configuration of the devices, alarm capabilities for minor and major alarms, and network mapping. All provided benefits to network managers who no longer had to configure a device on site or look at the LEDs for alarms. Network management could now be controlled via a centrally located administration package compatible with industry-standard SNMP.
SNMP, in both agents and clients, is based on Management Information Bases (MIBs). MIBs (defined in detail in the section, The Management Information Base) can be standards-based, complying with those written for particular applications to collect statistics or track information on a wide variety of networking activities. These MIBs are publicly available to any manufacturer to incorporate into its products.
Proprietary MIBs are those written by a particular manufacturer to track either specific network anomalies, such as bandwidth utilization, or to track particular device activity, such as packet discards.
These MIBs are the sole property of the manufacturer and might or might not be made available to other companies. MIBs are typically created to make a companys own devices or network management software product more valuable to the end users.
SNMP does have drawbacks, however. Most SNMP capability is embedded in network devices like hubs, routers, FRADs, DSU/CSUs, and switches. These devices primarily pass or route data. Although they can provide snapshots of the network at intervals ranging from five to thirty minutes via SNMP get request. commands issued by the network manager, they have neither the processing power nor the memory capacity to store real-time data for any length of time. This does not enable you to see what is going on in your network 100% of the time; instead, you have to piece together snapshots. If you want to see everything going on, you need to consider adding a device (that is, specialized server or poller) specifically designed to fulfill this requirement. Another way of achieving this it through your Network Management System (NMS), which is discussed in the next section.
Network Management System (NMS)
The Network Management System (also known as the manager) is software that has the capability of operating on one or more workstations. This software can be configured so it can be utilized to manage different portions of a network or multiple managers can manage the same network. The managers requests are transmitted to one or more managed devices on the desired network. These requests are sent via TCP/IP. SNMP is not dependent upon TCP/IP for transport across a network. SNMP has the capability to be transported via numerous other transport mechanisms such as Novells NetWare IPX and various other transport protocols. Though as previously mentioned, this book concentrates on the TCP/IP implementation. You can specifically define the NMS as follows:
An agent is a network management software module that resides in a managed device. It has local knowledge of management information and translates that information into a form compatible with SNMP.
To be a managed device, each device must have firmware in the form of code. This firmware translates the requests from the SNMP manager and responds to these requests. The software, or firmware, not the device itself, is referred to as an agent. It is possible to manage a non-SNMP compatible device, but they must support a proprietary management protocol.