Macintosh WATCHER 4.1

Network Performance with SNMP

You can use simple network management protocol (SNMP) to gather detailed information about devices in your network. SNMP lets you make measurements of network traffic, error rates, and overall efficiency.

Making Measurements

To make measurements using SNMP, you request specific types of information from specific devices in your network by assigning management information bases (MIB) to them in the Add AppleTalk SNMP Devices and Add Internet SNMP Devices dialog boxes, and adding them to the main test list. (See the chapter Creating a Device List.)

Each MIB represents a specific kind of information. There are MIBs that provide information on device configuration, traffic level, error rate, and many other aspects of device status and performance. You can monitor any number of MIBs on any device.

For example, you may want to know the level of traffic passing through a gateway. WATCHER queries the device for the appropriate MIB, and the gateway responds with its current traffic level. WATCHER can display the traffic level in the main test list and in graphic form, and record its change across time in a file for later use.

MIB Definitions

WATCHER comes with a library of MIB1 and MIB2 definitions, as well as some private enterprise MIBs that support the most common network equipment. The use of some of these MIB definitions is described here.

Device Status

Use the following MIB to make sure a particular SNMP device is operating:

ï sysDesc system description

If the device is operating, the MIB will return information about the type of device and the software version.

Traffic Measurements

Use the following MIBs to make traffic measurements on many SNMP devices:

ï ifInOctets total octets received from the media

ï ifOutOctets total octets sent on the media

ï ifInUcastPkts unicast packets delivered above

ï ifInNUcastPkts broadcast/multicast packets delivered above

ï ifInDiscards packets discarded due to resource limitations

ï ifInErrors packets discarded due to format errors

ï ifInUnknownProtos packets destined for unknown protocols

ï ifOutUcastPkts unicast packets from above

ï ifOutNUcastPkts broadcast/multicast packets from above

ï ifOutDiscards packets discarded due to resource limitations

ï ifOutErrors packets discarded due to error

Internet Traffic Measurements

Use the following MIBs to make traffic measurements on many Internet SNMP devices:

ï ipInReceives total datagrams from below

ï ipInHdrErrors datagrams discarded due to format errors

ï ipInAddrErrors datagrams discarded due to misdelivery

ï ipForwDatagrams datagrams forwarded

ï ipInUnknownProtos datagrams destined for unknown protocols

ï ipInDiscards datagrams discarded due to resource limits

ï ipInDelivers datagrams delivered above

ï ipOutRequests datagrams from above

ï ipOutNoRoutes datagrams discarded due to no route

SNMP Histograms

WATCHER can show you graphical representations of the information returned by SNMP devices. These representations, called SNMP histograms, show the MIB information collected from SNMP devices over a period of time. An example is shown in Figure 12-1.



Figure 12-1 SNMP histogram

SNMP MIB Threshold dialog box

Use the SNMP MIB Threshold dialog box to start a histogram, to record histogram data, or to display SNMP data in the main test list for a particular SNMP device. Select the device in the main test list and then select SNMP MIB Threshold from the Device menu. The SNMP MIB Threshold dialog box shown in Figure 12-2 appears.



Figure 12-2 SNMP MIB Threshold dialog box

Entering threshold values and conditions

Enter a threshold for an SNMP MIB on a specific device in the Threshold Value field. Select a condition from the Down Condition pop-up menu. When this threshold condition is met, WATCHER shows the device as Down, and provides any attached notifications.

Entering a MIB suffix

Enter a suffix for the MIB. The suffix appears after the MIB value in the main test list, in the MIB data file, and on the histogram. For example, when monitoring traffic on a router, you may want to put a unit of measurement (bits/second) as the suffix.

Starting Histograms

Select Calculate rate/second if you want WATCHER to provide device metrics in the main test list. Select Display histogram if you want a graphical display of the information to be available from the Window menu.

Writing MIB Data to Disk

To begin writing histogram data to a file on your hard drive, select Write MIB data to file. The information in the file will include the MIB name, date, time, the value read, and the suffix you specified. Click OK.

Viewing Histograms

To view an existing histogram for a particular SNMP device, select SNMP Histograms from the Windows menu and drag through to the histogram you want. The window that appears contains bar graphs of the information from each MIB you've selected on that device. To see different graphs, scroll through the window. (See Figure 12-1.)

Histogram viewing options

You can select several color options that may make the histogram display more effective. Select Settings from the File menu and drag through to Histograms Color Options. The dialog box shown in Figure 12-3 appears.



Figure 12-3 Histogram Color Options dialog box

Use this dialog box to select the colors used in histograms for the window and scale, and for the graph under various device states.

Creating Reports

You can use the data WATCHER gathers about SNMP devices to create a variety of graphs and reports. WATCHER can maintain files containing SNMP data snapshots taken at intervals you specify in the Testing Options dialog boxes. The data is tagged with the date and time, and the suffix you entered in the SNMP MIB Thresholds dialog box.

To create a report using SNMP data, perform the following steps:

1. Make sure you have set the testing intervals and MIB suffix, as described earlier.

2. Record histogram data to a file using the SNMP MIB Thresholds dialog box, as described earlier in this chapter.

3. Test the devices for which you want to record data.

4. When enough time has passed to provide the required data, stop testing.

5. Open the data file using a spreadsheet program (for example, Excel).

6. Select the data you want to plot and use the spreadsheet's graphing functions to produce a graph. (Refer to your spreadsheet's user guide for more information.)

The data WATCHER provides can be used to create very informative graphs and charts. An example is shown in Figure 12-4 of router traffic levels, graphed in Excel.



Figure 12-4 WATCHER SNMP data in Excel

SNMP MIBs Editor

You can create your own custom MIB definitions, to serve specific needs or to accommodate specialized SNMP devices or agents. WATCHER includes a MIBs editor that lets you build up a set of MIB objects from a number of different MIB categories. The information you specify is collected from network devices and will be available for use in reports or histograms.

You should be familiar with the SNMP MIB definitions supported by the SNMP device or agent you plan to monitor, and with SNMP as a whole, before using the MIBs editor.

To use the SNMP MIBs editor, select Settings from the File menu and drag through to SNMP MIBs Editor. The SNMP MIBs Editor dialog box appears. (See Figure 12-5.)



Figure 12-5 SNMP MIBs Editor dialog box


The SNMP MIBs editor provides you with the following buttons and functions:

Level

Click on the pop-up menu to change the SNMP hierarchy level you are working on.

Remove

Click Remove to delete the selected MIB definitions.

OK and Cancel

Click OK to save your changes and close the dialog box. Click Cancel to abort your changes and close the dialog box.

Import

Use this option to import all MIBS from the ???.ini file to the drop-down MIB tree.

New

Click New to create a new MIB node or definition. The dialog box shown in Figure 12-6 appears.



Figure 12-6 New MIB dialog box

Enter a name and identifier for the MIB definition, and a short description. Select Information node if the node is an end node (that is, if the node actually contains the requested information).

Go To

Click Go To to jump to another MIB definition elsewhere in the SNMP hierarchy. The dialog box shown in Figure 12-7 appears.



Figure 12-7 SNMP MIBs Editor GoTo dialog box

Enter a name or identifier for the MIB definition you want to edit next. Select either Identifier or Name and specify your preference with the Search from buttons.

Edit

Select a MIB and click Edit to modify existing MIB definitions or create new ones. The dialog box shown in Figure 12-8 appears.



Figure 12-8 SNMP MIBs Editor edit dialog box

You can change the MIB definition name, identifier and description. Click OK to make your changes, or Cancel to abort them.

Community

If you use an SNMP community other than public, click Community. The dialog box shown in Figure 12-9 appears.

You can also get this dialog box from the main test list, by selecting an SNMP device, then selecting SNMP MIB Community from the Device menu.



Figure 12-9 SNMP MIBs Editor community dialog box

Enter a name for your SNMP community. Click OK to make your changes, or Cancel to abort them.

Sequence Editor

You can edit SNMP sequences using the sequence editor available through the SNMP MIBs editor.

To use the sequence editor, click Sequences... in the SNMP MIBs Editor dialog box. The SNMP sequence editor dialog box appears. (See Figure 12-10.)



Figure 12-10 SNMP Sequence Editor dialog box

Editing an Existing Sequence

You can edit existing SNMP sequences using the sequence editor. Select a sequence and click Edit... in the sequence editor dialog box. The Edit Sequence dialog box appears. (See Figure 12-11.)



Figure 12-11 Edit Sequence dialog box

To change the order of a sequence in the list, just click on it and drag it to the new location.

Editing an Existing Object

Click Edit... in the Edit Sequence dialog box to edit existing SNMP objects. The Edit Object dialog box appears. (See Figure 12-12.)



Figure 12-12 Edit Object dialog box

You can change the object name and description, or select a data type from the pop-up menu.

Creating a new object

Click New... in the Edit Sequence dialog box to create new SNMP objects. The Create New Object dialog box appears. (See Figure 12-13.)



Figure 12-13 Create New Object dialog box

Enter a new object name and description, and select a data type from the pop-up menu. Click OK to add the object. Click Cancel to close the dialog box.