Documentation forSolarWinds Platform

IT management data types

This topic applies to all SolarWinds Platform products.

Data is passed from managed devices to a Network Management System (NMS), such as NPM, as a stream of bits that are assembled into frames, packets and Protocol Data Units (PDUs). The exact method of decoding the bit streams to IT management data is beyond the scope of this paper. What is important here is to understand some of the properties of the data types. This will help you understand how the data can be used and some inherent limitations.

Below is a list of the most common data types used in network management.

Data Type

Properties

Counter

A 32 or 64-bit positive number with the maximum value depending on the bit size. (232-1 or 264 -1). Counters increase in size until they reach their bit limit when they begin counting again at zero plus the remainder of the last counter update. This is known as counter rollover. Counters are used to count bits transmitted or received as well as other similar data. Example: an automobile’s odometer.

Gauge

A 32-bit number which may increase or decrease in value but not exceed 232-1. Gauges are used for data that varies upward and downward often, such as CPU load, but can also be used for static information like interface speed. Example: an automobile’s tachometer.

Integer

A 32-bit number typically used to indicate an object state, such as 1=up, 2=down, 3=unknown.

IP Address

32-bit dotted decimal for IPv4 or 128-bit hexadecimal for IPv6 indicating the IP address of a node.

Network Address

32-bit dotted decimal for IPv4 or 128 bit-hexadecimal for IPv6 indicating a network or subnet.

Object Identifier

Dotted decimal string indicating a position within a MIB.

Octet Strings

Byte strings used to indicate text or layer 2 addresses.

Time ticks

A 32-bit number used to measure time in 1/100ths of a second.

Raw vs. cooked data

Some data is displayed as raw, unaltered data. A CPU gauge is a good example, displaying in the same value as was collected. For other data types, displaying raw data would be of little use.

For example, the number of bytes received on an interface is raw, counter data. In a polling cycle the NMS might receive a number such as 456723. All this number means is that since the interface counter was reset, or possibly rolled over, 456723 bytes of data passed through the interface. Displaying this data as– is using a gauge would be meaningless. This data must be processed before it can be shown as useful information. The result is sometimes known as cooked data. It is common to use both raw and coked data in IT management.

The below table shows how polled interface utilization data is cooked into useful information.

Poll Time

(Seconds)

Raw, Absolute

Raw Polled Data

(Agent Counter Octets)

Raw, Absolute

Data Delta

(This poll minus last) Cooked, Absolute

x8

(Bytes to bits)

Cooked, Absolute

Bits per second

Cooked, Relative

Percent Utilization

(1.544 Mbps)

Cooked, Relative

0

2156

Null

Null

Null

Null

540

175769

173613

1388904

2572

0.17

1080

3287098

3111329

24890632

46094

2.99

1620

8760987

5473889

43791112

81095

5.25

2160

68734870

59973883

479791064

888502

57.55

2700

98965567

30230697

241845576

447862

29.01

3240

200159898

101194331

809554648

1499175

97.10

3780

265159898

65000000

520000000

962963

62.37

4320

265329899

170001

1360008

2519

0.16

 

As shown in the table, raw data goes through four operations before it is readily usable information, the percent utilization of the T-1 interface.

Absolute vs. relative data

The above table contains two data types that are commonly confused with one another. The first four columns contain absolute data. In column three, the numbers are a result of subtracting a counter number from the latest counter number. The result is still an absolute count. The multiplication by 8 to convert units does not change the fact the data is just a count, and still absolute. The next calculation to bits per second creates a rate, which is relative data. Once data is relative, it remains relative unless the operation that converted it is reversed. In the last column, Percent Utilization, the data is relative.