Measurement Job Types are top-level descriptions of what the Netsight system can measure. The Type of a Measurement Job determines what quantities it measures, and what method it uses to make the measurement. There are several categories of measurement job type in Netsight.
The Network Time Protocol (NTP) is a method for keeping clocks synchronised. A packet is sent from a source interface to a target interface. It returns with the time it was sent from the source, the time the target received it and the time the target sent the response. This allows you to calculate a round-trip time for the packet. From these data you can calculate the offset of the target interface clock with respect to the source Interface clock, taking the round-trip time into account. Netsight then stores this offset as a time series. You can thus use the Netsight NTP Job Type to check whether components in the network have their clocks synchronised, and take appropriate action if an excessive offset is noted.
The Internet Control Message Protocol (ICMP) Echo job type — more commonly known as "Ping" — sends a simple request packet to a target and looks for a response. The result of a ping is the time taken for a complete packet round trip: its round-trip time (RTT). Not all target nodes will respond to pings, depending on their configuration. However, in cases when you are sure a ping response would be expected, the absence of a response can itself be used to measure network availability (the ping request will time out after 5 seconds). Otherwise the RTT can be a useful measure of the performance of the network.
Netsight ping jobs send several packets in a measurement interval to take two different measurements. Firstly the average of the trip times from all the pings in the interval is calculated and becomes the round-trip time datum for that interval. Secondly, Netsight calculates the percentage of the packets that returned before the timeout for that packet. This datum is the Ping Response. Ping Response is the data type used for calculating Traffic Light statuses.
SNMP data collection focuses on retrieving data going across an interface in either direction. Netsight uses a data gatherer to send packets of the correct type to the target router, which the router interprets and returns a result to you. This system allows you to read almost any data regarding the state of the router and the traffic travelling across its interfaces. SNMP Job Types include a list of OIDs (object IDs), which address the required variables, interrogate them, and return their value to you.
In theory you can gather any data that you have an OID for with an SNMP Job Type. In some cases the data type of the returned value is important, as Netsight may need to carry out some manipulation of the returned data. For this reason, only a limited range of OIDs are acceptable in a Netsight Measurement Job Type. Netsight does however, allow for configuration of new Job Types that gather data for OIDs that can be handled.
An important type of SNMP job that is built into Netsight is for traffic monitoring. This measures the number of bytes entering and leaving an interface, and optionally the number of discarded packets or packets in error the router has received or been sent. These data are displayed on graphs in terms of the rate at which data is crossing the interface.
Cisco IP-SLA is a functionality set which sits on most Cisco routers. It allows you to configure the router to pro-actively monitor connections from it to other routers. It differs from simple SNMP reads of data travelling through the device since with IP-SLA the router creates traffic specifically to take measurements.
IP-SLA Jobs are set up on the target Node, and the operation will then run for the specified lifetime, collecting statistics. Netsight then lifts these statistics from the router and saves them to the database. As with SNMP, you request the data you want to gather by specifying Object Ids in the Job Type. Again, you can in theory collect data for any OID that you know, but this must match an SNMP data type the Netsight recognises. Available types are shown when you specify the Job Type.
It is possible to make many more network monitoring measurements using SNMP and IP-SLA, than are possible with the Netsight built in Job Types. Netsight allows System Administrators to define Job Types for some of these measurements, which can then be applied by other Netsight Users when creating Measurement Jobs. See the Job Types Maintenance help page for further details.