Areas of Measurement


OpenNMS? daemons: Concurrent management tasks
OpenNMS?'s monitoring, control, and data collection features are handled by a set of concurrent tasks called daemons (BSD UNIX conventions). Table 1 is a compilation of these concurrent management tasks, which are also depicted in Figure 2.

Table 1. Concurrent management tasks in OpenNMS?

Concurrent TaskName of daemonDescription
Action daemonactiondAuto-action execution facility, for automated action (workflow) based on incoming events.
Collection daemoncollectdCollects data from managed nodes.
Capability daemoncapsdPerforms capability check on discovered nodes. It typically checks the ports of an interface for support of known service protocols.
DHCP daemondhcpdProvides DHCP client functionality for OpenNMS?.
Discovery daemondiscoveryProvides initial and ongoing regular discovery of managed network nodes.
Events manager daemon eventdManages and stores (into RDBMS) events originating from other concurrent tasks
Notification daemonnotifdPerforms external notification to users.
Outage manager daemonoutagedConsolidates events to provide an ongoing historical outage view to each managed node/service.
Poller daemonpollerdPolls managed nodes/services regularly to determine operational status.
RTC manager daemonrtcdCollects data in real time to provide availability information for user-defined categories of managed nodes/services.
SNMP trap daemontrapdHandles SNMP traps (events).
Threshold service daemonthreshdMonitors managed nodes/services based on attribute values reaching specified thresholds.

Network Mask vs. Prefix -----------------------------

This page has a good explanation of both of these measures. http://www.gadgetwiz.com/network/netmask.html

Netmask v. Address Prefix length


Netmask v. Address Prefix Length

Two notations are used to specify subnets: Netmask and Address Prefix Length:

   192.168.0.0/255.255.255.248  (Netmask)
   192.168.0.0/29 (Address Prefix Length)

Both are regularly used around the network. The Netmask specifies a bit pattern that indicates the number of bits available for a particular network. For a netmask, the number of 0's indicate the number of hosts within a given network range.

For instance, the above netmask of 255.255.255.248 (the same as 192.168.0.0/29) looks like this in binary:

11111111111111111111111111111000

That would be 29 1's followed by three 0's. The three 0's are hosts available to that particular subnet. In this example, three zeros would indicate 8 possible host since three binary digits correspond to 0-7 (including 0, there are eight possible numbers).

A simple way to think about this (in fact, the way netmasks were designed) is to mask an IP address with the netmask. If we masked (top and bottom are both 1) 192.168.0.29 (11000000 10101000 00000000 00011101), we would wind up with the 192.168.0.24:

11000000 10101000 00000000 00011101 (192.168.0.29)
 11111111 11111111 11111111 11111000 (255.255.255.248)
-------------------------------------
 11000000 10101000 00000000 00011000 (192.168.0.24)

This means that 192.168.0.29/29 is on the 192.168.0.24 subnet and that there are 8 hosts (24-31) available.

Netmasks are only counted as the number of zeros from the right; there are no zeros in the middle of a netmask. After all, a netmask like 255.255.255.250 (...11111010) wouldn't make much sense since it would refer to a range including only odd ip addresses. It wouldn't be a range at all! Consequently, there are only a few valid network masks. Each specify a number half the size of the prior netmask:

0 - 256 Hosts or Subnets
128 - 128 Hosts or Subnets
192 - 64 Hosts or Subnets
224 - 32 Hosts or Subnets
240 - 16 Hosts or Subnets
248 - 8 Hosts or Subnets
252 - 4 Hosts or Subnets
254 - 2 Hosts or Subnets
255 - 1 Host or Subnet

Netmask / Address Prefix Conversions

Netmask Address Prefix Length Hosts / Class C's / Class B's / Class A's
255.255.255.255 /32 1
255.255.255.254 /31 2
255.255.255.252 /30 4
255.255.255.248 /29 8
255.255.255.240 /28 16
255.255.255.224 /27 32
255.255.255.192 /26 64
255.255.255.128 /25 128
255.255.255.0 /24 (Class C) 256 / 1
255.255.254.0 /23 512 / 2
255.255.252.0 /22 1,024 / 4
255.255.248.0 /21 2,048 / 8
255.255.240.0 /20 4,096 / 16
255.255.224.0 /19 8,192 / 32
255.255.192.0 /18 16,384 / 64
255.255.128.0 /17 32,768 / 128
255.255.0.0 /16 (Class B) 65,536 / 256 / 1
255.254.0.0 /15 131,072 / 512 / 2
255.252.0.0 /14 262,144 / 1024 / 4
255.248.0.0 /13 524,288 / 2048 / 8
255.240.0.0 /12 1,048,576 / 4096 / 16
255.224.0.0 /11 2,097,152 / 8129 / 32
255.192.0.0 /10 4,194,304 / 16,384 / 64
255.128.0.0 /9 8,388,608 / 32,768 / 128
255.0.0.0 /8 (Class A) 16,777,216 / 65,536 / 256 / 1
254.0.0.0 /7 33,554,432 / 131,072 / 512 / 2
252.0.0.0 /6 67,108,864 / 262,144 / 1,024 / 4
248.0.0.0 /5 134,217,728 / 524,288 / 2,048 / 8
240.0.0.0 /4 268,435,456 / 1,048,576 / 4,096 / 16
224.0.0.0 /3 536,870,912 / 2,097,152 / 8,192 / 32
192.0.0.0 /2 1,073,741,824 / 4,194,304 / 16,384 / 64
128.0.0.0 /1 2,147,483,648 / 8,388,608 / 32,768 / 128
0.0.0.0 /0 (The Internet) 4,294,967,296 / 16,777,216 / 65,536 / 256







/etc/exports and Address Prefix Length

/etc/exports does not use the the Address Prefix length. In fact, nfs will interpret the /29 above as a 0.0.0.29 netmask. So much for security!


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