This MIB modules defines objects that describe common aspects
of IP address pools.

IP Address Pool Manager
=======================
The IP address pool manager consists of the software that
maintains IP address pools and supports the
following capabilities:

    - Create an IP address pool group.

    - Destroy an IP address pool group.

    - Create an IP address pool and add it to an IP address
      pool group.

    - Remove an IP address pool from an IP address pool group
      and destroy it.

    - Create a range of IP addresses and add it to an IP
      address pool.

    - Remove a range of IP addresses from an IP address pool and
      destroy it.

    - Allocate an IP address from an IP address pool.

    - Return a previously allocated IP address to the IP address
      pool that it was allocated from.

    - Create a set of IP prefixes and adding it to an IP address
      pool.

    - Remove a set of IP prefixes from an IP address pool and
      destroy it.

    - Allocate an IP prefix from an IP address pool.

    - Return a previously allocated IP prefix to the IP address
      pool that it was allocated from.

IP Address Pool
===============
An IP address pool consists of a collection of IP addresses from
which a client (e.g., PPP or DHCP) can allocate an IP address
for the purpose of assigning it to a remote peer.  This
collection consists of a one or more range of IP addresses.

Observe that human interfaces allow a user to specify ranges of
IP addresses using a variety of means to simplify the process.
For example, a human interface may simply allow a user to
specify a subnet.  No matter what abstraction a human interface
employs, the end result is always one or more range of IP
addresses.  Thus, this MIB module abstracts an IP address pool
as one or more range of IP addresses.  This places the burden on
any application employing other abstractions to transform to the
abstraction defined by this MIB module.

Alternatively, an IP address pool can also consist of a
collection of IP prefixes from which a client can allocate an IP
prefix for the purpose of assigning it to a remote peer.  This
collection consists of one or more set of IP prefixes.  Observe
that the term 'IP prefix' here can refer to an IPv4 subnet or an
IPv6 prefix.

IP Address Pool Group
=====================
An IP address pool group contains the IP address pools belonging
to the same administrative domain.  Examples of administrative
domains include a Virtual Route Forwarding (VRF) instance and a
Virtual Private Network (VPN).  Observe that the IP addresses
contained by the IP address pools in two distinct IP address
pool groups may overlap.

IP Address Pool Threshold Monitoring
====================================
An IP address pool manager maintains a number of gauges for the
purpose of monitoring the number of allocated IP addresses.  We
refer to these gauges as 'in-use gauges'.

Each in-use gauge has a corresponding state that can have one of
two values:

1)  Off

    The IP address pool manager monitors the number of allocated
    addresses or prefixes.  If this value is greater than or
    equal to the configured rising threshold and the previous
    value was less than the same rising threshold, then the IP
    address manager transitions the state to 'On'.

2)  On

    The IP address pool manager monitors the number of allocated
    addresses or prefixes.  If the value is less than or equal
    to the configured falling threshold and the previous value
    was greater than the same falling threshold, then the IP
    address manager transitions the state to 'Off'.

Observe that while the values of the configured rising and
falling thresholds may be the same, this may result in
undesirable behavior (i.e., the IP address pool manager may
generate more threshold crossing notifications than desirable).

The IP address pool manager only generates threshold crossing
notifications when it transitions the corresponding state of an
in-use gauge and the value of ciapSystemNotifyEnable is 'true'.

The IP address pool manager may maintain in-use gauges for the
following:

    - A range of IP addresses comprising an IP address pool

    - A set of IP prefixes comprising an IP address pool

    - An IP address pool

    - An IP address pool group

Observe that the IP address pool manager must initialize the
state of each in-use gauge to 'Off' for threshold monitoring to
operate in the prescribed manner.