3.
Introduction
Various Simple Network Management Protocol (SNMP)
Application Programmers Interfaces (APIs) exist which allow for the creation of
network management applications. The majority of these APIs provide a large
library of functions which require the programmer to be familiar with the inner
workings of SNMP and SNMP resource management. Most of these APIs are platform
specific, resulting in SNMP code specific to an operating system or network
operating system platform and thus not portable. Application development using
C++ has entered the main stream and with it a rich set of reusable class
libraries are now readily available. What is missing is a standard set of C++ classes
for network management. An
object oriented approach to SNMP network programming provides many benefits
including ease of use, safety, portability and extensibility. SNMP++ offers
power and flexibility which would otherwise be difficult to implement and
manage.
3.1.
What
Is SNMP++?
SNMP++ is a set of C++ classes which
provide SNMP services to a network management application developer. SNMP++ is not an additional layer or
wrapper over existing SNMP engines. SNMP++ utilizes existing SNMP libraries
in a few minimized areas and in doing so is efficient and portable. SNMP++ is not meant to replace other
existing SNMP APIs such as WinSNMP, rather it offers
power and flexibility which would otherwise be difficult to manage and
implement. SNMP++ brings the Object Advantage to network
management programming.
3.2.
Objectives of SNMP++
3.2.1.
Ease
of Use and SNMP++
An Object Oriented (OO) approach to SNMP
programming should be easy to use. After all, this is supposed to be a simple
network management protocol. SNMP++ puts the simple back into SNMP! The
application programmer does not need be concerned with low level SNMP
mechanisms. An OO approach to SNMP encapsulates and hides
the internal mechanisms of SNMP. In regard to ease of use, SNMP++ addresses the
following areas.
3.2.1.1. Provides
an easy-to-use interface into SNMP
A user does not have to be an expert in
SNMP to use SNMP++. Furthermore, a user does not have to be an expert in C++!
For the most part C pointers do not exist in SNMP++. The result is an easy to
use straight forward API.
3.2.1.2.
Provides easy migration to SNMP
version 2
A major goal of SNMP++ has been to develop
an API which scales to SNMP version 2 with minimal impact on code. The SnmpTarget
class makes this possible.
3.2.1.3. Preserves
the flexibility of lower level SNMP programming
A user may want to bypass the OO approach and code directly
to low level SNMP calls.
SNMP++ is fast and efficient. However, there may be instances where the
programmer requires coding directly to a lower level SNMP API.
3.2.1.4. Encourages
programmers to use the full power of C++ without chastising them for not
learning fast enough
A user does not have to be an expert in
C++ to use SNMP++. Basic knowledge
of SNMP is required, but as will be shown, a minimal understanding of C++ is
needed.
3.2.2.
Programming
Safety and SNMP++
Most SNMP APIs require the programmer to
manage a variety of resources. Improper allocation or de-allocation of these
resources can result in corrupted or lost memory. SNMP++ provides safety by managing these
resources automatically. The user
of SNMP++ realizes the benefits of automatic resource and session management.
In regard to programming safety, SNMP++ addresses the following areas.
3.2.2.1. Provides
safe management of SNMP resources
This
includes SNMP structures, sessions, and transport layer management. SNMP classes are designed as Abstract Data
Types ( ADTs) providing data
hiding and the provision of public member functions to inspect or modify hidden instance
variables.
3.2.2.2. Provides
built in error checking, automatic time-out and retry
A user of SNMP++ does not have to be
concerned with providing reliability for an unreliable transport mechanism. A
variety of communications errors can occur including: lost datagrams, duplicated datagrams, and
reordered datagrams. SNMP++ addresses each of these possible
error conditions and provides the user with transparent reliability.
3.2.3.
Portability and SNMP++
A major goal of SNMP++ is to provide a
portable API across a variety of operating systems (
3.2.4.
Extensibility and SNMP++
Extensibility is not a binary function but
rather one of degree. SNMP++ not only can be extended, but can and has been
extended easily. Extensions to SNMP++ include supporting new OS’s, NOS’s , network management platforms, protocols, supporting SNMP version 2, and adding
new features. Through C++ class derivation, users of SNMP++ can inherit what
they like and overload what they wish to redefine.
3.2.4.1.
Overloading SNMP++ Base Classes
The application programmer may subclass
the base SNMP++ classes
to provide specialized behavior and attributes. This theme is
central to object orientation. The base classes of SNMP++ are meant to be
generic and do not contain any vendor specific data structures or behavior. New
attributes can be easily added through C++ sub-classing and virtual member
function redefinition.