Network planning is a technique that is helpful in planning, scheduling, and controlling the projects that consists of many interrelated activities. Two network planning techniques are developed in 1950’s they are..

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1. Program evaluation and review technique (PERT)
2. Critical path method (CPM)

CPM is akin to PERT; it was developed independently by Du Pont Company in the US to solve scheduling problems. CPM is primarily concerned with cost and time. It has been applied in many projects, Research and development program, starting a new venture etc. The common characteristics of PERT and CPM techniques are,

1. The project can be broken down into well-defined set of jobs or activities.
2. The activities must be performed in a certain sequence.
3. Within a defined s sequence the activity should be started and stopped.

Other forms of network planning network-planning techniques have been developed since then they are..

1. Precedence diagramming method (PDM)
2. Graphical evaluation review technique (GERT)

Network planning techniques are often compared with somewhat familiar tool known as Gantt chart. This is an older planning and scheduling tool, however it remains popular because of its simplicity. The Gantt chart combines two functions planning and scheduling. With the Gantt charts, the scheduling of activities occurs simultaneously with their planning. The person drawing the activity lines or bars must be aware of the interrelationships of the activities that is the activities must be finished before the others start and which activities can be performed concurrently.

One of the major drawbacks of Gantt chart is that it does not graphical display the interrelationship of activities. However, most project management software packages can produce Gantt charts that display the interdependencies among the tasks by connecting arrows. Because planning and scheduling are done simultaneously in the traditional Gantt chart, it is cumbersome to make changes to the plan manually.

Network techniques, on the other hand, separate planning and scheduling functions. A network diagram is the result, or the output, of the planning function and is not drawn to a tome scale. The network diagram is also referred as project graph, which shows activities and events of the project and their logical relationship.

Time Estimation in network diagram:

1. Optimistic time
2. Most likely time
3. Pessimistic time

Network principles: There are different formats used in the drawing the network diagram

1.Activity in the box (AIB)
2.Activity on the arrow (AOA)

Activities have a precedential relationship i.e. they are linked in a precedential order to show which activities must be finished before others can start. AN activity cannot start until all of the preceding activities that are linked to it by arrows are completed.

Preparing a network diagram:

First select the format to be used, next start drawing the activities in their logical precedential order, as the project should progress from initiation to completion. When deciding the sequence in which the activities should be drawn to their logical precedential relationship to one another, you should ask the following questions to be asked regarding each activity.

1. Which activities must be done finished immediately before the other activity starts?
2. Which activities should be run concurrently?
3. Which activities cannot be started until other activity is finished?

Guidelines for drawing detailed network diagram:

1. Activities should be identified for each package
2. Preferable to draw a summary-level network first diagram
3. Level of details should be determined
4. Activities should be no longer estimated duration than the time intervals

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