Network Diagram project management Forward Backward pass

Forward and Backward pass in Network Diagram is a very important topic of Software Project Management. In most of the examinations, it is asked by the teachers. So let’s discuss the topic.

What is the critical path?

A critical path is a path with the least amount of slack/float time.

What is a float/slack time?

Float/Slack time is the time that an activity can be delayed without delaying the project.

When we complete the project through a critical path, then it is the longest path as compared to other paths. If any activity is late in the critical path, then it delays all the projects. So we need to take care of a critical path.

Early Finish = Early Start + Duration

Late Start = Late Finish – Duration

Float/Slack Time = Late Start – Early Start


We can draw the network diagram by keeping in the

softtware project management
Figure 1: Predecessor activities and parent activities

In the above figure, A is predecessor of B and C, B is predecessor of D, D is predecessor of G,  C is predecessor of E and F, F is predecessor of H, E is predecessor of G and so on.

Early StartDuration of activity/taskEarly Finish
Late StartDuration of activity/taskLate Finish

forward pass in project software project management
Figure: forward pass in project software project management

In activity A, 0 is the early start time, 3 is the Duration of the activity, and 3 is the Early finish time.

backward pass in software project management
Figure: backward pass in software project management

In activity F, 14 in the Late Start time, 2 is the Duration of activity/task, and 16 is the Late Finish time and so on for each activity is mentioned in the above figure.

Advantages of network diagram

There are many advantages of making the network diagram. Some of the advantages are mentioned below;

  • To identify the potential risks of the given project
  • Documentation for external communication
  • To record and track the progress of the project
  • For Planning the overall structure of the given project
  • For Coordinating with updates
  • For the time estimation of the given project
  • To ease the planning of the given project
  • To ease the organising of the given project
  • To ease the controlling of the given project
  • To sell the project proposal to financial stakeholders of the given project
  • When proposing changes to stakeholders
  • To identify the opportunities
  • To show the progress of the activities according to the Software requirement specification.
  • To identify the dependencies of the activities
  • To elaborate the project workflow

Frequently Asked Question (FAQ)

What is a network diagram used for?
Network Diagrams are a graphical representation of the activities of a given project. In Network Diagram we try to show that how each activity relates with other activities in the given project. Network Diagram represents the sequence of activities.

Why are activities drawn in a serial relationship in a network diagram?
Sequence of activities is very important in network diagram because sequence represent that how much important is the initial activity for some  other activity to perform a task.

What is dummy activity in network diagram?
A Dummy activity is an activity which does not require a time or resource. A Dummy activity is an imaginary activity. We show the dummy in a network diagram to identify the dependence among other operations in the diagram.

Best network diagram software

  1. (FREE)
  2. Microsoft Visio (PAID)
  3. SmartDraw (PAID)
  4. LucidChart (PAID+FREE)
  5. ConceptDraw (PAID)
  6. Creately (PAID+FREE)
  7. Visual Paradigm (PAID)
  8. Edraw (PAID)
  9. Dia Diagram Editor (FREE)
  10. SolarWinds Network Topology Mapper (PAID)
  11. Intermapper (PAID)
  12. Network Notepad (FREE + PAID)
  13. LanTopoLog (FREE)

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