In an OSP project, a circuit can be many things: a service between two points A and Z on a map, an MPLS connection going over […]

Circuits in Fiber Plant Documentation

In an OSP project, a circuit can be many things: a service between two points A and Z on a map, an MPLS connection going over […]

outside plant infrastructure showing connections in a city

In an OSP project, a circuit can be many things: a service between two points A and Z on a map, an MPLS connection going over fiber, or really — any logical relationship between points that uses physical resources of the network. One thing is quite consistent in fiber plant layouts, however: circuits traverse from A to Z, over strands that are inside cables (probably in some conduit) and through several hops…and there can be thousands of them.

In past versions of netTerrain, users created circuits as simple links between two nodes. This is possible to do in OSP projects as well, but not very practical. Traditional netTerrain links are not always well suited for this type of behavior. Therefore, in version 8 we have created a specific entity called ‘circuits’, perfectly optimized for fiber plant projects.

Some of the advantages of using this type of entity to represent your OSP circuits over a traditional link are as follows:

  • Easy mapping of circuit to strand without having to individually bundle each hop
  • Smart algorithm to find the optimal path between two endpoints
  • Automatic patching of circuits along its path
  • Automatic reservation of resources
  • Convenient menu options to create a diverse and redundant circuit from an existing one
  • Dedicated circuit views and searches
  • Better performance

Components of a circuit

A netTerrain circuit consists of the following:

  • A name
  • Properties
  • One or more paths
  • Physical infrastructure to support it

The name and the properties are obvious: we have dealt with this for every other object category in netTerrain: the name is whatever you want it to be and the properties are whatever custom fields were defined in the catalog. A power-user can define as many custom properties for circuits as needed.

The paths are the different routes that a circuit can take. And as the wording suggests, you can have more than one path for a circuit. We allow this because you may want to have a main and a secondary (possibly diverse or redundant) route. If a circuit has more than one path, the endpoints always coincide. We will review paths in more detail later.

The physical infrastructure needed for the circuit are the strand (or pair of strands) used for each path and the circuit end ports.

Anatomy of a circuit path

Before digging deeper into the process of creating a circuit, we’ll spend a few lines talking about paths. As we mentioned above paths are the different routes that a circuit can take, but what exactly are these paths? For starters, a path must already exist before we use them in a circuit. Second, paths manifest themselves as routes on a map, which implies that for a path to exist, it needs to be associated as routes throughout nodes laid out on a map (as displayed below).

Two paths to get from one point to another

When discussing paths, you may run into the following concepts:

  • Main path: this typically refers to the first path created for a circuit, usually the shortest route between the endpoints
  • Secondary path: usually refers to a path created for a circuit that already has a main path, which is typically diverse or redundant
  • Diverse path: a secondary path that has no common elements between the main path, except, of course, for the endpoints
  • Redundant path: a secondary path that traverses the same hops on the map as the main path


In the picture above, notice that the highlighted top path to get from building A. Alber to E. Bmore traverses through Orleans and Orleans2. These are intermediate hops. The top path has 3 hops to get from A to Z, the bottom path only 1, as it is a direct path.

In short, hops are the all the number of jumps on a map going from node to node, to make the trip from A to Z. When choosing an optimum path between A and Z netTerrain tries to minimize the number of hops.

So, when creating a new circuit who decides which path it should take and how is that accomplished? There are basically three ways to define a path for a circuit:

  • By selecting the path on the map manually
  • By having netTerrain choose the shortest path between the endpoints
  • By having netTerrain choose the shortest path and then modifying it

In a subsequent blog, we will review all the different ways of creating a circuit (now that we know the different types of paths that can comprise it).

Jan Durnhofer
Jan Durnhofer
As CEO / Product and Engineering Manager, Jan joined Graphical Networks with the purpose of creating the most advanced DCIM and IT visualization company in the market.

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