Main Ring 
is a schematic layout algorithm that applies to diagrams that present loops.
This layout algorithm arranges the diagram features around the main ring and hierarchically lays out the subset of diagram features that connect to each diagram junction placed along the main ring.
Barrier flags can be set up on diagram features before executing the Main Ring layout. In this case, the algorithm searches for a main ring that doesn't include any flagged features.
The main ring is the loop formed by the largest number of edges in the network diagram.
If the network diagram contains no loops, the Main Ring layout algorithm execution has no effect.
This layout algorithm is typically used in the telecommunications industry.
The examples below show a diagram before and after applying the Main Ring layout, respectively: 
Apply the Main Ring layout on an active diagram map view
When applying this layout on a network diagram, the following prerequisites must be met:
- Since this operation is transactional, edits must be saved before it is run.
- The input network diagram layer to which the layout applies must be from either a utility network or trace network in a file or mobile geodatabase, or a network diagram service. When working with a utility network or a trace network in an enterprise geodatabase, the input network diagram layer must be from a service
To apply the Main Ring layout on an active diagram map view, do one of the following:
- On the Network Diagram tab, click the drop-down arrow on the Diagram Layouts button in the Layout group, and click the Main Ring layout item in the gallery.
- Load the Apply Main Ring Layout tool in the Geoprocessing pane.
Then, adjust the Main Ring layout parameters and click Run.
Note:
To apply the layout on a subset of features in the network diagram, use one of the Select Features tools (for example, Select By Rectangle, Select By Polygon, and so on) and select the diagram features before running.
Configure the Main Ring layout on a diagram template
To configure this layout on your diagram template, use the Add Main Ring Layout tool.
Main Ring layout parameters
The sections below clarify the Main Ring diagram layout parameters.
Preserve container layout
Most of the layout algorithms work with the Preserve container layout option. This option allows controlling the algorithm execution so it executes either on the top graph of the diagram—Preserve container layout checked, or on both content and noncontent features in the diagram—Preserve container layout unchecked.
Ring Type
This parameter specifies the type of the ring, that is, whether the diagram features of the detected main ring will display along an ellipse (Ring Type set to Ellipse) or along a rectangle (Ring Type set to Rectangle):
Spacing values interpreted as absolute units in the diagram coordinate system
Some layout algorithms work with the Spacing values interpreted as absolute units in the diagram coordinate system option. This option specifies how the layout algorithm parameters representing distances will be interpreted:
- Checked—The layout algorithm will interpret any distance values as linear units.
- Unchecked—The layout algorithm will interpret any distance values as relative units to an estimation of the average of the junction sizes in the current diagram extent. This is the default.
Ring Width and Ring Height
The Ring Width and Ring Height parameters are used to set the width and height of the ring. The examples below show a diagram after applying the Main Ring layout with different width and height values.
The first example shows the layout obtained with Ring Width set to W1 and Ring Height set to H1. 
The next example shows the same diagram after applying the layout with Ring Width set to W2, equal to 1/2 W1, and Ring Height set to H2, equal to H1. 
The third example shows the diagram after running Main Ring with Ring Width set to W3, equal to 1/2 W1, and Ring Height set to H3, equal to 1/2 H1.
Hierarchical Tree Type
This parameter specifies how the trees coming out of the main ring's junctions will be positioned:
- Smart tree—Each tree will be displayed hierarchically as a smart tree.
- Both sides—Each tree displays along a main line, and its related branches are arranged on both the left and right sides of this main line.
- Left side—Each tree displays along a main line, and its related branches are arranged on the left side of this main line.
- Right side—Each tree displays along a main line, and its related branches are arranged on the right side of this main line.
Between Junctions Perpendicular to the Direction
This parameter concerns the layout of the trees coming out of the main ring's junctions. Depending on the specified Hierarchical Tree Type setting, it is used to set the spacing between diagram junctions that are displayed as follows:
- Perpendicular to the smart tree direction and belonging to the same subtree level—Smart tree
- Along the axis perpendicular to the main line—Both sides of mainline, Right side of mainline, or Left side of mainline
Between Junctions Along the Direction
This parameter concerns the layout of the trees coming out of the main ring's junctions. Depending on the specified Hierarchical Tree Type, it is used to set the spacing between diagram junctions that are displayed, such as the following:
- Along the smart tree direction—Smart tree
- Along the main line, as well as the spacing between diagram junctions that are displayed along the axis parallel to the main line—Both sides of mainline, Right side of mainline, or Left side of mainline
Learn more about the Between Junctions Along the Direction parameter for Smart Tree layout
Learn more about the Between Junctions Along the Direction parameter for Mainline Tree layout
Edge Display Type, Break Point Relative Position, and Offset
Learn about the Edge Display Type, Break Point Relative Position, and Offset parameters