The SRLG window provides a method of grouping links and/or nodes that are likely to fail together if they fail at all. The facility definition is used in failure simulations where accurate modeling requires the simultaneous failure of specific links and/or nodes. It can also be used for diverse path design where primary and backup paths for tunnels (Router model) or 1+1 demands (SONET model) are required to be routed on facility-diverse paths.
Facilities can be used to model SRLGs (shared risk link groups) when only specifying a group of links. If several links travel over the same fiber, so that a fiber cut will break all of them at once, it's good to define a facility containing those links. Facilities can also be used to group together links on the same card. Another example of a facility is the set of switches on one floor of a large data center, together with the links going into or out of that floor.
Add: Opens the Add Facility window which allows you to add a new facility and select the nodes and links that belong to the facility.
Modify: Opens the Modify Facility window which allows you to modify the facility groupings. Use the mouse to highlight elements you desire to be in the selected facility. Deselect those elements to be removed from the facility. There are multiple ways to select elements. You can select nodes and/or links directly from the list provided. Click the first element and then <Shift>-click the last element to select a range of elements. <Ctrl>-click an element to toggle the selection of a particular element in the facility. Alternatively, to add elements from the map, highlight the nodes and links on the map (for example, selected by <Ctrl>-click or by drawing a box around a group of nodes and links) and then click.Add from Map. Another method is to clickAdd Links from Filter and then enter in advanced filtering criteria as described in Advanced Search.
Delete: Deletes the selected facility group.