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Multilayer Feature Overview

The multilayer feature enables NorthStar Controller to receive an abstracted view of an underlying transport network and utilize the information to expand its packet-centric applications. NorthStar Controller does not use the information to compute paths for the transport domain. The transport layer topology information comes in the form of a YANG-based data model over southbound RESTCONF and REST APIs.

The following sections describe how multilayer support is integrated into the NorthStar Controller:

Supported Interface Standards

NorthStar currently supports the following interface standards:

The NorthStar user interface for configuring and working with transport domain data and the work flow are the same, regardless of the interface standard. There are, however, a few differences in terms of supported features, and those are noted in the documentation.

Key Features of NorthStar Controller Multilayer Support

The following features apply to NorthStar Controller multilayer support:

  • A single instance of NorthStar Controller (or multiple NorthStar Controller instances deployed as a high availability cluster) can receive abstract topology information from multiple transport controllers simultaneously.

  • You can configure multiple devices associated with a single transport controller, and at least one device is required. If multiple devices are configured, NorthStar Controller attempts connection to them in round-robin fashion.

  • The transport controller should provide the NorthStar Controller with the local and remote identifier information for each interlayer link. If the transport controller is not able to provide the interlayer link identifiers on the packet domain side, it provides open ended interlayer links that you can complete using the NorthStar Controller Web UI.

  • Juniper Networks provides an open source script to be used optionally for configuring interlayer links.

  • Transport link failures can be reported by transport controllers and are displayed in the NorthStar Controller UI as failed transport links. Only failures reported in the traffic engineering database (TED) are taken into account for rerouting. IP links associated with transport link failures reported by a transport controller are not considered down by NorthStar Controller unless reported down in the TED.

  • Transport controller profile configuration can be done in the NorthStar Controller Web UI or directly via the NorthStar Controller’s northbound REST API. You can view and manage transport layer elements in both the web UI and the NorthStar Planner.

  • The web UI and the northbound REST API offer premium delay-related path design options for transport links. In the web UI, navigate to Applications>Provision LSP, and click the Design tab. These options are also available in the NorthStar Planner.

    When the transport domain is known, the delay information does not need to be populated manually or imported from a static file because the information is learned dynamically by NorthStar Controller.

  • Once the interlayer links mapping is completed, the data used by the path design options (delay, SRLGs, Protected) is populated automatically and updated dynamically through communication between the transport and NorthStar controllers.


NorthStar Controller considers transport shared risk link group (SRLG) information whenever a path optimization occurs or whenever some event triggers rerouting.

By default, NorthStar Controller associates transport SRLGs to IP links based on information received from the transport controller. Connecting NorthStar Controller to more than one transport controller introduces the possibility of overlap of SRLG ranges, which might not be desirable. The configuration of transport controller profiles in the NorthStar Controller Web UI allows for the specification of an additional TSRLG prefix (a prefix extension) for each transport controller to prevent unintentional overlap.

Preventing unintentional SRLG range overlap requires particular vigilance when you have transport controller ranges and you also manually assign SRLGs to IP links in NorthStar Controller.

Maintenance Events

Maintenance events that include transport layer elements can be scheduled in the NorthStar Controller UI because transport SRLGs are automatically discovered by NorthStar Controller. You can select any transport layer elements or combination of transport and packet layer elements to be included in a maintenance event. Of the transport layer elements only the transport SRLGs can trigger the rerouting of packet layer LSPs.

Both the NorthStar Controller and NorthStar Planner support creation of maintenance events that include transport layer elements. The transport controller is not made aware of these maintenance events as they exist only in the scope of NorthStar.



Latency information is not available from proNX Optical Director.

NorthStar Controller can dynamically learn latency information for transport links and interlayer links, to support latency-based routing constraints for packet LSPs. There are three possible sources for latency values. All of the values are collected and saved, but when multiple values are present for the same object, the NorthStar Controller can only accept one. The NorthStar Controller resolves conflicts by accepting latency values according to their source in the following order of preference:

  • Manual configuration by the user

  • Probes on the routers that support analytics

  • Transport controller

SRLG Diverse LSP Pairs

In the web UI, you can create LSP pairs that are SRLG-diverse to each other. Use the same processes and UI windows you use to create other diverse LSP pairs, and specify SRLG for diversity. This functionality is also available in the NorthStar Planner.

Protected Transport Links

NorthStar supports preferred protected links routing constraint for packet LSPs. When this constraint is selected, NorthStar computes the path that maximizes the number of protected links, and therefore offers the best overall protection. Protected links can be implemented by way of REST APIs or using the web UI. In the web UI, navigate to Applications > Provision LSP, and click the Advanced tab. By default, the Route on Protected IP Link option is not selected.


You can also access the Provision LSP window from the network information table. From the Tunnel tab, click Add at the bottom of the table.