Perform Capacity Planning

As demand grows on your network, you need a way to address the additional traffic and congestion. To alleviate congestion, you can:

  • Upgrade existing circuits by adding more capacity to them

  • Augment these circuits with associated port circuits

  • Add parallel circuits to existing circuits

  • Specify new adjacencies between nodes that were not initially connected

To perform these planning optimization investigations, Cisco Crosswork Planning includes a Capacity planning optimization tool. The goal of a capacity planning optimization is to minimize the addition of any required capacity to be installed on the network. The capacity planning optimizer operates on Layer 3 network elements, as well as across failure sets, so you can use a combination of elements in a layered fashion to reach an acceptable solution to meet maximum utilization requirements.

This section contains the following topics:

Optimize capacity

You can set optimization parameters to relieve network congestion and augment capacity. You start by defining a maximum utilization threshold for a specified set of interfaces, and then layering additional options that operate on Layer 3 and across failure sets.


Note
Some of the optimizer options are mutually exclusive; for example, if you tell the optimizer to create port circuits, it cannot create parallel circuits at the same time. Other options are complementary; for example, you can specify the creation of parallel circuits and new adjacencies together.

Procedure

Step 1

Open the plan file (see Open plan files). It opens in the Network Design page.

Step 2

From the toolbar, choose any of the following options:

  • Preset workflows > Perform capacity planning

    OR

  • Actions > Tools > Capacity planning optimization

Step 3

From the Circuits panel, choose the circuits you want the optimizer to consider. Decide on the Layer 3 optimization options to use. The options are described in Optimization options.

You can upgrade all existing circuits or a subset of these circuits. If you want to allow the upgrade of just certain circuits, indicate those circuits to be modified. This is useful if you want to limit your upgrades to a certain geographical location in the network.

To create new port circuits or parallel circuits, choose one of the following options:

  • Create new port circuits (LAGs): In this case, the optimizer augments the existing circuits with associated port circuits (LAGs) with additional port circuits. The optimizer converts non-LAG circuits to LAGs.

  • Create new parallel circuits: In this case, the optimizer creates new circuits that are parallel to existing circuits.

Note

 
You can specify both the capacity increment and the existing capacity of LAG circuits in tandem.

Note

 
You can apply the IGP metric to new adjacencies, but not to parallel circuits.

Step 4

(Optional) Override the defaults for how upgraded circuits and new objects are tagged.

Step 5

Click Next.

Step 6

(Optional) In the Optimization objective section, choose the options to provide additional capacity planning. Describe the cost for the various elements in your design. In the Failure sets section, choose the failure sets, as required. For more information, see Advanced optimization options.

Step 7

(Optional) Specify the maximum number of threads. By default, the optimizer tries to set this value to the optimal number of threads based on the available cores.

Step 8

Click Next.

Step 9

On the Run Settings page, choose whether to execute the task now or schedule it for a later time. Choose from the following Execute options:

  • Now—Choose this option to execute the job immediately. The tool is run and changes are applied on the network model immediately. Also, a summary report is displayed. You can access the report any time later using Actions > Reports > Generated reports option.

  • As a scheduled job—Choose this option to execute the task as an asynchronous job. Set these options:

    • Priority: Select the priority of the task.

    • Engine profiles: Select the engine profile as per your requirement. This section lists all the available asynchronous engine profiles.

    • Schedule: Set the time at which you want to run the tool.

    The tool runs at the scheduled time and using the selected engine profile. You can track the status of the job at any time using the Job Manager window (from the main menu, choose Job Manager). Once the job is completed, download the output file (.tar file), extract it, and import the updated plan file into the user space to access it (for details, see Import plan files from the local machine).

    Note

     
    Ensure that you save the plan file before you schedule the job. Any unsaved changes in the plan file are not considered when you run the tool as a scheduled job.

Step 10

(Optional) If you want to display the result in a new plan file, specify a name for the new plan file in the Display results section.

In the previous step:

  • If you have selected to run the task immediately, by default, the changes are applied on the current plan file. If you want to display the results in a new file, select the Display results in a new plan file check box and enter the name of the new plan file.

  • If you have scheduled the task to run at a later time, by default, the results are displayed in the Plan-file-1. Update the name, if required.

Step 11

Click Submit to create the capacity planning optimization reports.

Cisco Crosswork Planning routes the traffic and looks at the utilization threshold, and any other optimization parameters you specified. If you have specified any advanced options, the optimizer takes into account whether it makes sense to upgrade existing circuits or set up new adjacencies, and considers capacity increments, cost options, and feasibility limits.

After running an optimization, you can look at the summary report to see what the optimizer did to remove congestion. The key metric to look at is the Total Capacity Added (Mb/s). For details, see Analyze optimization reports.

Example

Design before optimization shows an example of a network design before optimization, where extra demands were placed on the network. As a result, you can see congested interfaces in red.

Figure 1. Design before optimization

Design after optimization shows the design after optimization using the following parameters (For the remaining options, the default values are used.):

  • Maximum interface utilization—100%

  • Capacity increment—2488 Mbps

  • Circuits—Upgrade All circuits and Create Port circuits (LAGs)

  • Create new adjacencies—Restrict new adjacencies between all nodes

  • Failure sets—Circuits

In this case, the optimizer proposes to set up two new adjacencies:

  • One between Atlanta (atl) and New York City (nyc)

  • One between Washington, D.C. (wdc) and Chicago (chi)

Figure 2. Design after optimization

Optimization options

You have several Layer 3 options for capacity planning. These parameters tell the optimizer what your preferences are in terms of utilization thresholds, capacity increments, and whether to upgrade existing circuits, create new adjacencies between nodes, create port circuits, or create parallel circuits.

Table 1. Layer 3 optimization options

Option

Description

Interface utilization & capacity

Maximum interface utilization

Defines the maximum utilization threshold that you want to use for all interfaces in the network. By default, the capacity planning optimizer sets the threshold at 100% congestion. However, for future planning purposes, you might want to set the utilization to a lower number, such as 90%.

Capacity increment

Defines the bandwidth increment value (that is, the allowed capacity increment). You can think of this value as the capacity of the ports. The default is 100000 Mb/s.

Use capacity of existing LAG members

Augments capacity based on the capacity already defined in the existing LAG Members instead of using the Capacity increment.

Circuits

Upgrade Circuits

You can upgrade all circuits, or just a subset of circuits to reduce congestion. If you want to allow the upgrade of just certain circuits, select those circuits to be modified. This is useful if you want to limit your upgrades to a certain geographical location in the network. By default, none of the circuits are selected.

Create

  • Port circuits (LAGs)

  • Parallel circuits

  • The optimizer augments the existing circuits with associated port circuits (LAGs) with additional port circuits. The optimizer converts non-LAG circuits to LAGs.

  • The optimizer creates parallel circuits to reduce congestion. If you tell the optimizer to create parallel circuits, you cannot tell it to create port circuits and vice versa.

Adjacencies

Restrict new adjacencies between nodes

By default, the optimizer does not create new adjacencies. If you specify a set of candidate nodes for it to use, the optimizer proposes new adjacencies. The optimizer restricts a new adjacency between the specified candidate nodes. For example, you might require that only core nodes be directly connected. In this case, specify only core nodes as your candidate nodes.

Maximum number of new adjacencies

Specifies the maximum number of adjacencies to create between candidate nodes. By default, this is an unbounded number.

Set IGP metric of new interfaces to

  • Shortest IGP metric minus decrement

  • Fixed metric

  • Sets the IGP metric of the interfaces corresponding to new adjacencies to be the shortest path minus the value specified in the metric option. This is how the IGP metric of such interfaces is set by default. The IGP metric of new interfaces due to parallel circuit upgrades is the same as the metric of the parallel interfaces.

  • Defines a fixed IGP metric to use when creating new interfaces. The metric of new interfaces is equal to the value specified in this field. Enter a positive integer as a value in this field.

Tag upgraded circuits with

Defines tags for any upgraded circuits. By default, the optimizer tags upgraded circuits with the label CapacityOpt::Upgraded.

Tag new objects with

Defines tags for any new objects the optimizer creates. By default, the optimizer tags upgraded circuits with the label CapacityOpt::New.

Advanced optimization options

Use the advanced optimization options to:

  • Choose whether to optimize for capacity or cost.

  • Define what failure scenarios to consider.

When you run the optimizer, the tool generates a report on the overall cost, including the cost of the added ports, and recommends the most cost-efficient solution.

Table 2. Advanced optimization options

Option

Description

Optimization objective

Minimize capacity

Minimizes the capacity that is added to your network. This is the default option.

Minimize cost

Select this option to run the optimization with the objective of reducing the overall cost when adding new capacity. Click Add icon to manually enter a cost unit for capacity, L3 port costs, and the feasibility limit. Alternately, click to import cost values from a file.

Failure sets

Choose the options that you want the optimizer to consider (Circuits, Nodes, Sites, and so on). Entries appear dimmed if they are not available in your design plan.

Maximum number of threads

Specify the maximum number of threads. By default, the optimizer tries to set this value to the optimal number of threads based on the available cores.

Parallel circuits design example

Adding parallel circuits to increase capacity shows the first design in this chapter with parallel circuits added to increase capacity. In this case, the optimizer proposes four sets of parallel circuits as indicated by the dotted lines:

  • One between Atlanta (atl) and Washington, D.C. (wdc)

  • One between Washington, D.C. (wdc) and New York City (nyc)

  • One between New York City (nyc) and Chicago (chi)

  • One between New York City (nyc) and Boston (bos)

Figure 3. Adding parallel circuits to increase capacity

Analyze optimization reports

Each time the Capacity planning optimization tool is run, a report is automatically generated. You can access this information at any time by choosing Actions > Reports > Generated reports and then clicking the Capacity Planning Optimization link in the right panel. Note that new reports replace the previous ones.

The Summary tab provides useful metrics at a glance. It provides details on the:

  • Input parameters used for optimization

  • Total capacity added as a result of the optimization

  • Number of new adjacencies

  • Number of upgraded circuits

  • Number of new circuits

  • Number of new ports

  • Number of new port circuits

The Capacity Upgrades tab provides details on how the optimizer upgraded circuits.