Modeling a Simple Network

This chapter provides a tutorial on using the NMT to model a simple network and contains the following sections:

• Configuring Sites

• Saving Your Work

• Configuring Links

• Configuring Traffic

• Optimizing Your Configuration

• Analyzing Line Failures

• Simulate All

The procedures explain how to input data and generate reports, as well as revise and enhance the network. Before starting this tutorial, you should review the sections "Menus" and "Keyboard Commands" in the chapter "Using the NMT."

To model a simple network, you need to describe the nodes, links, and types of traffic. Figure 3-1 illustrates a proposed network, and Table 3-1 lists the proposed connections and types of traffic. The table shows the minimum information required for effectively using the NMT.

Figure 3-1: Proposed Network

Table  3-1: List of Proposed Connections

Site 1 (Master)	Site 2 (Slave)	Quantity	Description	Type	Status
Paris	Denver	12	Voice	A32	Current
Denver	Boston	8	Voice	C32	Current
Paris	Denver	12	Voice	L16	Current
Paris	Boston	1	Data	L4	Current
Paris	Denver	3	Frame Relay	V	Current
Paris	Boston	10	Frame Relay	T1	Current

Creating a Network Configuration

This section describes how to input a network configuration into the NMT. In this example, we are working with an existing network, as indicated by the Status column in Table 3-1.

To model a network, perform the following steps:

• Create a network configuration by configuring sites, links, and traffic, and reviewing warning and error messages.

• Enhance the configuration by using NMT's optimization tools (for example, the Optimize, Route, and Fail Analysis menu selections) and adding resilient links.

To start the NMT, type nmt at the UNIX command line. You are transferred to the NMT design window, shown in Figure 3-2.

Figure 3-2: NMT Design Window

Configuring Sites

In this procedure, you enter the information shown in Table 3-2 into the Sites table.

Table  3-2: Field Changes for the Sites Table

Site	Type	Size	Power	IGX	BC (Back Card)	FC (Front Card)	RLC (Redundant Link Card)
Paris	IGX	32	D	N	E1	NTC	Y
Boston	IGX	16	A	Y	T1	NTM	N
Denver	IGX	8	A	Y	T3	BTM	N

Except where noted in this table, each node uses default values. For a description of each field, see the appendix "Configuration Tables and Fields."

Step 1 Use the left and right arrows to highlight Configure and press Enter. Select Sites and press Enter. A new Sites table is displayed.

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Note You can select a menu choice by using the up and down arrow keys or by typing the first letter of the item selected.

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Step 2 Highlight the Site field by pressing the Down arrow. Type Paris. You have now created a site.

Step 3 To modify the NMT default site values, cursor or tab to each of the fields listed in Table 3-2 and enter the data that applies to the Paris site. There are two ways to enter data:

• Press the Help key to see a list of choices. Lists of choices are available for most fields that accept three or more non-numeric values. Make a selection using the cursor. Press Enter.

• Type directly into the field. Press the Delete key if you make a mistake.

Step 4 Press the down arrow to insert a new line in the table.

Step 5 Repeat Step 2, Step 3, and Step 4 for Boston and Step 2 and Step 3 for Denver. The Sites table should look like the one shown in Figure 3-3.

Step 6 Press Escape to accept the entries and return to the Configure menu.

Figure 3-3: NMT Network Sites Table

Saving Your Work

Step 1 To save your configuration, select Write from the Configure menu. Press Enter.

Step 2 Enter a name in the Enter Name box and press Enter. (See Figure 3-4.)

You should save your work on a regular basis.

Your file is saved and you are returned to the Configure menu.

Figure 3-4: File Save Window

Configuring Links

In this procedure, you enter the information in Table 3-3 into the Links table.

Table  3-3: Field Changes for the Links Table

					Second Screen
Site 1	Site 2	Trunk	Trunk Card Site 1/Site 2	Reserve	Distance	$/Month
Paris	Denver	T1	NTM/NTM	592/592	0	43500
Denver	Boston	T3	ALM/ALM	992/992	1767	0
Paris	Boston	E3	ALM/ALM	992/992	0	16670

Except where noted in this table, each link uses default values. For a description of each field, see the appendix "Configuration Tables and Fields."

Step 1 Select Links from the Configure menu and press Enter. A new Links table is displayed.

Step 2 Highlight the Site 1 field by pressing the Down arrow. Type Paris. Cursor or tab to the Site 2 field and enter Denver. If you are inputting site names by pressing the Help key, use the up and down arrows to scroll through the site names. Press Enter to select the site.

Step 3 Cursor or tab to each of the fields listed in Table 3-3, and enter the data that applies to the Paris/Denver link.

To go to the Distance and $/Month fields, press F5, which takes you to the second screen of the Links table. (Press Escape to return to the previous screen.)

Step 4 Press the down arrow to insert a new line in the table.

Step 5 Repeat Step 2, Step 3, and Step 4 for the Denver/Boston link and Step 2 and Step 3 for the Paris/Boston link. The Links table should look like the one shown in Figure 3-5.

Step 6 Press Escape to accept the entries and return to the Configure menu.You may have to press Escape two times.

Figure 3-5: NMT Links Table

Configuring Traffic

For NMT to assist you in modeling a network, you must describe the traffic. The network in this tutorial uses voice, data, and bursty traffic.

Configuring Voice Traffic

In this procedure, you enter the information shown in Table 3-4 into the Voice Connections table.

Table  3-4: Field Changes for the Voice Connections Table

Site 1	Site 2	Quantity	Type	Utilization Site 1/Site 2
Denver	Boston	8	C32	40/40
Paris	Denver	12	A32	100/100
Paris	Denver	12	L16	100/100

Except where noted in this table, each link uses default values. For a description of each field, see the appendix "Configuration Tables and Fields."

Step 1 Select Voice Traffic from the Configure menu and press Enter. A new Voice Connections table is displayed.

Step 2 Highlight the Site 1 field by pressing the down arrow. Type Denver. Cursor or tab to the Site 2 field and enter Boston.

Step 3 Cursor or tab to each of the fields listed in Table 3-4 and enter the data that applies to the Denver/Boston connection.

Step 4 Press the down arrow to insert a new line in the table.

Step 5 Repeat Step 2, Step 3, and Step 4 for the first Paris/Denver link and Step 2 and Step 3 for the second Paris/Denver link. The Voice Connections table should look like the one shown in Figure 3-6.

Step 6 Press Escape to accept the entries and return to the Configure menu.

Figure 3-6: NMT Voice Connections Table

Configuring Data Traffic

In this procedure, you enter the information shown in Table 3-5 into the Data Connections table.

Table  3-5: Field Changes for the Data Connections Table

Site 1	Site 2	Quantity	Utilization Site 1/Site 2	Back Card Site 1/Site 2
Paris	Boston	1	60/60	L4/L4

Except where noted in this table, each link uses default values. For a description of each field, see the appendix "Configuration Tables and Fields."

Step 1 Select Data Traffic from the Configure menu. A new Data Connections table is displayed.

Step 2 Highlight the Site 1 field by pressing the Down arrow. Type Paris. Cursor or tab to the Site 2 field and enter Boston.

Step 3 Cursor or tab to each of the fields listed in Table 3-5 and enter the data that applies to the Paris/Boston connection. The Data Connections table should look like the one shown in Figure 3-7.

Step 4 Press Escape to accept the entries and return to the Configure menu.

Figure 3-7: NMT Data Connections Table

Configuring Bursty Traffic

In this procedure, you enter the information shown in Table 3-6 into the Frame Relay and ATM Connections table.

Table  3-6: Field Changes for the Frame Relay and ATM Connections Table

Site 1	Site 2	Quantity	MIR (Minimum Information Rate)	PIR (Peak Information Rate)	BC (Back Card)
Paris	Denver	3	64/64	256/256	V/V
Paris	Boston	10	256/256	256/256	T1/T1

Except where noted in this table, each link uses default values. For a description of each field, see the appendix "Configuration Tables and Fields."

Step 1 Select Bursty Traffic from the Configure menu. A new Frame Relay and ATM Connections table is displayed.

Step 2 Highlight the Site 1 field by pressing the down arrow. Type Paris. Cursor or tab to the Site 2 field and enter Denver.

Step 3 Cursor or tab to each of the fields listed in Table 3-6 and enter the data that applies to the Paris/Denver connection.

Step 4 Press the down arrow to insert a new line in the table.

Step 5 Repeat Step 2 and Step 3 for the Paris/Boston connection. The Frame Relay and ATM Connections table should look like the one shown in Figure 3-8.

Step 6 Press Escape to accept the entries and return to the Configure menu.

Figure 3-8: NMT Frame Relay and ATM Connections Table

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Note If you have not saved your configuration, you should do so now.

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Warnings and Errors

When you leave the Configure menu, the NMT checks your input. If the program identifies any problems, it instructs you to check your Warning browser. To view warnings:

Step 1 Press Escape to exit the Configure menu. A message box displays the following message: "Checking current configuration; New warning messages generated. Check your warning browser."

Step 2 Select Warnings & Errors from the Display menu. The Warnings browser shows that the NMT modified the capacity of trunks as listed in the Links table. (See Figure 3-9.)

For more information on the Warnings browser, see "Modeling Processes" in the chapter entitled "Using the NMT."

Step 3 Press Escape twice to exit from the Warnings browser and the Display menu.

Figure 3-9: NMT Warnings Browser

Enhancing the Configuration

This section describes how to optimize your configuration and perform failure analysis to add resiliency to your network.

Optimizing Your Configuration

When you select Optimize, the NMT processes your configuration to design a least-facilities-cost network. Selecting Optimize eliminates any unused links (links that are not used for routing traffic) from the topology. These unused links remain in the Links table for possible later use.

The following procedure describes how to use the Optimize facility to review the optimized model and add a resilient link to the optimized model.

Optimize

Step 1 Select Optimize from the Execute menu. Press Enter.

When you run Optimize it performs several steps, each of which displays a message window. First, the system calculates a topology in which all traffic is routed at the lowest possible cost. Second, the NMT builds the site. Third, the connections are routed. Fourth, the program generates reports. For a complete description of the Optimize process, see the section "Model Optimization Methods" in the chapter entitled "Using the NMT."

Press Escape until you exit the Execute menu.

Display Results

Step 2 Select Links from the Display menu to display the results in a table format. Press Enter to display the results (Figure 3-10).

Only two links are listed (Denver/Boston and Boston/Denver) because the NMT calculated that it is cheaper to go from Paris to Denver by way of Boston, than to go directly from Paris to Denver. This calculation was based on the information you entered in the Distance and $/Month fields in the Links table.

Press Escape to exit the Links display.

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Note In addition to the Links display, you can select other reports from the Display menu. These reports display information about parts required, sites, resources used (slots occupied in the switch), and so on.

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Figure 3-10: Links Display After Optimize Is Run

Step 3 To create a graphic representation of the topology

(a) Select Map from the Display menu to display the results graphically. It may take several seconds for the Map window to display.

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Note Select Map tool menus by using the left mouse button, except where noted.

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(b) Click on the Update menu in the Map menu bar. Click on Update Map.

(c) Click on the menu bar Map button and choose Select. Select the world map from the list. (This command also returns a map to its default size.)

(d) Drag the icons Paris, Denver, and Boston to their respective locations. The icons are small boxes initially stacked in the upper left corner of the Map window. Drag each icon to a new location by holding down the left mouse button and moving the mouse.

(e) To save this map, select Save from the menu bar Utility menu.

The map shows that the optimized configuration consists of only two links (Paris/Boston and Boston/Denver). See Figure 3-11.

Add Resilient Link

Step 4 Go to the Network Modeling Tool window and select Links from the Configure menu. (You may need to first press Escape to exit from the Display menu.)

Cursor or tab to the Keep field of the Links table. Set all the Keep values to 1.

By changing the Keep value from 0 to 1, you instruct the NMT to create a resilient link--traffic can still be routed even if one link goes down. In this example, the resilient link is Paris to Denver.

Press Escape until you exit the Configure menu.

Figure 3-11: Network Map

Step 5 Select Route from the Execute menu to instruct the NMT to create routes for as many Link table entries as possible.

The Route command creates routes for each entry in the Links table that has a Keep field value of 1 or more. For a complete description of the Route process, see the section "Model Optimization Methods" in the chapter "Using the NMT."

Press Escape.

Step 6 Repeat Step 2 to Display your results. If the map window is still open, repeat Step 3b. If the window is closed, repeat Steps 3a and 3b. Observe that both the links display and the topology map now include a Paris to Denver link. (See Figure 3-12.)

Analyzing Line Failures

Adding resiliency to a network is seldom as simple as looking at the topology and making sure the nodes are connected. Utilization rates, bandwidth, delay factors, and more must be taken into account before you or the NMT can determine if a link is resilient. The NMT can compute which lines have enough extra bandwidth, according to values input in the configuration, to support extra traffic in the event a line goes down.

The following procedure demonstrates how to do failure analysis in the NMT.

Step 1 Select Optimize from the Execute menu. (You must select Route or Optimize before running failure analysis.) Press Enter twice. For a complete description of the Optimize process, see the section "Model Optimization Methods" in the chapter "Using the NMT."

Step 2 Select Fail Analysis from the Execute menu. This calls up a submenu.

Step 3 Select Fail Line from the Fail Analysis submenu. The Fail Line table appears.

Figure 3-12: Before and After: Impact of Keeping Paris to Denver Link

Step 4 Change N to Y in the first line of the Fail Line table to tell the NMT to fail the link between Paris and Denver.

Press Escape to return to the Fail Analysis submenu.

Step 5 Select Alt-Route from the Fail Analysis submenu to process the change you made in the previous step. Press Enter.

Press Escape until you return to the Fail Analysis submenu.

Step 6 Select Results from the Fail Analysis submenu. (See Figure 3-13.)

Figure 3-13: Fail Analysis Results Table

The table shows the following:

• Not Routed Connections. This shows all the connections that could not be rerouted when the specified links failed. In this example, all channels are routed.

• Link Load. This shows the link loads after the rerouting due to the failed link(s). In this example, you can deduce from this list that the packet load of the failed line has been rerouted to the Denver to Boston and the Paris to Boston lines. Because the line failed, this listing no longer contains the direct route that linked Paris to Denver.

Step 7 Go to the Map window and click on the Update menu in the Map menu bar. Click on Update Map. (For more information, see the instructions for using the Map tool in the section "Optimizing Your Configuration" earlier in this chapter.)

Notice that the Paris to Denver link is displayed in red. This indicates that the link is down according to the last failure analysis run.

Simulate All

The Simulate All menu selection allows you to perform a failure analysis for each link, one at a time.

Step 1 Select Route from the Execute menu and press Enter. When the routing process stops, press Enter again. Press Escape.

Step 2 Select Simulate All from the Fail Analysis submenu.

Step 3 Enter a file name. Press Enter.

Step 4 Press Escape until you exit the Execute menu.

Step 5 Select View from the Report menu and select the file name you chose in Step 3.

This report first shows the link loads for all links with no link failures. Then it displays the connections not routed and the link loads for each link failure. (If you select Results from the Fail Analysis submenu in the Execute menu or View Results from the Display menu, you will see the results of only the last link failure.)