Library: Test Plans

OSPF Testing

1. Overview
2. 1. OSPF Conformance Test
   
3. 2. OSPF Route Capacity Test
   
4. 3. OSPF Route Convergence Test
   
5. 4. OSPF Topology Scalability Test
   
6. 5. OSPF Equal Cost Path Verification Test

Overview

The test plans presented here include conformance, functional, and performance tests designed for network and QA engineers testing OSPF devices and networks, and provide a baseline for achieving network quality.

1. OSPF Conformance Test

Objective
Verify the Device Under Test's (DUT's) compliance with the following capabilities defined in various OSPF RFCs:

• OSPFv2 - RFC 1583, RFC 2328
• OSPF Opaque LSA - RFC 2370
• OSPF NSSA - RFC 1587
• OSPF Database Overflow - RFC 1765
• OSPFv3 (OSPF for IPv6) - RFC 2740

Figure 1. OSPF conformance test setup.
Setup
A minimum of two network connections are required from the test tool to the DUT - one for request packets and one for response packets. Ixia's IxANVL conformance test solution is run from a Linux workstation either connected directly to the DUT, or via Ixia test hardware (see Figure 1). IxANVL emulates various OSPF topologies, depending on the configuration of each test case.

Input Parameters
Two sets of parameters are required prior to running conformance tests: one for test tool configuration and one for DUT configuration. The test tool configuration describes the interface and protocol configuration of the tester, while the DUT configuration describes the OSPF features of the DUT using Expect scripts (see Table 1).

Parameter	Description
Test Tool Configuration	Tester Test IP Addresses, DUT IP Address, OSPF protocol parameters (Hello interval, router priority, authentication, etc.)
DUT Configuration	OSPF features (TOS Routing, Database Exchange Timeout, Routing Table Update Timeout, etc) via Expect scripts

Table 1. Conformance test input parameters.
Methodology
Conformance testing is an important tool to verify how a DUT complies with specific protocol standards. Conformance test tools perform their tests as a dialog: they send packets to the router being tested, receive the packets sent in response, and then analyze the response to determine the next action to take. This methodology allows conformance test tools to test complicated scenarios much more intelligently and flexibly than achievable by simple packet generation and capture devices. Conformance testing also includes negative test cases to help validate device response to "killer packets". For OSPF conformance testing, a number of test cases are run against the DUT based on the direct interpretation of various OSPF RFCs.

1. Enter parameters to describe both the Conformance Tester and DUT configuration.
2. Select all or a set of test cases to run (see Figure 2).
3. Run the conformance tests from the user interface, or in a batch mode via command scripts, reconfiguring the DUT as required between test cases to match the test setup.

Figure 2. OSPF test case selection.
Results
Number of tests passed/failed, including reasons for failed cases (Figure 3). IxANVL also keeps the history of each pass or fail test case in the Test Journal (Figure 4).
Figure 3. OSPF test results.

Figure 4. OSPF test case journal.

2 OSPF Route Capacity Test

Objective
Determines the number of routes that an OSPF DUT can sustain at a single time. This scalability test is designed to help network and test engineers to:

• Evaluate devices to be purchased or used in the network.
• Test capacity and understand network limitations before actual deployment of new network elements and services.

Setup
The test requires two tester ports - one to transmit traffic and one to receive. The transmit direction of traffic is unidirectional. Test port 2 is used to advertise the OSPF network topology and routes, while test port 1 sends traffic to verify the advertised topology (Figure 5). During the test, tester port 2 gradually increases the number of advertised routes until the maximum sustainable route capacity can be determined. Ixia's IxScriptMate application can be used to configure, control, and execute this test. IxScriptMate also provides comprehensive test results showing frame loss percentage based on the ability to forward under maximum route capacity.
Figure 5. OSPF route capacity test topology. Input Parameters

Parameter	Description
Max Rate	Rate at which frames will be sent to advertised routes
Tolerance	Percentage of traffic loss tolerance
Route Step	Number of routes to increase per iteration
Number of Routes	The number of prefixes to generate at the beginning of the test
Advertise Delay Per Route	The maximum time in seconds the router is allowed to absorb the advertised route. This number is multiplied by the number of routes to calculate the "Max Wait Time"

Table 2. OSPF route capacity test input parameters.
Methodology

1. Test port 2 advertises the initial number of routes defined by the parameter "Number of Routes".
2. After passing the "Max Wait Time" (determined by "Advertised Delay Per Route"), test port 1 sends traffic targeting each advertised route behind port 2. The traffic throughput rate is set by the parameter "Max Rate".
3. Test port 2 verifies packets received within the defined loss "Tolerance".
4. Test port 2 advertises more routes increased by the amount defined by "Route Step".
5. Repeat step 2 through step 4 until port 2 receives no packets or packet loss is above the "Tolerance" level.

Results
When the test completes and the tolerance has been exceeded, the test results will show the maximum number of routes learned by the DUT. Figure 6 shows an example results page created in IxScriptMate. The results are broken down per frame size and show the resulting numbers for "max routes verified", "total loss percentage", and "tolerance". The "Max Routes Verified" value shows the maximum number of routes that could be sustained at that particular traffic rate and frame size. This test can be executed manually as well but automation with IxScriptMate helps to simplify and speed the testing process.
Figure 6. OSPF route capacity test results.

3 OSPF Route Convergence Test

Objective
Verifies the ability of a router to switch between preferred and less-preferred routes when the preferred routes are withdrawn and re-advertised. The test calculates convergence by taking an average convergence latency of multiple topological changes.

Setup
This test uses three test ports - one to transmit and two to receive (see Figure 7). Both receive ports emulate OSPF networks. The transmit direction of traffic is unidirectional. The DUT must have three ports utilized with two enabled for OSPF. All three ports should be configured for IP and have unique subnets in which to communicate with the tester ports. Ixia's IxScriptMate application can be used to configure, control, and execute this test.
Figure 7. OSPF convergence test topology. Input Parameters

Parameter	Description
Max Rate	The rate at which frames are transmitted. This is the percentage of the maximum theoretical frame rate
Number of Routes	The number of prefixes to generate at the start of the test
Advertise Delay Per Route	The maximum time, in seconds, to allow the router to absorb each route. This time is multiplied by the number of routes to calculate the "Max Wait Time" - the amount of time the test will wait for the entire topology to stabilize

Table 3. OSPF convergence test input parameters

Methodology
This methodology can be executed manually or by script. The key to determining an accurate convergence time is understanding the DUT capabilities and properly manipulating the test parameters.

1. Test ports 1 and 2 advertise the same OSPF topology and routes with different metrics. The path via port 1 will be used as the preferred route, while the path via port 2 will be used as the alternate route.
2. After the "Max Wait Time", the Tx port sends traffic to target all advertised routes. The DUT should route the traffic via the preferred routes to test port 1.
3. Routes are withdrawn from test port 1 (the preferred path). Traffic should reroute to arrive at test port 2 (the alternate path).
4. Measure the timestamp T1 of the last packet targeting a specific route delivered on the preferred path. Measure the timestamp T2 of the first packet targeting the same route arriving via the alternate path.
5. Calculate the convergence time for one specific route = T2 - T1.
6. Repeat step 4 and 5 to obtain convergence time for all withdrawn routes. Calculate average convergence for all routes.

Results
The test results provide an average convergence time for all routes. Figure 8 displays example results for the automated OSPF convergence test in IxScriptMate. In addition to convergence time, this test also indicates the amount of lost packets caused by the convergence.
Figure 8. OSPF convergence test results.

4 OSPF Topology Scalability Test

Objective
This test builds an OSPF topology and tests the DUT's capability to learn intra-area LSAs. A given number of LSAs are generated and traffic sent to all routes advertised to verify.

Setup
The test requires at least two test ports - one to transmit and one to emulate and advertise the OSPF intra-area topology, as shown in Figure 9. The OSPF tester port must be able to generate OSPF LSAs to construct topological databases. Tester ports can be added on the Rx side to increase the OSPF database to scale. Ixia's IxExplorer OSPF Routing Protocol Emulation can be used to run this test.
Figure 9. OSPF topology scalability test. Input Parameters

Parameter	Description
Traffic rate	Rate at which traffic is sent to the destination routes
Number of ports	The number of Tx(traffic) and Rx (OSPF) ports
Number of routes	The number of routes is dependent on the number of emulated routers.
Number of routers	The number of emulated routers dictates the number of routes, depending on whether the configuration is broadcast or point-to-point

Table 4. OSPF topology scalability test input parameters.

Methodology

1. Configure at least two test ports - one to transmit and one to receive for OSPF.
2. The OSPF port(s) advertise Type 1 router LSAs. The LSAs mesh together to create a logical topology similar to Figure 9. The OSPF grid building feature of Ixia's IxExplorer OSPF Routing Protocol Emulation is shown in Figure 10.
3. Verify all OSPF neighbors per port are in full state on the DUT.
4. Confirm the DUT has learned all LSAs and can effectively forward traffic to all destinations within the topology. Transmit traffic from the Tx test port to accomplish the verification. Packets are counted on the Rx ports and analyzed for missing frames.
5. If route verification is successful, the test can be scaled by adding physical ports, additional emulated routers per port, or more LSAs to each router. Traffic rates can be increased for forwarding performance measurements.
6. Continue to add ports and LSAs until the DUT can no longer forward to all destinations successfully.

Figure 10. OSPF grid configuration example.
Results
This test results in a calculation of the DUT's intra-area LSA storage capacity. The result should be easily viewable in graph or raw numbers of a packets received statistic. Figure 11 show an example of test results using Ixia's IxExplorer OSPF Routing Protocol Emulation.

Figure 11. OSPF graph form results.

5 OSPF Equal Cost Path Verification Test

Objective
This test confirms OSPF load balancing features, given four equal cost paths to the same destination.

Setup
This test requires a minimum of three ports - one to transmit and two to receive and represent four routers with same cost paths to the same destination prefix as shown in Figure 12. Two OSPF Rx ports each advertise two OSPF neighbors, each with the same route advertisement. Ixia's IxExplorer OSPF Routing Protocol Emulation can be used to run this test.
Figure 12. OSPF equal cost path verification test topology.
Input Parameters

Parameter	Description
Traffic rate	Rate at which traffic is sent to the destination network
Number of ports	The number of Tx (traffic) and Rx (OSPF) ports
Number of routes	The number of routes can be increased and load balancing take place over several destinations
Number of routers per port	The number of emulated routers per physical port can be varied

Table 5. OSPF equal cost path verification test parameters.

Methodology

1. Establish the number of test ports needed to advertise the number of OSPF adjacencies required.
2. Advertise LSAs from each peer for the same route. Each emulated router advertises one route path with the same metric.
3. Confirm that the DUT has reached full state with each OSPF router and verify equal cost paths exist and are all in the forwarding table.
4. Run continuous traffic to destination IP addresses in the advertised networks.
5. Increase the number of ports or adjacencies per port with the same route.

Results
This test results in a traffic rate metric for each destination port. Figure 13 shows example test results using Ixia's IxExplorer application. Notice the semi-even traffic distribution across the four equal cost paths.
Figure 13. Statistical results.

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