Agilent N2X Testing IPTV Channel Zapping

Agilent N2XTesting IPTV Channel Zapping

Application Note

Channel zapping is a key element of the end user's IPTV QoE (Quality of Experience). The Agilent N2X provides the most powerful channel zapping test solution for accurately measuring the scalability and capacity of IPTV infrastructure devices, and characterizing end-user Quality of Experience (QoE) under real-world loads.

Agilent N2X - Testing IPTV Channel Zapping

Introduction

Agilent N2X

Agilent N2X is the industry's most comprehensive test solution for testing the development and deployment of network services for converging network infrastructures. Service providers, network equipment manufacturers (NEMs), and component manufacturers can verify service attributes of entire networks end-to-end, while also isolating problems down to individual networking devices and subsystems.

IPTV

Internet Protocol Television (IPTV) services, are being rolled out at an unprecedented rate as a key component of service providers' "triple-play" service offerings. These new services are expected to yield additional profits for Communication Service Providers (CSP) and drive increased competition in the television industry. Customer expectations are high and the "quality of experience (QoE)" they receive from their IPTV service will be paramount.

IPTV service delivery is also driving CSP capital expenditures in the race to upgrade their access networks to accommodate the demands of TV service delivery over an IP network core. By way of example, a standard IPTV channel using MPEG-2 encoding requires 3.5Mbps. Provisioning 2~3 channels per household along with other network services over the same physical connection will require a minimum of 10Mbps into the premise. Very few CSP access networks today can accommodate this capacity to any great scale.

Powering the next generation access network are a new range of devices including B-RAS (Broadband Remote Access Server), EAR (Ethernet Aggregation Router), or IP/Ethernet-based DSLAM (Digital Subscriber Line Access Multiplexer). Network equipment manufacturers must accurately characterise channel zapping performance times of their B-RAS and IP-DSLAMs under the complexity and volatility of real world network conditions. Service providers must also validate zapping times across their networks end-to-end to have confidence that their service will meet the expected service levels.

Test your network device's IPTV channel zapping performance with Agilent N2X.

The end user experience of service quality is critical to the success of a service provider's IPTV deployment program. A key element of IPTV quality of experience (QoE) is how quickly and reliably end users can change TV channels, often referred to as "channel zapping".

Network equipment use multicast to deliver IPTV channels to consumers. Set-Top Boxes in the home use IGMP (Internet Group Management Protocol) to change channels, by leaving and joining multicast groups representing channels.

The speed at which multicast groups are left and joined greatly affects user viewing experiences.

If users expect a channel zapping delay of one second, each device in the end-to-end IPTV network can introduce only tens to hundreds of milliseconds of delay. This Application Note describes how to use N2X to quantify the channel zapping performance of IGMP-capable devices.

Copyright © Agilent Technologies, Inc. 2005 2 www.agilent.com/comms/N2X


Below is a diagram of a standard Agilent N2X and IGMP-capable network equipment setup.

Use N2X to measure the channel-zapping performance of an IGMP-capable device such as a B-RAS (Broadband Remote Access Server), DSLAM (Digital Subscriber Line Access Multiplexer), EAR (Ethernet Aggregation Router), or EPON (Ethernet Passive Optical Networks) device.

To test IPTV channel zapping performance, follow these steps:

1. (Optional) Do a pre-test setup check

2. Configure the test cases

3. Run the test cases

4. Analyze the test results

Step 1. Do a pre-test setup check

Before running the IPTV test for the first time, you should ensure that the SUT (System Under Test) can establish link-layer communication with and forward multicast traffic to N2X. You do not need to do this each time you run the IPTV test-the IPTV test automatically configures all required test session components when started. You should however do this check to troubleshoot any pre-existing link or multicast problems between the SUT and tester. Do the following:

1. Physically connect the SUT interfaces to the N2X test ports.

2. Launch the N2X Packets and Protocols application.

3. Establish link-layer communication. If using Ethernet, verify that ARP resolves all MAC addresses.

4. Configure IGMP sessions, define the multicast groups, and enable IGMP sessions to join/leave groups.

5. When you have verified that this is working, clear all multicast groups from the SUT.

Simulated video sourcesand background traffic

Simulated subscribers

SystemUnder Test

N2X Test Port 1 N2X Test Port 2

SUT Port 1 SUT Port 2

VLAN 1VLAN 2

.

.

.VLAN n

DSLAM

DSLAM

Internet

Video On Demand

Broadcast

Voice

Video Sources

BackgroundTraffic

Figure 1. Standard N2X and SUT setup



Step 2. Configure the test cases

Use the following general configuration steps for all IPTV Channel Zapping Test Cases. This Application Note illustrates Ethernet as the link-layer protocol.

Procedure:

1. Start the IPTV Channel Zapping Productivity Application. You can launch the application from the N2X Packets and Protocols application (Release 6.5 onwards).

2. In the main IPTV window, click the Configure icon to display the Configure Parameters dialog.

1.1 - In the Application area1.2 - Click the Productivity tab1.3 - Double-click on the IPTV test2 - In the main IPTV window, Click “Configure” to display the Configure Parameters dialog

Figure 2. IPTV Channel Zapping main window



3. From the Configure Parameters dialog, click the Configure Session tab. Then click the Select button.

4. Identify the N2X controller PC you are using to run the test. This can be localhost (which indicates the local PC you are using) or the host name or IP address of a remote PC. Then select the N2X test session to use for the IPTV test.

Note: Before you run the IPTV test, you must launch the N2X Packets and Protocols application, start a test session, select the test ports used in the IPTV test, and enable any optical transmit lasers. By default, the IPTV test uses the first test session; select a different test session as needed.

3.1 - Click on “Configure Session”3.2 - Click “Select”

4 - Select the N2X test session to use

Figure 3. N2X controller and session configuration



5. Click the Configure Test tab. Then click the Interfaces tab to configure video sources and subscribers.

6. Click Add Port to use a new N2X test port to simulate video sources. Or, select an existing or predefined port and click Edit to modify its settings. Sub-interfaces representing video sources can be added to the port. Port types can be Ethernet, ATM, Frame Relay, or POS.

7. To simulate video sources on sub-interfaces, click the Add Sub-Interfaces button and configure the options. If the native test port interface is being used, you must remove the default VLAN (101/1/1).

8. You can use any N2X ATM port, GbE port, or tri-rate Ethernet port to simulate IPTV subscribers. Click Add Port to add a test port. Or, select an existing port and click Edit to modify its settings.

9. To add a group of subscribers, select a test port and click Add Subscriber Pool. Subscriber pools allow you to scale to thousands of subscribers easily. However, each subscriber in a pool watches and changes the same channels during the test cases. To simulate several blocks of subscribers changing to different channels, use several subscriber pools. The subscriber VLANs/PVCs must be in the range selected in the Add/Edit Source Port dialog.

Note: The test results are displayed both per subscriber pool as well as per individual subscriber.

5.1 - Click “Configure Test”5.2 - Click “Interfaces” to configure video source and subscribers6.1 - Click “Add Port” to add a N2X test port as a video source.6.2 - To edit an existing port, select it and click “Edit”

7 - If video sources are on sub interfaces(i.e. VLAN or ATM/Frame Relay PVC’s)click “Add Sub-Interface” to configure them

8 - Click “Add Port” to add a N2X test port for Video

9 - Click “Add Subscriber Pool” to configure the subscribers and their sub-interfaces

Figure 4. Interfaces tab, used to configure video sources and subscribers



10. Click the Multicast tab to configure the TV channels. Here you can select the version of IGMP to use (v2 or v3), specify whether the IPTV configuration is displayed in full or summary when viewed through the N2X application (Routing dialog), and configure the TV channels (i.e. the multicast groups).

11.Click the Traffic Profile Manager button to review and change as needed the video encoding formats. There are predefined profiles such as MPEG2-HDTV and MPEG4-SDTV, which automatically set the appropriate IP packet length, type, and rate. In addition, you can define 3 custom profiles.

12.The First 23 bits of Multicast Address are the same for all channels. Change these bits as needed.

13.You can simulate and get real-time statistics for 512 TV channels (i.e. multicast addresses). Four channels are set up by default; you can keep these or add more. To add channels, click Add and configure the number of channels, multicast group addresses, source port, and traffic profile.

10.1 - Click “Multicast”10.2 - Select the IGMP version and other IGMP settings

11.1 - Click “Traffic Profile Manager” to determin the video encoding formats (e.g. MPEG2-SDTV) You can define three custom formats

12 - The first 23 bits of multicast addresses are the same for all groups.To change these bits, type the new values and click “Appply” to update existing groups

13.1 - To add a new TV channel click “Add”13.2 - Configure the number of channels, multicast addresses, traffic profile, etc.

Figure 5. Multicast tab, used to configure TV channels and traffic profiles



14. Click the Test Scenario tab to select a test case and define how IPTV subscribers change channels.

15. From the Test Case drop-down menu, select an IPTV test case:

• Channel Zapping-Determines the latency between leaving one channel (IGMP group) and joining another channel.• Join Delay-Determines how quickly a SUT starts forwarding traffic after receiving an IGMP Join message.• Leave Delay-Determines how quickly a SUT stops forwarding traffic after receiving an IGMP Leave message.• Resilience to Peak Load-Measure the performance and functionality of changing channels under stress conditions. This may be a large-

scale test with 1000s of sub-interfaces (subscribers) changing channels at the same time. All subscribers change to and from the same channels.

• Sustained Performance-Tests sequential Join/Leave delays over a long period of time. Sustained performance of a varying channel surfing load is measured, involving many simulated subscribers switching TV channels at various times.

For each test, you can select subscriber pools (that is, groups of subscribers defined in Interfaces tab): In the Watching Channels area, click the Enable checkbox for a subscriber pool.

14 - Click on the “Test Scenario” tab

16 - Select the channels recieved by the subscriber pool

17 - Define how a subscriber pool changes channels

15 - Select a test case

Figure 8. Test Scenario tab, used to select channels and define channel changing



16. To configure the channels each subscriber pool watches, select a subscriber pool and click Select Channels. The Channel Selector dialog is displayed. A subscriber, which can be a household or a business, can receive up to 4 channels at the same time. Typically, this represents 4 separate televisions. However, it can also represent fewer televisions displaying several channels at the same time (for example, using a picture-in-picture feature). You can define how each received channel stream changes channels.

17. On the Test Scenario tab, click Define Times to display the Define Zapping Times dialog and define how long subscribers view each channel. You can also configure the set-top box delay and the channel watching times for each channel.

18. Click the Background Traffic tab to fill the bandwidth with other types of traffic, for example, to simulate subscribers who receive other triple play or Internet services. Here you can customize the traffic sources and destinations; frame contents; and transmit load.

Note:

• For details about a setting on this tab, click the Help button.• The ports used to send and receive the background traffic must first be configured on the Interfaces tab, in order to establish port framing

and default addressing.

Figure 6. Background Traffic tab, used for optional background traffic



19. Click the Test Control tab to review other default settings and change as needed. For most basic test scenarios, you can use the default values.

Note:

• For details about a setting on this tab, click the Help button.• If you defined Background Traffic, you use this tab to enable and disable it for each test.• For the Sustained Performance and Resilience to Peak Load test cases, change the default test duration as needed.• The Run Mode determines what happens when you click the Start button on the main IPTV window:

• Setup and run-configures the IPTV test, starts the routing engine (to begin IGMP emulations), and starts traffic (both video and background)

• Setup only-configures the IPTV test only. You can then use N2X Packets and Protocols to fine-tune the test (e.g. establish PPPoX sessions for subscribers, define more background traffic)

• Run only-starts the routing engine and traffic only. If you are running the same test repeatedly, use this to avoid configuring the test each time.

Figure 7. Test Control tab, used for optional parameter configuration



Step 3. Run the test cases

In the main IPTV window, click the Start button. The test stops automatically at the specified test duration. You can manually stop a test by clicking the Stop button.

To determine the SUT's performance and scalability limits, change the following after each test iteration:

• Number of subscribers• Number of channels• Number of ports• Bandwidth and packet size of video streams (i.e. MPEG-2 SD/HD, H.264, etc.)• Type of access (Bridged Ethernet, VLAN, ATM….)• Amount of background traffic

Start the test

Click the “Report” tabto see the key test results in text format

Click the “Graph” tabto see full test resultsin a graph or histogram

Click the “Test Log” tabto see a trace of the test configuration

Figure 9. Main screen, used to start and stop tests



Step 4. Analyze the test results

Using the Channel Zapping test case as an example, below is a comparison and explanation of the graphical results for two tests, run using the same SUT and configuration. One test consists of 1000 subscribers (20 subscriber pools, 50 subscribers each) and the other test consists of 150 subscribers (3 pools, 50 subscribers).

Join/Leave/Zap Latency vs. Channels.

These graphs show how the number of channels in the test affects latency.

Figure 10. Latency vs. Channels, 1000 subscribers

Figure 11. Latency vs. Channels, 150 subscribers



Latency Distribution.

This graph shows the latency distribution, grouping together subscribers with the same latencies; from the diagrams below it is evident that increased numbers of subscribers dramatically impacts latency.

Figure 12. Latency Distribution, 1000 subscribers

Figure 13. Latency Distribution, 150 subscribers


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Copyright © Agilent Technologies, Inc. 2005Specifications subject to changeSeptember 09, 20055989-3885EN

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Agilent N2X Testing IPTV Channel Zapping