7.4 Designing a VoIP Quality Assessment

To begin designing your assessment, click the Design view tab. The Using the Design View window provides a brief tutorial. Clear Show this upon entering Design view if you do not want to see the tutorial anymore. Re-invoke it anytime by clicking Help > Using the Design View.

The Design view offers five tools for building VoIP Quality assessments. Mouse over a tool button to view the tool name.:

Tool

Description

Selection tool

Lets you select and manipulate Design tools.

Endpoint

Creates an endpoint and places it on the network diagram. Endpoints are computers on which Performance Endpoint software is installed.

Endpoint Group

Creates a group of endpoints and places it on the network diagram. Endpoint groups let you create multiple call groups with fewer connectors.

VoIP Connector

Connects two endpoints to form a call group. Specifies the type and quantity of calls to be sent between the endpoints

Background Traffic Connector

Sends TCP/IP data between two endpoints Specifies the data rate for this network traffic.

To design a VoIP Quality assessment, first use the Endpoint tool to add an endpoint or group to the Network Diagram. The Create an Endpoint dialog box lets you enter an IP network address to represent a VoIP-enabled computer on your network. For more information, see Section 7.4.2, Creating an Endpoint.

Next, connect two endpoints or endpoint groups using the VoIP Connector tool. The Create a VoIP Connector dialog box lets you select key parameters for the voice traffic that will be sent between the, including the type of codec emulated and the number of simultaneous calls represented. The combination of two endpoints or endpoint groups and a VoIP connector makes a call group, the basic unit of a VoIP Quality assessment.

For more information, see the following topics:

7.4.1 Reviewing Design Features

Vivinet Assessor offers several features that help you design and run a VoIP Quality assessment:

Feature

Description

Drag-and-drop interface

After an endpoint appears in the Endpoint and Group List, you can drag it to the diagram and drop it. This action opens the Create an Endpoint dialog box and places an icon for the endpoint on the diagram.

Disable Connector option

To exclude a call group or background traffic from an assessment without deleting the connector, click to select a VoIP or Background Traffic connector, then right-click and select Disable Connector. You can enable it again later.

Endpoint verification

Save time by making sure endpoints are available before trying to verify or run the VoIP Quality assessment. To verify an endpoint, select it in the Endpoint and Group list. Then right-click and select Verify Endpoint. A green check mark appears next to any endpoint that has been successfully verified. If the endpoint cannot be reached, a red X appears.

Endpoint Information

Once an endpoint has been successfully verified, information is available about the computer where it is installed. Click to select any verified endpoint in the Endpoint and Group list. Right-click and select Endpoint Information. A dialog box provides information about the operating system and memory on the endpoint computer, the version of the endpoint software, and whether any verification errors have occurred.

7.4.2 Creating an Endpoint

You use the Endpoint tool to add an endpoint to the Network Diagram.

To create an endpoint:

  1. Drag the Endpoint tool to the Network Diagram.

  2. Complete the fields in the dialog box as discussed below:

    Field

    Description

    Endpoint name

    The name of the endpoint computer. Can designate an actual computer on the network, or a network location.

    Address type

    The network addressing scheme that applies to this endpoint computer’s network interface card (NIC). A single computer can be assigned multiple IP addresses for advanced assessments. Choose from Single IP Address or Range of Virtual IP Addresses.

    Choose Range of Virtual IP Addresses to create assessments with many simultaneous calls using different addresses, but with only a few computers to represent those calls. Provide the first and last IP addresses in the range in the To and From fields. If necessary, use the Increment by field to delineate separate subnets or classes of address within a single range.

    Network address

    An endpoint computer’s network address, or a set of addresses assigned to that computer’s NIC. Type a DNS hostname, such as headquarters, or the IP address of the endpoint computer in dotted notation, such as 135.25.25.5.

    Advanced

    Provides more options for testing through a NAT-enabled device or using an alternative network for test setup flows.

    Setup Address (optional)

    The network address at which the Vivinet Assessor Console should contact an endpoint. The Console sends the endpoint setup information about the type of VoIP traffic to simulate. It can send these setup flows over a different connection from the one specified in the Network address field. This is the address by which Vivinet Assessor identifies the endpoint containing the virtual addresses, if any are used. You should also enter a setup address if the Console must contact an endpoint behind a NAT-enabled firewall.

    Contact endpoint using setup address

    Instructs the Console to use an alternative IP address to contact this endpoint. If this box is checked, you must also enter a Setup address. The Network address you entered for this endpoint will still be used for test traffic between the endpoints

    Network Address Translation (NAT) Information

    If an endpoint is located behind a router or firewall that performs NAT, you need to do some extra configuration to allow the VoIP Quality assessment to proceed. For more information, see Section 7.8.2, Working with Firewalls.

    Be sure to read the section titled Section 7.12.5, Performing Assessments with NAT before you configure a VoIP Quality assessment through a NAT-enabled device.

    Contact endpoint behind NAT device

    Signals to the Console that this endpoint must be contacted at the IP address provided in the NAT address field.

    NAT address

    The endpoint IP address that is used on the public or non-secure side of a network protected by a firewall that performs network address translation.

  3. Click OK. An icon for the new endpoint is displayed on the Network Diagram.

7.4.3 Creating an Endpoint Group

You can organize your endpoints into endpoint groups. Endpoint groups are particularly useful if you are trying to assess the performance of VoIP calls between two sites—over a WAN link, for example. With groups of , you spend less time creating endpoints and VoIP connectors if you want to emulate multiple calls. You can even add existing endpoint groups to new endpoint groups.

To create an endpoint group:

  1. Drag the Endpoint Group tool to the Network Diagram.

  2. Complete the fields in the dialog box as discussed below.

    Field

    Description

    Endpoint group name

    The name of the group of endpoints you are creating. Identifies the icon that appears on the diagram after you add endpoints to the group. Required field.

    Available endpoints and groups

    A list of endpoints and endpoint groups that you have already created. Highlight the endpoint or groups you want to add to the new group you are creating and click Add. Your selection is displayed in the Endpoint group members list.

    Remove

    Removes an endpoint or endpoint group from the endpoint group you are creating. Does not delete the endpoint from the Endpoint List.

    Endpoint Quick Add

    Lets you add a new endpoint to your list of endpoints It is “quick” because you do not have to open a separate Create an Endpoint dialog box. This method of creating a new endpoint does not allow you to choose a different IP address for assessment setup.

    Add Endpoint

    Adds the endpoint you just created using Endpoint Quick Add to the endpoint group you are creating.

  3. Click OK to save the endpoints in the Endpoint group members list. Their group name appears in the Available endpoints and groups list, and a set of grouped icons is displayed on the Network Diagram.

7.4.4 Creating a VoIP Connector

By connecting two , VoIP connectors create call groups that emulate VoIP calls between endpoint computers on your network. The Create a VoIP Connector dialog box lets you select the parameters that match your VoIP application.

To create a VoIP connector:

  1. Click the VoIP Connector tool.

  2. Click an endpoint or endpoint group icon on the Network Diagram and drag the solid arrow to another endpoint or endpoint group.

  3. Complete the fields in the dialog box as discussed below.

    Field

    Description

    From Endpoint or Endpoint Group

    The first endpoint in the call group. Endpoints are computers that initiate and receive bi-directional, simulated VoIP calls during the assessment. Designated as Endpoint 1 in the Call Groups--MOS Summary of Verification Calls table in the Verify view.

    To Endpoint or Endpoint Group

    The second endpoint in the call group. Designated as Endpoint 2 in the Call Groups—MOS Summary of Verification Calls table in the Verify view.

    Call Script

    The type of codec used to send VoIP datagrams, plus any additional parameters that affect the calls that are sent on the network. Choose one of the supported call scripts from the list. For more information, see Section 7.11.2, Reviewing Codec Types.

    View this Call Script

    Click to view details about the codec selected in the Call Script list.

    Connector multiplier

    The number of times the identical connector will be represented in the assessment. This value corresponds to the number of simultaneous calls Vivinet Assessor will emulate between these endpoints Values must be between 1 and 1,250, inclusive. The default value is 1. For more information, see Section 7.1, Planning a VoIP Quality Assessment.

    Connector Comment (optional)

    Identifies the VoIP connector on the Design diagram.

    Use default comment

    By default, the Connector Comment is the call script selected, plus the names of the endpoints Endpoint 1 is listed first.

    Port Range (optional)

    A range of ports to use for the simulated VoIP traffic sent between the endpoints Remember that RTP uses even-numbered ports. This port range will override the one you set on the Firewall tab of the Assessment Options dialog box. Accepted values are 1 - 65535, inclusive. The first value must be less than the second value.

    NOTE:If the Port Range you set here does not include Port 10115 (endpoint-to-endpoint configuration traffic) and Port 10116 (endpoint-to-Console results traffic), these ports will still be used, and so need to be configured at the firewall. For more information, see Section 7.8.2, Working with Firewalls.

  4. Click OK. After you create a call group, the Call Count in the lower right of the assessment window shows you how many VoIP calls will be emulated.

NOTE:Any VoIP connector you create is enabled by default. To disable a connector for a particular assessment run, select the connector on the diagram. Then click Disable Connector on the Edit menu.

7.4.5 Creating a Background Traffic Connector

Background Traffic connectors send TCP/IP packets between the endpoints on a particular network segment. Select the data rate to match an expected or projected level of network bandwidth utilization for that segment. The extra network traffic helps you test the effects of QoS, or it shows how VoIP quality is affected when small VoIP packets get behind larger TCP/IP packets in the network.

To create a background traffic connector:

  1. Click the Background Traffic Connector tool.

  2. Click an endpoint or endpoint group icon on the Network Diagram and drag the dashed arrow to another endpoint or endpoint group.

  3. Complete the fields in the Create a Background Traffic Connector dialog box as discussed below.

    Field

    Description

    From Endpoint or Endpoint Group

    The endpoint that will send the TCP packets. Designated as Endpoint 1 in the Background Traffic -- Summary table in the Verify view.

    To Endpoint or Endpoint Group

    The endpoint that will receive the TCP packets. Designated as Endpoint 2 in the Background Traffic -- Summary table in the Verify view.

    Connector Comment (optional)

    Identifies the connector on the Design diagram.

    Use default comment

    By default, the Connector Comment consists of the data rate and the names of the endpoints Endpoint 1 is listed first.

    Data Rate

    The rate at which packets will be sent between the —the throughput to be attempted. Should match an expected or projected level of bandwidth utilization. Default is 28.8 kbps (modem).

    Custom

    Lets you define a custom data rate, including the number of bytes to send (the packet size), the number of times to send a packet, and an interval between SENDs (in seconds). For more information, see Section 7.4.6, Setting a Custom Data Rate.

    Port Range (optional)

    A port or range of ports to use for the TCP traffic sent between the endpoints Accepted values are 1 - 65535, inclusive. Enter the same value in each field to specify a single port.

    Initial Delay

    Optional parameter. Set a value for the endpoints to wait before beginning to send background-traffic data. Select the Type of delay, and then indicate the Value for the length of the delay. For more information, see Section 7.10.2, Setting the Initial Delay.

  4. Click OK.

NOTE:Any Background Traffic connector you create is enabled by default. To disable a connector for a particular assessment run, right-click the connector on the diagram and select Enable Connector.

7.4.6 Setting a Custom Data Rate

The custom data rate option is particularly useful for testing VoIP QoS at slower link speeds. You determine how often the endpoints send a data packet or packets, and you set the number of packets to send and the number of bytes in each packet. When they compete with the VoIP packets, larger data packets may cause certain VoIP performance metrics to degrade each time they are sent, showing the effects of queuing in the network.

Fill in each field on the Background Traffic Connector dialog box to set a custom data rate for background network traffic. The first field determines the number of bytes to be sent in each data packet. The second field determines how many packets to send at the same time. The third field determines how often a packet is sent while simulated calls are running, or, technically, how frequently the endpoints issue a SEND command.

Background traffic runs only as long as the call duration you set in the Schedule view. For more information, see Section 7.10.2, Setting the Initial Delay.

The following is an example of how you might set a custom data rate. To send two packets of 1500 bytes each every five seconds during each set of calls, you would enter the following:

Send 1472 bytes 2 times, every 5 seconds.

Headers will add a few bytes to the number of bytes you set. Thus in our example, the actual datagram size would be 1500 bytes after the addition of a

  • 20-byte IP header, and an

  • 8-byte UDP header.

NOTE:Background Traffic connectors normally send data using TCP. However, when you specify a custom data rate, the data is sent using UDP so that the endpoints can generate the exact packet size requested. Otherwise, TCP buffering would prevent the endpoints from sending packets of the specified size.

7.4.7 Viewing Network Diagram Objects

Vivinet Assessor includes standard Windows options for viewing and organizing the endpoints and call groups you have added to the Network Diagram. You can also control how open windows are displayed.

Tool

Description

Draw menu

Lets you change your network diagram organization.

Order

When your network diagram contains many , you can place their icons over each other by clicking and dragging. To view an endpoint or group icon that is partially obscured, first click it to select it. Then choose one of the following menu items:

  • Bring to Front — Places a selected icon in front of another icon.

  • Send to Back — Places a selected icon behind another icon.

Zoom In or Out

Gives a closer or broader view of the network diagram objects. Correspond to “+” and “-” buttons on the Design toolbar.

View menu

Lets you switch between views. Each view provides access to different menus and functionality as you design and run an assessment.