Dialogic Support Helpweb
Dialogic® Host Media Processing (HMP) Software
How to Replay an RTP Stream to a Remote end-point
Summary::This document provides information on how to use the VSendCap utility to replay a Real Time Transport Protocol (RTP) stream to a remote end-point.
Symptom:
Users in the IP-based community need the capability to replay a RTP stream from a network trace to a Dialogic® Host Media Processing (HMP) software-based system or Dialogic® System Release (SR) software 6.X system including Dialogic® IP boards (e.g., Dialogic® DM/IP boards). In such a scenario, the RTP stream is a collection of RTP packets filtered from a network trace, captured with Wireshark (formerly Ethereal) network protocol analyzer.
Reason for the problem:
Specifically, this refers to issues involving DTMF detection from digits sent and clarity of audio in the RTP stream.
Fix / Solution:
This technical note describes how the VSendCap utility can be used to replay the RTP stream from a network trace to a remote end-point system running Dialogic based hardware/software. The following three steps are required to do this:
- Install the VSendCap utility on the sending system.
- 2. The attached utility, VSendCap, can be run on Windows® Operating Systems, including Windows® 2000, 2003, or XP.
- Please note the following pre-requisite: WinPCap Version 3.0 or later must be installed on the system.
- Configure the VSendCap utility to replay the captured file to the remote end-point.
The following dialog box appears when you run the VSendCap utility:
Override Source Information
When configuring the Override Source Information fields, set the IP Address, MAC Address, and Port Number to that of the sending system where VSendCap is running. Note: Each of these parameters is optional, as the utility will not be reading anything sent back from the remote end-point; however, it is recommended to set them so as to ensure that packets sent are not denied, such as due to restrictions on potential mid-points while packets traverse the network to reach the remote end-point.
Override Destination Information
When configuring the Override Destination Information fields, set the IP Address, MAC Address, and Port Number to that of the remote end-point which receives the RTP stream. Note: To determine the RTP port of IP channels on Dialogic HMP software and Dialogic SR software 6.x based systems, see the following: For Dialogic HMP software, the default RTP port range starts at 49152 for channel 1, 49154 for channel 2, and so on, following that sequence for the amount of IP channels on the system. For Dialogic SR software 6.x the default RTP port range starts at 2326 for channel 1, 2328 for channel 2, and so on, following same sequence as above.
If the sending system (i.e. the one running VSendCap) and the remote end-point (i.e. the one receiving RTP stream) are on different subnets, then set the MAC address to that of the default gateway on which the sending system resides. If the MAC address of the default gateway is unknown, then press the button marked as and located next to the MAC address field. Doing this will cause the following dialog box with the correct MAC address of the available gateways to be displayed.
Then select the network adapter which will be used to send the capture file. Its not recommended to use wireless or dial-up adapters if available.
Press Browse and select the capture file to be sent. The capture file should be pure RTP, not RTP with other packets. If you need to filter the capture file, see the section below titled: Additional Information below.
- 5. Perform the replay and capture the data on the remote end-point. At this time, the VSendCap is ready to replay the capture file to the remote end-point; to do so, click the Send button. Be sure the remote end-point has a Dialogic-based application started to open an IP media session in order to receive the incoming packets that are sent. In this case, the application can perform a recording to capture the audio of the incoming RTP stream, which will be used for investigation of the potential issue raised.
Here are the steps to filter RTP packets from looking at the network capture in Ethereal/Wireshark:
- Select the packet RTP stream you are interested in.
- If required, Right click and “decode as” RTP on selected UDP packet
- Note the SSRC value of the RTP stream
- Put in a display filter of “rtp.ssrc==<value>” (no quotes)
- Go to Menu – File / Save As – put in a file name and under Packet Range select “Displayed”.
- Click Save
- File Menu Fields:
- Load Saved Parameters: This saves the current parameter settings in a XML file. This menu item brings up a file dialog where you choose a directory and filename for the saved parameters.
- Saved Parameters: This loads the parameters back into the form. This menu items brings up a file dialog where you choose the xml file to be loaded.
- For Override Information fields:
- Source IP Address: If checked, the source IP address in the file will be replaced with the address specified.
- Source MAC Address: If checked, the source MAC address in the file will be replaced with the address specified.
- Source Port: If checked, the source port in the file will be replaced with the port specified.
- Destination IP Address: If checked, the destination IP address in the file will be replaced with the address specified.
- Destination MAC Address: If checked, the destination MAC address in the file will be replaced with the address specified. This should be set to the MAC address of the remote end-point or default gateway of the machine running VSendCap. If there is only one choice, this will be filled in automatically. Even though it is filled in, it will not be applied unless the checkbox is selected.
- ellipsis (...) button: In the case that there are multiple choices for MAC addresses, this button will bring up a dialog to allow you to choose a MAC address. You should choose the default Gateway for the machine running VSendCap. In most cases this is associated with IP address xxx.xxx.xxx.250.
- Destination Port: If checked, the destination Port in the file will be replaced with the port specified. By default, this is initially set to 49152. (This is the first port number that Dialogic HMP software opens.) Even though it is filled in, it will not be applied unless the checkbox is selected.
- Respect Timestamps in File: If set to yes, the packets will be sent out with delays calculated from the timestamps in the file. This is the default and recommended setting. If set to no, the packets will be streamed out with no delay.
- File: This is the name of the prepared capture file to send to the remote end-point. The browse button brings up a file dialog to enable you to find the file.
- Adapter: This is the name of the device that is used to send the file. Choose from the dropdown list of available adapters on the system.
- Send: This begins sending the prepared capture file to the remote end-point. If there are any invalid parameters, they will be highlighted with a red exclamation mark. Allow your cursor to hover over the mark to see what is wrong with the field.
- Exit: Quits the program.< /ul>
Product List
Dialogic® Host Media Processing (HMP)software
Dialogic® System Release software 6.x (w/ Dialogic® DM/IP Hardware)
Glossary of Acronyms / Terms
MAC: Media Access Control
RTP: Real-time Transport Protocol
This document discusses one or more open source products, systems and/or releases. Dialogic is neither responsible for your decision to use open source in connection with Dialogic products (including without limitation those referred to herein), nor is Dialogic responsible for any present or future effects such usage might have, including without limitation effects on your products, your business, or your intellectual property rights.
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