HOWTO One-way audio

TABLE OF CONTENTS

• Introduction
• One-way audio occurred on a single extension
• One-way audio system-wide issue

Introduction

If you are encountering one-way audio problems, start by identifying whether the issue is affecting the entire system or is isolated to a specific tenant or extension. This initial step is crucial in diagnosing and addressing the problem effectively. To do this, check if the audio issue persists across different users or devices within the same system. If it is localized, you might need to delve deeper into the configurations or settings related to that particular tenant or extension to resolve the problem(mostly network which tenant/extension uses).

One-way audio occurred on a single extension

There are cases where only one extension is experiencing these issues. In such cases, you should check the following:

Extension -> Advanced Options -> Network Section -> NAT  set to Yes

Additionally, if the issue persists after making this change, please try switching the protocol to TCP as well. Furthermore, if you need further assistance with troubleshooting the issue, refer to the section below where the use of the sngrep tool is explained.

One-way audio system-wide issue

Troubleshooting path:

1. SSH into your PBXware system.
2. Use the ifconfig command to check if the PBXware is behind NAT.
3. If PBXware is behind NAT, verify that the NAT settings are properly configured under:

Master Tenant -> Settings -> Protocols -> NAT section 

• The external IP address field is correctly populated.
• The local networks field has the proper local range set.
• NAT is set to Yes

The second step would be to confirm that under: 

Settings -> Protocols -> RTP tab

The option called "Strict RPT protection" is set to NO,  as this can sometimes cause one-way audio issues.

NOTE: Once the first 2 steps have been checked and confirmed, in case you had to set up everything you should restart PBXware for all of the above to take effect. After restarting the services, check if one-way audio issues still occur.

If they do, the next step is to use sngrep to determine the issue at the SIP level. 

/opt/pbxware/sh/sngrep -r

Note: It is important to understand that any type of audio issue, cannot be identified from the written report (CLIR report) since it only contains segments of Asterisk output and does not include SIP flow information. We must acknowledge that a SIP trace with RTP is the only method to verify the RTP flow and detect potential packet loss. 

What should be done here is to verify the call to ensure that RTP is present from both ends, which would not be the case if there were a one-way audio issue.  

If RTP is being sent from both the client and server sides, you can confirm that RTP is being transmitted correctly and also check if the codecs being used are the same.

In many cases, it becomes apparent that RTP traffic is directed to the private IP addresses of devices, suggesting that SIP ALG may be the cause of the issue. Please advise the customer to meticulously examine both the router positioned in front of the PBXware and the routers at their site. 

For example, to identify whether the router in front of the PBXware is responsible for the problem, you can check sngrep when registering your device, which will reveal that traffic is being routed to the device's private IP address.