Audiocodes tunneling: Difference between revisions

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== VoIPmonitor Configuration for Audiocodes Tunneling ==
= AudioCodes Tunneling =
This guide explains how to configure VoIPmonitor to process packets that are tunneled from an Audiocodes Session Border Controller (SBC). This specific setup is for capturing data sent through the Audiocodes tunnel and differs from the standard configuration for capturing direct network traffic.
[[Category:Configuration]]
[[Category:Sensors]]


=== Overview ===
AudioCodes tunneling allows AudioCodes SBCs to encapsulate and forward SIP/RTP packets to VoIPmonitor via the "Debug Recording Server" feature, as an alternative to traditional SPAN port mirroring.
AudioCodes tunneling allows AudioCodes Session Border Controllers (SBCs) to encapsulate and forward SIP/RTP packets to VoIPmonitor, instead of using traditional network port mirroring (SPAN).


The setup involves two components:
<kroki lang="mermaid">
%%{init: {'flowchart': {'nodeSpacing': 15, 'rankSpacing': 40}}}%%
flowchart LR
    subgraph Network["VoIP Network"]
        Phone1["SIP Phone"]
        Phone2["SIP Phone"]
    end


# '''AudioCodes SBC Configuration''' - Configure the AudioCodes device to forward packets to VoIPmonitor
    subgraph SBC["AudioCodes SBC"]
# '''VoIPmonitor Server Configuration''' - Configure VoIPmonitor to receive and process the tunneled packets
        TLS["TLS Termination"]
        Debug["Debug Recording<br/>Server Feature"]
    end


=== Step 1: Configure the AudioCodes SBC ===
    subgraph VM["VoIPmonitor Server"]
        Sniffer["Sniffer<br/>Port 925"]
        DB[(Database)]
    end


On the AudioCodes device, you need to enable the packet forwarding feature and configure it to send packets to the VoIPmonitor server.
    Phone1 -->|"SIP/TLS + RTP"| TLS
    Phone2 -->|"SIP/TLS + RTP"| TLS
    TLS --> Debug
    Debug -->|"Decrypted<br/>SIP/RTP<br/>UDP/TCP 925"| Sniffer
    Sniffer --> DB
</kroki>


**Required Settings (AudioCodes Device):**
== When to Use AudioCodes Tunneling ==


Access the AudioCodes SBC configuration interface (web GUI or CLI) and locate the following setting:
This method is ideal for:
* '''TLS 1.3 / ECDHE encrypted traffic''' - The SBC decrypts internally, no SSL key logger needed
* '''MS Teams Direct Routing''' - SBC-to-Microsoft traffic uses PFS where private key decryption is impossible
* '''Cross-segment monitoring''' - When SBC and VoIPmonitor are on different network segments
* '''Closed appliances''' - When you cannot inject SSL key logger libraries


* '''Debug Recording Server''' (or equivalent log/mirroring server setting)
{{Note|1=For MS Teams Direct Routing, AudioCodes tunneling is often the most practical solution because it does not require access to Microsoft's private keys.}}
* Set this to the '''IP address of your VoIPmonitor server'''
* The AudioCodes SBC will then encapsulate SIP/RTP packets and send them to this IP address


The exact configuration steps vary by AudioCodes model and firmware. Refer to the AudioCodes documentation for:
For other TLS decryption methods, see [[Tls|TLS Decryption Guide]].
* "Configuring the Debug Recording Server"
* "Log server configuration"
* "Session mirroring"


**Network Ports Used by AudioCodes:**
== Configuration ==


By default, AudioCodes uses the following port for forwarding packets:
=== Step 1: AudioCodes SBC ===
* '''UDP/TCP 925''' (Default port)


You can configure a different port if needed, but ensure it matches the VoIPmonitor configuration (see Step 2).
On the AudioCodes device:
# Locate '''Debug Recording Server''' (or "Log server" / "Session mirroring")
# Set the IP address to your '''VoIPmonitor server IP'''
# Default port: '''UDP/TCP 925'''


'''Important:''' This method is preferred over traditional SPAN mirroring when:
Refer to AudioCodes documentation for model-specific steps.
* The AudioCodes SBC and VoIPmonitor sensor are on different network segments
* You need to avoid configuring switch-level SPAN ports
* You want more control over which traffic is forwarded


=== Step 2: Configure VoIPmonitor to Receive Tunneled Data ===
=== Step 2: VoIPmonitor Server ===


To enable the processing of data from an Audiocodes tunnel, the following options must be enabled in the sniffer's configuration file (<code>voipmonitor.conf</code>).
Edit <code>/etc/voipmonitor.conf</code>:


audiocodes           = yes
<syntaxhighlight lang="ini">
# The main switch that activates the Audiocodes tunnel processing feature.
audiocodes = yes
udp_port_audiocodes = 925
tcp_port_audiocodes = 925
</syntaxhighlight>


# Next, define the ports on which the sniffer will listen for incoming tunneled data.
Restart the service:
# These must match the port configured on the AudioCodes SBC.
<syntaxhighlight lang="bash">
# Choose the transport protocol (UDP/TCP) used by your Audiocodes SBC and enable the corresponding option.
systemctl restart voipmonitor
udp_port_audiocodes  = 925
</syntaxhighlight>
tcp_port_audiocodes  = 925


# Ensure your firewall allows these ports (default: 925)
{{Note|1=Ensure your firewall allows incoming traffic on port 925.}}


=== Special Options for RTP/RTCP Handling ===
== RTP/RTCP Handling Options ==
These options address scenarios where VoIPmonitor can see both 'pure' (non-encapsulated) network packets and packets encapsulated within the Audiocodes tunnel for the same call. They allow you to specify which packets should be assigned to the final CDR, preventing data duplication.


audiocodes_rtp  = no/yes/only/only_for_audiocodes_sip
These options control how VoIPmonitor handles RTP/RTCP packets when both tunneled and pure (non-encapsulated) packets are captured:
audiocodes_rtcp = no/yes/only/only_for_audiocodes_sip


<syntaxhighlight lang="ini">
audiocodes_rtp  = yes | no | only | only_for_audiocodes_sip
audiocodes_rtcp = yes | no | only | only_for_audiocodes_sip
</syntaxhighlight>


The values for these options mean:
{| class="wikitable"
* <code>no</code> - Disables processing of RTP/RTCP packets that arrive encapsulated in the Audiocodes tunnel.
|-
* <code>yes</code> - Enables processing of RTP/RTCP packets from the tunnel. This is the '''default''' value.
! Value !! Description !! Use Case
* <code>only</code> - Assigns '''only''' RTP/RTCP packets that are encapsulated in the Audiocodes tunnel to the call/CDR. Any pure (non-encapsulated) packets for the same call, if also seen by the sniffer, will be ignored.
|-
* <code>only_for_audiocodes_sip</code> - Tunneled RTP/RTCP packets are assigned to a CDR '''only if''' the SIP signaling for that call was also delivered through the Audiocodes tunnel.
| <code>yes</code> || Process tunnel RTP/RTCP ('''default''') || Tunnel-only capture, no SPAN
 
|-
=== Common Scenarios and Troubleshooting ===
| <code>no</code> || Ignore tunnel RTP/RTCP || Use only pure packets
 
|-
'''Problem: Mixed RTP Streams (RTP + SRTP)'''
| <code>only</code> || Use '''only''' tunnel RTP/RTCP for all calls || Exclusively use tunnel data
|-
| <code>only_for_audiocodes_sip</code> || Use tunnel RTP only if SIP was also tunneled || '''Recommended for mixed capture''' (tunnel + SPAN)
|}


When the sniffer captures traffic where plain SRTP is received via the Audiocodes tunnel alongside other traffic (e.g., mirrored traffic on a SPAN port), the resulting RTP streams can become mixed or incorrectly correlated. This happens because VoIPmonitor sees both the encapsulated packets from the tunnel and the pure packets on the network interface.
=== Mixed Traffic Configuration ===


'''Solution:'''
When capturing both AudioCodes tunnel and SPAN traffic, use:
 
To ensure RTP packets from the Audiocodes tunnel are correctly assigned only to those calls that also use AudioCodes SIP signaling, use the following configuration in your <code>voipmonitor.conf</code>:


<syntaxhighlight lang="ini">
<syntaxhighlight lang="ini">
[general]
audiocodes          = yes
audiocodes          = yes
audiocodes_rtp      = only_for_audiocodes_sip
audiocodes_rtp      = only_for_audiocodes_sip
Line 84: Line 102:
</syntaxhighlight>
</syntaxhighlight>


This configuration ensures that:
This ensures correct pairing between tunnel RTP and tunnel SIP, preventing stream mixing.
* Only RTP/RTCP packets from the AudioCodes tunnel are used for calls where the SIP signaling also came through the tunnel
* Pure (non-encapsulated) packets seen on the wire are not mixed with tunnel packets
* The correct association between tunnel RTP and tunnel SIP is maintained


'''When to Use Each Option:'''
== Verification ==


* Use <code>yes</code> (default) when you only capture from the AudioCodes tunnel and no other traffic
'''On the AudioCodes SBC:'''
* Use <code>only</code> when you want to EXCLUSIVELY use tunnel RTP for ALL calls (ignore any pure packets)
<syntaxhighlight lang="bash">
* Use <code>no</code> when you want to ignore tunnel RTP and use only pure packets
tshark -i pkt1 port 925
* Use <code>only_for_audiocodes_sip</code> when you have mixed traffic (tunnel + pure) and want to ensure correct pairing between tunnel RTP and tunnel SIP (this is the recommended setting for most mixed-capture scenarios)
</syntaxhighlight>
 
'''On the VoIPmonitor server:'''
<syntaxhighlight lang="bash">
tcpdump -i any port 925 -w /var/tmp/capture.pcap
</syntaxhighlight>


=== Performance Impact on the SBC ===
== Known Limitations ==


When using AudioCodes tunneling, it is important to assess the performance impact on the AudioCodes SBC itself, particularly in high-traffic environments.
=== IP Addresses Logged as 0.0.0.0 ===


'''Monitoring SBC Performance'''
RTP packets may show <code>0.0.0.0</code> IP addresses in CDR because the AudioCodes encapsulation strips IP header information.


To determine if tunneling affects your AudioCodes SBC performance:
{| class="wikitable"
|-
! Aspect !! Details
|-
| '''Impact''' || Display limitation only; SIP signaling IPs and call recording remain intact
|-
| '''Workaround''' || Use SIP History tab to see actual IPs from signaling packets
|-
| '''Status''' || Expected behavior, not fixable via configuration
|}


1. Check the current baseline: Monitor SBC CPU usage and network load before enabling tunneling
== Performance Considerations ==
2. Enable the tunneling feature via UDP on the SBC
3. Monitor the SBC's CPU and network load during normal operation


You can perform this performance test without configuring a VoIPmonitor listener to isolate the SBC's performance impact from the sensor's processing load.
Monitor SBC CPU and network load before/after enabling tunneling:


Refer to the AudioCodes SBC documentation for specific instructions on enabling tunneling and monitoring performance metrics.
# Check baseline SBC metrics (CPU, network)
# Enable tunneling via UDP on the SBC
# Monitor metrics during normal operation
 
{{Tip|1=You can test SBC impact without configuring VoIPmonitor listener to isolate SBC performance from sensor processing.}}
 
== See Also ==
 
* [[Tls|TLS Decryption Guide]] - All TLS decryption methods
* [[Sniffing_modes|Deployment & Topology Guide]] - Alternative capture methods (SPAN, GRE, HEP)
* [[Sniffer_configuration|Sniffer Configuration]] - General sensor configuration


== AI Summary for RAG ==
== AI Summary for RAG ==
'''Summary:''' This guide covers the complete setup for AudioCodes tunneling between AudioCodes Session Border Controllers (SBCs) and VoIPmonitor. It explains both sides of the configuration: (1) configuring the AudioCodes SBC's "Debug Recording Server" setting to forward packets to VoIPmonitor's IP address using UDP/TCP port 925 by default, and (2) configuring VoIPmonitor to receive and process tunneled packets by enabling audiocodes= yes and setting udp_port_audiocodes/tcp_port_audiocodes. The guide also explains handling RTP/RTCP packet assignment when both tunnel and pure traffic are available (audiocodes_rtp options: yes, no, only, only_for_audiocodes_sip) and monitoring SBC performance impact.


'''Keywords:''' audiocodes, tunnel, SBC, debugging recording server, configuration, port setup, udp, tcp, rtp, rtcp, mixed streams, only_for_audiocodes_sip, encapsulation, span port, mirroring, performance impact, CPU load, network load
'''Summary:''' AudioCodes tunneling allows AudioCodes SBCs to encapsulate and forward SIP/RTP packets to VoIPmonitor using the "Debug Recording Server" feature (default port UDP/TCP 925). Configuration: (1) SBC - set Debug Recording Server IP to VoIPmonitor server, (2) VoIPmonitor - enable <code>audiocodes=yes</code> and set <code>udp_port_audiocodes/tcp_port_audiocodes=925</code>. For mixed capture (tunnel + SPAN), use <code>audiocodes_rtp=only_for_audiocodes_sip</code> to prevent stream mixing. Key use case: Decrypt TLS 1.3/ECDHE traffic (including MS Teams Direct Routing) without SSL key logger. Known limitation: RTP IPs may show as 0.0.0.0 due to encapsulation format.
 
'''Keywords:''' audiocodes, tunnel, SBC, debug recording server, port 925, udp_port_audiocodes, tcp_port_audiocodes, audiocodes_rtp, only_for_audiocodes_sip, mixed streams, TLS decryption, ECDHE, PFS, TLS 1.3, MS Teams Direct Routing, 0.0.0.0 IP, SPAN alternative


'''Key Questions:'''
'''Key Questions:'''
* How to configure AudioCodes SBC to forward packets to VoIPmonitor?
* How to configure AudioCodes SBC to forward packets to VoIPmonitor?
* Where to configure the Debug Recording Server on AudioCodes devices?
* What is the default port for AudioCodes tunneling?
* Which network ports are required for AudioCodes tunneling to VoIPmonitor?
* How to configure VoIPmonitor to receive AudioCodes tunneled data?
* How to configure VoIPmonitor to receive AudioCodes tunneled data?
* What port does AudioCodes use for packet forwarding (default)?
* How to fix mixed RTP streams when capturing both AudioCodes tunnel and SPAN traffic?
* How to fix mixed RTP streams when capturing both AudioCodes tunnel and regular traffic?
* What is the difference between audiocodes_rtp options?
* What is the difference between audiocodes_rtp options (yes, no, only, only_for_audiocodes_sip)?
* Can AudioCodes tunneling decrypt TLS/ECDHE encrypted SIP?
* When should I use audiocodes_rtp = only_for_audiocodes_sip?
* Why are IP addresses logged as 0.0.0.0 with AudioCodes tunneling?
* What is the performance impact of AudioCodes tunneling on the SBC?
* How to monitor MS Teams Direct Routing traffic?

Latest revision as of 16:47, 8 January 2026

AudioCodes Tunneling

AudioCodes tunneling allows AudioCodes SBCs to encapsulate and forward SIP/RTP packets to VoIPmonitor via the "Debug Recording Server" feature, as an alternative to traditional SPAN port mirroring.

When to Use AudioCodes Tunneling

This method is ideal for:

  • TLS 1.3 / ECDHE encrypted traffic - The SBC decrypts internally, no SSL key logger needed
  • MS Teams Direct Routing - SBC-to-Microsoft traffic uses PFS where private key decryption is impossible
  • Cross-segment monitoring - When SBC and VoIPmonitor are on different network segments
  • Closed appliances - When you cannot inject SSL key logger libraries

ℹ️ Note: For MS Teams Direct Routing, AudioCodes tunneling is often the most practical solution because it does not require access to Microsoft's private keys.

For other TLS decryption methods, see TLS Decryption Guide.

Configuration

Step 1: AudioCodes SBC

On the AudioCodes device:

  1. Locate Debug Recording Server (or "Log server" / "Session mirroring")
  2. Set the IP address to your VoIPmonitor server IP
  3. Default port: UDP/TCP 925

Refer to AudioCodes documentation for model-specific steps.

Step 2: VoIPmonitor Server

Edit /etc/voipmonitor.conf: 

audiocodes = yes
udp_port_audiocodes = 925
tcp_port_audiocodes = 925

Restart the service: 

systemctl restart voipmonitor

ℹ️ Note: Ensure your firewall allows incoming traffic on port 925.

RTP/RTCP Handling Options

These options control how VoIPmonitor handles RTP/RTCP packets when both tunneled and pure (non-encapsulated) packets are captured: 

audiocodes_rtp  = yes | no | only | only_for_audiocodes_sip
audiocodes_rtcp = yes | no | only | only_for_audiocodes_sip
Value Description Use Case
yes Process tunnel RTP/RTCP (default) Tunnel-only capture, no SPAN
no Ignore tunnel RTP/RTCP Use only pure packets
only Use only tunnel RTP/RTCP for all calls Exclusively use tunnel data
only_for_audiocodes_sip Use tunnel RTP only if SIP was also tunneled Recommended for mixed capture (tunnel + SPAN)

Mixed Traffic Configuration

When capturing both AudioCodes tunnel and SPAN traffic, use: 

audiocodes          = yes
audiocodes_rtp      = only_for_audiocodes_sip
audiocodes_rtcp     = only_for_audiocodes_sip

This ensures correct pairing between tunnel RTP and tunnel SIP, preventing stream mixing.

Verification

On the AudioCodes SBC: 

tshark -i pkt1 port 925

On the VoIPmonitor server: 

tcpdump -i any port 925 -w /var/tmp/capture.pcap

Known Limitations

IP Addresses Logged as 0.0.0.0

RTP packets may show 0.0.0.0 IP addresses in CDR because the AudioCodes encapsulation strips IP header information.

Aspect Details
Impact Display limitation only; SIP signaling IPs and call recording remain intact
Workaround Use SIP History tab to see actual IPs from signaling packets
Status Expected behavior, not fixable via configuration

Performance Considerations

Monitor SBC CPU and network load before/after enabling tunneling:

  1. Check baseline SBC metrics (CPU, network)
  2. Enable tunneling via UDP on the SBC
  3. Monitor metrics during normal operation

💡 Tip: You can test SBC impact without configuring VoIPmonitor listener to isolate SBC performance from sensor processing.

See Also

AI Summary for RAG

Summary: AudioCodes tunneling allows AudioCodes SBCs to encapsulate and forward SIP/RTP packets to VoIPmonitor using the "Debug Recording Server" feature (default port UDP/TCP 925). Configuration: (1) SBC - set Debug Recording Server IP to VoIPmonitor server, (2) VoIPmonitor - enable audiocodes=yes and set udp_port_audiocodes/tcp_port_audiocodes=925. For mixed capture (tunnel + SPAN), use audiocodes_rtp=only_for_audiocodes_sip to prevent stream mixing. Key use case: Decrypt TLS 1.3/ECDHE traffic (including MS Teams Direct Routing) without SSL key logger. Known limitation: RTP IPs may show as 0.0.0.0 due to encapsulation format.

Keywords: audiocodes, tunnel, SBC, debug recording server, port 925, udp_port_audiocodes, tcp_port_audiocodes, audiocodes_rtp, only_for_audiocodes_sip, mixed streams, TLS decryption, ECDHE, PFS, TLS 1.3, MS Teams Direct Routing, 0.0.0.0 IP, SPAN alternative

Key Questions:

  • How to configure AudioCodes SBC to forward packets to VoIPmonitor?
  • What is the default port for AudioCodes tunneling?
  • How to configure VoIPmonitor to receive AudioCodes tunneled data?
  • How to fix mixed RTP streams when capturing both AudioCodes tunnel and SPAN traffic?
  • What is the difference between audiocodes_rtp options?
  • Can AudioCodes tunneling decrypt TLS/ECDHE encrypted SIP?
  • Why are IP addresses logged as 0.0.0.0 with AudioCodes tunneling?
  • How to monitor MS Teams Direct Routing traffic?
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