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There are several key aspects of voice quality monitoring (VQM) that should be reviewed when setting it up. I have listed some of these below. They can be found in the Configuring Voice Quality Monitoring in AOS document.
- By default, VQM is globally disabled on the AOS product, but it is enabled on each interface. Before VQM can gather statistics from an interface, it must be enabled globally.
- For VQM to function properly, the firewall on the AOS device must be enabled. When using VQM with Media Gateway Control Protocol (MGCP), the SIP back-to-back user agent (B2BUA), or SIP proxy, VQM only works on the default virtual router and forwarding (VRF) interface because MGCP, the SIP B2BUA, and SIP proxy only use the default VRF. When using the firewall SIP application layer gateway (ALG), VQM works over multiple VRFs, but in this configuration multiple IP addresses cannot be reused.
- When configuring VQM, you must keep in mind your firewall and SIP settings. If non-default access control policies (ACPs) are used with allow policy entries, you must make sure the SIP and RTP traffic do not match stateless allow policy entries. If you have to enable the firewall specifically for VQM functionality, performance of the AOS device can be diminished.
- VQM will not gather information on RTP traffic received on unsupported CODECs (a list of supported codecs is in the document listed above).
- VQM will not work on switched RTP traffic, RTP traffic over a virtual private network (VPN) or a generic routing encapsulation (GRE) tunnel that is not terminated by the AOS device, layer 3 switched interfaces, bridged traffic, or secure RTP packets.
After reviewing this information and the linked documentation, if you have further questions, do not hesitate to reply.
Not sure whether this will be helpful, but @noor just clarified a point for me that may relate to your question. Click here to view that thread. Basically, stateful policies must be used where RTP flows will happen. Stateless policies (common for trusted/private policies, including VPN selectors) will keep VQM from picking up RTP.
That document @levi linked is great too. One more thought: RTP monitoring can be enabled/disabled per interface.
I'm so confused. So basically, I cannot monitor RTP traffic across VPN or Private Network (from carrier) if the Adtran Router is not terminating the traffic. Is that correct?
Forgive me if I added to the confusion! I thought that maybe my parallel conversation might benefit you with yours.
I don't know your question's background circumstances. However, VQM can occur only for RTP flowing through an AOS router's firewall.
RTP within VPN tunnels can be monitored only by the router terminating the tunnel. This is because traffic within a tunnel is encrypted, and therefore not visible to routers where the tunnel merely passes through. The terminating router can monitor quality because it is decrypting RTP.
Non-encrypted traffic can be monitored in AOS even if it is merely passing through, so long as the firewall is running and properly configured (see earlier comments and the linked document).
This is meant to be a 'clarifying follow up' rather than a 'comprehensive answer.' I hope I'm not adding a layer of mud! An ADTRAN engineer will very likely reply again soon with a more well-put explanation.
I'm marking this post as "assumed answered," but if you have further questions on this topic to not hesitate to reply.
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