Message ID
60
Message
QoS mechanism may be compromised
Description
The QoS implementation does not appear to be functioning properly along the test path.
Recommendations
  1. Review the secondary messages and other VoIP-related diagnostics to help determine cause.
  2. Review the QoS implementation on your network. If IP QoS field is not being used, ensure the QoS option is deselected in VoIP test settings. If used, review test results along this path to determine which device might be violating QoS procedures, and follow up accordingly. In networks where end-device QoS configuration is disregarded, ensure the monitoring point has the correct network address and VLAN assignment.
  3. Retest.
  4. If problem still exists, try replacing or circumventing the questionable device and retest.
Explanation

Various methods exist to implement QoS within a network. In one approach, hosts and routers can set a QoS value in the IP header as part of the overall implementation. This value can determine the per-hop behavior a packet experiences at each node. However, some devices do not respect this field and alter the value. This is one way that QoS can be compromised. Depending on its usage, this QoS field is known either as TOS, or DS. The altering of the value in this field does not guarantee that QoS is broken, but should be investigated if usage of this field is important to your application.

A QoS strategy may also be implemented at the network level, where end-device QoS configuration is disregarded. In situations like this, a network element such as a switch, router, or gateway makes an assessment of QoS requirements based on network address or other packet characteristics. To effectively evaluate QoS with Delivery monitoring in environments like this, the monitoring point must have the correct network address and VLAN assignment so that it is consistent with the QoS policy.

Possible secondary messages
  • IP QoS affected