I'm currently prepare my ONT certification Exam.
In all document I seen where QoS configuration is explain, they set voice signalling trafic just below voice and video trafic classes. In practice exam was for which 2 types of trafic we need QoS in converge network ? in the response choice : voice, voice signaling and mission critical misson data and some others with definete lower importance.
The answer was the pratice test was waiting for is voice and mission critical data.
I would like to know if voice signalling was'nt a good answer, why we provide priority higher of the most of other data trafic. Even if the exam was OK or not, I would like to know we have to provide higher priority for voice signalling then interactive data or web data trafic.
Thanks a lot for your help !
VoIP signaling is definitely also an answer that would need to be considered, in almost any situation where you're going to apply QoS to a system when it comes to VoIP you always allocate X BW for the RTP and also a minimum Y BW for signaling.
the reason is that without signaling you cannot establish a call, if you drop a packet that had a DTMF call will fail, you can get delay on softkey response, delay on dial tone, etc. also since the keepalives are also SCCP the drop of this packets can make a phone to lose the connection to CUCM.
the recommendation is always to provide BW on priority Q for RTP with EF PHB and allocate a minimum guaranteed BW for signaling which has CS3 PHB.
signaling can definitely support a little more delay than RTP or any other critical data within a company. at least from a VoIP perspective there should be QoS also for signaling.
if this helps, please rate