How to prioritize VoIP Internet traffic when using a Cisco 871 router and Grandstream UCM6104 IP PBX?

Question

Telephony

Hello.
There is an office - about 15 computers and 15 IP phones. Telephony works through the internal IP-PBX Grandstream UCM6104. The office PBX is connected to the Internet through a Cisco 871 router. The channel to the Internet provider is 20 Mbps.
Telephony users say that communication periodically leaves much to be desired. They compare with analog communications, which we recently abandoned. It is difficult to pinpoint the exact cause of poor communication quality. VoIP provider is large. Ping 5ms. One of the possible reasons may be that the Internet channel is clogged with various non-priority downloads, watching YouTube, etc. Therefore, I would like to configure the prioritization of VoIP telephony traffic when using an Internet channel.
How to configure prioritization of VoIP traffic?I suspect that QoS can be used. QoS I have never configured. In the PBX settings, there are only two fields about QoS. (see screenshot). Probably the main settings are made in a tsiska.
As an alternative to prioritization - configure shaping on a tsiska. For example, plug a PBX into one port, and all the others (connected through a large hub) into another port. At the same time, limit the bandwidth of the common port to the speed of the Internet channel minus 1Mbps.
Here the nuance is that phones and computers are connected through one port to the cisco and this port passes traffic both to the Internet and from phones to the internal PBX, which can be connected to a neighboring port on the cisco. It is not possible to separate telephony and computers on different ports of the tsiska. And there is no experience in setting up shaping either.
In general, what do you recommend? Should I bother with priorities? How best to set up?

Answer 1

Good afternoon. QoS would be nice to set up. But it won't give a significant improvement in your case. Because you can only effectively influence the traffic outgoing from you towards the ISP. And incoming traffic to you shapes your ISP up to 20Mbps, and it is unlikely to prioritize VoIP traffic.
In your case, the easiest way is to request another VoIP-only connection from the ISP. 1 Mbps will be more than enough. To save money on connection, you can ask the ISP to give you a new channel with a tag over an existing cable.