Quality of Service (QoS) is a feature on most business grade firewalls that allows prioritization of VoIP traffic over other types of traffic (i.e. Youtube or email). Depending on the internet connection and the local network, QoS can greatly increase the voice quality on calls, and it needs to be implemented for every customer.
The configuration of QoS rules vary wildly from one firewall brand to the next, but there are some general guidelines:
- Prioritize all traffic with a destination for our server IP addresses:
- If applicable, set the DSCP tagging to 46(EF).
- When setting up QoS rules, add a rule instructing the firewall to always allow traffic from Cytracom servers.
- If a bandwidth minimum/guarantee needs to be set, it can be calculated at 70kb/s per phone. If 10 phones are installed at a location, allocate a minimum/guarantee of 700kb/s.
- If a bandwidth maximum needs to be set, normally 10-15x the bandwidth minimum or the WAN network maximum (what the ISP is providing) is best practice with no penalty provided if applicable.
Note: These are general rules for setting up QoS. Each firewall will have a different configuration. VLAN tagging is not a requirement for the phones but is suggested where networks have heavy traffic usage and isolation is needed to ensure proper traffic flow. Linked here is a guide for setting up VLAN tagging for relevant Grandstream products.