[Glossary](https://telxpress.com/glossary/) / Network # QoS (quality of service) **Quality of service** (QoS) is the network configuration that identifies time-sensitive traffic such as voice and video and gives it priority over downloads and backups, so calls stay clear when the network is busy. - Network - Updated October 11, 2026 - Written by the Telxpress advisory team 01 In depth ## What it is, why it matters and *what to ask a vendor* Voice and video packets must arrive on time; a file transfer only needs to arrive eventually. QoS lets switches, routers and firewalls tell the difference, usually by marking packets with a differentiated services code (DSCP, defined in RFC 2474) and then queueing marked traffic ahead of the rest. It helps most on the links that are actually congested: the uplink to the internet and Wi-Fi. For a growing business QoS is the difference between a phone system that sounds fine on day one and one that still sounds fine when the team doubles and someone starts a large cloud backup at noon. It is configuration, not hardware, so it is often skipped, and the symptoms (choppy audio, frozen video) get blamed on the provider. Ask whoever manages your network whether voice is marked and prioritized end to end, including on the firewall and Wi-Fi, whether your internet provider honors or strips the markings, and how they verify it. Ask your phone provider which markings their phones and apps use so the two configurations agree. 02 Related terms ## Terms that usually come up *alongside it* - Network ### [Jitter](https://telxpress.com/glossary/jitter/) Jitter is the variation in the time it takes voice or video packets to arrive; when it is high, a call sounds choppy or robotic because the receiving device cannot smooth the uneven stream. - Network ### [Latency](https://telxpress.com/glossary/latency/) Latency is the time a packet takes to travel from one end of a connection to the other; on a phone or video call, high latency makes people talk over each other and pause awkwardly. - Network ### [Packet loss](https://telxpress.com/glossary/packet-loss/) Packet loss is the share of packets that never reach their destination; on a voice or video call even a small amount causes dropped words, frozen video and a line that seems to cut out. - Phones ### [VoIP](https://telxpress.com/glossary/voip/) VoIP (voice over internet protocol) carries phone calls as data over an internet or private IP network instead of traditional copper phone lines; cloud phone systems, UCaaS and SIP trunks are all built on it. - Network ### [VLAN](https://telxpress.com/glossary/vlan/) A VLAN (virtual local area network) splits one physical network into separate logical networks, so that phones, computers, guest Wi-Fi, cameras and building systems are kept apart for security and performance without separate cabling. 03 At Telxpress ## Where this shows up *at Telxpress* The pages and articles where this term does real work: what we advise, build and support. - Page ### [Business Networking, Firewalls & Managed Wi-Fi](https://telxpress.com/solutions/business-technology/networking/) Switching, routing, Fortinet firewalls, Ubiquiti and Cisco Meraki Wi-Fi and managed network services for offices that depend on reliable connections. - Page ### [Business VoIP & Cloud Phone Systems in Irvine](https://telxpress.com/solutions/business-technology/phone-systems/) VoIP, cloud phone systems, UCaaS and SIP trunks from Yealink, Nextiva, Avaya, Yeastar and Polycom, installed, supported and ready for AI call handling. - Article ### [Boost Your VoIP Calls: Top Tips for Crystal Clear Communication](https://telxpress.com/insights/boost-your-voip-calls-top-tips-for-crystal-clear-communication/) The steps we check on a site visit when business calls sound choppy or delayed, in order, from bandwidth and QoS to hardware, failover and codecs. 04 Sources ## Public *references* The standard or law this definition rests on, as published by its owner. Fetched and checked on the review date above. - [RFC 2474, Definition of the Differentiated Services Field](https://www.rfc-editor.org/rfc/rfc2474) rfc-editor.org Next step ## Want This Applied *to Your Business?* Book a free 30-minute AI readiness consultation. You'll leave with three AI opportunities specific to your business, whether you work with us or not. [Book My Free Consultation](https://telxpress.com/book/) [Take the Free AI Readiness Assessment](https://telxpress.com/ai-readiness/) [Or call 24/7: (949) 861-4500](tel:+19498614500) Last reviewed: October 11, 2026. Published by Telxpress, Irvine, CA.