[Glossary](https://telxpress.com/glossary/) / Phones # 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. - Phones - 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* VoIP turns your voice into packets of data, sends them across the network and reassembles them at the other end. A codec is the method used to compress the audio; common ones trade bandwidth for quality, and HD codecs sound noticeably better than the old phone network. Signaling, the setup and teardown of a call, usually uses SIP. Because the call shares the network with everything else, its quality depends on latency, jitter and packet loss rather than on the phone. For a growing business that means the phone project is also a network project: enough bandwidth, QoS rules that put voice first, PoE switches for the handsets and a plan for when the internet fails. Ask a provider which codecs they use and whether HD voice is standard, what network changes they require, how they measure call quality, how E911 is handled, and whether the phones you already own (Yealink, Polycom and others) can be reused. Ask for a network assessment before, not after, the cutover. 02 Related terms ## Terms that usually come up *alongside it* - Phones ### [UCaaS](https://telxpress.com/glossary/ucaas/) UCaaS (unified communications as a service) is a cloud subscription that combines business phone calling, video meetings, team messaging, voicemail and often contact-center features in one platform managed by the provider. - Phones ### [SIP trunk](https://telxpress.com/glossary/sip-trunk/) A SIP trunk is a virtual phone line delivered over the internet that connects your own phone system (an on-site or hosted PBX) to the public telephone network, replacing traditional analog or digital carrier lines. - Phones ### [Cloud phone system](https://telxpress.com/glossary/cloud-phone-system/) A cloud phone system is a business phone service hosted by a provider and delivered over the internet, so phones, apps and features are managed through a web portal rather than hardware in your office. - Network ### [QoS (quality of service)](https://telxpress.com/glossary/qos/) 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 ### [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. 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 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. - 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. 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 3261, SIP: Session Initiation Protocol](https://www.rfc-editor.org/rfc/rfc3261) rfc-editor.org - [47 CFR 9.11, interconnected VoIP 911 service obligations (Cornell LII)](https://www.law.cornell.edu/cfr/text/47/9.11) law.cornell.edu 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.