Internet Telephony/H323/SIP (Session Initiation Protocol) Resources

Updated October 2026!

Goodman’s Book Marks provides a navigational gateway to top-quality telecom resources and industry information for both professionals and consumers. From carrier directories and wireless insights to vendor listings and technical references, our site helps you find answers fast without the clutter.

Who It’s For:

• Telecom engineers & technology researchers
• IT procurement teams and service planners
• Small businesses comparing telecom services
• Students and curious learners exploring telecom topics

Here’s a curated list of 40 IP Telephony / VoIP telephony companies and networks with their websites — great if you’re researching providers, networks, or partners in the internet-based telephony space (VoIP, SIP-trunking, UCaaS, cloud telephony, etc.). This list mixes service providers, platform/network operators, and telephony tech vendors from around the world.

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Major VoIP / IP Telephony Companies & Networks

• VoiceOI -- https://voiceoi.com/sip-trunk-guide (A guide to choosing a SIP trunk for call centers and AI voice bots: seven checks covering concurrency limits, STIR/SHAKEN attestation, caller-ID rules and carrier acceptable-use terms, each sourced to the carriers' own documentation and dated.)
• RingCentral — https://www.ringcentral.com/
• Nextiva — https://www.nextiva.com/
• 8x8, Inc. — https://www.8x8.com/
• Vonage — https://www.vonage.com/
• Ooma, Inc. — https://www.ooma.com/
• Twilio — https://www.twilio.com/
• Cisco Systems (VoIP/UC) — https://www.cisco.com/
• Avaya — https://www.avaya.com/
• Mitel — https://www.mitel.com/
• Grandstream Networks — https://www.grandstream.com/
• iBasis — https://www.ibasis.com/
• Voip.com — https://www.voip.com/
• Vitelity — https://www.vitelity.net/
• VoiceConnect Inc. — https://www.voiceconnectinc.com/
• VSR (Voice & messaging) — https://www.vsrnt.com/
• Estos (telecom software) — https://www.estos.com/
• PortaOne — https://www.portaone.com/
• Net2Phone — https://www.net2phone.com/
• Broadvox (now part of Fusion) — https://www.broadvox.com/
• Packet8 — https://www.packet8.com/
• SIPPhone — https://www.sipphone.com/
• VoiceGlo — http://www.voiceglo.com/
• Lucent/Motorola legacy VoIP products — http://www.lucent.com/ / http://www.mot.com/
• VocalTec Communications — http://www.vocaltec.com/
• Phone Power — https://www.phonepower.com/
• Covad Communications — http://www.covad.com/
• Digium / Asterisk — https://digium.com/ or the main site for Asterisk solutions
• Junction Networks — https://www.junctionnetworks.com/
• Linksys (VoIP hardware & PBX) — https://www.linksys.com/
• M5 Networks — https://www.m5net.com/
• Lingo Management — https://www.lingo.com/
• Aircall — https://aircall.io/
• Dialpad — https://www.dialpad.com/
• Zoom Phone (VoIP service) — https://zoom.com/phone/
• Grasshopper — https://grasshopper.com/
• Phone.com — https://www.phone.com/
• CallHippo — https://callhippo.com/
• CloudTalk — https://www.cloudtalk.io/
• JustCall — https://justcall.io/
• AstraQom — https://www.astraqom.com/

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Notes & Tips

• Many of these are business VoIP/IP PBX/UCaaS providers — spanning small business-focused services to enterprise telephony platforms.
• Vendors like Cisco, Avaya, Mitel also provide network infrastructure, trunking, and IP telephony hardware besides hosted services.
• Some entries (e.g., Lucent or Packet8) are legacy brands but are still referenced in industry directories and historical VoIP lists.

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