[{"data":1,"prerenderedAt":462},["ShallowReactive",2],{"blog-\u002Far\u002Fblog\u002Fwhat-is-sip-trunk-how-it-works":3},{"id":4,"title":5,"body":6,"date":452,"description":453,"extension":454,"meta":455,"navigation":456,"path":457,"readTime":458,"seo":459,"stem":460,"__hash__":461},"content\u002Fblog\u002Fwhat-is-sip-trunk-how-it-works.md","What Is a SIP Trunk and How Does It Work?",{"type":7,"value":8,"toc":432},"minimark",[9,14,18,21,25,28,33,36,60,64,67,82,86,89,93,201,205,210,221,226,234,237,241,244,248,268,272,298,302,322,326,329,398,401,405,408,422],[10,11,13],"h2",{"id":12},"sip-trunking-in-plain-language","SIP Trunking in Plain Language",[15,16,17],"p",{},"A SIP trunk is a virtual phone line that connects your business phone system to the public telephone network (PSTN) over the internet. Instead of physical copper wires running to your office, a SIP trunk uses your existing internet connection to carry voice calls.",[15,19,20],{},"Think of it as the bridge between your internal phone system and the outside world — the piece that lets you dial regular phone numbers and receive incoming calls from landlines and mobile phones.",[10,22,24],{"id":23},"how-sip-trunking-works","How SIP Trunking Works",[15,26,27],{},"The process involves three layers:",[29,30,32],"h3",{"id":31},"_1-your-phone-system-the-endpoint","1. Your Phone System (the endpoint)",[15,34,35],{},"This is where calls originate and terminate. It can be:",[37,38,39,48,54],"ul",{},[40,41,42,43,47],"li",{},"A ",[44,45,46],"strong",{},"SIP softphone"," app (like Softphone Plus) on your computer or mobile",[40,49,42,50,53],{},[44,51,52],{},"hardware IP phone"," on your desk",[40,55,42,56,59],{},[44,57,58],{},"PBX"," (Private Branch Exchange) managing multiple extensions",[29,61,63],{"id":62},"_2-the-sip-trunk-the-connection","2. The SIP Trunk (the connection)",[15,65,66],{},"The SIP trunk provider connects your phone system to the PSTN. When you dial a number:",[68,69,70,73,76,79],"ol",{},[40,71,72],{},"Your softphone sends a SIP INVITE message to the trunk provider",[40,74,75],{},"The provider routes the call to the destination via the PSTN",[40,77,78],{},"Audio flows as RTP (Real-time Transport Protocol) packets over your internet connection",[40,80,81],{},"When either party hangs up, a SIP BYE message terminates the session",[29,83,85],{"id":84},"_3-the-pstn-the-destination","3. The PSTN (the destination)",[15,87,88],{},"The public telephone network that connects to landlines, mobile phones, and other businesses worldwide.",[10,90,92],{"id":91},"sip-trunk-vs-pri-vs-analog-lines","SIP Trunk vs. PRI vs. Analog Lines",[94,95,96,115],"table",{},[97,98,99],"thead",{},[100,101,102,106,109,112],"tr",{},[103,104,105],"th",{},"Feature",[103,107,108],{},"SIP Trunk",[103,110,111],{},"PRI (T1\u002FE1)",[103,113,114],{},"Analog Lines",[116,117,118,133,147,161,174,187],"tbody",{},[100,119,120,124,127,130],{},[121,122,123],"td",{},"Connection",[121,125,126],{},"Internet",[121,128,129],{},"Dedicated circuit",[121,131,132],{},"Copper wire",[100,134,135,138,141,144],{},[121,136,137],{},"Channels",[121,139,140],{},"Flexible (scale up\u002Fdown)",[121,142,143],{},"Fixed (23 per PRI)",[121,145,146],{},"1 per line",[100,148,149,152,155,158],{},[121,150,151],{},"Cost",[121,153,154],{},"Pay per channel\u002Fusage",[121,156,157],{},"$300–$600\u002Fmonth per PRI",[121,159,160],{},"$30–$50\u002Fline\u002Fmonth",[100,162,163,166,169,172],{},[121,164,165],{},"Setup",[121,167,168],{},"Minutes",[121,170,171],{},"Weeks",[121,173,171],{},[100,175,176,179,182,185],{},[121,177,178],{},"Long-distance",[121,180,181],{},"Usually included or very cheap",[121,183,184],{},"Per-minute charges",[121,186,184],{},[100,188,189,192,195,198],{},[121,190,191],{},"Redundancy",[121,193,194],{},"Automatic failover possible",[121,196,197],{},"Hardware-dependent",[121,199,200],{},"None",[10,202,204],{"id":203},"when-do-you-need-a-sip-trunk","When Do You Need a SIP Trunk?",[15,206,207],{},[44,208,209],{},"You need a SIP trunk if:",[37,211,212,215,218],{},[40,213,214],{},"You have an on-premise PBX (like Asterisk, FreePBX, or 3CX) and need to connect it to the phone network",[40,216,217],{},"You want to port existing phone numbers to a VoIP setup",[40,219,220],{},"You need multiple simultaneous call channels that scale with demand",[15,222,223],{},[44,224,225],{},"You DON'T need a SIP trunk if:",[37,227,228,231],{},[40,229,230],{},"You use a cloud-based softphone platform like Softphone Plus — the trunk is already built into the service",[40,232,233],{},"You have a hosted PBX where the provider manages everything",[15,235,236],{},"This is an important distinction. Many businesses over-engineer their phone setup by buying a PBX, a SIP trunk, and a softphone separately. A cloud softphone platform combines all three into one managed service.",[10,238,240],{"id":239},"how-to-choose-a-sip-trunk-provider","How to Choose a SIP Trunk Provider",[15,242,243],{},"If you do need a standalone SIP trunk, evaluate based on:",[29,245,247],{"id":246},"pricing-models","Pricing Models",[37,249,250,256,262],{},[40,251,252,255],{},[44,253,254],{},"Per-channel pricing"," — Pay for a fixed number of simultaneous calls (e.g., $15–$25\u002Fchannel\u002Fmonth)",[40,257,258,261],{},[44,259,260],{},"Per-minute pricing"," — Pay for actual usage, better for low-volume callers",[40,263,264,267],{},[44,265,266],{},"Unlimited plans"," — Flat rate for unlimited domestic calling",[29,269,271],{"id":270},"technical-requirements","Technical Requirements",[37,273,274,280,286,292],{},[40,275,276,279],{},[44,277,278],{},"Codec support"," — G.711 is universal; G.729 saves bandwidth; Opus delivers the best quality",[40,281,282,285],{},[44,283,284],{},"SRTP support"," — Encrypted media for secure calls",[40,287,288,291],{},[44,289,290],{},"Failover"," — What happens if the primary route goes down?",[40,293,294,297],{},[44,295,296],{},"Number porting"," — Can you bring your existing numbers?",[29,299,301],{"id":300},"reliability","Reliability",[37,303,304,310,316],{},[40,305,306,309],{},[44,307,308],{},"Uptime SLA"," — 99.99% is standard for quality trunk providers",[40,311,312,315],{},[44,313,314],{},"Geographic redundancy"," — Multiple POPs (Points of Presence) for reliability",[40,317,318,321],{},[44,319,320],{},"Support"," — 24\u002F7 technical support for trunk issues",[10,323,325],{"id":324},"sip-trunking-costs-breakdown","SIP Trunking Costs Breakdown",[15,327,328],{},"For a typical small business with 10 employees:",[94,330,331,347],{},[97,332,333],{},[100,334,335,338,341,344],{},[103,336,337],{},"Component",[103,339,340],{},"Traditional PRI",[103,342,343],{},"SIP Trunking",[103,345,346],{},"Cloud Softphone",[116,348,349,363,375,387],{},[100,350,351,354,357,360],{},[121,352,353],{},"Monthly line cost",[121,355,356],{},"$500 (1 PRI)",[121,358,359],{},"$150–$250 (10 channels)",[121,361,362],{},"$40 (10 seats × $4)",[100,364,365,368,371,373],{},[121,366,367],{},"Hardware",[121,369,370],{},"PBX: $2,000–$10,000",[121,372,370],{},[121,374,200],{},[100,376,377,380,383,385],{},[121,378,379],{},"Maintenance",[121,381,382],{},"$100–$300\u002Fmonth",[121,384,382],{},[121,386,200],{},[100,388,389,391,393,396],{},[121,390,178],{},[121,392,184],{},[121,394,395],{},"Usually included",[121,397,395],{},[15,399,400],{},"The cloud softphone model (like Softphone Plus) eliminates the PBX and trunk entirely — you're paying for one service that does everything.",[10,402,404],{"id":403},"the-simpler-alternative","The Simpler Alternative",[15,406,407],{},"SIP trunking makes sense if you're running an existing on-premise PBX and need to cut costs on your phone lines. But if you're starting fresh or ready to modernize, a cloud-based softphone platform is the simpler path:",[37,409,410,413,416,419],{},[40,411,412],{},"No PBX hardware to buy or maintain",[40,414,415],{},"No SIP trunk to configure and manage",[40,417,418],{},"No separate bills from three different vendors",[40,420,421],{},"One dashboard for calling, recording, analytics, and team management",[15,423,424,431],{},[425,426,430],"a",{"href":427,"rel":428},"https:\u002F\u002Fportal.softphone.plus\u002Fregister",[429],"nofollow","Try Softphone Plus free for 14 days"," — no PBX, no trunk, no hardware required.",{"title":433,"searchDepth":434,"depth":434,"links":435},"",2,[436,437,443,444,445,450,451],{"id":12,"depth":434,"text":13},{"id":23,"depth":434,"text":24,"children":438},[439,441,442],{"id":31,"depth":440,"text":32},3,{"id":62,"depth":440,"text":63},{"id":84,"depth":440,"text":85},{"id":91,"depth":434,"text":92},{"id":203,"depth":434,"text":204},{"id":239,"depth":434,"text":240,"children":446},[447,448,449],{"id":246,"depth":440,"text":247},{"id":270,"depth":440,"text":271},{"id":300,"depth":440,"text":301},{"id":324,"depth":434,"text":325},{"id":403,"depth":434,"text":404},"2026-03-05","SIP trunking explained in plain language. Learn how SIP trunks connect your business phone system to the public phone network, and when you need one.","md",{},true,"\u002Fblog\u002Fwhat-is-sip-trunk-how-it-works","6 min read",{"title":5,"description":453},"blog\u002Fwhat-is-sip-trunk-how-it-works","pD5KicJ1lNe8_GKKQIq78-tKY-VKc5bv66qLXy0D7Xs",1775659544996]