Wholesale SIP trunking connects a business's IP PBX to the public network using the Session Initiation Protocol, letting buyers purchase concurrent call channels in bulk over the internet at carrier-scale rates well below retail, often under $10 per channel at scale, making it popular with resellers and MSPs who rebrand it as well as enterprises and call centers with heavy volume. Channel sizing means provisioning one channel per simultaneous call rather than per employee, using rules of thumb like one channel per three to four staff for general business use, closer to one-to-one for sales and call center teams, and a peak estimate where a 100-seat office with 20 percent simultaneous usage needs about 20 channels. Key benefits include steep cost reduction on international routes (some falling from $0.05 to below $0.008 per minute at wholesale scale), instant elastic scalability without hardware, global reach and same-day DID provisioning across 150-plus countries through one connection, redundancy across multiple Points of Presence, LCR and quality-based routing that protects ASR and PDD, faster deployment than legacy ISDN/PRI lines, and reseller margins of 50 to 75 percent versus 15 to 25 percent for traditional commissions. On pricing, 2026 channel plans typically run $15 to $25 per channel monthly for domestic calling, metered rates run $0.005 to $0.02 per minute, and buyers should watch for DID fees ($1 to $5 monthly), E911 charges ($1.50 to $3), regulatory surcharges of 15 to 25 percent, and bursting fees. Softtop cites its own 99.99 percent uptime, Tier-1 routes across 150-plus countries, 70-plus global Points of Presence, a 60-plus percent Answer Seizure Ratio, and over a decade serving 1,000-plus active clients as the benchmark for a dependable wholesale SIP trunking network.