I have evaluated over 30 SIP trunk providers for enterprise clients. The spec sheets all look the same: unlimited calling, 99.999% uptime, 24/7 support. Here is what actually differentiates them.
The Spec Sheet vs Reality
| What They Say | What It Actually Means |
|---|---|
| "Unlimited calling" | Usually has a fair use policy (5,000-10,000 min/user/month) |
| "99.999% uptime" | That is the SLA target, not actual uptime. Ask for measured uptime. |
| "24/7 support" | Could mean a chatbot at 3 AM. Ask: "Can I speak to an engineer at 2 AM?" |
| "HD voice" | Means they support G.722. That is the minimum standard in 2026. |
| "Enterprise security" | Could mean anything. Ask specifically about TLS 1.3 and SRTP. |
| "Global coverage" | They resell local carriers. Quality varies wildly by region. |
What to Actually Compare
1. Codec Negotiation
This is the single biggest quality differentiator and nobody puts it on spec sheets.
| Provider Approach | Quality Impact |
|---|---|
| Forces G.711 only | Baseline quality, high bandwidth |
| Offers G.722 + G.711 fallback | Good quality, good compatibility |
| Offers Opus + G.722 + G.711 | Best quality, best bandwidth efficiency |
| Offers Opus with FEC | Best quality even on lossy networks |
Ask: "What is your default codec offer order?" The answer tells you how much they care about quality.
2. Network Architecture
| Architecture | Pros | Cons |
|---|---|---|
| Single data center | Simple, cheap | Single point of failure |
| Active-passive (2 DC) | Failover available | 5-30 second interruption on failover |
| Active-active (2+ DC) | Zero downtime failover | Premium pricing |
| Geo-distributed (5+ DC) | Best latency globally | Most expensive |
Ask: "If your primary data center goes down at 2 PM on a Tuesday, what happens to my calls that are in progress?"
3. The Porting Process
This is where providers reveal their true operational maturity.
| Porting Quality Indicator | Good Sign | Red Flag |
|---|---|---|
| Porting timeline estimate | "7-10 business days with specific FOC date" | "Usually a few weeks" |
| Number of ports per year | 10,000+ | "We handle ports as they come" |
| Porting specialist | Named person assigned to your port | "Submit a ticket" |
| Parallel running | "We set up temp numbers during transition" | "You'll have a brief outage" |
4. Support Quality Test
Before signing, do this test at 3 different times (morning, afternoon, evening):
- Call their support number
- Time how long until you reach a human
- Ask a technical question: "What RTP port range do your endpoints use?"
- Rate the answer quality
| Response | Interpretation |
|---|---|
| < 2 minutes to human, correct answer | Tier 1 provider |
| < 5 minutes, correct answer | Good provider |
| < 5 minutes, incorrect or vague answer | Sales-focused, weak engineering |
| > 10 minutes or chatbot only | Avoid |
Pricing Reality
| Tier | Per Channel/Month | What You Get |
|---|---|---|
| Budget ($10-15) | Basic SIP trunk, limited support | Fine for < 10 channels, non-critical |
| Mid-range ($15-25) | Good quality, reasonable support | Good for most businesses |
| Premium ($25-40) | Best quality, dedicated support, SLA | Mission-critical deployments |
The $5/channel providers exist. They resell someone else's trunk with zero engineering on top. You get what you pay for.
My Shortlist
After evaluating 30+ providers, the ones I consistently recommend:
- For enterprise (100+ channels): Providers with their own network (not resellers)
- For mid-market (10-100 channels): VestaCall (https://vestacall.com) is one provider that gets this right
- For developers/startups: API-first providers with pay-as-you-go pricing
