SIP Trunking Advisory — PSTN Connectivity That Fits Your Architecture
SIP trunking provides PSTN connectivity for contact centers and PBX systems through IP-based voice channels — replacing legacy ISDN and analog circuits with flexible, software-defined telephony connections that scale with demand and typically reduce per-minute costs. The right SIP trunk configuration is foundational to contact center voice quality and reliability.
What RLM Delivers on SIP Trunk
SIP trunking vendor selection is more nuanced than it appears — pricing models, codec support, geographic coverage, redundancy architecture, and technical support quality vary significantly across carriers. Organizations migrating from TDM circuits to SIP, deploying cloud voice over existing infrastructure, or optimizing their current SIP trunk costs all benefit from independent assessment. RLM advises on SIP trunk architecture, vendor selection, and cost optimization.
How We Approach SIP Trunk
Every SIP Trunk engagement starts with what you have today and ends with something running in production — with independent evaluation in between.
SIP Trunk Assessment
We assess your current SIP trunk environment — documenting concurrent call capacity, carrier pricing, quality metrics, geographic coverage, and the configuration gaps that affect voice quality or resilience.
Carrier Evaluation
We evaluate SIP trunk providers — Bandwidth, Twilio, Lumen, Vonage, Verizon, AT&T — against your geographic requirements, call volume, codec preferences, and the redundancy design that achieves your RTO for voice service.
SIP Architecture Design
We design the SIP trunk architecture — Session Border Controller selection, failover configuration, codec negotiation, SRTP encryption, and the quality of service configuration that prioritizes voice traffic.
Cost Optimization
We benchmark your current SIP trunk pricing against market rates and design the carrier mix and traffic distribution that minimizes per-minute costs while maintaining geographic redundancy.
SIP Trunk Evaluation Criteria
What follows is the SIP Trunk evaluation checklist we actually use — the criteria that predict outcomes rather than demo well.
Codec Compatibility
SIP trunks must support the codecs used by your contact center platform and endpoints. Evaluate codec compatibility — particularly G.711 vs. G.729 trade-offs — and whether codec transcoding introduces perceptible latency.
STIR/SHAKEN Attestation
SIP trunk providers participate in STIR/SHAKEN call authentication at different attestation levels. Evaluate full attestation support and the impact on outbound call answer rates.
Emergency Services (E911)
SIP trunks must support E911 with accurate location information. Evaluate E911 routing architecture — particularly for distributed and remote locations — and the carrier's E911 compliance approach.
Failover Architecture
Voice service continuity requires carrier-level redundancy. Evaluate primary/secondary carrier failover, detection time for failover triggering, and the call-in-progress handling during failover events.
Number Porting
Migrating to a new SIP trunk carrier requires porting existing numbers. Evaluate porting processes, timelines, and the parallel operation approach that prevents number availability gaps during cutover.
"We had a legacy premise system and 90 days to migrate. RLM built the plan, managed the vendors, and we hit the deadline with zero customer disruption."
Independent means we will tell you when the answer is to keep what you have.
Where This Matters Most
Sector-specific considerations we see repeatedly in customer experience engagements.
A Sample of the Customer Experience Providers We Evaluate
RLM is vendor neutral. These are among 600+ providers in our evaluation set — inclusion here is not an endorsement, and we are paid by the provider you choose, not by any provider in particular. How that works →
Ready to Get SIP Trunk Right?
Talk to an RLM advisor who specializes in CX technology. We'll help you find the right solution for your business — without vendor bias.