SIP Trunking Migration Guide: Replacing PRI and Analog Lines for Business

SIP trunking replaces traditional PRI circuits and analog phone lines with internet-based voice connections. For most businesses, the migration delivers 40-60% cost savings while adding flexibility and disaster recovery capabilities that legacy systems cannot match.

## What Is SIP Trunking?

SIP (Session Initiation Protocol) trunking delivers voice calls over your internet connection instead of dedicated copper or fiber circuits from the phone company. Your existing PBX connects to a SIP trunk provider via your data network.

## Pre-Migration Planning

### 1. Inventory Current Services Document every phone number, hunt group, auto attendant, fax line, alarm line, elevator phone, and fire panel connection. Missing even one line during migration causes problems.

### 2. Assess Network Readiness Each concurrent call requires approximately 100 Kbps of bandwidth. For a business with 50 phones where 20 may be active simultaneously: - Required voice bandwidth: 2 Mbps dedicated - QoS must prioritize voice over data traffic - Jitter buffer and packet loss must meet VoIP thresholds

### 3. PBX Compatibility Not all PBX systems support SIP trunking natively: - **IP PBX systems** (Asterisk, FreePBX, 3CX): Native SIP support - **Hybrid PBX systems** (Avaya, Mitel, NEC): May need SIP gateway card - **Legacy PBX** (analog-only): Requires an Analog Telephone Adapter (ATA) or full replacement

### 4. Choose a SIP Provider Evaluate providers on: - Geographic redundancy of their infrastructure - Number porting support and timeline - E911 compliance and PSAP routing - Codec support (G.711 for quality, G.729 for bandwidth) - Failover options (cellular, secondary internet)

## Number Porting Process

Number porting transfers your existing phone numbers from the legacy carrier to the SIP provider:

## Failover and Redundancy

SIP trunking enables failover options that PRI cannot match:

### Internet Redundancy - Primary: Business fiber or cable connection - Secondary: Backup internet via different carrier and path - Automatic failover at the router level

### SIP Provider Redundancy - Register SIP trunks with two providers - Primary handles all calls; secondary activates on failure - DNS SRV records enable automatic provider failover

### Cellular Failover - 4G/5G router as last-resort backup - Forward critical numbers to cell phones during extended outage - Some SIP providers offer native cellular integration

## Fax and Specialty Lines

### Fax Migration Fax over SIP (FoIP) using T.38 protocol works but can be unreliable. Better options: - Online fax services (eFax, RingCentral Fax) - Dedicated ATA with T.38 support on a separate SIP trunk - Keep one analog line for mission-critical fax (elevator, alarm)

### Alarm and Elevator Lines Many alarm monitoring and elevator phone systems require analog connections: - Use an ATA to convert SIP to analog for these devices - Verify with your alarm company that SIP-based connection is approved - Some jurisdictions require traditional copper for elevator phones

## Cost Savings Breakdown

| Item | PRI (Monthly) | SIP Trunking (Monthly) | |------|--------------|----------------------| | 23-channel circuit | $500-800 | — | | 20 SIP channels | — | $300-500 | | Long distance | $200-400 | Included or metered | | DID numbers | $50-100 | $20-50 | | **Total** | **$750-1,300** | **$320-550** |

Annual savings: $5,000-9,000 per location

Summit DNC manages SIP trunking migrations for businesses across Southern California. We handle network assessment, provider selection, number porting, PBX configuration, and QoS optimization — ensuring zero downtime during your transition.