📞 Telephony Server Setup (FreeSWITCH N+1)

Horizontally scalable call processing with FreeSWITCH

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📋 Overview

Telephony servers handle all voice traffic:

SIP registration and authentication
Call routing and switching
Media processing (RTP)
IVR, queues, and applications
Recording and transcoding

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🔄 Horizontal Scaling Architecture

Plaintext

                              ┌─────────────────────────────────────────────────────────────┐
                              │                    SIP LOAD BALANCER                        │
                              │              (OpenSIPs, Kamailio, or DNS SRV)               │
                              └─────────────────────────┬───────────────────────────────────┘
                                                        │
           ┌────────────────────────────────────────────┼────────────────────────────────────────────┐
           │                                            │                                            │
           ▼                                            ▼                                            ▼
┌─────────────────────────┐              ┌─────────────────────────┐              ┌─────────────────────────┐
│   📞 TELEPHONY-01       │              │   📞 TELEPHONY-02       │              │   📞 TELEPHONY-N        │
│   ─────────────────     │              │   ─────────────────     │              │   ─────────────────     │
│                         │              │                         │              │                         │
│   ┌─────────────────┐   │              │   ┌─────────────────┐   │              │   ┌─────────────────┐   │
│   │   FreeSWITCH    │   │              │   │   FreeSWITCH    │   │              │   │   FreeSWITCH    │   │
│   │   ───────────   │   │              │   │   ───────────   │   │              │   │   ───────────   │   │
│   │   SIP: 5060     │   │              │   │   SIP: 5060     │   │              │   │   SIP: 5060     │   │
│   │   RTP: 16384+   │   │              │   │   RTP: 16384+   │   │              │   │   RTP: 16384+   │   │
│   └────────┬────────┘   │              │   └────────┬────────┘   │              │   └────────┬────────┘   │
│            │            │              │            │            │              │            │            │
│   ┌────────┴────────┐   │              │   ┌────────┴────────┐   │              │   ┌────────┴────────┐   │
│   │  HAProxy Local  │   │              │   │  HAProxy Local  │   │              │   │  HAProxy Local  │   │
│   │  Port 5000/5001 │   │              │   │  Port 5000/5001 │   │              │   │  Port 5000/5001 │   │
│   └────────┬────────┘   │              │   └────────┬────────┘   │              │   └────────┬────────┘   │
│            │            │              │            │            │              │            │            │
│   ┌────────┴────────┐   │              │   ┌────────┴────────┐   │              │   ┌────────┴────────┐   │
│   │ GlusterFS Mount │   │              │   │ GlusterFS Mount │   │              │   │ GlusterFS Mount │   │
│   │ /recordings/    │   │              │   │ /recordings/    │   │              │   │ /recordings/    │   │
│   └─────────────────┘   │              │   └─────────────────┘   │              │   └─────────────────┘   │
│                         │              │                         │              │                         │
│  ┌───────────────────┐  │              │  ┌───────────────────┐  │              │  ┌───────────────────┐  │
│  │ Capacity:         │  │              │  │ Capacity:         │  │              │  │ Capacity:         │  │
│  │ • 10,000 ext      │  │              │  │ • 10,000 ext      │  │              │  │ • 10,000 ext      │  │
│  │ • 1,500 calls     │  │              │  │ • 1,500 calls     │  │              │  │ • 1,500 calls     │  │
│  └───────────────────┘  │              │  └───────────────────┘  │              │  └───────────────────┘  │
│                         │              │                         │              │                         │
└─────────────────────────┘              └─────────────────────────┘              └─────────────────────────┘
           │                                            │                                            │
           └────────────────────────────────────────────┼────────────────────────────────────────────┘
                                                        │
                                                        ▼
                              ┌─────────────────────────────────────────────────────────────┐
                              │                POSTGRESQL CLUSTER (via HAProxy)             │
                              │              ┌──────────┐ ┌──────────┐ ┌──────────┐        │
                              │              │ Primary  │ │ Replica  │ │ Replica  │        │
                              │              └──────────┘ └──────────┘ └──────────┘        │
                              └─────────────────────────────────────────────────────────────┘
                                                        │
                                                        ▼
                              ┌─────────────────────────────────────────────────────────────┐
                              │                  GLUSTERFS / NAS STORAGE                    │
                              │                   /var/lib/freeswitch/recordings            │
                              └─────────────────────────────────────────────────────────────┘

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📊 Capacity Planning

Servers	Extensions	Concurrent Calls	Recordings/Day	RAM Required
1	10,000	1,500	~50,000	16-32 GB
2	20,000	3,000	~100,000	32-64 GB
5	50,000	7,500	~250,000	80-160 GB
10	100,000	15,000	~500,000	160-320 GB
20+	200,000+	30,000+	~1M+	320+ GB

> 💡 Scaling Rule: Add one server for every ~10,000 extensions or ~1,500 concurrent calls needed.

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🛠️ Step 1: Environment Preparation

1.1 Configure Hostname

Bash

hostnamectl set-hostname tele-node-01  # Increment for each server

1.2 Name Resolution

Add to /etc/hosts:

Text

# Database Cluster
192.168.10.31 pg-node-01
192.168.10.32 pg-node-02
192.168.10.33 pg-node-03

# File Server Cluster
192.168.10.34 fs-node-01
192.168.10.35 fs-node-02
192.168.10.36 fs-node-03

1.3 Copy Credentials

Bash

mkdir -p /etc/softswitch
scp root@192.168.10.31:/etc/softswitch/db-credentials /etc/softswitch/

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📦 Step 2: Install Telephony Package

Bash

# Add Ring2All repository
curl -fsSL https://repo.ring2all.com/gpg.key | gpg --dearmor -o /etc/apt/keyrings/ring2all.gpg
echo "deb [signed-by=/etc/apt/keyrings/ring2all.gpg] https://repo.ring2all.com/apt stable main" > /etc/apt/sources.list.d/ring2all.list

apt update

# Install telephony package
apt install -y softswitch-telephony

# Install audio packages (recommended)
apt install -y softswitch-music
apt install -y softswitch-voiceguide-emma    # English
apt install -y softswitch-voiceguide-paloma  # Spanish

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⚖️ Step 3: Install HAProxy Sidecar

Each telephony server needs its own HAProxy to connect to the database cluster:

Bash

apt install -y haproxy

Configure /etc/haproxy/haproxy.cfg:

Haproxy

global
    log /dev/log local0
    chroot /var/lib/haproxy
    stats socket /run/haproxy/admin.sock mode 660 level admin
    user haproxy
    group haproxy
    daemon

defaults
    log global
    mode tcp
    option tcplog
    timeout connect 5000
    timeout client  50000
    timeout server  50000

# Write Pool (Port 5000)
frontend postgres_write
    bind *:5000
    default_backend backend_postgres_write

backend backend_postgres_write
    option httpchk GET /master
    http-check expect status 200
    default-server inter 3s fall 3 rise 2 on-marked-down shutdown-sessions
    server pg-node-01 192.168.10.31:5432 maxconn 100 check port 8008
    server pg-node-02 192.168.10.32:5432 maxconn 100 check port 8008
    server pg-node-03 192.168.10.33:5432 maxconn 100 check port 8008

# Read Pool (Port 5001)  
frontend postgres_read
    bind *:5001
    default_backend backend_postgres_read

backend backend_postgres_read
    balance roundrobin
    option httpchk GET /replica
    http-check expect status 200
    default-server inter 3s fall 3 rise 2 on-marked-down shutdown-sessions
    server pg-node-01 192.168.10.31:5432 maxconn 100 check port 8008
    server pg-node-02 192.168.10.32:5432 maxconn 100 check port 8008
    server pg-node-03 192.168.10.33:5432 maxconn 100 check port 8008

Start:

Bash

systemctl restart haproxy
systemctl enable haproxy

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📂 Step 4: Mount File Server

Bash

# Install GlusterFS client
apt install -y glusterfs-client

# Create mount point (if not created by package)
mkdir -p /var/lib/freeswitch/recordings

# Add to /etc/fstab (read-write for recordings)
echo "fs-node-01:/gv_recordings /var/lib/freeswitch/recordings glusterfs defaults,_netdev,backup-volfile-servers=fs-node-02:fs-node-03 0 0" >> /etc/fstab

# Mount
mount -a

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🔌 Step 5: Configure ODBC

The softswitch-telephony package creates ODBC config automatically. Verify /etc/odbc.ini:

Ini

[ss_telephony]
Description = Ring2All Telephony Database
Driver = PostgreSQL Unicode
Servername = 127.0.0.1
Port = 5000
Database = ss_telephony
Username = ss_db_user
Password = YOUR_PASSWORD
ReadOnly = No

Test ODBC:

Bash

isql -v ss_telephony ss_db_user YOUR_PASSWORD

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🚀 Step 6: Start FreeSWITCH

Bash

systemctl enable --now freeswitch
systemctl status freeswitch

Verify:

Bash

fs_cli
sofia status
# Should show internal and external profiles
/exit

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🔥 Step 7: Firewall Configuration

Bash

# SIP and RTP ports
ufw allow 5060/udp     # SIP UDP
ufw allow 5060/tcp     # SIP TCP
ufw allow 5061/tcp     # SIP TLS
ufw allow 16384:32768/udp  # RTP Media

# Optional: Allow from specific networks only
# ufw allow from 192.168.0.0/16 to any port 5060

ufw enable

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➕ Adding More Telephony Servers

To add capacity, simply repeat this entire process on a new server:

Set unique hostname (tele-node-02, tele-node-03, etc.)
Install packages
Configure HAProxy sidecar
Mount file server
Configure ODBC
Start FreeSWITCH

No configuration changes needed on existing servers!

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📈 SIP Load Balancing Options

To distribute SIP traffic across multiple telephony servers:

Option 1: DNS SRV Records

Dns

_sip._udp.pbx.example.com. 86400 IN SRV 10 50 5060 tele-node-01.example.com.
_sip._udp.pbx.example.com. 86400 IN SRV 10 50 5060 tele-node-02.example.com.

Option 2: SIP Proxy (OpenSIPs/Kamailio)

For advanced routing, use a dedicated SIP proxy server.

Option 3: Per-Domain Assignment

Assign specific telephony servers to specific domains in the Ring2All Admin panel.

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❓ Troubleshooting

FreeSWITCH Not Starting

Bash

journalctl -u freeswitch -f
fs_cli -x "console loglevel debug"

ODBC Connection Failed

Bash

# Test connection
isql -v ss_telephony ss_db_user PASSWORD

# Check HAProxy
ss -tlnp | grep 5000
curl http://192.168.10.31:8008/master  # Should return 200

No Audio (RTP Issues)

Bash

# Check firewall
ufw status

# Check RTP ports
ss -ulnp | grep freeswitch

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✅ Verification Checklist

[ ] FreeSWITCH service running
[ ] ODBC connection to database working
[ ] HAProxy routing to database cluster
[ ] GlusterFS mounted for recordings
[ ] SIP profiles loaded (sofia status)
[ ] Test call successful

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Next: 7. HAProxy Load Balancer Setup