SDN Appliance · Technical Specification

VoIP Software-Defined Networking Appliance.

The VoiceTel SDN Appliance intelligently controls the network from the end-user's LAN and delivers unobstructed communications to the VoiceTel core, with optional in-call High Availability (HA). This is the white paper, requirements, installation, and configuration reference.

Sign up SDN appliance overview

VoiceTel SDN appliance — a small Raspberry Pi-form-factor device
The VoiceTel SDN appliance — Raspberry Pi form factor, deploys alongside any PBX or SBC.

Problem

Firewalls are devices that inhibit or prevent the flow of IP communications. When not optimally configured, they can cause:

  • Dropped calls
  • No audio
  • One-way audio
  • Unclear audio
  • Rejected calls

Even perfectly configured end-user firewalls can occasionally suffer from these issues, since network assets beyond the end-user's control — routers, modems, upstream policies — can affect IP communications.

Background

VoiceTel provides free end-user support to address firewall and traversal issues. However, each hardware vendor is unique and there is no standard for configuration options or naming conventions. Some firewalls also react in unexpected ways across firmware and model variations, making proper configuration of unobstructed IP communications challenging.

Solution

VoiceTel offers a VoIP SDN Appliance as a service to address obstructed IP communications. The appliance is placed in the end-user's LAN and automatically establishes an encrypted IP tunnel to the VoiceTel infrastructure. The end-user VoIP infrastructure registers directly to the appliance and benefits from unfettered connectivity without any modification of LAN routing policies. Optionally, the appliance follows intelligent routing to maintain in-call HA when redundant connectivity exists, for full Business Continuity Management (BCM).

Requirements

Hardware

  1. Raspberry Pi 3 Model B+ or newer.
  2. 8 GB or larger MicroSD card.

LAN

The VoiceTel VoIP SDN appliance minimally requires that the end-user's LAN have:

  • DHCP enabled
  • Allow outbound connections
  • UDP timeouts greater than 10 seconds
  • The appliance is located on the same LAN as your endpoint

Installation

Download and write the image to your MicroSD card. Once complete, place the card into the appliance and boot the device. We must authorize the appliance's MAC address to connect to our network, so contact us after the device has been booted for the first time. You can optionally purchase a preconfigured and authorized device that ships ready to deploy. If you don't already have an account, sign up here.

Download Image

Download the VoiceTel VoIP SDN image.

Verify MD5 Sums

8e1a4d6b8bda4c44d8e33922868b16b6  sdn.img
93827769dd93abc1e8f641ca532a6567  sdn.zip

Write Image

Write the image to the 8 GB or larger MicroSD card using the platform-appropriate tool:

Configuration

Authentication

The endpoint must register to the LAN address of the SDN appliance using Digest authentication.

Portal → Settings → Authentication → Digest

DID Routing

Routing of a DID can be one of the following:

  • User: sends the call to the account username.
  • SDN: sends the call to the DID number.

Portal → Settings → DID

Asterisk

Change allowguest=yes in the [general] section of sip.conf. Then run:

asterisk -rx 'sip reload'

FreePBX

Change Allow Anonymous Inbound Calls to Yes in the Asterisk SIP Settings module, then click Apply Config.

FreeSWITCH

Add the IP address of the appliance as an allow node in the domains list of acl.conf.xml. Then run:

fs_cli -x 'reloadacl'

FusionPBX

Go to Advanced → Access Controls. Click the edit icon for domains. Under nodes, click the plus icon and then save. Go to Status → SIP Status and click reloadacl.