SOHO Network for VoIP

The next level up from a personal home network is a Small Office Home Office (SOHO) network. The requirements change from a purely experimenter, low VoIP usage to one where the end user is expecting a higher quality of service (QoS). The end user wants a reliable voice connection at all times, basically because they are running a business from home and require a professional appearance. The budget is still low so some compromises are taken.

The SOHO is an interesting situation as there are a number of choices available with some that do not require hosting your own PBX:

  • Rent Phone Service - One choice is to rent a phone service from a VoIP service provider - they will provide the IP phones, or you can configure your own soft or hard IP phone to work with their system. They will configure and maintain the PBX that is hosted at the service provider. The end user has limited interaction with the PBX and pays a very competitive monthly rate. This is ideal if you don't have the technical knowledge or time to learn and play with a PBX. And lastly it is very quick and easy to set up.

  • Service Provider Hosts PBX - In this scenario, the PBX is hosted at the VoIP service provider. The user does the software configures of the PBX while the hardware is maintained by the service provider. Usually, the PBX is a virtualized on a powerful server as opposed to being a physical machine. The service provider is responsible for keeping the server up, backed up and its network connections running. The service provider will provide the connection to the PSTN.

  • Host the PBX - The PBX is located at the SOHO on a PC or low end server. It uses the SOHO 's Internet connection and either connects to the PSTN via legacy telephony cards, an Analog Telephony Adapter (ATA) or through a VoIP service provider. The end user takes care of both the software configuration of the server and the hardware - the end user owns the PBX. This will be a steep but fun learning experience for those who like a technical challenge.

  • Host your own PBX - There are several off the shelf PBX offerings that can be utilized and many free open source PBX engines: Asterisk , FreeSwitch, YATE, etc.. The open source PBX engine is just one component in creating a fully functional PBX. Online communities have combined the PBX engine into a distribution consisting of software and tools that they feel are required to make a fully functional PBX. Examples are PBX in a Flash, Elastix, FreePBX, Blue.Box, etc.. In choosing a distribution, the most important consideration is support and documentation as you will be on a steep learning curve . Check out what documentation is available, what online support is available and the attitudes in the online support. Check out how friendly and helpful the forums are to new user postings.

Traffic Issues

Once, you reach the SOHO level, quality becomes an issue and the configuration and design of the network becomes of concern. Data traffic starts to interfere with the voice traffic causing poor audio quality, dropped calls and break-up. What can be done?

The first step is to identify the areas of the network where the bottlenecks are between data and voice traffic. The second step is to limit the traffic by separating the two as much as possible. Let's take a look at a typical SOHO network topology (drawing of the layout) which adds a separate Ethernet switch to provide more network connection than a standard wireless router.

Typical SOHO network

There are three areas of concern for VoIP traffic (which is the main focus of this website):

  1. Local Traffic - This is traffic within the local network. The Ethernet switch will provide a circuit switched path between all devices on the network so there is no bottleneck on the copper side. There is a bottleneck concerning the wireless laptop when it needs to connect to the local copper LAN. Its traffic must pass through the wireless router/Ethernet switch connection and fight for bandwidth with Internet traffic. There is a QoS issue with wireless traffic.

  2. Outgoing Traffic to the Internet - All traffic to the Internet must pass through the Ethernet switch/Wireless Router connection. Outgoing voice traffic will be fighting with data traffic for the port's bandwidth.

  3. Incoming Traffic from the Internet - You have no control over the incoming traffic from the Internet at the SOHO level in this typical SOHO setting. If you have a hosted PBX then this can be an issue as voice traffic will be competing with data traffic for bandwidth.

Congestion on the SOHO Network

Simple Solution

The simplest and least expensive solution is to purchase another inexpensive Ethernet switch and separate the voice and data traffic. One switch for voice. and the other for data traffic. This moves the bottleneck to inside the wireless router where there are usually methods to set the priority of data and voice traffic.

Separate Voice and Data Ethernet Switches

One Network

A very important point is that even though there are two Ethernet switches, there is still only one network with one network address (ex. 192.168.1.0/24) that spans across both switches. This means that broadcast traffic from both switches will appear throughout the network.

Router Traffic Management

A lot of wireless routers provide traffic management and QoS through their web based GUI. The traffic management really only deals with outbound traffic. Priority can be given to voice protocols like SIP. The router recognizes the voice traffic and given the choice between sending out data or voice, it will send the voice first. Each router is different and its capabilities would need to be explored to see how it can manage traffic.

Aftermarket Router Firmware

There are several aftermarket router firmware upgrades that are both free open source and paid upgrades that can add more capabilities to your wireless router. The result is that your el-cheapo router gets a hit of steroids and provides features normally seen only on expensive enterprise class routers. One of these is DD-WRT which allows you to set priority based on the physical Ethernet port. You could set the port connected to the voice Ethernet switch as having priority over the data Ethernet switch's traffic. Aftermarket router firmware upgrades require a higher level of expertise and patience to get working correctly.

VLANs and QoS?

Instead of using two separate Ethernet switches, you can upgrade to a more expensive switch that features VLANs (virtual LANs). The physical switch is able to divide itself into virtual switches. These virtual switches appear as if they were separate physical switches as discussed previously and as separate networks with unique network addresses (ex. 192.168.1.0/24 and 192.168.2.0/24). QoS (Quality of Service) can be controlled and configured in both the switch and the router. This is a step up in cost and complexity and the network design is now moving closer to the Business Network.

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Copyright July 2013 Eugene Blanchard