Melissa Swartz,  March 26, 2019

All new communication technology utilizes VOIP (Voice Over IP) technology.  If you want to install a new solution, it will use your data network to carry voice traffic.

Voice and video traffic have different requirements than data traffic.  They are considered “real time applications”. They must flow evenly, and quickly, through the network.  If packets are lost, they can’t simply be retransmitted (as data packets are).  Lost packets end up as silence in a telephone conversation or frozen video.  If they are too slow, or not sent evenly, the callers hear stutter and echo.  In a data-only environment, your network could have bottlenecks that your users are not aware of.  Lost packets are re-sent, and those that arrive slowly or unevenly are grouped correctly before presentation to the user.  Since voice and video require real-time transmission, bottlenecks in the network become very apparent, and even worse, they are service affecting.

Here are the main areas that must be considered when determining if your network will be able to support voice and video.

Data Infrastructure

Voice and video real time applications must be given priority in the network. The real time voice and video packets must be logically separated from other data traffic for optimum performance.  This is done using Virtual LANs (VLANs) for traffic segmentation, and giving these applications higher priority requires switches and routers that have the ability to provide Quality of Service (QoS) priority based on traffic type.


A VOIP implementation requires at least Cat 5 (preferably Cat 5e or Cat 6) cable to run properly.  If a building does not have Cat 5e in place, it must be installed.  Ethernet cable foot limitations must also be considered.  Phones must be within 300 cable feet of the switch that supports them.

The data cable can be used for IP Telephony in locations where the phone is located next to a computer.  However, there are phones located in areas where there is no existing computer (break rooms, conference rooms, etc.).  In the instances where these phones are now connected by Cat 3 cable, the cable will have to be replaced by Cat 5e or Cat 6 cable to support IP phones.

If there are phones located more than 300 feet from a switch closet, an analog device must be used to provide phone service at those locations or a switch must be added.

Power and Backup

In addition, each IP phone requires electrical power.  IP phones get power locally (with a power brick at the desk), or in-line (power over the cable that connects them to the data switch).  Switches that provide in-line power (known as Power over Ethernet, or PoE), of course, cost more than switches that do not.  Without PoE switches, you may power your phones by providing a power brick at the desktop.  However, your phones will not work during a power outage.  With PoE switches, typically a UPS is required in each network closet to power the phones during a power outage.

If there are existing UPS systems, it is important to know how long they will provide backup power.  Often, the UPS systems in the closets are configured to provide 10 to 30 minutes of backup, for data devices only.  This allows devices time to shut down before losing power.

PoE switches that are supporting telephones use considerably more power, so the UPS may not last as long as originally intended.  Furthermore, UPS systems that support voice are usually engineered to provide two hours of power.  This allows people to remain in the building with communications capabilities.

Read more about disaster recovery for VOIP.

WAN capacity

It’s likely that your wide area network (WAN) is your most expensive network bandwidth.  For this reason, many organizations do not have a lot of unused bandwidth in their WAN.  Adding voice or video to your WAN may be enough extra traffic to cause congestion.  To avoid this, you must know your current utilization and also the potential bandwidth required for voice and data.


In the traditional TDM world, the voice network is totally separated from the data network and is not subject to the security problems that plague data networks.  However, in a VOIP environment, voice resides on the data network and is open to all of the threats (viruses, Trojans, denial of service attacks, etc.) that can compromise a data network.  In addition, enabling mobility and remote worker capabilities with IP Telephony can create additional security issues.

For these reasons, the scope of your data network security must be expanded to include IP Telephony devices and servers as part of a layered defense system that includes firewalls, anti-virus, physical security, etc.  Some organizations are going as far as encrypting the voice packets so that, if they are intercepted, they cannot be recognized.

How can you be sure that your network is ready to support VOIP and video?  The best way is to do a network assessment that simulates the additional traffic and identifies and bottlenecks or configuration issues.  The time and money spent on a network assessment can help you avoid quality problems in the future.

Read about other considerations for replacing your system.


One Thought to “Infrastructure Considerations for VOIP”

  1. […] for the first time, your network may not be ready to support a real-time application such as voice. This article covers the basic requirements that must be […]

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