LWC Training Corp.

Voice over IP Online Course

Lesson 2 - Why VoIP?

C. Issues with VoIP

Issues with VoIP

Organizations may still be leery of VoIP for several reasons. They may wish to test out and play with the technology before committing to a full scale implementation.

One cable system

One of the benefits of VoIP, a single cable system to install and manage, can also be a weakness. If the network is down both your data and telephone systems are out of action.

IT is not telephony

Telephone systems normally have 5 9's (99.999%) uptime. Data networks can't say the same. To put this in perspective, 5 9's means that the system can be down only 5 minutes per year. IT personnel will need to take extra telephony training and be cautious around their networks. No more playing around with the server in the middle of the day. Data networks are also notorious for weak security and viruses. These will impact negatively on the telephone service.

Upgrade the system

Besides the telephone equipment itself, the network infrastructure will probably need to be upgraded. This may include upgrading the network cabling and devices such as hubs and switches to handle fast Ethernet. Routers will need to be upgraded to handle quality of service.

Power can't be interrupted

Analog telephone sets receive power over the telephone wire. This provides dial tone even when there is a power outage. In order to provide this same service, servers and other network devices need uninterruptible power supplies (UPS). IP telephone sets will need to rely on the building's protection from power outages or embrace Power over Ethernet.


Emergency services depend on being able to find someone who dials 911. This is not a problem with the PSTN since telephone numbers, including extension numbers in office buildings, are mapped to physical locations. IP telephones can easily be moved from location to location. When plugged in, they receive their IP configuration from a DHCP (Dynamic Host Configuration Protocol) server and they are back in service again. Some method must be found to map IP addresses to physical locations in order for Emergency services to respond quickly.

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