Equipments

IP or ISND connection?

The main difference is the speed and the reliability of the connection. Even though the internet connections (IP) have improved a lot everyone knows that sometimes the speed decreases.

ISND connection
ISDN lines are much more reliable and stable. There are not speed fluctuations and the connection is rarely broken.

Not all the phone lines are ISND and that’s why you should check if yours is ISDN. When you want to use the ISDN line for a videoconference you can not use it for telephone communications during the videoconference. Another option (more expensive) is to have an ISND line exclusively for videoconferences.

Each ISDN line is formed by two telephone simple lines. Each of these simple lines gives a transmission speed of 64k. This means 128k with one ISDN line. If we want more speed we need more ISDN lines.

With 128k of speed the sound is received perfectly but not the image when it is moving. For better image quality you need 248k.

The disadvantage is the price of the phone call. You must multiply it by the number of simple telephone lines (2 per ISDN) used in a videoconference.

The ISDN lines use the H.320 protocol.

IP connection
You only need an internet connection. The minimum speed for professional equipment is 128k. With a basic internet connection (512k) you can do a videoconference with a speed of 128k and with good sound quality and some problems with the image.

The main advantage of an IP connection is the price. And the main disadvantage in the stability. The IP connection would be shared with other users of your local network services: e-mail, web…

Sometimes you have problems while configuring the IP connection because of the systems of security as firewalls.
The IP connections use H.232 protocol.

Which one is the best option?
It is worthy to have the possibility for using both connections and depending on the circumstances use one or another. Some criteria we have to take into account:

• Not everybody has both types of connections and those with an old one would have an ISDN.
• If you can guarantee 128k there won’t be any problems. It is worthy to do a first try of connection before each videoconference in order to check that everything works properly.
• If you are looking for high quality in your connection the best option is ISDN.
• Price: an ISDN connection costs as a telephone call. It will be more expensive if you use more simple lines. If it is a national videoconference the price will be ok, but it will be really expensive if it is an international videoconference.