Bandwith usage with VoIP?

Reading up on this forum I am getting a better understanding of PBX and VoIP. But I have not seen any estimates regarding the bandwith usage.

Example 1:
Company A has 10 employers, they are a travel agancy.
They use the phone on and off the whole day, and have a rather hefty bill. If they switch to VoIP what amount of bandwith will the VoIP consume?

Example 2:
Company B also in the travel buisness, but a larger company with 50 people. Many simultaneously calls, but they also have drop-in customers so not tied up on the phone all day.

Example 3:
Company C is a call center, with as much as 100 people working from 3 different locations in the city. No need to explain that they will be “always” on the phone. What bandwith consumption are we looking for?

all of them depend on the codec being used. the bandwidth required for G711 codecs is going to be a lot more than G729a for example.

also, are you confident enough in your VoIP providers uptime and stability to drop any landlines altogether ? or are you going to keep them as ‘incoming’ and ‘outgoing backup’ ? … ulator.php

I better explain better.
This is strictly hypothetical speaking. I am working on a project in university, read more

I will read up on the different codec’s, there pros and cons and then I will post follow-up Q’s if needed.

But in generall, will VoIP work with a singel ISDN channel or a PSTN phone line, or are we talking major bandwith usage? I belive I read on the skype site that it was possible to run Skype-to-phone from a PSTN line. If this is the case, will the VoIP bandwith be = or > 56kb per user per call? (Did that make sense at all? as you might see english is not my native language)

And then for the examples we could simply say bandwithusage=56kbX#of users? This is with the codec skype uses, and will then be different with other codecs? Is this how it scales or is there a more advanced way to calculate the bandwith consumption? And how much room/overhead for future growth?

As of now the codec that seems correct is the ITU g.711

Thx for the link btw.

so you already have the information you need then. cool.

now where’s the ignore option ??