Bandwith is limited and it is shared by multiples applications (web, email, files downloading, FTP, ...)
On Internet bandwith is defined as the bit rate measure of available or consumed data communication resources expressed in bits/second or multiples of it (kilobits/s, megabits/s etc).
If our voip calls share bandwith with other applications is possible to not have enough resources to keep a voip connection properly.
The bandwidth needed for VoIP transmission will depend on a few factors: the compression technology, packet overhead or network protocol. For example, if we are using G.711 codec for voice encoding we need 64 Kbps only for this process. Then, we need to add the overheads. It is estimated that we need 80 Kbps to transmit just one conversation..
If we use a codec with more compression, for example G.729 codec at 8 Kpbs, then again we need to add the overheads so it is estimated that 24 Kbps is needed just for one conversation.
If we have problems with the bandwith we have some differents ideas to solve the problem
- Trying to get more bandwith (normally paying more to our providers or changing old networks)
- Sacrificing other data types (for example avoid using heavy file downloading P2P)
- Using a codec needing less bandwith. (Example: G729)