AltiGen MAXCS 7.0 Update 1 ACM Administration - Manual (Page 324)

Understanding VoIP Bandwidth Requirements
308 MaxCS 7.5 Administration Manual
Understanding VoIP Bandwidth Requirements
Before starting VoIP related configurations, it is helpful to have some understanding of VoIP bandwidth require-
ments, so that you can plan your VoIP deployment properly. Also see Network Configuration Guidelines for
VoIP
.
The data network bandwidth required to carry VoIP depends on the following factors:
• Codec and Compression – This is the encoding of analog voice to digital form, decoding of digital form
to analog wave form, and compression of digital form to a smaller size. MAXCS supports several type of
codec: G.711, G.722, G.729, G.723.1.
• Packet Length (Frame Size) – The size of the voice frame data (payload) transmitted in a packet. For
G.711, G.722, and G.729, you have choice of 10, 20, and 30 ms lengths. For G.723.1, the packet length
is a fixed 30 ms. A larger packet length decreases the transmission overhead. However, it will increase
the latency and have a negative effect on the voice quality if a packet is lost during transmission. For
G.711, G.722, and G.729, 20 ms is efficient and recommended.
• IP Header – The IP/UDP/RTP header adds 40 octets per packet. With a packet length of 20 ms, the IP
headers will require 16 kbps of bandwidth in addition to whatever codec is being used.
• Transmission Medium – In order to travel through the IP network, the IP packet is wrapped in another
layer by the physical transmission medium. The transmission medium, such as Ethernet, will add its own
header, checksums, and spacers to the packet. With a packet length of 20 ms, the transmission medium
requires additional 15.2 kbps of bandwidth to carry the packets to their destination.
• Silence Suppression – You can suppress the transmission of data during periods of silence. This can
reduce the demand for bandwidth by as much as 50 percent. However, it may have a negative impact on
the voice quality. Some users may feel the conversation is not "natural" when artificial comfort noise is
generated during periods of silence.
The following table lists bandwidth requirements for various transmission media with different codecs and
frame sizes. It assumes silence suppression is not turned on.
Codec
Voice
Encoding
(kbps)
Frame
Size
PPP
(kbps)
Frame
Relay
(kbps)
Ethernet
(kbps)
G.711/G.722 64 10 ms 100.8 102.4 126.4
G.711/G.722 64 20 ms 82.4 83.2 95.2
G.711/G.722 64 30 ms 76.3 76.8 84.8
G.729 8 10 ms 44.8 46.4 70.4
G.729 8 20 ms 26.4 27.2 39.2
G.729 8 30 ms 20.3 20.8 28.8
G.723.1 6.4 30 ms 18.7 19.2 27.2
VoIP Bandwidth requirement for WAN connection varies depending on the type of WAN. Bandwidth
requirement typically is less than Ethernet requirement.
Opening Enterprise Manager
To open Enterprise Manager, use one of the following methods:
• For a single-system installation without a Domain Master, this first method is recommended. From Max-
Admin, select VoIP > Enterprise Network Management. Enterprise Manager opens without a login dia-
log box.