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Lines and VoIP Bandwidth Calculator
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Here is a
brief introduction to the calculator. For more detailed information, press the Help
Button. For a running record of the results calculated, press the Results button.
Both these functions open new browser windows on your desktop.
- This calculator can be used to estimate the bandwidth required to transport a given
number of voice paths through an IP based network. Reverse calculations are also
possible. These estimate the number of voice paths that can be transmitted though an
IP network if the available bandwidth is known
- Before a calculation can be performed, details of the voice compression scheme must be
entered into the first two areas of the calculator.
- Use the first drop down box to select the CODEC being used. CODECs convert
analogue voice signals into data streams through sampling and quantisation. CODECs
vary in their quality and delay characteristics and, although there is not yet an agreed
standard, G.723.1 and G729A are the most common CODECs used for Internet voice
transmission.
- The frequency at which the voice packets are transmitted have a significant bearing on
the bandwidth required. The selection of the packet duration (and therefore the
packet frequency) is a compromise between bandwidth and quality. Lower durations
require more bandwidth. However, if the duration is increased, the delay of the
system increases, and it becomes more susceptible to packet loss; 20ms is a typical
figure.
- To perform a calculation, select the value which you want to calculate by clicking on
the radio button representing that parameter. Then, enter the known value into the
edit box representing the other parameter. When the Calc. button is
pressed, the result will be shown in the other edit box.
- For example, to work out how much bandwidth is required to transmit 10 voice paths (or
channels) through an IP network using the G.723.1 (6.4kbps) coding scheme with 30ms packet
duration, follow these steps:
- Use the Coding algorithm drop down list to select G.723.1 (MP-MLQ) 6.4 kbps
compression.
- 30ms should automatically be selected as the Packet duration. With
this coding scheme, lower packet durations are not possible.
- Ensure that the Unknown radio button in the Bandwidth area is
selected.
- Enter 10 into the edit box within the Voice paths area.
- Press the Calc. button. After a short time, 171 should appear in
the Bandwidth edit box, indicating that a bandwidth if 171kbps would be required.
- Mechanisms are being developed which reduce the overhead of IP / UDP and RTP headers;
examples include RTP header compression and multiplexing. This calculator does not
take these into account.
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| A Windows version of this calculator is available for only 99 US Dollars. VoIP Lite is a low cost calculator based on the calculator on this
page. Additionally, it supports cRTP header compression to 2 and 4 octets. 
VoIP Lite, showing the Lines and IP Bandwidth
Calculator
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| Westplan is a revolutionary software package which simplifies the
complicated design process involved in creating effective voice networks that are based on
either traditional circuit switching or Voice over IP. All calculations are based on an
inter-nodal traffic model which you can specify yourself, or allow Westplan to estimate. 
Westplan main window, with a network drawing in view
By allowing you to try different network topologies, Westplan quickly helps you to make
informed judgements on the suitability of particular voice networking strategies to your
company. You will be in a stronger position to understand your voice network costs and
therefore to control your network resources.
Westplan supports these features:
- Point and click network diagrams
- Voice over IP bandwidth calculations
- Layer 2 support for PPP, Frame Relay, Ethernet, ATM and HDLC.
- Analogue, T1 and E1 transmission facilities
- User-definable routing rules
- RTP compression for VoIP
- Full justification reports for each analysis
- Clear printed reports
- Context sensitive help
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