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Bandwidth & Codecs

Capacity and quality management information.

How much bandwidth do I need for my SIP trunk?

The amount of bandwidth your specific implementation needs depends on the number of concurrent calls during your peak hours you will need to support and the CODEC (compression method) you intend to use for your SIP trunk.  IPComms supports both G.711 & G.729 CODECs.

To keep it simple, use this formula:

Peak Capacity * Codec payload = Total Bandwidth required


Peak Capacity is the total number of simultaneous calls during peak business hours. Do not include inner-office calls, only calls that will be traversing your external broadband connection.

Codec Payloads:

G.711 = 87Kbps per call

G.729 = 31 Kbps per call


Here's an example:

1. You have no more than 10 calls during your busiest calling period

2. You plan to the G.729 codec 

Calculation: 10 * 31Kbps = 310Kbps needed during peark hours.

What is a Codec?

In communications engineering, the term "Codec" is a technical term for the "compression/decompression" of data.  Codecs vary in the sound quality, the bandwidth required, the computational requirements, etc.

IPComms supports two Codec types: G.711 and G.729.

G.729 has a 8k bitrate.  it provides good audio quality with low bandwidth requirements. it is the most commonly used codec in VoIP calling.

G.711 has a 64K bitrate and is best used where there is a lot of bandwidth available.

How do I choose a Codec?

The easiest way is to determine which codec is best for you, is to consider how much bandwidth is available in your business scenario, and balance that with what quality you are comfortable with.  

While both G.711 and G.729 are very good quality.  There is a difference (however slight it might be audibly).  As a rule of thumb, G.729 is slightly less then the quality of an excellent cell phone call while G.711 is typically better or at least equal to the quality of an analog land-line.

What Codecs does IPComms Support

IPComms supports G.711 & G.729 Codecs.