How: calculating bandwidth for voice

"VoIP" (voice over Internet Protocol) requires a certain amount of bandwidth to work properly.

Bandwidth is the rate of data transmission and is measured in bits per second (FPS). The formula used to calculate the call bandwidth required is: bandwidth = combined size of the package * PPSPPS is an acronym for "Packets per second" and is calculated as: (bit rate codec) / (voice payload size) = PPS a further element in the calculation of the bandwidth, calculates the total size of the package, by: total packet size, layer 2 header) = + (IP/UDP/RTP headers) + (voice payload size) these forms seem daunting, but step by step we will discover numbers, fill out the form. Level of difficulty: Moderately easy

Instructions

1. 1

   Discover the codec of your VoIP software used.

A codec is a standard in digital signal conversion and vice versa. There are eight different codecs, some may have more than one flow. Codec flow comes from the size of the sample codec / codec sample interval. Codec sample size is the number of bytes that digital signal at each interval sampling codec captured by the processor (DSP). Here is a list of codecs and bit rates: g. 711. 64 KbpsG. 729... 8 KbpsG. 723. 1 6.3 kbit/S or KbpsG. 726 5.3... 32 Kbit / S or 24 KbpsG. 728... 16 KbpsG722_64k... Kbpsilbc_mode_20 64 15.2 Kbpsilbc_mode_30 13 33KbpsFor use this calculation example we 729 codec with a bit rate 8 Kbps

2

Discover the size used by your software VoIP voice payload.

This is a multiple of the size of the sample codec be. This is necessary to the tail berechnenDas overall package and the PSP. In this example we use the default 729 20 bytes.

3

Entd

corners what 2 layer system you run. Multilink point-to-point protocol (MP) or frame relay Forum (FRF. 12) that is Ethernet. Each creates a different size above in the package header: 6 bytes for MP or FRF. 12. 18 Bytes for Ethernet (including taxes sequence frame or the 4-byte cyclic redundancy check). For our example, we use a PM 6-byte header.

4

Discover your program what the session and transport layers used.

Be calculate cost on the IP header size to be added. As standard this header is typically 40 bytes: 20 bytes of the IP, 8 bytes of the UDP (User Datagram Protocol) and 12 bytes for real-time Transport Protocol (RTP). Compressed files time Transport Protocol (touring) the combined header will be reduced to 2 or 4 bytes. Travel can be used in conjunction with Ethernet. For our example, we use a travelling 2-byte header.

5

The total size of in bytes of the packet from calculate: total = packet size, layer 2 header) + (IP/UDP/RTP headers) + (size of the payload of the voice) in our example is the header layer 2 2 bytes is 6 bytes, IP/UDP/RTP headers and payload is the byte packet size: total 20 = 6 bytes + 2 bytes + 20 bytes = 28 Bytesor, there are 8 bits in a byte packet size: total (bits) 28 8 = 224 = bits

6

Calculate the packets per second using formula set: PPS = (bit rate codec) / (voice payload size) in our example we use a bitrate codec 8 kbit / s (8000 FPS) and a voice of 20 byte payload volume

s (160 bit) so we get PSP: PSP 8000 = 160 = bandwidth would 50Available capacity must be sufficient for allowing the transfer of 50 packets per second.

7

The requirements for calculating bandwidth with the derived numbers: Bandwidth = combined size of the package * PPSWe have

n a total size of the package of 224 bits and a precondition for 50 packets per second. Therefore the bandwidth we need is: 224 50 = 11200 bits per SecondThis expresses more regularly in kbit / S 11.2 per call.