bandwidth calculation

[spanton]

How is the bandwidth calculated for IP traffic?

 

[I2007]

It depends on which codec you use. If you use the standard G.711 codec it will use 180Kb pr.call. If you use G.729 it will be apx 90Bk pr.call. And you have further codecs that compresses it even more, but then again you will have voicequality like having a conversation with a toilet. These numbers are what Nortel have given me, and what I really measure when I test connections.

i2007

 

[spanton]

Thank you for the info..........do you know wht the bandwidth for the G723.1

 

[janchundia]

also depend of the payload size that you´re going to use.
20 ms, 30ms, etc..
Check in the NTP the bandwith for codecs, payloads and the layer 2 protocol (PPP, FR, ATM, etc,...)

 

[spanton]

what is the NTP number?

 

[janchundia]

Meridian 1
Succession 1000
Succession 1000M
Succession 3.0 Software
Data Networking for Voice over IP

NTP 553-3001-160

Regards

Javier

 

[Pudge99]

I have a very comprehensive Excel spreadsheet for anyone with this requirement, with different codecs, payload, VAD on or off and transport methods (ie: ATM, FRAME, PPP etc). Not sure how to share the document, if e-mail and phone numbers are not to be posted? Any suggestions?

 

[svhtech]

If it's not too big how about cut and paste ?

Experience is that marvelous thing that enables you to recognize a mistake when you make it again.
Franklin P. Jones

 

[janchundia]

isn´t posibble becuase is a excell spreadsheet where you enter different parameters and immediately show you the results for those options (payload, coedc, protocol, etc..)

 

[janaya]

[(O + P)*(1000ms / S)]*8=B

O = Overhead in bytes
P = Payload size in bytes
S = the actual size in milliseconds of the individual voice payloads
B = Bandwidth

So three simultaneous calls using G723.1 over Ethernet

Overhead for Ethernet will be (assuming on interframe gap)

Ethernet w/o IF Gap = 26 bytes
IP = 20 bytes
UDP = 8 bytes
RTP = 12 bytes

Total Overhead = 66 bytes

Payload size = 20 bytes (for example purposes. 723.1 produces one of 3 segment sizes 24, 20 or 4 bytes.

Size of the payload = 723.1 produces 30ms blocks

using the above formula [(O + P)*(1000ms / S)]*8=B

[(66 + 20)*(1000/30)]*8=B
[(88)* (33.34)]*8=B
[2933.92]*8=b
23471.36 = bytes per second
23.47kpbs = Bandwidth for one call
23.47 * 3 = 70.4 kbs for three simultaneous calls using a 20byte payload over G732.1 over Ethernet w/o Interframe Gap.

I'm tired now and I have a headache. For those of you that are unfortunate and have not taken the 801 VOIP Test from Nortel and have to now take the 805, you have to know this formula along with the others in the Nortel NTP's and have to take the test with NO documentation and no references. Makes for fun studying.

I hope this helps. If you know your exact payload and transport method just leave here and I can help figure it out.

OR.....just ask your Nortel Rep for the excel spreadsheet. they are supposed to make this available to customers.

John

 

[Pudge99]

svhtech,
The cut and paste is a good suggestion, although it is too large, as it has various sheets to the workbook. And as janchundia mentioned, different parameters (trunk numbers) exist to do the calculations for you.