SIP over TLS bandwidth consumption

Question

let's say I have connection using SIPS (SIP secure) using g729 codec. Does anyone know how many bandwidth it takes?

I know call using g729 codec 10ms is about 11Kb bandwidth consumption.

Answer 1

According to me:

• SIP or SIPS use almost the same bandwidth. It will makes no difference.
• The SIP bandwidth compared to RTP is insignificant.

Imagine you have a one minute call. The total exchange would be, for example:

For SIP:

1000 bytes for INVITE
1000 bytes for 200 OK for INVITE
500 bytes for ACK
500 bytes for BYE
500 bytes for 200 Ok for BYE
total = 3500 bytes

For RTP and g729, with 10ms:

Each of my RTP packet is 22 bytes. (not including UDP headers)
G729 payload: 10 bytes
RTP header: 12 bytes
total = 100 * 22 = 2200 bytes/second (which is 17,6kb/s)
total = 100 * 22 * 60 = 132000 bytes for a one minute call

For only one minute, the ratio is already

132000/(132000+3500) = 97,4%
3500/(132000+3500) = 2,6%

If you have longuer call duration, the sip related bandiwdth would drop quickly under 1%.

If you have frequent SIP messages during the calls (like INFO), may be you can take them into account, but this is usually not the case.

NOTE: I used an 8kbit/s G729 stream encoder instead of 11kbit/s. Just replace with your own values.

EDIT: With usual SRTP encryption method, if you use SRTP, the encrypted payload will remain the same size. However, an additionnal authentication tag is usually used. With AES_CM_128_HMAC_SHA1_80 being used, 10 bytes will be added to each packet.