[SOLVED] Why Data Rate & Actual Speed are different with ADSL2+ ?

[hero355]

Hello, I have ADSL2+ connection line up and Data rate shows 10240kb. But Actual speed is 7.5-7.8mbps maximum. In theory it should be 10mbps right? Is there any loss happening?

 

[bill001g]

There likely is overhead in the DSL transmission protocols. ADSL uses something called ATM to send the data and this must be converted to ethernet frames. Been a long time since I looked at the details but there is overhead. It is similar to if you compare a file download to speedtest numbers. In addition to one being in bytes/sec and the other in bits/sec file downloads only consider the actual data file itself they do not include any of the overhead for all the things like the space IP addresses and other stuff take up in every data packet being sent.

I used to know this stuff but then VDSL came out which works differently but I still suspect it is purely related to overhead in the data transmission.

 

[hero355]

There likely is overhead in the DSL transmission protocols. ADSL uses something called ATM to send the data and this must be converted to ethernet frames. Been a long time since I looked at the details but there is overhead. It is similar to if you compare a file download to speedtest numbers. In addition to one being in bytes/sec and the other in bits/sec file downloads only consider the actual data file itself they do not include any of the overhead for all the things like the space IP addresses and other stuff take up in every data packet being sent.

I used to know this stuff but then VDSL came out which works differently but I still suspect it is purely related to overhead in the data transmission.

Thank you very much. So should i talk wih ISP about overhead loss? I see here i get loss from 10240kb/10mb about 22-25% atm overhead?

 

[bill001g]

Only the ISP can change any configuration options. It has been so long since I looked at the details of how you actually configure the ISP equipment I forget what they can do.