Understanding Frequencies of Copper & ADSL/SDSL

[1DMF]

Hello,

Can someone explain the reasoning behind ADSL having such a rubbish up stream to the downstream.

I have spoken with an ISP and they say it is the capabilities of the copper wire and frequencies used.

Now I'm a complete idiot when it comes to this type thing, but I do know basic physics and that electricity goes the same speed down a wire in both directions.

So if the electricity can go down a wire near the speed of light in either direction, why can't the ADSL.

if that was the case how can the same phone line support SDSL, if as they claimed the copper wire cannot support the frequencies needed for the same up speed as down speed.

is this ISP talking complete balony, or can someone explain how the same peice of copper can run ADSL with 4mbps down and 250kbps up , but also 8mbps down with 512 kbps up or even SDSL with 4mb up and down.

If the same peice of copper is used (phone line) for either service how can it be to do with the frequency capabilities of the copper wire.

any help understanding how this works is much appreciated.

Regards,
1DMF


"In complete darkness we are all the same, only our knowledge and wisdom separates us, don't let your eyes deceive you.

 

[allteltec]

The none hosting ADSL user likes fast downloads there is only so much band with based on distance from the DSLAM and gage of cable to your house so most of the band with is devoted to download not upload. Most DSLAMs I have tested have a max 850K up and 8 meg down this is build in to the hardware by the DSLAM designer.

 

[1DMF]

Hey allteltec, thanks for that.

That's what I thought, it's more how the hardware and multiplexing is done rather than the copper wire persae.

It's no different than ethernet going from 10mb to 100mb and now gigabit and beyond, all we needed to change is the network cards, hubs and routers, not the CAT5/6 UTP cable connecting it.

I would have thought ISP's, especially those unbundling the exchange, would have greater control over the ratio though.

OK the quality of the copper link between the exchange and myself along with distance will effect overall bandwidth capabilities of the line, however if it's possible to get 8mb down and 850k up, then surely by some form of configuration they can change it to 4mb down and 4.85mb up.

that would still be ADSL not SDSL as one way is not the same as the other, but my up stream is faster than my down.

Just seems odd to me that there isn't some form of utility to configure the bandwidth characteristics.

If Cisco & NetFlow can do it on a per process basis or by application, If I can set limits for email in exchange, disk quota's, transmission sizes etc...
I would have thought the same would be possible by the broadband exchange software.

Oh well whether it is or isn't our ISP isn't preparded to do toffee about it to help our situation, and with no budget to upgrade there isn't a lot I can do. hey ho

regards,
1DMF


"In complete darkness we are all the same, only our knowledge and wisdom separates us, don't let your eyes deceive you.

 

[allteltec]

If you need the up speed you get T-1's T-3's OS-3,12,48 Thay will be the same speed up an down, Down side is thay are big $$$$.

 

[1DMF]

I know, I have spoken with other ISP and we have all agreed the person from EasyNet was talking out their backside.

Although obviously the quality of the cooper wire makes a difference , the distance from the exchange etc... they were just trying to blind with science and make excuses for not offering us a better service for our money.

We are looking to move over to another ISP (BullDog), but need to give them a while as they are new in our area and want to wait and see if they proove themselves.

As the saying goes, better the devil you know!

Us in the UK just get screwed left/right & center over broadband, but what can you do?

"In complete darkness we are all the same, only our knowledge and wisdom separates us, don't let your eyes deceive you.

 

[jamesbird]

Imagine it to be like a multi lane road - you can fit in say 6 lanes total, as city traffic planner you can decide how to divide up the lanes say 5 into town, and 1 out of town. The quality of the copper define how many lanes you can fit in, the ISP/ telco decide how best to allocate the lanes. Like life it's a trade off!
All the best
James