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Sephiroth · 17-10-2009, 22:39

Try this link to see if you have alternatives.

http://www.farina1.com/adsl/

I can't vouch for the results but you might be able to see where I'm going. I don't know if Virgin National use ADSL2+ and there's no consensus about whether or not ADSL2+ can improve reliability or speed. It all depends on attenuation and SNR. You'll need to winkle these numbers out of your router by logging onto the router and reading out from the status screen. We'd like to see those figures here, too.

As to what may have changed - it's a complex set of possibilities. I'll try and explain. The key word is CONTENTION. I'll assume for added "simplicity" that your VM service has bought BT capacity wholesale and haven't installed any infrastructure from your local exchange.

1/
You have an individual line to the exchange. You don't share anything with anyone else at this point.

2/
At the exchange up to 50 lines converge into a box where the signal is converted for use across the network and is then piped at 4 Mbps to a router. If you have 40 houses in Harlosh and 20 of them are bashing away at ½ Mbps, there is already contention and oversubscription on the available 4 Mbps.

3/
At your exchange either more villages come in to separate boxes as in (2) above and everything is then put into the network cloud (ATM) at 155 Mbps or if yours is a purely local exchange it goes to a larger exchange at 30 Mbps where it is concentrated onto the 155 Mbps pipe.

4/
Referring to (3) above, you'd really need to know what's at Harlosh exchange. How many villages (each one narrowed into the 4 Mbps pipe) are contending for the 30 Mbps pipe to the larger exchange. (Or the 155 Mbps pipe from Harlosh if it's a larger exchange, or how many smaller exchanges focus on a larger exchange and then feed 155 Mbps).

5/
The 155 Mbps pipe goes into the BT network cloud, routed to a PoP (Point of Presence). I don't know the basis for this routing - whether or not there is some algorithm to allow load balancing across the POPs (there are at least 11 BT PoPs in the cloud). Anyway, when you are routed at logon to a PoP, you reach a RAS (Remote Access Server handling thousands of connexions from hundreds of exchanges = contention) which authenticates you and assigns an IP address and during your session you are subsequently passed through to BT's Internet Backbone running at GigaBit rates. Since you don't know what anyone else is trying to do on the internet, there is more contention for you to consider.

6/
From BT's backbone, you go to a Gateway. Here the ISPs (like VM) lease a pipe of 155 Mbps or 622 Mbps depending on what they want to pay BT. Another point of traffic contention. Is VM 155 or 622? Have VM suddenly brought on a number of new subscribers from a number of additional exchanges? That adds to a change in contention you experience.

7/
So you've reached VM via the Gateway. Who knows what goes on in there and on the web?

8/
Oh - by the way, upstream capacity is about 50% of downstream. So there's delay and contention there to consider.

So - you see anything could have, and probably did, change pretty well overnight. And that's assuming you haven't changed any network card settings.

Finally, unless I missed something in your earlier posts, did you askyour neighbours what's happening to them?

Whew. End of massive!

17-10-2009, 22:39	#12
Sephiroth Wisdom & truth Join Date: Jul 2009 Location: RG41 Services: RG41: 1Gig VOLT Rutland: Gigaclear 400/400 Posts: 12,699	Re: Small connection issue Try this link to see if you have alternatives. http://www.farina1.com/adsl/ I can't vouch for the results but you might be able to see where I'm going. I don't know if Virgin National use ADSL2+ and there's no consensus about whether or not ADSL2+ can improve reliability or speed. It all depends on attenuation and SNR. You'll need to winkle these numbers out of your router by logging onto the router and reading out from the status screen. We'd like to see those figures here, too. As to what may have changed - it's a complex set of possibilities. I'll try and explain. The key word is CONTENTION. I'll assume for added "simplicity" that your VM service has bought BT capacity wholesale and haven't installed any infrastructure from your local exchange. 1/ You have an individual line to the exchange. You don't share anything with anyone else at this point. 2/ At the exchange up to 50 lines converge into a box where the signal is converted for use across the network and is then piped at 4 Mbps to a router. If you have 40 houses in Harlosh and 20 of them are bashing away at ½ Mbps, there is already contention and oversubscription on the available 4 Mbps. 3/ At your exchange either more villages come in to separate boxes as in (2) above and everything is then put into the network cloud (ATM) at 155 Mbps or if yours is a purely local exchange it goes to a larger exchange at 30 Mbps where it is concentrated onto the 155 Mbps pipe. 4/ Referring to (3) above, you'd really need to know what's at Harlosh exchange. How many villages (each one narrowed into the 4 Mbps pipe) are contending for the 30 Mbps pipe to the larger exchange. (Or the 155 Mbps pipe from Harlosh if it's a larger exchange, or how many smaller exchanges focus on a larger exchange and then feed 155 Mbps). 5/ The 155 Mbps pipe goes into the BT network cloud, routed to a PoP (Point of Presence). I don't know the basis for this routing - whether or not there is some algorithm to allow load balancing across the POPs (there are at least 11 BT PoPs in the cloud). Anyway, when you are routed at logon to a PoP, you reach a RAS (Remote Access Server handling thousands of connexions from hundreds of exchanges = contention) which authenticates you and assigns an IP address and during your session you are subsequently passed through to BT's Internet Backbone running at GigaBit rates. Since you don't know what anyone else is trying to do on the internet, there is more contention for you to consider. 6/ From BT's backbone, you go to a Gateway. Here the ISPs (like VM) lease a pipe of 155 Mbps or 622 Mbps depending on what they want to pay BT. Another point of traffic contention. Is VM 155 or 622? Have VM suddenly brought on a number of new subscribers from a number of additional exchanges? That adds to a change in contention you experience. 7/ So you've reached VM via the Gateway. Who knows what goes on in there and on the web? 8/ Oh - by the way, upstream capacity is about 50% of downstream. So there's delay and contention there to consider. So - you see anything could have, and probably did, change pretty well overnight. And that's assuming you haven't changed any network card settings. Finally, unless I missed something in your earlier posts, did you askyour neighbours what's happening to them? Whew. End of massive!