Does it make a difference if I use BT, Sky or Virgin when using ADSL Broadband? I have the impression that if I am going to use the same broadband (telephone) line anyway there shouldn't be any difference at all.
Could you explain the technical aspects of this and tell me if my assumption is true?
I've got the impression, I am going to use the same broadband (telephone) line anyway, so there shouldn't be any difference at all.
That is an incorrect assumption.
Yes, you're using the same copper and going through the same DSLAM, but eventually your traffic lands on your ISP's network and is subject specifically to how they manage their network, including any performance gains or bottlenecks that come along with their service.
Well, considering this is for your business of which you are a sysadmin, you probably want to pick the company that will provide the best level of service for your organization. Which company has the best local reputation, which has the highest quality network, which has built in redundancy, which has the best SLA. How much money will it cost your company to be "offline" per hour? Find out which company is going to keep you online.
There are two ways to answer your question, the first being the quick one: yes, there's a difference.
The long answer starts at your phone socket in your home. This is actually the property of Openreach or Virgin, depending on who installs your service. The copper cable going from your socket goes to one of three places, depending on which service you get installed.
If you have ADSL2 (the most common form of broadband in the UK), the cable will terminate in your local BT telephone exchange. If you have VDSL2 (also known as "fibre broadband", the cable will terminate in a cabinet near your home, which then uses fibre-optic cable to connect back to a BT exchange in your town, or one of many if you are in a large built-up area. If you have Virgin cable, the cable will terminate in a cabinet near your home, which then uses fibre-optic cable to connect back to your local Virgin headend. Note that Virgin have an ADSL2 based product for customers who aren't in a "cabled" area; this uses an Openreach phone line like other ADSL2 ISPs.
From the BT exchange or Virgin headend, the connection then goes over fibre-optic cable on their backbone network to their main points of presence, where traffic will go out onto the public Internet.
Virgin cable is pretty simple: you get your service from Virgin and they provide the end-to-end connectivity exclusively over their network to get out onto the Internet.
For almost every other retail broadband provider in the UK, they will purchase wholesale service from Openreach to utilise that copper connection to your home. Most of the major ISPs will have equipment in the BT exchange to take your data connection and then ship the data over their own fibre-optic backhaul onto their network, then on to the Internet. For VDSL2 ("fibre") products like BT Infinity and Sky Fibre, the equipment in the street cabinets is owned and operated by Openreach, although this may change in future. For smaller ISPs, they may use an Openreach wholesale product where data is shipped over BT's network to a point of presence operated by the ISP or one of their suppliers, and from there you connect out to the Internet.
This is a pretty simplified answer (believe it or not), but the long and short of it is, for providers that aren't Virgin, the experience will differ dependent on the provider you select, and the makeup of their network and their relationship with their wholesale suppliers. The ISP may use a lower capacity backhaul network connection to get data from you to the Internet, or may oversell their capacity, expecting their users not to use all of the capacity at the same time, and you may find if a large number of people in your local area use the same ISP, that the connection gets slower when they are all using the network at the same time - this is known as "contention". You may have heard of people complaining that their Internet connection is slow at peak times. This can happen when the connection from the exchange onwards is "over contended", e.g. a link designed to handle 100 people maxing out at 16Mbps each is actually being used by the equivalent of 200 people trying to max out at 16Mbps each will mean an effective average speed of 8Mbps for all.
Larger ISPs such as BT, Sky, Plusnet, Talktalk, etc can afford to put larger capacity links in place, meaning there is less of a chance of over contention, and you are more likely to get the full speed that you sync at.
Another way in which experience can differ is the distance of the phone line from your home to the exchange/headend or cabinet. The longer the line, the more chance that you will get less of the speed that you may think you are buying. This is why most broadband in the UK is sold as "up to" a particular speed, as the actual speed that you sync at is usually less than the "up to" speed, except under optimal conditions. This is usually less of an issue for VDSL2 (aka "fibre"), as the line distance between your home and the street cabinet is usually much less than that to your exchange.
Latency (or "ping speed", measured in milliseconds) can also be impacted by which ISP you go with (some may introduce an artificial delay in latency either by deliberate throttle or by choice of network equipment) and your distance from your home to the ISP's exit point onto the Internet (usually London). Generally in the South East of England, you can expect to see latency of around 6-12ms, but as you travel further north or west of London, latency can rise to 20-40ms or more. Latency can also be affected by the quality of signal on the line, but with a fully operational phone line and undamaged internal cabling, this normally is not a problem.
You did ask!
