Broadband speed

What do we mean by "broadband speed", and what are the factors that affect it?

I had intended this to be one of my blog posts aimed at my less technical readers (Hi, Pauline), and explain some of the issues in a non technical way. It seems, however, that people like the ASA, OFCOM and Which may do well to read it as well. Again, they miss the point hugely (see recent ispreview article).

Technology

First I'll just summarise some of the different technologies and what they mean. Some technology can be used by many different ISPs via a whole sale service (i.e. exactly the same equipment and wires used, so no difference technically). In some cases multiple ISPs can use the same type of equipment, so the same technology and basically the same speed and service offered but by different actual equipment. In some cases an ISP will have their own dedicated equipment and so offer a very different service to other ISPs even to the same address.

• FTTC (Fibre to the Cabinet) is one of the most common technologies now. It is provided using a normal copper pair (phone line) that has equipment connected at the main street cabinet to provide broadband over that phone line. The cabinet has glass fibre back to the exchange and on to the ISP and the Internet. It is almost always a BT plc t/a Openreach cabinet and equipment which connects to an ISP or back-haul carrier at the exchange. This same technology can be sold by lots of ISPs and the link speed will be the same regardless. Typically it can be provided with a cap at 80Mb/s down and 20Mb/s up, or a lower cap of 40Mb/s down and 10Mb/s or 2Mb/s up. These are usually tariff options. The speed depends on the line length and quality from the cabinet to the premises. It can reduce a bit over time as more lines on the same cabinet get service. It makes no difference to the actual sync speed which ISP you choose when buying this sort of service.
• ADSL (Asymmetric Digital Subscriber Line) uses a copper pair (phone line) from the exchange to the premises with equipment in the exchange. Glass fibre is used to connect from the exchange on to the ISP and the Internet. There are typically two variants: ADSL1 and ADSL2+. The former allows up to around 8Mb/s sync speed (around IP 7.15Mb/s data rate), and the latter up to 24Mb/s sync (21Mb/s IP data rate). Again, the sync depends on the line length. Speeds can be as low as 250kb/s on very long lines. Apart from some areas with older ADSL1 only BT kit, most ISPs can offer ADSL2+ either using BT, or TalkTalk or some other back-haul carrier, or even their own kit. In general, it will make no difference to sync speed which ISP you go for. It may matter if one can only offer ADSL1 and another can offer ADSL2+, especially if you are close to the exchange and could get speeds over 8Mb/s.
• FTTP (Fibre to the Premises) is similar to FTTC but has a fibre from the cabinet to the premises instead of copper wires. There is technology provided by BT plc t/a Openreach with 40/10, 80/20 and even 330Mb/s speeds. Unlike FTTC the speed is the same regardless of distance. There are some ISPs that offer different direct fibre services, and some that even provide gigabit (1000Mb/s) services. This is much rarer.
• Coax (cable). In lots of places there are alternatives that don't actually use phone lines. Virgin have a network of cable installations originally for cable TV services. These use coax to a cabinet nearby, and may then use more coax to a main cabinet further way. These are then typically connected using glass fibre to a core network and on to the Internet. Like FTTC, this is not a "fibre" service. The speed depends on the length of coax, and can be quite fast (e.g. 100Mb/s). Typically such services are not available to other ISPs, so this is an area where choosing the ISP offering this service may provide a very different service to choosing a different ISP which is inherently using a different technology.
• Radio. Like WiFi but over a wider area, some ISPs provide radio links. The speed can depend on distance to their nearest mast. Like coax/cable, this is typically a very different offering to other ISPs using different technologies.

Advertised speed

There are different sorts of underlying technology used to provide a broadband (Internet access) service. What we see is companies advertising a possible speed - usually as "up to" some number of megabits per second. This is actually a data throughput, not speed, but that is not really important here.

One of the problems is that some of the technologies used are adaptive to the underlying phone line that is used, and so a long phone line will have lower speed. This is a simple fact of physics, and generally, for a specific technology, the speed you can get will be around the same.

The ASA were unhappy with people advertising ADSL2+ technology as "Up to 24Mb/s". The technology can do that, on short and good quality lines, but on longer lines it is slower. The "up to" is quite correct. Read that as "not more than" and it makes as much sense. However, the ASA felt that this was somehow misleading almost all customers, and they felt that ISPs should only mislead 90% of customers rather than 100%, so they insist that "Up to" speeds are set at a speed that at least 10% can achieve. This is, of course, a totally daft thing to do - if customers do not understand "up to", then all you do is reduce complaints by 10%. What you need to do is make sure customers understand what the statement means.

OFCOM stated that "BT’s ‘up to’ 76 Mbps package: Only 1% of customers received the maximum advertised speed.". For a start, that surprised me - and I suspect they are not actually looking at the line speed but perhaps measuring speeds of transfers in to the Internet (see below). I would expect that 10% of lines can get 76Mbit/s or more on that service. In fact I would say that 90% get what was advertised, which is "not more than 76 Mb/s" and 10% don't (i.e. they get more than 76Mb/s so the advert was misleading to them).

The good news is that regardless of the "up to" rate, ISPs provide means to get a speed estimate for a specific installation, and that is all that matters. It does not matter if you are buying an "up to 40Mb/s" service or an "up to 80Mb/s" service if the service you can get at your address is only 25Mb/s.

If anything, I think adverts should explain the technology and carrier used. This would allow comparison to be simpler. If comparing two ISPs, if both use "BT Wholesale" then the underlying technology that both ISPs can use will be the same. Speeds will be the same. It matters if you order FTTC 40/10 or FTTC 80/20 or ADSL2+, but typically you could order those from any ISP using BT Wholesale backhaul. Similarly, using Talk Talk wholesale backhaul would offer ADSL2+ which will work at basically the same speed as BT Wholesale ADSL2+. For FTTC on TalkTalk the underlying modem and line is identical to BT as it uses Openreach modems in the cabinet. Now, some ISPs are different - some use radio, or coax, and so on. Some even use fibre, and there really should be a ban on claiming that copper coax or copper telephone lines are "fibre" to avoid confusion and aid comparison.

Explaining the underlying connection type would allow people to compare ISPs and the packages more sensibly.

Up To

I have raised this before, but one issue with "up to", and I think a key confusion, is that there are two "up to" speeds involved. One is the fact that the line speed will depend on length of line and quality, and so for a service the speed may be "up to 80Mb/s" meaning that one address may get 80Mb/s and another may get 45Mb/s, etc. It is not a variable, it is pretty much fixed for the address based on its line characteristics. It can change over time (as more lines get broadband in they area).

The other "up to", and perhaps what people are confusing the advertising with, is that a line synced at 80Mb/s is not always transferring data. If you transfer a file, you will get a speed of transfer for that file. If sending several files at once, each file will share that one link. The speed the file transfers will be anything "up to" the line speed you have. When it is the only use of the line, and the other end is not busy and well connected to the ISP, the speed will be the line rate. So a line synced at 45 Mb/s can transfer files "up to 45Mb/s".

The problem I see is that people buying a service that is "up to 80Mb/s" expect that, at some times, when "the Internet is not busy" that they will be able to transfer a file at 80Mb/s. They don't realise that this is not what they are buying. It is an "in some places may be 80Mb/s" service, not a service that "for anywhere that you can get it, can, at times, get 80Mb/s". The "up to" part is ambiguous!

Throughput to the Internet

The other issue is how fast can you download something from the Internet. This is generally what people actually care about, not the sync speed.

There is a huge problem here - the ISP has some control over the service they sell in terms of the technology used to provide it (the "up to 80Mb/s" bit) and the backhaul they install or buy, and the links they have "to the Internet". However most of the services that customers which to access are outside the control of the ISP. Indeed, most are outside of the control of anyone the ISP contracts with.

Now, there are things an ISP can do such as choosing good peering and transit, but ultimately an ISP cannot be responsible for the speed of third parties.

Unfortunately it is very hard to tell if there is a problem with speed to the Internet, whether it is something the ISP does control (back-haul from ISP to premises, core network, choice of links to peering points), or something outside their control (transit, far end congestion, busy servers).

Now, maybe OFCOM could commission some independent speed test equipment that they connect to LINX and LONAP and other peering points, and use that as a reference. The issue is that it is not hard for an ISP to prioritise these speed tests and still have congestion for other connectivity!

What would be good is ISPs having to publish loss and latency from premises in to their core network - that is the area that is most likely to have congestion as it is the most expensive aspect.

Faults

Another issue which OFCOM seem to be trying to address, but in an insane way, is lines that are faulty. The problem here is that a long line running at 500kb/s may be perfect and the best you can get on such a line, and not a fault, but a short line running at 500kb/s may be faulty.

OFCOM tried to define faulty lines by saying that they are the lowest 10th percentile - defining 10% of an ISPs customers as having a fault - which is crazy!

Defining that long slow line as faulty does nothing to actually get it fixed, and allowing a customer to leave with no penalty does not help the ISP or get any investment in infrastructure that could help the customer.

This is especially true when dealing with links such as BT Wholesale. The ISP may be penalised by insisting customers can leave with no penalty even though the ISP may have paid for installation and a router, and hence making a loss. However, BT Wholesale see no issue. Indeed, they see migration fees and maybe even install and cease fees much more often as a result of OFCOM rules. BT Wholesale are not penalised or incentivised to get BT plc t/a Openreach to install an FTTC cabinet instead. OFCOM are penalising the wrong people.

To add to the fun, a line that should get 20Mb/s and is getting 10Mb/s because of a fault is probably not bad enough to meet OFCOMs 10th percentile rule, and so that customer does not have the right to leave with no penalty!

It would make a lot more sense to say that a line that cannot sync at the forecast minimum speed can be ceased with no penalty, and apply that rule at wholesale level as well as retail. That would allow individual lines that do not live up to expectations to be fixed or penalise the people actually providing the faulty service itself (the carrier) rather than the end ISP.