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UPDATE Identifying Slow Speed as a Fault on FTTC Superfast Broadband Lines

Posted Thursday, December 27th, 2012 (1:42 am) by Mark Jackson (Score 7,404)
slow broadband speed

Most people aren’t familiar with the point at which BT identifies slow speeds as a fault on its Fibre-to-the-Cabinet (FTTC) based superfast broadband ISP network. Did you know that a fault can be declared if the line rate drops by more than 25% over a 14 day continuous period? No? Read on.

UPDATE: Since first writing this article it should be noted that FTTC has been changed to handle minimum speeds of at least 2Mbps (the article below states the old minimum of 5Mbps).

Firstly, it’s critical to note that FTTC works by delivering a fast fibre optic cable to your local street level cabinet, while the remaining connection (between cabinets and homes) is done using VDSL2 technology via existing copper cable. This is similar to current ADSL broadband but faster over short distances.

The ”last mile” run of existing copper cable, which takes the operators service directly into your home, is crucial because the copper and VDSL2 components are still very much distant dependent technologies and can thus be highly susceptible to interference (e.g. such as the disruption created over longer lines).

In short, FTTC services are usually happiest when they’re being pushed down lines of 400 metres or less from your local cabinet and once you get above that the speeds really begin to fall away (the current maximum speed is 80Mbps). Experiences vary but we know of people who have gained a download rate of around 16Mbps at some 2000 metres from their street cabinet.

But distance isn’t the only factor. Faults can be caused by all sorts of things, such as physical line damage, water ingress into cables, local electrical interference, line card problems, lightning, nuclear strikes, a zombie apocalypse.. you get the picture. But, short of a total service breakdown, how far does your speed have to fall before it officially becomes a fault and thus worthy of further investigation? There are several considerations.

Take note that the following applies to FTTC products delivered over the BT Wholesale Broadband Connect (WBC) platform, which dominates the UK and is also relevant to some unbundled (LLU) ISPs with FTTC products. The separate Digital Region network in Yorkshire has its own unique variant of FTTC that is semi-separate from BT’s network and may adopt a different solution.

Fault Threshold Rate (Download)

The first and most recognised port of call is the “Fault Threshold Rate” (FTR). BT’s latest FTTC products come with a threshold of either 5Mbps or 15Mbps. Service download (downstream) speeds that fall outside of these, whichever is relevant to your particular line when you first sign-up, would require BTWholesale to investigate (Note: ISP’s won’t sell you an FTTC service unless your line can get above 5Mbps and some ISPs will only support products delivered via the 15Mbps Threshold).

In other words, if you sign-up to a line that can only deliver speeds of between 5Mbps to 15Mbps then you’d typically come under the 5Mbps Threshold (i.e. sub-5Mbps is considered a fault that should be investigated). Alternatively if an ISP promises you speeds of above 15Mbps on FTTC then the same would apply via the 15Mbps Threshold (i.e. sub-15Mbps is classed as a fault).

It’s worth pointing out that both BTWholesale and Ofcom (Broadband Speed Code 2010) have separate but similar measures that allow ISP customers to have their connection ceased free of charge, albeit only if your service speed experiences a significant fall that the provider cannot adequately fix (usually applicable within the first 90 days of service provision).

Ofcoms Broadband Speed Code 2010 (Line Speed)

ISPs must state with equal prominence to other written information provided that if the consumer receives an access line speed which is significantly below the estimated access line speed range then the customer will have the ability to leave their contract without penalty if [the ISP is not] able to resolve the problem.”

Just remember that these rules all relate to actual line speeds and would not apply if, for example, the slow performance is caused not by the line itself but by you having a poor wifi (wireless) signal from your router. The latter could be solved / tested by simply switching to a wired connection.

Fault Thresholds Rate (Upload)

Even FTTC upload speeds have an Upstream FTR, although these adopt a more dynamic method from that of the above pre-defined downstream level. Generally speaking most current FTTC products come with a maximum upload speed of either 2Mbps, 10Mbps or 20Mbps.

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2 Responses
  1. dragoneast

    So how do you reliably measure your download, or upload, rate?

    I ask as I read with interest lots of boasts and complaints, but don’t personally find any of the available options consistent. But not being a stats junky (the exception, not the rule, I know), I just judge my connection OK as it works when and as I want to use it).

  2. cyclope

    Anything that has DLM in charge has the potential to horribly wrong for the customer, Most lines will generate errors, but if those errors are not having a negative impact on the connection, it’s best left alone, try educating BT on that

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