Difference between backhaul carriers

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We provide broadband services via number of different back-haul carriers. In some cases customers have a choice of carrier for their line. In some cases we choose the carrier for you (e.g. Home::1 and Office::1). In some cases we may change the carrier we are using for a line as part of an upgrade we are doing. Mostly they work in the same way - providing connectivity from you to us so we can offer you Internet access. There are a few subtle differences though.

What does it mean - back-haul carrier?

The copper phone line is always the same, regardless, and this is maintained by BT plc t/a Openreach. You need a phone line for ADSL, and you can pay BT directly or someone else. We can provide these lines and include the price on the same bill if you like (no outgoing calls).

At the exchange the phone line is then connected to equipment (an MSAN or DSLAM) which has a broadband modem. It may also be connected to test systems. This equipment is owned by the back-haul carrier, so different carriers have slightly different equipment.

The carrier then has links (fibres) connecting the exchange equipment via their network and other equipment within their network (BRAS, etc) and then via fibres to connect to us. This is all carrier specific.

Finally, all of these carriers, connect to our equipment (LNSs) and we connect you to the Internet (via various peers and transit carriers).

Why different carriers

One of the main reasons for different carriers is where customers have two or more lines. Whilst it is possible for a fault on multiple lines (in the bundle of cables from the premises to the exchange), it is more common that faults are on one line, or are within the equipment at the exchange or the back-haul network. There can be major issues that affect one carrier for many hours at a time, but the chances of two carriers having issues at the same time are greatly reduced.

Because the carriers have different equipment and systems, there can be technical differences in the service we can offer. However, even with the same systems at the exchange (ADSL2+) the level of control we have and the testing and monitoring we can do will depends on the carrier and their systems and can vary a lot between carriers.

Pricing differences

The TalkTalk and BT 21CN services work out very similar in costs for us. Some other carriers we have used have very different pricing structures.

Technical differences

From the customers point of view all of these carriers can provide ADSL and so the options are much the same. The VPI/VCI settings are the same. PPPoE and PPPoA both work. On PPPoE, if your modem/bridge can handle it, baby jumbo frame negotiation is usually supported allowing 1500 byte MTU connections (we have modem/bridges that work with this).

Carriers and other telco's retail offering

It is important not to confuse the carriers we are talking about here with retail offerings from other telcos. For example, BT Retail offer various broadband services, and whilst they use the same back-haul network, the services they offer depend very much on their business model and their equipment which is different to ours. So just because you have heard bad things about a particular retail offering does not mean their carrier / wholesale back-haul network is bad in some way. This is particularly important when considering issues such as shaping policies or censorship - the back-haul networks we use are transparently passing PPP packets between you and us and we bypass any such measures used in their retail offerings.

Keeping a sensible mix

We aim to operate with at least two back-haul carriers providing coverage over most of the country. This gives us better bargaining power, and means we can offer multiple line resilient services to customers. We may add new carriers from time to time, and even retire existing carriers. Please do bear in mind that our terms allow us to make technical changes to the service, which includes changing the carrier used for your line.


The rest of the country can have connections using BT's "21st Century Network" equipment. This is ADSL2+ allowing speeds up to 24Mb/s down and 2Mb/s up (annex M, extra cost option).

BT lines all have DLM (Dynamic Line management) which constantly adjusts line settings to get the best performance and stability for a line. Whilst this may work well on many lines, there are lines that it fails to stabilise, and it cannot be properly turned off. The controls we have to adjust settings are very limited. Some settings take a working day to change. Some can be changed more quickly but then cannot be changed within the following 10 days.

BT can also provide FTTC lines.


TalkTalk wholesale back-haul is available to about 88% of the population. It is ADSL2+. Annex M is available (extra cost option).

There is no DLM. The level of monitoring and control of the ADSL lines is excellent, with a choice of dozens of line profiles and instant updates when we make changes. These features are now integrated in to our control pages to give customers direct control over their line profile.

MPF, SMPF and costs for changing carrier

There are different ways that different ISPs and telcos makes use of the telephone line for providing telephone and broadband services to their customers. The different methods can have an impact on the costs and hassle of changing provider later.

MPF (Metalic Path Facility) means that the copper pair from your premises to the exchange is connected to a telco directly and that telco provides the telephone service (if any) and broadband (if any) and anything else on that copper pair. It is entirely their's to use as they wish (within some rules).

SMPF (Shared Metalic Path Facility) means a copper pair to the exchange that goes to two telcos, one for telephone service and one for broadband. Normally this means telephone from BT, and can mean broadband from BT or from another provider.

FTTC (Fibre To The Cabinet) means that the copper pair is shared at the cabinet rather than at the exchange. At the exchange is a telephone service, which could be via BT or via MPF to another telco, but at the cabinet it is also connected to a broadband service. This is usually BT but there is also sub loop unbundling allowing other telcos to install a cabinet and use the copper pair at that point (rare).

When either the telephone or broadband is connected to BT kit, then providers like A&A can provide services using those connections. This is WLR (Wholesale Line Rental) for the telephone line and BTW (BT Wholesale) for the broadband. This is what we normally use, so we either provide a phone line or you have a phone line from another WLR provider or BT directly, and we provide broadband by SMPF to BTW kit.

We can also provide broadband via TalkTalk kit, also using SMPF so shared with a WLR based telephone service (which could be via us or another telco using WLR).

Where any of this matters is when you make a change. If you have broadband from us using SMPF and go to a telco that uses MPF for telephone (with or without broadband) that will cut off you broadband with us - so be careful. And change to/from MPF or between MPF providers means changing telephone and broadband services and may also mean porting a phone number, all of which adds hassle and cost.

Also, there is usually extra cost if changing to/from MPF, somewhat lower extra cost in changing SMPF between broadband back-haul, and even lower cost when changing ISP but using the same broadband back-haul. Whether there would be any extra cost depends what connections you have now and what you want to move to and these costs will depend on the new ISP and their policy - some will simply absorb the extra cost and some will not.

In general, our services are SMPF using BTW or TalkTalk broadband back-haul and WLR phone line, so moving to another other provider will either involve no extra jumpering at the exchange, or just re-jumpering for SMPF change of back-haul carrier.