Two or more ADSL lines can be ‘bonded’ together, aggregating both the upload and download bandwidth into a single virtual connection offering much improved speed and resilience.

There are various types of bonded ADSL, delivering different levels of quality and added value: choosing the right Bonded ADSL supplier is of critical importance.

What is Bonded ADSL?

Bonding basics

Bonding basics

Bonding takes traditional broadband circuits, such as ADSL and FTTC, and Ethernet type circuits such as EFM and FTTP, and brings them together as a single virtual connection.

The bandwidth of the individual connections is aggregated in the single virtual connection, while the multiple, diverse line structure of the bonded connection allows for automatic failover, delivering much enhanced resilience.

Bonding was originally conceived to address poor performance in individual ADSL lines. As a result Bonded ADSL is the most common form of bonded internet connection. More recent advances have allowed other connection types to be bonded, including Fibre Broadband (“Fibre To The Cabinet” – FTTC) where fibre connections are available.

Evolving Networks’ bonded connections combine best-of-breed packet management algorithms with a world class contention-free network and unique user experience upgrades such as QoS, Bandwidth Amplification.

Why bond?

Some years ago, with only ADSL and ADSL Max available, bonding was a simple matter of achieving higher bandwidth and resilience than these limited technologies could offer.

Today, with Next Generation Access (NGA) technologies such as Fibre To The Premises (FTTP) and FTTC available only in certain areas of the country, Bonded ADSL 2+ and Bonded ADSL Max are still very much part of the communications landscape. In fact, the need for Bonded ADSL has increased in these areas where connection technologies have not kept pace with increasing bandwidth requirements.

Each location is different, served by a different combination of circuit types, and with different bandwidths and connection qualities available. Coupled with the fact that every business has its own unique and evolving needs, this inevitably means that the reasons for bonding vary widely from installation to installation.

Because of these diverse reasons for bonding, we always advise on the best bonded internet connection for each situation, recommending additional services as appropriate, to counter the inherent problems with the UK’s broadband infrastructure and optimise both the connection and users’ experience.

Key Benefits of Bonded ADSL

Bonding delivers bandwidth impossible with individual ADSL lines, enhancing data throughput speeds and application performance. This is often highly attractive to businesses with sites in poorly served areas, with substantial bandwidth requirements, or which need more cost effective connections than leased lines.

A bonded connection’s multiple physical connections deliver enhanced resilience: the more lines the bonded connection encompasses, the lower the chance of all of them failing at once. This built-in resilience is further enhanced by bonding diverse connection types.

While there are other resilience issues to consider (in particular in the ISP’s core network) a bonded ADSL connection will always be more resilient than a single ADSL line, a bonded FTTC connection will always be more resilient than a single FTTC connection, and even Ethernet First Mile (EFM – itself is a form of bonded copper pairs) can be made more resilient by bonding it with other EFM circuits, with ADSL 2+ lines, or with FTTC, if it’s available.

As soon as there is an interruption in the flow of data on any given individual circuit, the bonder and central server stop sending data over the faulty line, diverting it over the other lines in the bonded connection. Once they detect that the line is back up, they start sending data over it again. Failover times can vary greatly between different bonding suppliers – always ask for the details.

Apart from older bonding technologies (more correctly referred to as load balancing) any bonded connection, regardless of circuit type, should give you a single public IP range to work with. Always check that this is the case. Without it, failover will not be transparent: changing IP addresses or DNS for critical services when circuit faults occur is inconvenient! It’s also important for failover to work both upstream and downstream – some forms of bonding only operate in one direction, or only on HTTP traffic.

Evolving Networks bonded internet connections bond every type of traffic in both directions, and give you a single IP range. As far as your firewall is concerned, you have a single internet connection – much more secure than multiple connections.

While the price and performance of all connections are location dependent, for businesses which still don’t have access to FTTC, EFM, or even ADSL 2+, a bonded ADSL connection is usually substantially more cost effective than a leased line.

A Bonded ADSL connection is not synchronous, but for many businesses, the ability to upload at more than 2mbps or 4mbps, along with a dramatic increase in download bandwidth, makes the cost of the bonded connection – usually tens of thousands of pounds cheaper than a fibre leased line – a wise investment indeed.

More one in three UK telephone exchanges have no plans to upgrade to FTTC, and at present less than half of the UK’s exchanges are FTTC enabled. Even once an exchange is upgraded, there’s no guarantee of FTTC availability at the cabinet local to any given business on that exchange.

For those many UK businesses which aren’t served by an upgraded cabinet (many exchanges haven’t even been upgraded to ADSL 2+, much less FTTC) and for which there is no likelihood of that changing in the foreseeable future, Bonded ADSL is a key option to consider. In many cases it may be the only way, short of a leased line, to achieve required levels of bandwidth and resilience.

It’s most important to make a thorough check of the availability of all circuit types at your exchange and cabinet before making any purchasing decisions. We have written extensively about the FTTC checking process and how the data given to the public is incomplete and often wrong – read about it here.

A comprehensive audit of the connection types available is essential, and something Evolving Networks undertakes for every customer as a matter of course.

When selecting a Bonded ADSL provider, it is important to be clear on a number of key issues which can affect performance and resilience.

Bonding has come a long way since its inception, but many suppliers have not kept up with the significant capabilities of this rapidly advancing technology.

Some still use Multi-Link Point to Point Protocol (MLPPP) – a long outdated protocol. Others require customers to use expensive Cisco routers or Linux servers which they must manage. Some bond the download stream but not the upload, or bond both but limit bandwidth to 6mbps.

The bonding hardware and software itself can limit the performance of Bonded ADSL. Be sure your provider has a flexible, modern hardware platform with no bandwidth limits. Check that their bonding system can cope fully with diverse line speeds and types.

It’s important to note that more primitive bonding technologies, which do not allow for differing line rates or circuit types, only bond at the speed of the slowest connection at hand, so if a bonded connection were created from a 4mbps ADSL line and a second, 5mbps one, the bonded connection would only perform at 8mbps.

All Evolving Networks bonded connections deliver the sum of the full bandwidth of all the bonded links – in this example, the Evolving Networks bonded connection would deliver 9mbps, not 8mbps.

Check also for lower bandwidth limits on the individual ADSL connections in the bond. Some bonding providers will only bond lines with bandwidths of 2mbps and higher, ruling out many businesses with the greatest need of improved throughput. Evolving Networks has no lower or upper bandwidth limits.

A Bonded ADSL connection requires a central bonding server, which handles all traffic through the connection.

Some ISPs operate these servers without any redundancy or failover provision at all. In the event of a bonding server failure, a spare server needs to be brought online, configured and made live. Without automated failover, this takes time, during which the bonded connection is completely dead.

Make sure you understand how resilient your Bonded ADSL provider’s central infrastructure is. Look for a provider with its central bonding servers on a resilient virtual platform, or, better, its bonding infrastructure mirrored between geographically distinct datacentres. This will provide true resilience, without the provider being a single point of failure.

Many suppliers make much of being able to bond any ISP’s connections, encouraging businesses to buy individual ADSL lines for themselves, and then have them bond those lines.

This can lead to serious problems with resilience – a key issue for many businesses considering bonded ADSL.

Secure routes – "tunnels" – are made across the internet from the customer to a central ISP datacentre where the bonding servers sit. This datacentre is operated by a single ISP, so the customer’s Bonded ADSL connection relies entirely on their IP connectivity irrespective of how many different ISP lines the customer has. The bonding datacentre is itself a single point of failure.

Furthermore, the customer, having sourced the ADSL circuits directly, will be responsible for all the lines faults of those ADSL circuits, and for getting the most out of them, and all traffic through the bonded connection is subject to the full end-to-end latency of the ISP’s network.

Check carefully that your provider’s central bonding servers are resilient across multiple datacentres, so that, in the event of a central failure of some kind, failover will be near instant.

Effective monitoring is key to keeping a Bonded ADSL connection running optimally, but most bonded connection providers do not provide any monitoring tools.

Monitoring tools should show live throughput in real time, as well as historical information on speed, download and upload usage, and percentage utilisation.

Robust monitoring greatly enhances technical support. With all bonded connections constantly monitored, IT and the wider enterprise can focus on their core activities, knowing that should an issue arise, it will be caught and resolved, often before anyone else knows anything is amiss.

To find out more about how Bonded ADSL could help your business, call 0330 55 55 333 or email us today.

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