Interconnect Multiple Offices
In today’s dynamic, customer-oriented business world, it is becoming increasingly common for UK companies to occupy several buildings in a campus or operate from several offices in the same urban area.
Some businesses do it by necessity. Others, for the opportunities it brings, especially in customer-driven fields like retail. For historical context, the ONS’s 2017 UK business activity release reported more than 60,000 multi-site enterprises and showed that more than 25% of local units belonged to enterprises operating from multiple sites. These dated figures describe the 2017 business population and should not be read as a current market total.
Interconnecting multiple sites in a single, private network is one of the most significant technical challenges that a business can face. There are multiple solutions – all of them offering a different mixture of distance, bandwidth, cost and security – and choosing the right one is one of the most critical decisions that business owners and IT managers face.
Let’s explore these options together.
Multi-Site Connections over Short Distances
Speaking strictly in technical terms, the easiest scenario is when the offices that you want to connect are close to each other. This can mean as close as across the street from each other, or as far apart as a few hundred of meters or even a few kilometres away, but within the limits of the same property.
VPN links over existing infrastructure.
The most straightforward option is to connect all sites to the Internet using regular broadband line, and run a virtual private network (VPN) over the Internet. Alternatively, Passive Optical Networks (PON) provide a simplified and efficient solution for interconnecting multiple offices. Learn more in our article, ‘Passive Optical Network: The Unlikely Revolution of Simplicity.
A VPN is much like a wired link established between two endpoints (i.e. between the LAN networks in each building), where the data isn’t transmitted over a single, wired link, but routed over the Internet. The data is encrypted since it needs to pass through equipment not owned by the VPN’s operator.
A VPN over such an infrastructure is the most cost-effective solution, but it suffers from high and variable latency. The latency is inherently high because traffic needs to pass through the Internet provider’s infrastructure – and it can vary significantly, because there is no guarantee that it will take the same path all the time, and whatever path it takes can be too busy to accommodate all the traffic you need.
These factors can be mitigated to some degree by using a dedicated or leased line. A dedicated line is a direct link to the Internet provider’s core network, which is not shared with any other users – unlike typical broadband links, which are used by several users in the same building (or sometimes by several buildings at once).
This means that the entire capacity of the line is available for your network and that the data path will usually be the same at all times. Leased-line cost and availability depend on location, carrier infrastructure, bandwidth, service level, construction work and contract term. Obtain current carrier quotations for the required sites rather than relying on a historic generic monthly range.
Besides bandwidth, latency and convenience, the most compelling advantage of a direct wired connection is security. Network cables can be tapped, but if they are installed on secure premises, they are as secure as anything else on that property.
Dedicated, on-premise copper or fibre cables are not shared with other users, so there is no way that a malicious user can exhaust the network’s capacity. And they do not depend on any ISP’s infrastructure, so if an attacker (even one not directly interested in your business) brings your ISP offline, your organisation’s internal traffic is not affected.
Finally, your company’s internal traffic never has to flow through infrastructure not owned by your company and not under your control, which makes it much harder to compromise data at the network’s physical layer.
Wireless options: Wi-Fi and Free-to-Air.
Over distances up to about 100 meters, even regular, off-the-shelf Wi-Fi equipment can be an option. Installing Wi-Fi repeaters allows you to extend this range. This option is cheap, but it is highly sensitive to environmental condition, and usually results in high latency. Over these distances, copper or fibre optic cabling will invariably offer better performance.
When higher bandwidth, lower latency, or longer distances – up to a few kilometres – are required, free to air solutions are a class of useful alternatives. The “free” in “free-to-air” refers to licence-exempt radio operation. It is not unconditional: the permitted band, EIRP, indoor or outdoor use and technical measures such as DFS or TPC depend on current Ofcom interface and exemption requirements. Each proposed link must be checked against the rules and equipment approval applicable at the time of design.
There are two primary options for free-to-air links over short distances: Free Space Optics (FSO) laser , and short-range microwave links. Both offer competitive speeds, but are more complex than copper or fibre cabling.
FSO laser links are point-to-point links which use highly-focused laser beams to transfer data – a method that enables data transmission at rates of up to 10 Gb/s, with very low latency levels. FSO laser links don’t require a license to operate (or approvals to bury cables) and are immune to RF interference. However, they cannot penetrate walls and are susceptible to environmental conditions such as rain and fog.
Microwave links are point-to-point links, just like FSO links, but use radio signals in the microwave spectrum instead of optical signals. They are very cost-effective and easy to install, but are susceptible to environmental conditions (particularly those that involve high humidity levels – fog, rain or snow) and RF interference. They can offer a bandwidth of up to 300 Mbps, which is more than enough for most business applications.
Both FSO and microwave links are point-to-point technologies, so they need to have antennas and associated radio equipment installed on both sites. They also require a clear, unobstructed line of sight between its two endpoints. Maintenance and operating costs do tend to be lower than those of a leased line. But the radio equipment involved is nonetheless more complex than your typical Ethernet switch, so there are other associated costs in terms of engineering talent and logistics.
Long-range microwave links are the only mainstream wireless alternative for long-distance data links. Like line-of-sight microwave links, they use radio waves in the microwave spectrum to connect two sites – but they also use additional equipment between them to relay the signals, thus covering longer distances
Such systems can reach speeds of up to 1.25 Gbps, and cover distances of up to 60 kilometers. They offer excellent latency and speed, a great deal of flexibility and a high level of security – but they are significantly more expensive than a VPN link over a dedicated line.
Which Way to Go?
The rule of thumb is that if you can run your own copper or fibre cables, and you have the means to maintain a networking infrastructure that’s partially outdoors, you should. The most straightforward way to interconnect two networks is to run a cable between them; if you can, you should.
For most small and medium businesses, VPN links are a perfectly appropriate and secure option, at any distance. For small distances within the confines of the same property, you should think of other options first – but if running your own cables is difficult, a VPN is the first thing you should consider.
In terms of cable choice, your first option should be shielded, twisted-pair copper cables. They are cheaper and easier to install. If bandwidth or distance requirements exceed their capabilities, fibre optic is the next best alternative.
Over short distances, free-to-air data links offer excellent latency levels, which is particularly important for applications such as high-frequency trading and other financial operations. Free-to-air data links can also be cheaper than a leased line, especially in crowded urban areas. However, they do require the installation and maintenance of dedicated laser or RF equipment. Extreme weather conditions can also affect their operation, to a much higher degree than that of leased lines.
For long distances, VPN connections are a far more compelling alternative, especially for typical office use scenarios, where a leased line can more than match the bandwidth requirements of a busy office day, and the latency requirements are relaxed. However, wherever latency and security concerns can justify the installation and maintenance costs, long-range microwave links can support even the most demanding applications.
Conclusions
There are many methods, both wired and wireless, which can be employed to provide a reliable connection between a business’s offices. Each of these options lands in a different spot within a perimeter defined by distance, latency, bandwidth, security and cost.
Wired infrastructure, using copper or fibre optic cabling, is the most accessible choice. Where they cannot be deployed, for example, due to distance and legal constraints, point-to-point line-of-sight technologies can be a viable option.
Especially when long distances and high-level security concerns are involved, these infrastructure-related decisions are long-term commitments; they can be expensive and difficult to roll back once they have been deployed.
So you need to make sure that your investment is future-proof. We can help with that! Our FREE, no-obligations survey is designed to help you find the best solution in terms of costs, reliability and performance for inter-building communications.
Related topics: How to set up Wi-Fi in Office
Frequently Asked Questions – Connecting Multiple Offices
Q. How do I connect multiple offices into one network?
Start with the distance between them. Buildings on the same site are best joined by fibre or copper cable, or by a wireless bridge where cabling is not possible. Offices in different parts of a town or the country are usually joined over the internet with a site-to-site VPN, or over a private circuit bought from a carrier.
Q. How do I connect two offices over the internet?
Put a business firewall or router at each office and set up a site-to-site VPN between them. The VPN creates an encrypted tunnel across the internet, so staff at each office can reach shared files, phones and printers as if they were on one network. Each office needs a reliable internet line with enough upload speed for the traffic between sites.
Q. What is the best way to connect offices in different cities?
For most small and medium businesses, a site-to-site VPN over good business internet lines is the best value. Larger firms that need guaranteed speed and low delay buy private circuits or a managed network from a carrier. Wireless bridges and your own cables are only practical over shorter distances where you control the route.
Q. How do I connect two buildings on the same site?
A fibre cable between the buildings is the most reliable option, and the only wired one beyond about 100 metres, the limit for copper network cable. Fibre also avoids electrical problems between buildings. Where a cable route is not possible, a point-to-point wireless bridge or laser link across the gap is the usual alternative.
Q. How do I connect office locations securely?
Use encrypted links only: a site-to-site VPN between properly configured firewalls, or a private circuit from a carrier. Keep firmware up to date, allow only the traffic each site needs, and require multi-factor sign-in for remote access. Physical security matters too: cabinets and outdoor equipment such as wireless bridges should be locked and monitored.
Q. Does every office need its own leased line?
Not always. Small branch offices often run well on business broadband with a VPN back to head office, keeping a leased line for the main site where most traffic meets. Sites where the internet connection is critical, such as call centres or offices running cloud phone systems, benefit from their own leased line and a backup connection.
Q. What is a laser link between buildings?
A laser link, or free-space optical link, sends network data between two buildings on a beam of light instead of radio. It needs a clear line of sight, but it is immune to radio interference and needs no spectrum licence. Heavy fog can interrupt it, so links are designed with the local weather and a backup path in mind.
Q. What is multi-site office connectivity?
It is the set of links that lets several offices or buildings share one business network: the same files, phone system, Wi-Fi settings and security everywhere. It can be built from cables, wireless bridges, VPNs over the internet or private carrier circuits, and is usually a mix chosen by distance, cost and how much the business depends on it.
Written by
Wayne founded ACCL in 1997 and has led more than 28 years of project delivery, helping organisations design, install and modernise the network infrastructure behind reliable connectivity, office moves and refurbishments. His experience spans copper cabling, fibre backbones, data centre infrastructure, Wi-Fi, CCTV and access control. About ACCL
