Virtual Leased Line: The Key Facts You Need To Know

A virtual leased line is an apparent point-to-point ethernet leased line that uses pseudo-wire encapsulation for transporting Ethernet traffic over an MPLS tunnel across an MPLS core network.

Now I know what you’re thinking. You’re thinking “What’s that in English?”

A Simple Example of a Virtual Leased Line

Imagine that you have two offices. One in London and the other in Reading. You want to join their LANs together with a 10Mbps ethernet leased line.

You might guess that your leased line provider would provide what amounts to a very long 10Mbps Ethernet cable, one end in London, one end in Reading. And that IS what it would LOOK like to you. But in reality, they’d probably provide:

• a 10Mbps leased line from your London office to their data centre closest to London
• a 10Mbps leased line from your Reading office to their data centre closest to Reading
• a 10Mbps virtual leased line to connect the two data centres. The virtual connection would be provisioned over their existing MPLS core network, probably over a high-capacity 1Gbps or 10Gbps fully-redundant ring.

Those leased lines at each of your offices are dedicated to you, but what about that bit in the middle? How can your ISP ensure that the 10Mbps you need is available when you need it, given that there are lots of other customers using the same MPLS core network?

Here’s the answer: MPLS enables your ISP to give your point-to-point leased line first refusal on that 10Mbps of connectivity between their London and Reading data centres. When you need it, it’s yours. When you don’t need it, other customers can use it.

Why Can’t I Just Go For A Real Point-to-Point Leased Line and Forget About Virtual Leased Lines?

Perhaps you’re wondering “why would I want to share that middle bit? Why can’t I just have a point-to-point circuit where it’s ALL dedicated to me, ALL of the time?”

Well, you CAN. But there are several reasons why you might want to go for a more typical network topology;  one where your leased lines pass through your provider’s data centres:

• Fault Visibility - Your leased line provider can see whether your leased line is up or down, rather than having to wait for YOU to spot downtime and to inform them of it.
• Internet Access - Your provider can add additional services such as Internet access and SIP telephony on to your leased line.
• WAN Scalability - If you want to increase the number of sites on your WAN, it’s simpler to do that if each of your sites already connects to a single network – your leased line provider’s one.
• Different Speeds for Different Sites – The connection speed at each site can be independent. With point-to-point links the speeds at both sites need to be the same.

How Virtual Leased Lines Can Save You a Bit of Money

Major leased line providers set up points of presence in multiple locations, then link these using ultra-high-capacity circuits.

These circuits cost a fortune, but bit-for-bit they’re great value. For example, a 10,000 Mbit/s connection has 1000 times the bandwidth of a 10 Mbit/s connection, but it only costs 10-20 times as much. In other words, the bandwidth on the big circuit is 98-99% cheaper than the bandwidth on the little one!

Your provider can take advantage of this to reduce your costs slightly, by using these cheap, ultra-high-capacity circuits to carry your data for part of its journey. They set up virtual leased lines over these big fat circuits. Your provider can then rent shorter circuits – which are cheaper – from their suppliers. Much of this savings will be passed on to you.

They use MPLS to ensure that these ‘virtual leased lines’ perform like a dedicated circuit, giving you first refusal on the bandwidth you’ve signed up for.

So how much will your UK Leased Line Cost?

One of the easiest ways to find out how much a leased line will cost is to visit our site, www.hso.co.uk/leased-lines/ . The site gets real-time quotes from several top-tier carriers, and compares them to find the lowest price.