Friday, November 04, 2016


By John Shepler

SD-WAN has become a hot service recently. It is often touted as an alternative or replacement for MPLS networks. Just comparing costs makes a compelling argument that SD-WAN may do to MPLS what MPLS did to Frame Relay. Is this really the case? Let’s take a look.

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What Problem Are We Trying to Solve?
The issue is networking, specifically computer networking. Most of us have some need for computers as part of our job. That could be a traditional desktop computer, a laptop in a hotel room or conference center, or perhaps a tablet or or cellphone while we move around. It could also be a point of sale terminal, an industrial process controller, a 3D printer or just a laser printer in the office. All of these things need to be hooked together, or networked, or they just plain won’t work.

It’s actually worse than that. Remember when you bought software in a box? Not much software is sold that way anymore. Now everything is apps and they are delivered and updated virtually. The really heavy lifting software doesn’t even reside on your device. It’s at a remote data site or vendor’s platform. Without a connection, you can’t even run the application.

Private Lines: The Old Gold Standard
If you want to stay in complete control of every aspect of your network, you build your own for your exclusive use. Most companies do that internally. It’s when you leave the building that you have a problem. You need to hand off your packets to a service provider, or carrier, to transport them to another location.

The closest thing to stringing the wires yourself is to order private point-to-point circuits. T1, DS3 & OCx SONET are the traditional PTP circuits. More modern replacements are Ethernet over Copper and Ethernet over Fiber. All of these are still extremely popular with high performance, high security and high reliability. Cost and provisioning time are really the only issues.

MPLS Networks Save Money and Go Worldwide
You can approach the quality and security of private point to point lines using MPLS networks. MPLS or Multi-Protocol Label Switching is a replacement for the old-timey Frame Relay networks that were popular when high speed was 64 Kbps. It’s a privately run wide area network that handles multiple customers at the same time without them being aware of each other. Since the core network is shared, the cost is lower than running private lines to every satellite office you want to connect. Plus they’re already built-out, so you only need to provision an access line for each location.

MPLS networks are very popular for connecting companies with multiple business locations in the US or worldwide. Once again, they offer high performance, high security and high reliability. Also once again, cost can be an issue.

Why Not The Internet?
The lure of the Internet is strong. It’s the lowest cost of any method to reach anyone, anywhere in the world. However, there are issues.

Security is an obvious one. Just read the headlines any day and you’ll feel insecure about being online. Encryption, especially IPsec and SSL, make the risk acceptable for e-commerce and banking. However, performance is variable and out of your control. Latency, Jitter and packet loss are not only variable, they’re unpredictable. Companies running high performance business-critical applications wince at the thought of trusting their livelihood to the public Internet. Even so, the cost is really, really attractive compared with other solutions.

The Hybrid Network Compromise
Fact is, most companies need a broadband Internet connection for communications with suppliers and customers and access to the nearly unlimited news and information available online. A popular compromise is to use the MPLS network for internal communications and the Internet to go outside in a hybrid network arrangement.

Another use of the Internet is as a backup in case your private network fails. That happens enough with line cuts that it has a name: backhoe fade. If the broadband connection is just there on standby, all that bandwidth goes to waste most of the time.

SD-WAN Makes the Internet Suitable
The Software Defined Network (SDN) was invented to reduce the time and labor required to run complex networks. It “virtualizes” the network so you don’t have to deal with all the complexity of so many diverse routers, switches and appliances spread throughout the physical network.

SD-WAN or Software Defined Wide Area Network does the same thing for outside networks to connect far flung locations. SD-WAN manages multiple connections according to rules that you set up through a control panel. Once running it automatically directs traffic and works around problems without you having to get involved.

For instance, the SD-WAN can make use of Cable broadband, DSL, T1 lines, MPLS networks, LTE wireless, Satellite links and whatever else you have. It will monitor the characteristics of each path, in both the upload and download directions, for bandwidth congestion, packet loss, jitter and latency. It decides what path to use for each packet based on the instantaneous characteristics of the paths available. These can vary all over the place and change in milliseconds. You couldn’t possible keep up with all of this manually, but the SD-WAN system can stay on top of it.

With SD-WAN, you don’t need to waste the perfectly good bandwidth of your backup connection when the main link is running. SD-WAN will combine the bandwidths and make sure that the more critical apps, like VoIP and UC voice and video run on the best paths available and less critical file transfers use the lower performance paths.

Companies are finding that even having two diverse Internet broadband connections can give excellent performance compared with a single broadband service as long as they are being managed by SD-WAN. Two broadband services can easily cost only a fraction of even one private line for the same or less bandwidth. The core of the Internet usually runs pretty well. It’s the access connections, like WiFi and cable or DSL, that generally get flakey. Using SD-WAN to watch and select the best path at any given instant can dramatically improve the performance of the “virtualized” WAN network.

Is SD-WAN right for your business? You’d be remiss if you didn’t at least take a closer look at what connections are available and at what price for your particular business locations. Remember that you don’t have to go 100% on the Internet. SD-WAN will manage private lines, MPLS networks, satellite and wireless connections as well.

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