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The 2020 WAN takes shape -- SDN, virtualization, and hybrid WANs

Hank Levine | Aug. 17, 2015
It’s not clear how fast MPLS will go the way of Frame Relay and ATM, but changing apps and bandwidth needs will force enterprises to embrace a new set of technologies.

The gold standard for corporate networks today is MPLS, but carrier pricing issues and MPLS's failure to play well with new, cost-efficient forms of network access are causing problems for the legion of enterprise customers that rely on it.


  • TDM dedicated access (T-1 and DS3) is expensive; Ethernet access isn't universally available and, though economical on an ongoing basis, can cost a bundle (and take months) to install because only about half of the major commercial buildings in the US are served by fiber.
  • It takes a lot of CPE and management to integrate MPLS with broadband public Internet access, which is widely available and fast, but doesn't come with robust SLAs (other than site availability).
  • MPLS itself may not require a lot of management, but the CPE that accompanies it does.
  • The explosion of collaboration tools like Skype for Business and cloud based apps are straining capacity and management. The desire to leverage today's robust software/cloud applications is driving a need for more sophisticated routing schemes and greater control over how WAN traffic is handled.

It's not clear how fast MPLS will go the way of Frame Relay and ATM, but changing apps and bandwidth needs, coupled with the impending disappearance of TDM access, will soon force enterprises to embrace a set of technologies -- software defined networks ("SDN"), virtualization, and hybrid WANs -- that address many of MPLS's cost and performance issues. Together they are likely to be very big very soon, initially as part of "managed solutions" and then on an unbundled basis.

Software Defined Networks

SDN basically separates the brains (the network control function) from the body (the data plane). The biggest thing in network architecture since packet switching, SDN will become predominant in corporate networks by 2020 or shortly thereafter.

The guts of a modern network are the routers, which receive streams of data and send (route) them on their way. In the legacy -- e.g., Cisco -- world, the routers don't just do routing, they also have a lot of control (and other) software and application-specific integrated circuits (ASICS), pretty much all of which is proprietary. In the SDN world, a centralized controller houses most of the software/brains and basically runs everything -- often using open source software -- and the routers are relatively dumb "appliances" (they can even be virtual, and in fact SDN is frequently tied to Network Function Virtualization, which is touched on below). In sum, SDN separates the control from the flow.

That may not sound like a big deal, but the difference turns out to have enormous financial and technical implications.

First, SDN routers cost less than half as much as proprietary routers, a cost advantage that is not overcome by the expense of separate SDN controllers. And open source software is far cheaper than Cisco's or Juniper's or anyone else's secret sauce. The savings from "genericization" may be small in the beginning because of the need to invest in new equipment, but in the medium to long run it will be large.


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