Networking Pendulum

What was once old, is new again


One of the benefits of age is perspective. You notice that many of the “new” ideas are simply old ones that have come back into vogue, like the swing of the pendulum. The aptness of the metaphor is clear, as history demonstrates a tendency for human events to swing back and forth from one extreme to another.

We see this in politics (conservative vs liberal), we see this in fashion and in telecom networking. Early in my career, while still a systems engineer, I remember one of my first published articles being about the swing from companies using public networks based on X.25 packet protocol (like Datapac) to private networks using their own multiplexors and leased lines. (Note I had just moved from Bell Canada where I supported Datapac to General DataComm where we were selling muxes)

We’ve seen this pendulum swing between using public and private networks for a company WAN many times over the years. Leased private lines gave way to X.25 packet networks, which ceded ground to T1 or T3 networks (or fractional T1 like Megastream). Frame Relay, ATM and then the rise of MPLS, “Multiprotocol Label Switching”. Now we are seeing a challenger in the corporate networking world, SD-WAN, which uses the public Internet and extensive software to try to mimic and replace MPLS.

MPLS can be slow to implement, especially internationally, as it takes time to order and connect all of the connections, especially the final local Ethernet connections at each country. MPLS can also be expensive compared to DIA, Direct Internet Access. In MPLS’s favour, as with most private networks, is it’s inherent security, consistent latency, and guaranteed service levels and Quality of Service (QoS). For overseas voice circuits and critical enterprise data that is essential.

SD-WAN, based on the now ubiquitous public Internet, is now widely available, quickly deployable and seemingly less expensive. By using multiple business grade Internet connections (DIA which should be contention free) and some fancy software , it can approach the level of consistency of MPLS. Is it less expensive ? Well, vendors will make that case based on pure network costs, but soft costs of running and maintaining the equipment and connections have to be factored in.

The tension between secure and reliable private networks and less expensive shared public networks (like X.25, Internet and cloud) is one that has been going on for years, and watching this pendulum swing back and forth is something I find fascinating.

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