The traditional "last-mile problem" concerning enterprise access to a provider's network was always about how to...
connect new sites to the wide area network. But enterprises can now begin to think about "first-mile opportunity" for WAN access instead.
The last-mile problem was usually this: The carrier you wanted to go with for your WAN didn't have connectivity running near all of your locations. Instead of being able to do a simple cable pull to bring a connection into your facilities, either you or the carrier would have to trench or bore a path to lay conduit and pull connectivity in. The other option was that either you or the carrier would have to make a deal with another provider whose network passed close by. If the carrier made the arrangements, it would in essence become a managed network operator aggregating connectivity on your behalf. If the enterprise did it, you became the mobile network operator juggling providers. Neither choice was great.
Now, the last-mile WAN access problem is less of a concern for several reasons.
If you have a traditional WAN and are trying to work with a single carrier for network services, new options for last-mile connectivity have emerged, ranging from 4G LTE and Wi-Fi, to laser-radio free-space optics. Increasingly, too, these last-mile/first-mile connections are Carrier Ethernet services rather than multiprotocol label switching links. As a result, trenching or boring becomes steadily less necessary. Cable providers have also entered regional markets, and often have plant running next to nearly every commercial space in a metro area.
SD-WAN and hybrid options change the WAN access equation
With the emergence of the software-defined WAN model and hybrid WANs, however, you can stand the network access problem on its head. Instead of wondering how to get the last mile covered, the issue is about who can give you the best first-mile services to get you to the Internet, which you can use as your WAN backbone.
With the hybrid SD-WAN approach, you can look at not just the methods of connection that your preferred WAN carrier supports, but instead at all of the options available at a specific location: satellite, wireless LTE, Wi-Fi, cable, DSL, anything.
This hybrid WAN approach also makes it simpler to aggregate connectivity from several providers using different media, as in cable plus LTE plus DSL, or whatever mix makes the most sense. Multiple links from diverse providers and the use of diverse media improves the resilience of the network. The backhoe cut that kills a DSL link won't usually be anywhere near the cable provider's connection, and vice versa. Cutting any of those cables won't kill a 4G connection. Backbone problems for one carrier won't affect the others. And so, the availability of communications improves with each diverse path added.
Network performance can also improve with each added link, if the SD-WAN service aggregates links and makes all of the pooled bandwidth available. Choice of path offers robust SD-WAN options that include how best to route traffic for a session, or even how best to route each packet, based on current behavior from each carrier and path. Some SD-WAN services even take advantage of diverse paths to send a packet down both, to ensure delivery, and to allow the far end of the connection to always get the benefit of lower latency transit for each packet. This turns the variability of Internet middle-miles into an advantage you can leverage.
First-mile choice also opens up the option of engaging cloud-WAN or network as a service offerings. Using whatever option or options best serve for connecting to the Internet, enterprises get a link to the cloud-WAN provider's own closest point of presence, usually a short hop in terms of latency. From there, traffic jumps off the public Internet and onto a private backbone, as with a traditional carrier, attempting to provide the same benefits for performance and layered services that a traditional carrier core can, without restricting the enterprise's first-mile options.
Spurred by the current hubbub over SD-WAN, many enterprises have begun to re-examine their WAN access designs. All will be best served if they can invert their old mindset, and think in terms of a first-mile opportunity rather than a last-mile problem.
Coming soon: In this series on network services, Nemertes Research WAN expert John Burke will address WAN cloud exchanges and network-on-demand services.
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