The WAN Road Ahead: Ethernet or Bust

Ethernet isn't rolling out as quickly as you might think, but it's not because the Enterprise isn't asking for it.

Author: Irwin Lazar

Ethernet WAN MPLS vs. TDM
Ethernet services still aren't widely available outside of major metropolitan areas.
One of the key trends we've followed in our research is growing adoption of Ethernet as a WAN technology. Given Ethernet's dominance in the LAN, and the wreckage of Token Ring, FDDI, and ATM it left in its path, it stands to reason that Ethernet can do for the WAN what it did for the LAN, offer rapidly scalable bandwidth at a fraction of the cost of other technologies. So given that Ethernet WAN services have been around for several years now, it stands to reason that Ethernet is rapidly replacing MPLS and TDM as the de-facto WAN standard for most companies, right? Not quite.

Why? It comes down to two things: Applicability and availability.

Before evaluating any WAN technology it's important to first understand its applicability for different types of sites. A simple way to visualize site requirements is to group sites into one of three categories: Data centers and headquarter locations; branch and distributed offices; and remote sites and users. By definition, data centers include massive amounts of computing resources that serve up large volumes of data to the rest of the organization; even if very few humans reside at the data center, these sites require massive amounts of bandwidth (and generally very low latency). Other sites that may fall into this category include contact centers or very large administrative sites. Branch and distributed offices include multiple humans (and usually a certain amount of local computing resources). Remote sites and users encompass telecommuters, travelers, and very small (<5 person) sites with very limited computing resources.

In the first tier, Ethernet, fiber, or low-latency WAN services are ruling the day, as companies seek reliable, scalable bandwidth and low latency at the lowest cost. But IT architects routinely tell us that MPLS is and will continue to be the preferred WAN technology for the majority of branch & distributed locations for the foreseeable future. Eighty percent of firms have deployed MPLS as their primary WAN technology while a whopping 95% rate their MPLS deployments as "very" or "extremely" successful.

Why is Ethernet failing to conquer the branch? Certainly availability is an issue – Ethernet services still aren't widely available outside of major metropolitan areas. But perhaps more importantly, applicability is the deciding factor. MPLS is optimized to support real-time traffic such as voice and video. Even if one adopts multipoint Ethernet (VPLS), they still need to optimize traffic across the Ethernet service, adding additional complexity. Ethernet is also ill suited for large numbers of branches and requires routers at the carrier edge to prevent broadcast storms. Instead, most Ethernet deployments for branch sites are simply as an access protocol to an MPLS service. IT managers increasingly seek to take advantage of MPLS-bundled services such as Internet gateways in the cloud or directly connected co-location facilities. ts to gradually grow but only within Tier 1 deployments. In most cases, VPLS isn't replacing MPLS for branch and distributed office connectivity, rather it is supplementing MPLS for locations requiring high bandwidth and low latency connectivity.


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