Industry observer Jessica Scarpati has written a good overview of what WAN pros think of metro Ethernet.

Endlessly bonding multiple T1 lines is neither cost-effective nor scalable, and WAN pros who support increasingly distributed environments say managed MPLS networks are becoming too expensive to deploy everywhere. Some prefer Ethernet-based WAN services, carrier Ethernet WAN and metro Ethernet services.

They offer higher capacity links at lower cost per bit, among other advantages. Ethernet WAN services have seen steep rates of adoption since 2007, according to annual surveys of enterprises and small- to medium-sized businesses (SMBs), conducted by Nemertes Research.

Last year, 71 percent of the 203 businesses surveyed reported using an Ethernet WAN service, up from 46 percent in 2007, according to Nemertes' 2010/11 Communications and Computing Benchmark. Adoption is projected to reach 75 percent by the end of this year and 77 percent by the end of 2012.

Eric Mermelstein, enterprise infrastructure architect at Columbian Chemicals, said, "Some of the reasons I think people choose Ethernet are that it's easier to manage. It's not as complex as ATM or frame relay. It's a regular network patch cable, versus something like a T1 or an E1."

However, MPLS and Metro Ethernet services also aren't always mutually exclusive, according to Kevin O'Toole, vice president of commercial services at Comcast (News - Alert). While SMBs view Metro Ethernet as a replacement for MPLS and T1s, large enterprises more often use metro Ethernet for last-mile access to their MPLS clouds.

They’re not perfect -- some WAN managers say their Ethernet-based circuits lack the granular traffic management capabilities of MPLS and frame relay.

Ethernet WAN services are relatively simple, and networking pros have deep experience with managing the technology inside their own networks, making them an attractive WAN option, especially Ethernet-based Internet connections, according to Brian Washburn, research director at Current Analysis (News - Alert).

Feelings about Ethernet only go so far in selling WAN managers on Ethernet WAN and Metro Ethernet services. The true headliner is the sheer size of the pipes, which they say are orders of magnitude cheaper than other connectivity options.

Adding capacity to Ethernet WAN and Metro Ethernet services can be done quickly and easily because the service provider does not need to add new copper pairs, as is necessary to bond multiple T1 circuits, said Comcast's O'Toole.

Bigger pipes aren't just for bragging rights. Being able to afford these leaps in capacity has enabled WAN managers to support advanced services that were once unthinkable.