What is Metro Ethernet? It's Ethernet transport that's compatible with the Ethernet you run on your company computer network. But this type of Ethernet is designed for the WAN (Wide Area Network) rather than the LAN (Local Area Network). The generic term is Carrier Ethernet. When provisioned for metropolitan area access and connectivity, it's often called Metro Ethernet.
So what's the advantage of Metro Ethernet over, say, a T1 line? Speed for one thing. A T1 line runs at a fixed rate of 1.5 Mbps. You can order less speed with fractional T1 service or you can bond T1 lines together to get higher speeds of 3 to 12 Mbps. But that's about where T1 tops out. While it is technically possible to bond even more lines together, it's seldom cost effective. By the time you exceed 10 Mbps, it's usually cheaper to bring in DS3 service at 45 Mbps over fiber optic cable.
Metro Ethernet can also be provisioned over fiber optic cable to give you standard Ethernet at 10 Mbps, Fast Ethernet at 100 Mbps or even Gigabit Ethernet at 1000 Mbps and 10 GigE at 10,000 Mbps. It's often significantly cheaper than traditional SONET fiber optic services because Metro Ethernet is offered by competitive carriers who have their own nationwide fiber backbones and fiber within the metro areas. Since they completely control their network assets and don't need to subcontract to local phone companies, these carriers can often offer large cost reductions. That's especially true when they are trying to establish a major presence in an area.
Another service that you'll find with Metro Ethernet that makes lower bandwidth services even more cost effective is EoC or Ethernet over Copper. This is what it sounds like. It's Metro Ethernet provisioned over multiple copper pair, similar to T1 lines. But a different modulation technology is used for EoC that is more efficient for packet transmission, but at a tradeoff of being distance limited. In other words, you need to be within a few miles of the nearest carrier POP to take advantage of this service. If you qualify, you can get Ethernet over Copper in bandwidths from 1 to nearly 50 Mbps at costs per Mbps often well below other line services.
But what if you are located in a smaller town or rural area? Remember those bonded T1 lines? You can probably get bonded T1 service at 3, 6, 9 Mbps or more anywhere you can get business telephone service. Chances are that this service will be far cheaper than bringing in new fiber optic lines.