So What Do I Choose?

Considering the number of different options and the features that they may support, the Metro Ethernet service options you have could be quite large.
Fortunately, most providers don't really want to offer you a too many options since it typically means more maintenance for them. However, this doesn't mean that we can't consider what they might be and how we might use them.

Ethernet Private Line (EPL) service can provide the functional equivalent of a dedicated T-1 although in ths case it's an ethernet service and it can provide ethernet speeds. This could be used in the same way any other dedicated connection where all traffic that enters on one end exits on the other end. Proprietary and non-routable protocols, which can still be transported via ethernet, could be used on such a link.

Ethernet Virtual Private Line (EVPL) service can provide the functional equivalent of Frame Relay service. By using an 802.1q trunk interface and Virtual LAN (VLAN) interfaces or a Layer 3 interface with 802.1q encapsulated sub-interfaces (eg., Fa0/0.10 with 802.1q encapsulation and VLAN ID of 10) the functional equivalent of a Layer 3 serial interface with Frame Relay encapsulated sub-interfaces (eg., S0/0.10 with a DLCI of 10) can be attained. This could be used to provide the same type of hub-and-spoke topologies that are currently provided by a Frame Relay service. The advantage being that specialized hardware such as CSU/DSUs or special types of interface hardware on the router are not required. Another advantage is that since ethernet is a broadcast, multiaccess, environment customer endpoints need not be routed. This is to say that a remote location at the end of a spoke could be a small office with $49 ethernet switch -- no router required.

Transparent LAN Service (TLS) can provide a true multipoint environment for both routed and non-routable protocols. All remote sites appear to be in the same Layer 2 broadcast domain. With no routing required, the remote locations could be in the same IP network. This could be ideal for small sites where visibility of all locations and resources is desired. The afore mentioned $49 switches could be at all locations and the network users could utilize 'local' file and printer sharing services as provided within Windows or a Mac.

TLS could also provide EVPL-like capability where some sites are multipoint and some are hub-and-spoke -- in the same Layer 2 broadcast domain! This could lead to some design issues, but the key point of this is that customers are free to potentially create some very interesting topologies to meet their specific needs.

And this is where things get fun. Providers will want to limit options to keep thing easy to support, and customers will want to deploy topologies that meet their specific needs. As the cost of deployment continues to drop and more providers get in on the game, market forces should prevail and a healthy mix of customer demands and ready-to-order solutions should emerge. And just as with the initial introduction of VLAN technology, the way we use Metro Ethernet today may not resemble the way we use it in the future.