It sounds like a hybrid arrangement. DS3 is a commonly available telecom service offering 45 Mbps from a T-Carrier standard TDM (Time Division Multiplexing) technology. Most users of DS3 order it for dedicated point to point connections, broadband business access for larger organizations, and high volume telephone trunking in enterprise contact centers and commercial call centers. Why put a new protocol like Ethernet over a legacy protocol like DS3?
The big advantage of Ethernet over DS3 is that it gives you the Ethernet connectivity and services you desire in areas where Metro Ethernet or Carrier Ethernet services are not yet available or too expensive. You may already have DS3 brought into your building. If so, the physical layer already exists to transport any protocol that is compatible with that DS3 service.
Another situation is when SONET fiber runs close to your location and it is quite affordable to demultiplex a DS3 connection and bring a drop to your building. The native Ethernet over Copper and Ethernet over Fiber networks may not have build-outs anywhere near you. While the range of services and pricing from competitive carriers operating their own IP-core networks can be impressive, they may not have a service footprint in your area. DS3 is a more mature transport technology and may well be available to business locations nearby.
What can you expect from Ethernet over DS3? Bandwidth is limited to DS3’s rate of 45 Mbps, although Ethernet services are often very scalable and can be ordered from a few Mbps right on up to the limit of the port speed. If you need higher bandwidth, say 100 Mbps Fast Ethernet or higher, it may be possible to bond DS3 services the way T1 lines are bonded to multiply bandwidth. Also, If DS3 is available it is likely being carried on a SONET fiber optic service, such as OC3 at 155 Mbps. You may be able to get a higher bandwidth connection if there is extra capacity in the fiber service that delivers your DS3.
Is Ethernet over DS3 the right option for your business? The best way to find out is to get a set of competitive quotes for all bandwidth services available at your business location. There may be more options at lower prices than you expect.