What is a valid connection method between carrier-neutral facilities that are more than 20 miles away from each other?

A Carrier access Ethernet ring, a type of Metro Ethernet or Carrier Ethernet service, is a standard method for interconnecting geographically dispersed facilities like data centers. Service providers leverage extensive single-mode fiber optic networks, often with Dense Wavelength-Division Multiplexing (DWDM) technology, to offer high-bandwidth, resilient connections over metropolitan and wide areas. These services are specifically designed to span distances far exceeding 20 miles, making them a valid and common solution for Data Center Interconnect (DCI) between carrier-neutral facilities.

B. Private wireless connection: While microwave links can span long distances, they require a clear line of sight and are susceptible to atmospheric conditions, making them less reliable than fiber for primary DCI.

C. CAT6e connection: Category 6e copper cabling is restricted by the TIA/EIA-568 standard to a maximum length of 100 meters (328 feet), making it unsuitable for a 20-mile distance.

D. Multimode fiber connection: Multimode fiber is intended for short-reach applications, such as within a data center or campus, with maximum distances typically limited to a few hundred meters.

1. Cisco Systems, "Data Center Interconnect Solution Overview" (White Paper). This document discusses various DCI technologies. It explicitly mentions "Carrier Ethernet services (also known as Metro Ethernet)" as a primary transport option for connecting data centers over a metro area network, which aligns with the scenario of facilities being more than 20 miles apart. (Reference: See sections on "DCI Transport Options" and "Layer 2 DCI Technologies").

2. Cisco Systems, "Cisco Nexus 7000 Series NX-OS OTV Configuration Guide, Release 5.x". In the "Overlay Transport Virtualization Overview" chapter, the guide describes the underlying transport infrastructure required for DCI technologies like OTV. It lists "Layer 2-switched (Ethernet)" and "Layer 3-routed" infrastructures provided by service providers, which includes Metro Ethernet services capable of spanning long distances. (Reference: Chapter 1, "Information About OTV," section "OTV and the Underlying Transport Infrastructure").

3. Cisco Systems, "10-Gigabit Ethernet over Multimode Fiber: A Migration Brief" (White Paper). This document details the distance limitations of various multimode fiber types for 10GbE. It confirms that even the highest grade (OM4) is limited to 400 meters, demonstrating its unsuitability for a 20-mile connection. (Reference: Table 1, "10GBASE-SR Reach over Multimode Fiber Grades").

4. TIA-568-C.2, "Balanced Twisted-Pair Telecommunications Cabling and Components Standard". This industry standard, frequently cited in Cisco documentation, defines the physical and transmission characteristics for twisted-pair cabling. It specifies a maximum channel length of 100 meters for CAT6 and its variants, confirming the severe distance limitation. (Reference: Section 5, "Channel performance requirements").