The reason for this post is because I see this sometimes gets used incorrectly. I wrote the below piece in a difference blog post but I just added to it:

Speaking of MDF/IDF and Data Centers. This is so flexible these days and used differently so use it however you like :). You’ll see that “most” companies will go with:

MDF – Larger than the IDF but not exactly a fully built Data Center. These will house the Demarcs, Routers, Switches, Firewalls, etc…
IDF – Closets where the Switches go. They fiber back to the MDF. So end user cable runs will run back to the IDF to a bunch of patch panels. From there they get patched into the Access switch. The Access switches are uplinked to the MDF distribution switch.

When talking about remote sites or branch sites, above is how they are typically setup. Some people will call the MDF’s Data Centers. MDF’s could have servers in them so I believe that’s where it could get confusing but in reality, your corporate server farms are going to be sitting Data Centers. When thinking about Data center vs MDF, you have to think about:

  • Partially resilient vs. fully resilient (if any)
  • Well-connected WAN connections vs. 10Gb+
  • Remote access vs. being close to a technical resource
  • SLAs at a high level vs. SLAs at a low level
  • Best effort vs. constant supervision
  • Etc…

The MDF (Main Distribution Frame) is a cable rack that controls and interconnects telecommunications wiring between itself and any IDFs (Intermediate Distribution Frames). The MDF connects private or public lines entering a building with the internal network which is also known as the demarcation point, which is unlike an IDF, which connects internal lines to the MDF. So all IDF’s link back to the MDF’s using Fiber cabling.

For example, an enterprise that spans multiple floors may have one centralized MDF on the first floor and one IDF connected to the MDF on each floor.

Fiber optic cabling and fiber-ready enclosures, such as rack trays and wall-boxes, support extensive cable distances and extremely fast network speeds. They are commonly utilized for MDF and IDF wiring. Fiber-based systems easily outperform twisted pair-based systems in terms of distance (up to 100m / 330ft.) and network speeds (up to 10Gbps). To facilitate signal distribution to particular rooms and/or devices, multi-strand fiber optic cabling, such as 6 strands and 12 strands, commonly connects the MDF to the IDF’s.