When talking about the cabling of networks inside of our environment, there are few major terms you need to understand. They are not individual devices, but rather locations within the network infrastructure.
Main Distribution Frame
- MDF.
- Main Network Rack and closets. Where all of the different segments connect
- Typically the closet that has the connection to the internet.
- Source of internal backbone
- Near Demarc point
The main distribution frame is a cable rack that manages network cabling between any number of IDF and the Demarc. Unlike IDF, which also connects the internal line to MDF, it connects public or private lines entering into the building with the internal network.
MDF equipment is typically comprised of:
- Ventilation panels,
- Monitors,
- UPS,
- Library server,
- Patch panels,
- Servers (application, email server, DNS, etc)
Intermediate Distribution Frame
- IDF
- Smaller network closets on each floor of a location
- Network racks connect to backbone
- Connects additional network segments and devices
Demarc
- The point of demarcation
- Where ISP enters building
- Ownership transfer
Demarc Extension
- Keeps the ownership of the length of cabling under the ISP.
- We may want to run this extension from one side of a building to another if the Demarc point is not in a convenient location.
Smart Jack
- At the Demarc Point
- Common in T/E environments and PRI
- Translate the protocol from the ISP’s protocol to the network’s protocol.
- Located in the MDF
- IF there are problems across the network, check the smart jack for issues.
Vertical Cabling vs Horizontal Cross Connect
Vertical Cabling
Backbone cabling between the IDFs on different floors.
Horizontal Cross Connects
Connection to devices (switchs/hubs/drops) from IDF.
CSU/DSU
- Channel service unit/Digital service unit
- Sits on edge of network at Demarc point.
- Connects to CSU/DSU on the ISP’s end.
- Prevents echos from propagating.
