In larger networks it is not unusual to
have more than one wiring closet if there are hosts that need network
connectivity but are outside the 100-meter limitation for Category 5
UTP Ethernet.
By creating
multiple wiring closets, multiple catchment areas are created. The
secondary wiring closets are referred to as Intermediate Distribution
Facilities (IDF).
TIA/EIA- 568-A Standard specifies that IDFs
will be connected to the MDF using vertical cabling. This vertical
cabling is typically fiber-optic cable because fiber-optic cable can
be run longer distances.
In the MDFs and IDFs the major difference is the implementation of
another patch panel, which can be the vertical cross connect (VCC).
This VCC is used to interconnect the various IDFs to the central MDF.
Since the vertical cable lengths are
typically longer than the 100-meter limit for CAT 5 UTP cable,
fiber-optic cabling is normally used. 
Upcoming
Changes in Cabling Standards
Design Hint - Since the vertical
cabling will be carrying all data traffic between the IDFs and MDFs,
the speed of this connection should be designed to be the fast link in
the network. In most cases this link should be at least 100 Mbps.
Also, additional vertical cable runs should be installed to allow for
future growth in the network.
|