Information Technology Reference
In-Depth Information
The easy way to keep patch and equipment cords short is to locate the hori-
zontal wire terminations and the hubs in the same rack. The terminations might be
on connecting blocks, with cross-connects to patch panels, or directly to patch pan-
els. You can use wire management panels to route the patch wires to the side rails
and down to the hub. Most modern wire termination blocks feature a very high con-
nection density, so they should not take up much rack space. Also, patch panels with
96 or more jacks consume very little vertical rack space. So, it should be possible to
place both equipment and terminations in the same rack, with plenty of room for
future expansion of both. A popular alternative mounting scheme is to place the
wiring terminations in wall mountings and place the LAN hubs in relay racks. This
hybrid approach is serviceable, as long as the equipment cord runs are not too long
from the wall to the racked hubs. In a variation to this approach, you could place
the connecting block terminations on the wall, as before, and run cross-connect
jumpers to patch panels in relay racks. Then, relatively short equipment cords could
be connected between the patch panels and hubs in the same rack. Remember that
the cross-connect jumpers count as part of the 5-m (16-ft) limit.
“To patch or not to patch, that is the question.” You can get into a consider-
able debate with some wiring managers of large facilities about this very question.
There is definitely a downside to the use of patch panels in a large facility. The prob-
lems with patch panels are that they are an added expense, provide an additional
point of failure, may provide questionable long-term connections, and add lots of
spaghetti-mess (from the myriad of patch cords that must be used). Their modular
connectors may also add unnecessary crosstalk. If connections to the hubs can be
made with cross-connect wires, you may be able to avoid the use of patch panels
altogether. Simply terminate your station cables on the connecting block of your
choice and run a cross-connect jumper over to a mass-termination connector for the
hub. The larger card-cage hubs offer port connections on 50-pin telco connectors,
among other options. The hub's 50-pin connectors can be extended to connecting
blocks, such as the 110 system blocks, and the cross-connects can be made directly
to the station punchdowns, without using patch panels.
The patchless approach has at least three disadvantages. First, troubleshooting
is more difficult, as you cannot simply unplug a modular equipment cord and insert
a tester. You must either disconnect the cross-connect wire and use a test jack
adapter that fits onto the connecting block, or you must have used one of the types
of connecting blocks with a built-in disconnect capability and still use a test adapter.
Second, it is much more difficult, on average, to locate the connections for a partic-
ular station cable, since the circuit markings are imbedded in the high-density con-
necting block. Third, you may double the potential workmanship problems. For
example, if you had directly terminated on a patch panel, that would be the only
