The last thing which must be done in the office before we can start moving things is to hook up the network wiring.
I have been putting this off, because I know how maddeningly time consuming it is likely to be: individually unwrapping each cable end for all 18 ports; untwisting each of the eight wires in the cable; laying out and clamping each outlet; pushing wires into slots on the patch panels; then testing each connection. It's a lot of work, and it doesn't help that this is new to me - something I am mortally afraid of screwing up if only because I don't know how to recover any failures.
The initial prep was just to check that all of the wires had been labelled as expected. Our electrician did a good job of pulling the wires through and of carefully labelling them - each pair is numbered, and one cable of each pair is marked with green tape. I devised my connection scheme, and started doing some actual connections.
I'd bought two twelve port patch panels, low profile units which will mount on the wall (and which will be enclosed in a cabinet at some point). In order to make the numbering easier, I decided that one patch panel would be connected to the green taped wires. I work on one port pair at a time, since two ports is a good unit for testing purposes too. So the first thing I did was to wire up two ports.
The ports I bought were toolless keystone jacks, so "All I Needed To Do"TM was to strip off an inch of outer insulation, carefully lay the wires in the colour coded channels and snap them on.
Next time I do this I am buying punch down jacks. These toolless ones are a pain in the arse.
The basic problem is that the wires do not stay in the channels after they have been so carefully laid in them. I realised that I could wrap the wires over the ends of the channel piece to hold them in, but that's not a strong enough solution to overcome the second basic problem which is that the wires are not in the right order for the plugs.
A very quick summary of why this is so...
Cat 5 cabling consists of eight wires run as twisted pairs. Each pair consists of a solid and a striped wire of a particular colour. The RJ-45 connectors used to terminate these wires have eight pins. It would seem logical to have the matched pairs connected to neighbouring pins, and for the most part this is exactly what is done. One pair is always split, though - in the wiring standard which I am using it is the green pair which is split and laid either side of the blue pair.
I am sure that there is a really good reason for this, but it's frustrating to have either the green or the blue wires pop out while you are trying to lay the other coloured wire down in its little slot. Those are no sooner in place than an orange or a brown wire makes its bid for freedom.
This is why punchdown sockets should be better: you may have to go through exactly the same contortions to get the wires in the right places, but once they are punched into place they tend to stay there.
The third and final problem is that snapping the sockets together takes more force than I can apply with my weedy little computer programmer fingers. This is easily worked around by the use of pliers, but I shall always expect the next plug will be one where I overdo the carefully applied force and mash the socket into a twisted mess of plastic and tiny shards of metal.
By contrast, the patch panels are easy. They are punch down connections so the wires stay where they are put, and are very cunningly designed so that neighbouring connection pins are filled by matching colour pairs. The little bit of crossover logic required is embedded in a circuit board between the connector pins and the RJ-45 socket.
Thus far I have connected and tested exactly one network port and its corresponding patch panel plug. It's a start, anyway.
Posted by Dunx at August 2, 2004 02:06 PM