THINK DIFFERENT
Of course, I’m borrowing an old Apple theme, but it still rings true today. We’re invited to a campus whose mission is to teach grades K-8. When a teacher or staff member says, “video to the classroom would be great” then you know you will need to invest a lot more time in discovering what that means.
Building a campus network or any network isn’t just about connecting wires and fiber in an orchestrated effort. The users have needs and wants, and discovering those needs is just as important to the IT guy as it to the guy building the network. We always try to anticipate a certain level of growth, since customers do tend to either over-buy or under-buy. The reasons are many, but the key is to right-buy and allow enough wiggle room for the future. We use the time-tested method of “management by walking around,” to learn more and ask more questions. Taking inventory of a customer premise isn’t just determining how many drops are needed; anyone can do that, but the real value comes into play in understanding what the customer does, and wants to do in the near future. These incremental investments of time always have a way of paying off.
WHAT WE FOUND
“Seeing is believing” – and sometimes, even after you see something- you still really can’t believe it until you stop thinking like a contractor. Then, it makes sense, in a strange way.
Liquid Nails: In the past, someone thought of using Liquid Nails (a construction adhesive) to glue the former network cables to the classroom walls. The downside to using this construction adhesive is it was the wrong type and the glue permeated the outer jacket of the old Cat5 wiring. So the glue type was incompatible with the PVC wiring. The biggest benefit that we could determine was cost deterrence of wire-mold. Look carefully at the picture below. Liquid Nails leaves a gummy sticky appearance and any attempt to pull glued cable off the walls strips the outer jacket and leaves a mess on the wall.
Non-Plenum Wiring: Used in the school air plenum, this was a huge oversight. The former wiring Cat 5 that we found installed was mostly CMR- not CMP-rated wiring. (All cabling has printed on the outer jacket details about the product). The 1950s-era construction of the hallways used sky-lit breezeways that also served as the air plenum to the classrooms. This kind of mistake compromised public safety and misapplied technology--using PVC in a space that is hot and subject to UV. (PVC {CMR} is not UV resistant but Teflon {CMP} cables are UV-permanently-stable, and perform better in enclosed spaces subject to heat as are most ceilings/plenum spaces)
Oddball Wiring: It took me awhile to run down the two types of wiring that really caught our attention on the initial site surveys. The first type of wire was an under-carpet Cat5 wire and the other wire used was intended for bulk use in making patch cables. Patch cable wire and horizontal wire are very different. I don’t know the effects of using under-carpet wiring for horizontal wiring, if any, other than it was a donation that probably came off of someone’s truck or jobsite, because this type of cabling isn’t cheap.
Split the pairs: The photograph below is even more revealing. Northern Telecom manufactured a patch panel, rated Cat5, which splits the pairs and provides two connections by using just one Cat5 cable. (Two pairs are terminated on Jack A and two pairs are terminated on Jack B- remember, every Cat5 has 4-pairs or 8 conductors) The faceplate ends were duplex jacks splitting pairs while the Nortel patch panel did the same at the other end. I don’t know the original purpose of the Northern Telecom patch panel- maybe it was intended as we found it, or perhaps it was intended for something else. If you know- you win a prize: great satisfaction for knowing!
Anyway, please don’t split the pairs. “Just because you can, doesn’t mean you should” citing a Nortel executive a couple of VoiceCons ago. The practice of splitting pairs to avoid running two drops has caused businesses a lot of pain and suffering, not to mention service degradation. Also, forget about “structured” in the structured wiring concept or the use of PoE with split pairs. Splitting pairs is always a quick and dirty fix, but there’s still a price associated with doing so.
Hubs & cheap switches galore: They were everywhere. The IT contractor used an empty video cart to pick them up after we re-patched everything into the new network. This gear contributed to the instability of their network even after we’d put in a 1-Gbps fiber backbone the previous year. The fiber covered or masked many sins, but the new managed switches revealed them. Managed switches with port statistics often go unnoticed until you need the data, and the details to show the customer what’s going on in the network.
No thought to cabling layout: Was given to minimize latency, distance of cable drops and to minimize cabling costs. We used a blow-up aerial view of the campus to determine new fiber locations and to streamline the cabling effort. Planning time upfront always pays off, and we can effectively deliver more drops or do more for the same price. But it’s not without planning and remembering that the location of servers or switches is key.
Cheap imports: reading the cable jackets and the labels on old boxes of left-behind Cat5 wiring revealed “Cat5 verified 350 Mhz” on the cable jacket, but on the old boxes (still with the same wire), the labels read “tested and verified to 100 Mhz.” We did trace the wire back to a cheap (online) importer out of Los Angeles. Cost is still a good measure- if you are getting “cabling” materials at a great price, be cautious. Once a cable plant is pulled- it’s done. There’s no fixing it, because it’s the wrong kind or type of wire; it then becomes a replacement project.
