The type of cable chosen for a network is related to the network's topology, protocol, and size. Through the understanding of the characteristics of different types of cable and how they are interrelated to other aspects of a network successful development and implementation of an appropriate network design can be attained.
Cable Rules
Here are a few basic rules to follow whenever you are running cable:
- Slack - Always use more cable than you need. Leave plenty of slack
- Test - Always test every segment (the complete, unbroken length of cable running between two distinct points/nodes) of a network as you install it. Even if it is brand new, it may have problems that will be difficult to isolate later.
- Stretching - Avoid stretching UTP cables. The tension exerted when pulling cables should not exceed 10 Kilograms. Over-stretching of UTP will result in effectively untwisting the pairs within the cable sheath. As I will explain later the period of the twist of great importance in reducing cross-talk or noise.
- EMI Sources - Stay at least 3 feet away from EMI sources such as fluorescent lights and other electrical and electronic equipment in particular including copy machines, electric heaters, speakers, printers, TVs, copiers, welding machines, microwave ovens, telephones, fans, elevators, motors, electric ovens, dryers, washing machines, and shop equipment. Once again this is to reduce Electro-magnetic interference (noise).
The less interference/noise the better the signal will be at the receiving end. This helps to reduce corruption of data in transit and so reduces the amount of retransmissions that may be required for maintenance of data integrity throughout the transfer process. This in turn translates to greater effective data throughput which means your network is faster.
- Sensitive Electronics - Whenever you are planning your cable runs it is vital to consider the electrical and electronic environment into which the run will be performed. Just as other EMI sources can result in degradation of the signal in your transmission medium so your transmission medium can cause interference with other devices. Do not run trunk cabling next to life-support systems etc. as this can have consequences that I will not go into here.
- Mobile Phones - Mobile phones can also be an issue that needs to be carefully considered. If you are going to be running your cable through an area that is likely to be heavily populated with mobile phone users then it would be advisable to add additional protection for your cable. Using Shielded Twisted Pair (STP) or another medium that is not susceptible to EMI such as fiber optic cable while more expensive do not have the same susceptibility to EMI as Unshielded Twisted Pair (UTP).
- Open Spaces - If it is necessary to run cable across the floor always cover the cable with cable protectors and fix it firmly to the floor (duct tape does a good job here). For aesthetic reasons you might consider using a rug.
The reasons that you must cover and fix the entire cable firmly to the floor are so that the cable isn't damaged by traffic and that the traffic (people) is not damaged by tripping over a loose cable. Try to avoid open floor cables runs at all times even if it means using more cable by running the cable along a wall.
- Label Cable - Always clearly label your cable at both ends as you run it. This becomes particularly important when it comes time to attach the ends to other devices. It also makes future troubleshooting easier.
- Cable Ties - Apart from the use of duct tape to cover cross-floor cable runs always use cable ties and not tape to keep cables in the same location together.
- Staples - Never use a stapler to secure UTP or STP or any other cable transmission media; rather use telephone wire/RG-6 coaxial wire hangers instead. They are readily available at most hardware stores.
- Outside Use - Never run UTP cable outside of a building as it presents a very real danger in the form of a lightning hazard! It is also very prone to environmental degradation resulting from water damage. Remember electricity and water do not mix.
- Existing Infrastructure - Always inspect your existing infrastructure to make sure that those segments that are already in existence will be compatible with those which you plan to install. This is vital when it comes to such network infrastructure as switches and Network Interface Cards (NIC). You may well be installing higher performance transmission media but will not realise any benefit in data throughput if some elements of your network are incapable of the higher transfer rates.
For Example: installing new CAT 6 cable; which is capable of transmission rates of 1 Gigabit/sec, will have no measurable benefits if the older NICs of your PCs are rated at 10 Megabit/sec. The network will only operate at the speed at which the slowest member of the conversation can operate. So you may have to upgrade your NICs as well. Fortunately they are cheap.
