Horse Sense #122
Making the Connection--Cables and DNS
You Cannot Get Anywhere If Your Cabling Stinks
Copper Ethernet patch (sometimes called jumper) cables connect your computer to the wall or from a port on the rack to a switch. If the cable, ends, or connecting socket are bad, you might not be able to connect. Patch cables need a Category rating at least as high as the cabling in your walls. If you connect a Category 5 or CAT5 patch cable to CAT6 cables in your wall, then you might be unable to connect reliably at 1000Mbps and have to use a 100Mbps connection. You do not want to suffer a 10x performance decrease for a $10 cable!
You plug a patch cable in at both ends. Either end can be a point of failure, but even if they work, they tend to lower the total effective cable length you can use. 100Mbps Fast Ethernet allows up to 100 meters between end points on Category 5 or better cable. Even the best connection with a patch cable decreases that total distance about 5 meters per end. Be careful with long patch cables as you can exceed the maximum length for reliable communications without meaning to do so.
Buy tested patch cables. Do not try to make or fix a patch cable yourself. Special tools are required. CAT6 and better cables are backward compatible with earlier cables, so buy only those as they cost the same as lower category number cables. You can buy cables that are flat, armored, shielded, molded, bundled, and all sorts of lengths and colors to fit your needs.
If someone wires your office, have them test each connection with a cable tester and demonstrate that it is good with a compliance report. Get a wiring diagram as well. Make sure that you also test each connection with a PC. Sometimes a cable tester will pass a connection that still will not pass data reliably at the rated speed.
Cabling is specialty work that often requires licensed contractors to do the installation. Iron Horse does not offer these services directly to its clients, though we know people who do the work. We do sell the cables, connectors, racks, cable management and cabling tools, cabling, and patch cables all the time to our clients. Just ask!
-Do not crimp or kink a cable or bend it too tightly. The wires or shielding may break.
-Cables on the floor are a trip hazard. Put them in the walls. Route them around the room.
-Do not jam your PC up against the wall. It may bend the cables to tightly, break connections, etc.
-Cables should have play. Cables that are too tight will be forced into bad bends or break from being stressed. You may not be able to see breaks as the outer cable covering may look just fine while the inner cables are broken.
-Any patch cable that is frayed or separating from its connector should be replaced.
-As much as possible, separate power cables from video and data cables. Try to separate power and data cables by six or more inches. If you cannot keep them separate, make them cross each other at right angles and/or use magnetic chokes on video or power cables to help keep stray electromagnetic radiation from leaking into other cables.
-Surge protecting data cables as well as power cables may sound like overkill, but power spikes can travel through any copper wiring to reach ground, including data cables. We recommend them highly in areas with lots of lightning or poor power.
-Use colored cables and labeling machines to help you keep track of which cable is which. Always label your data and phone jacks. You will forget which cable and socket is which almost immediately.
-You can do cabling jobs yourself. You will probably do them badly and/or risk issues with the fire marshal or code enforcement people. A professional job will probably be far less expensive over the long run.
-"Over" cable your rooms. Draw "more" power, data, and phone lines than you think you will need. Cable is cheap. Pulling multiple cables to the same location is not a big deal in terms of additional labor. Having to put more cabling in later is very expensive and disruptive. "Gold plate" your cabling. You do not want to have to dig into your walls again if you can possibly help it.
-Fiber is more future proof than copper and has other advantages. See Horse Sense 52.
Why Can't I Get to That Web Site?
The Domain Name System (DNS) turns the name you type in your web browser into an IP address that computers can understand. If you knew the IP address, you could type that number in and get the web site to come up. But....DNS is not an assured response system. If the DNS servers do not respond in time, you will not get an IP address to use and you will not be able to send mail or access the web site. This happens more often than you might think. But, if your local DNS server, the one you usually ask for the number first, has saved a copy of the information (cached it), then it does not have to take the time going out to the Internet to ask other DNS servers out on the Internet for the information. Not only will your information request be answered, but it will be answered more quickly. Of course, this assumes that the person publishing the DNS information says that you can hold on to that information for a while. Many companies do not allow their information to be cached for very long. That means that what worked a few minutes ago might not work now because you have to ask for the IP address all over again. As the Internet has become more global, the response to your DNS request may have to come from somewhere on the far side of the globe. That takes a while, even at the speed of light. So, the next time you have a problem getting from here to there, maybe it is not that the end destination is not accepting visitors but that the directions are not available.
If you want to see if the web site is up, but you just cannot get from here to there, try this link: http://www.downforeveryoneorjustme.com
If you cannot connect to someone, if your mail is getting lost in cyberspace, if your connection to the Internet is slower than you think it should be, if you are getting spam or viruses, ... Now may be the time to call us.
©2015 Tony Stirk, Iron Horse firstname.lastname@example.org