Ethernet cables, by Karl shoemaker, AK2O

Some history in three areas:

  • Ethernet is the most popular and considered the networking topology standard for most computer connections. There have been many kinds of ethernet, but the most popular is 10/100mbps running over copper twisted pair wires. 100mbps ethernet is also called 100baset and fast ethernet.

  • Older ethernet standards ran on coax cable and were referred to as 10base2 thin ethernet and 10base5 thick ethernet. Some hubs still have a coax connector to bridge together twisted pair and thin ethernet networks.

  • A newer ethernet standard called gigabit ethernet or 1000baset also can run over copper wire but hubs and switches are very expensive.

    For this discussion we will cover current Ethernet cables only.

    Internal Cable Structure and Color Coding

    Cables come in several categories, depending on the RF frequency, which really is a function of the bandwidth needed to carry the information from one point to another. Inside the cable, there are 8 color coded wires. These wires are twisted into 4 pairs of wires, each pair has a common color theme. One wire in the pair being a solid or primarily solid colored wire and the other being a primarily white wire with a colored stripe. Sometimes cable doesn't have any color on the striped cable, the only way to tell is to check which other wire it is twisted around. Examples of the naming schemes used are: Orange (alternatively Orange/White) for the solid colored wire and White/Orange for the striped cable. The twists are extremely important. They are there to counteract noise and interference. It is important to wire according to a standard to get proper performance from the cable.
















    Protocol Details:

  • 10BaseT uses a symbol encoding of Manchester, with a rate of 10 Mbaud, with no data encoding, data bits per symbol of 1; one pair per channel, using two pairs, with a minimum cable category of 3.

  • 100BaseT4 uses a symbol encoding of Multi-level 2T/Hz, with a rate of 25 Mbaud, with data encoding of 8B6T, with data bits per symbol of 8/6; three pairs per channel, using four pairs, with a minimum cable category of 3.

  • 10BaseTX uses a symbol encoding of MLT-3, with a rate of 125 Mbaud, with data encoding of 4B5B, with data bits per symbol of 4/5; two pairs per channel, using two pairs, with a minimum cable category of 5.

  • 100BaseT2 uses a symbol encoding of PAM 5x5 (2D-PAM5), with a rate of 25 Mbaud, with no data encoder, with data bits per symbol of 2; two pairs per channel, using two pairs, with a minimum cable category of 3.

  • 1000BaseT uses a symbol encoding of 4D-PAMS, with a rate of 125 Mbaud, with no data encoding, with data bits per symbol of 2; four pairs per channel, using four pairs, with a minimum cable category of 5 or 5e, which ensures this operation.

  • 10GBaseT uses a symbol encoding of DSQ128 (2D-PAM16Z), with a rate of 800 Mbaud, with data encoding of LDPC(1723,2048,64B/65B, CRC8, with data bits per symbol of 3.125; four pairs per channel, using four pairs, with a minimum cable category of 5e or 6a, which ensures this operation.


    Other considerations

    The chart mentioned "rate" and "Frequency". That's because of the cable design (and some cost). Here's the current grades of cable quality, which most commonly are CAT5, CAT5e and CAT6, however we should briefly cover all of them so you have an understanding and appreciating on what you'll be using.

  • CAT 1: Currently unrecognized by TIA/EIA. Previously used for POTS telephone communications, ISDN and doorbell wiring.

  • CAT 2: Currently unrecognized by TIA/EIA. Previously was frequently used on 4 Mbit/s token ring networks.

  • CAT 3: Currently defined in TIA/EIA-568-B, used for data networks using frequencies up to 16 MHz. Historically popular for 10 Mbit/s Ethernet networks.

  • CAT 4: Currently unrecognized by TIA/EIA. Provided performance of up to 20 MHz, and was frequently used on 16 Mbit/s token ring networks.

  • CAT 5: Currently unrecognized by TIA/EIA. Provided performance of up to 100 MHz, and was frequently used on 100 Mbit/s ethernet networks. May be unsuitable for gigabit ethernet (1000BASE-T).

  • CAT 5e: Currently defined in TIA/EIA-568-B. Provides performance of up to 100 MHz, and is frequently used for both 100 Mbit/s and gigabit ethernet networks(1000BASE-T) however you need to be careful with kinks and connector termination practices..

  • CAT 6: Currently defined in TIA/EIA-568-B. It provides performance of up to 250 MHz, more than double category 5 and 5e. CAT6 is best for gigabit ethernet networks(1000BASE-T), however proper connectors may be hard to fine, presently.

  • CAT 6a: Future specification for 10 Gbit/s applications.

  • CAT 7: An informal name applied to ISO/IEC 11801 Class F cabling. This standard specifies four individually-shielded pairs (STP) inside an overall shield. Designed for transmission at frequencies up to 600 MHz.


    The "RJ-45" plug

    The "RJ-45" end is really a 8-position modular connector that looks like a large phone plug. Many (incorrectly) call it the "RJ-45", but since the "J" stands for jack in the UOSC it's really a (male) plug. However, for ease of understanding the whole system we'll use the (incorrect) term a few times in this document. There are a couple variations available. The primary variation you need to pay attention to is whether the connector is intended for braided or solid wire. For braided/stranded wires, the connector has contacts that actually pierce the wire. For solid wires, the connector has fingers which pierce the insulation and make contact with the wire by grasping it from both sides. The connector is the weak point in an ethernet cable, choosing the wrong one will often cause grief later. If you just walk into a computer store, it's nearly impossible to tell what type of connector it is. 10/100 ethernet cables have 8 wires, of witch 4 are used for data in the form of two pairs, in a twisted pair setup: one pair for transmit and one for receive. The other wires are twisted around the data lines for electrical stability and resistance to electrical interference. The cables end in RJ-45 connectors that resemble large telephone line connectors. It's important to be able to identify the pin number on these plugs.

    During some research an interesting type was found on Platinum Tools web site. Their connector lets you run the wires out front of it. In some cases this may help with flimsy wires, such as stranded. That may be another reason for going with solid; easier installation. In case their site's down, you can see the item, here.

    Later on you'll be working with Switches, HUBs, Routers and NICs ("NIC" acronym means Network Interface Card). Some or all are used in a LAN (Local Area Network). NICs have a RJ45 jack and are plugged into the mother board of a PC (Personal Computer). That is how a PC communicates to another devices on a LAN, or even the internet. When you connect a bunch of machines together using a hub, the hub relays all the information from all the transmit pairs to all the receive pairs. That is, each machine sees on its receive pairs the information sent on every machine's transmit pairs. The hub logically connects all the transmit pairs to all the receive pairs. Connections between 10/100 ethernet adapters are made using cables that run to an ethernet hub or switch. Hubs electrically connect your computers together and switches act like traffic cops making your network more efficient. All these devices can be studied and learned on other documentation. We are concentrating on the cables at this point.



    Now, for one of the most confusing part for the "Nebie". There are three kinds of wiring schemes are used for commercially made ethernet cables, which are:

  • Straight through (sometimes called a "patch" cable),

  • Crossover (similar to a serial cable's "null-modem")

  • Rollover For this article we will not be covering rollover.

    T 568 Standards:

    The TIA/EIA-568 specifies two wiring standards for a 8-position modular connector such as the RJ45. The two wiring standards, T568A and T568B vary only in the arrangement of the colored pairs. The only difference is in the orange and green pairs, for wire colors. You can use either standard, as the signals don't care what the colors are, just that you keep to the standard at each end. Your choice might be determined by the need to match existing wiring, jacks or personal preference, but you should maintain consistency. Sources suggest either way. Just to give you another (confusing) decision, sources indicate that traditionally B is used because of the AT&T 258A standard, however, The U.S. N.C.S. Federal Telecommunications recommendations do not recognize B. US Government specifies A since it matches USOC cabling for pairs 1 & 2, which allows it to "work for 1/2 line phones...".

    A straight through cable is used to connect DTE-to-DCE or DCE-to-DTE devices, like a hub or switch, or a NIC (in a PC) to a switch, because they are unlike devices. The wires are is just that; pin-for-pin on each end of the patch cable are the same colors, therefore, the transmit and receive wires are straight through. You can identify a straight through cable by holding both plugs (ends of the cable) side-by-side, in the same orientation. For example, hold both plugs with the locking clip pointing down and the cable pointing towards you. The color of wires will be the same on each plug. If a cable does not say crossover, it is a probably a standard patch cable. More on this thought, later.





    A cross over is used to connect DTE-to-DTE or DCE-to-DCE devices, like two NICs, (each inside two PCs) because they are like devices. An ethernet crossover cable has it's send and receive wires crossed. This type of connection in a peer-to-peer fashion can be done without a hub/switch. This is rather common in home networks.


    Watch out !

    Products sometime surprise you and cause confusion, so be ready. For example, when using a hub or switch, this is automatically done for you, so in that case you would not use a cross over cable. Some interfaces can cross and un-cross a cable automatically as needed, which can really quite nice, in a way, or cause confusion, when adding other devices to the mix. Examples would be cable and DSL modems that have their actual ethernet plugs reversed. This is to allow people to hook up a cable modem to a computer without this (special) crossover cable. TIP: If you run into trouble and your devices are not working, you might try a different cable standard in case the auto-crossover in some devices is "hosting" you up.

    Again, you can identify a cross over cable by holding both plugs (ends of the cable) side-by-side, in the same orientation. In this case, the color of wires will not same on each plug, left to right. You'll notice the green and orange pairs have been rolled, while the blue and brown pairs are straight as in the picture shows. As mentioned earlier, a crossover cable is not to be confused with a "roll over" cable, which is not covered here. The other pictures shows the alternative by using a cross over adaptor, with a straight through cable. Either way accomplishes the same task.



    The Author uses way to remember this by thinking that a crossover cable is the same as terminating one end with 568-A , while the other end with 568-B standard. When making up your own cables, the Author uses two other tricks, which are to label them and/or use different color cables for each type.

    The most popular crossover cables made are:

    Crossover cable

    Sample application

    Ethernet crossover cables

    Ethernet card to ethernet card type

    RS-232 serial crossover cables

    PC to PC, PC to printer type

    V.35 crossover cable

    Router to Router type

    RS-449/RS-422, X.21 and RS-530 crossover cables

    DSU/CSU to DSU/CSU type

    T1/E1 crossover cable

    Switch to Switch, DSU to DSU, etc


    How to wire your own ethernet cables and connectors.

    What You Need:
    CAT 5 Cable - bulk Category 5, 5e or 6 cable
    RJ45 Ends
    Crimper for RJ45
    Wire Cutters - to cut and strip the cable if necessary

    Also Recommend:
    Wire Stripper
    Cable Tester


    About the Cables and the Connectors for them

    Most professionals will advise you do not build your own cable, but rather to purchase factory made cables. It's an art to build a proper cable and connector. This will keep another variable in a troubleshooting nightmare, in the event this should happen to you. If you still choose to build your own you will need to know about cables, and the connectors for them. You can find bulk supplies of the cable at many computer stores or most electrical or home centers. You want UTP (Unshielded Twisted Pair) Category 5 cable for basic 10/100 functionality. You should run CAT5e whenever possible because there is usually not a cost difference from CAT5 if you look hard enough. Moreover, if you install higher rated cable, now it will give you a measure of future proofing.

    Bulk cable comes in 2 basic categories, solid and braided cable. Braided cable tends to work better in "patch" applications for desktop use. It is more flexible and resilient than solid cable and easier to work with, but really meant for shorter lengths. Solid cable is meant for longer runs in a fixed position. Plenum rated cable should/must be used whenever the cable travels through an air circulation space. For example, above a false ceiling or below a raised floor. At the store it may be difficult or impossible to tell from the box. If you're lucky the salesperson will permit you to open up an end for inspection.

    Connectors come in the 2 type as well; for solid and braided cable. Generally speaking if you mix the two types up you will run into big trouble. The main "don't" is using a stranded connector for sold cable. It's unknown if it's visa-vers at this time. At any rate you need to know the difference. The connector have little "prongs" on the crimp that need to provide a low resistant connection to the cable's conductors. You may find conflicting information, however presently, the Author understands that a connector for stranded cable has one little prog that will bit/bury itself into the strand of the wire. The connector for solid has two little "sub-prongs" that will bit on each side of the single conductor. With a microscope you may be able to see the difference.

    100 meters (about 330 feet) is your maximum distance for most twisted pair ethernet, with the exception of the latest type as discussed earlier. For longer distances you could install a switch, or some other device as a "buffer". Also, Ethernet to fiber media converters are starting to come down in price. When 100 meters is not enough distance, an ethernet to fiber media converter can be placed on each end making the maximum distance something like 40km. Another use for fiber is electrical insulation. Some people like to run cables underground between homes. If you run CAT5 cable, the homes have different 'ground potentials' and you can burn out network card during an electrical storm. One solution is fiber. Run fiber between the homes or run a pair of fiber converters on one end of the cable with a short fiber run. This will electrically separate the two homes. The Author does not run fiber between buildings and has been fortunate, so far, during lighting. The bottom line is you can make longer runs; just be prepared to have additional problems and issues. It's up to you.




    After crimping the modular ends verify the wires ended up the right order and that the wires extend to the front of the RJ45 end and make good contact with the metal contacts. Cut the cable to length - make sure it is more than long enough for your needs. Remember, an end to end connection should not extend more than 100m (~328ft). Try to keep cables short, the longer the cable becomes the more it may affect performance, usually noticeable as a gradual decrease in speed and increase in latency. If a cable tester is available, use it to verify the proper connectivity of the cable. That should be it, if your cable doesn't turn out, look closely at each end and see if you can find the problem. Usually a wire ended up in the wrong place or more commonly, one of the wires didn't extend to the front of the RJ45 connector and is making no, or poor contact. If you see a mistake or problem, cut the end off and start again.



    Ethernet 10baset or 100baset crossover cable diagrams

    Here is the pin out diagram for building an ethernet 10baset or 100baset crossover cable.

    Connector 1

    Connector 2


















    How to wire EIA 568-B crossover cables:

    Connector 1

    Connector 2

    1 WHT/ORG
    2 ORG/WHT
    3 WHT/GRN
    4 BLU/WHT
    5 WHT/BLU
    6 GRN/WHT
    7 WHT/BRN
    8 BRN/WHT

    1 WHT/GRN
    2 GRN/WHT
    3 WHT/ORG
    4 BLU/WHT
    5 WHT/BLU
    6 ORG/WHT
    7 BRN/WHT
    8 WHT/BRN

    USOC Crossover cables:

    1 WHT/BRN
    2 WHT/GRN
    3 WHT/ORG
    4 WHT/BLU
    5 BLU/WHT
    6 ORG/WHT
    7 GRN/WHT
    8 BRN/WHT

    8 WHT/BRN
    7 WHT/GRN
    6 WHT/ORG
    5 WHT/BLU
    4 BLU/WHT
    3 ORG/WHT
    2 GRN/WHT
    1 BRN/WHT

    The Author's been contacted by Steve Nikkel, in Canada, who's better knowledgeable than what's here. One of the subjects he covers is power over Ethernet: "It has been implemented in many variations before IEEE standardized 802.3af. 802.3af specifies the ability to supply an endpoint with 48V DC at up 350mA or 16.8W. The endpoint must be capable of receiving power on either the data pairs [Mode A] (often called phantom power) or the unused pairs [Mode B] in 100Base-TX. PoE can be used with any ethernet configuration, including 10Base-T, 100Base-TX and 1000Base-T. Power is only supplied when a valid PoE endpoint is detected by using a low voltage probe to look for the PoE signature on the endpoint. PoE power is typically supplied in one of two ways, either the host ethernet switch provides the power, or a "midspan" device is plugged in between the switch and end points which supplies the power. No special cabling is required."

    For a complete description of this subject please check his site out by clicking here

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