networking cabling

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The HARDWARE 2 course: server, network and communicationForum Hardware training YBET YBET

4. Ethernet networks.

4.1. Introduction - 4.2. Ethernet, IEEE 803.3 10 base 5 - 4.3. Ethernet, IEEE 802.3 10 base 2 - 4.4. Ethernet, IEEE 802.3 10Base T RJ45 - 4.5. Ethernet 100 bases T RJ45, fast Ethernet - 4.6. Giga Ethernet - 4.7. 10 Gigabit - 4.8. Network adapter -

4.9 .Duplex Half and Duplex Full - 4.10. Connection RJ45 - 4.11. Networks RJ45, problems of connection, tests equipments - 4.11.Mac adress

4.1. Introduction

Connection between computers requires a network interface card established in each PC (also called NIC, Network InterfaceCard). The most current local area networks boards are Ethernet type. This chapter gathers all types of Ethernet connection and wiring(manufacture, precaution...) of wire of connection

The Ethernet network appeared at the end of the Seventies in the United States. This network, most widespread from the localarea networks, was born from the complementary experiments of DEC, INTEL and Xerox, well before the projections of standardization.This implies that the main part of the road bases of OSI model is not specified.

All the PC can communicate on the cable network at the same time. It is necessary thus a rule if two stations would start tocommunicate at the same time. The method used is the contention. The principal method of application in local area networks is theCSMA/CD (Carrier Sense Multiple Access), with collision detection (CD). It is that of the Ethernet networks. It consists for a station, atthe moment when it emits, to listen if another station is not also emitting. If it is the case, the station ceases emitting and re-emits itsmessage at the end of a fixed time. This method is random , in the sense that one cannot envisage time necessary to a message to beemitted, transmitted and received. Let us see the evolution of Ethernet.

4.2. Ethernet, IEEE 803.3 10 Base 5
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10 Base 5 version (10Mbps on coaxial cable with a maximum length by segment of 500 meters) is the version of origin of Ethernet, it is represented below:

Each station is equipped with an network "Ethernet" adapter ( NIC, Network Interface Card ). This equipment ensures the

physical adaptation and manages algorithm CSMA/CD. As in all connections coaxial, the 2 ends of the cable are connected to a stopper (it is also called resistance of termination), a specific resistance which attenuates the reverberation of the signal on the cable.

The drop cable consists of twisted pairs and can have a maximum length of 50 meters. The coaxial cable is a thick cable of yellowcolor an half-inch in diameter of the type BELDEN 9580. The overall length of the network can reach 2,5 kilometers with 100 points of connection.

The 10 base 5 is used practically more only in the disturbed environments (electromagnetic radiation) or when one wants toguarantee the confidentiality of the exchanges (not radiation of the coaxial cable).


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4.3. Ethernet, IEEE 802.3 10 Base 2A cut-rate version of wiring IEEE 802.3 10 base 5 was carried out with fine coaxial cable (Thin Ethernet). This type of Ethernet

network is represented below:

This physical architecture of network is recommended for the realization of small networks 2 or 3 PC. Each network adapter isconnected to the cable via a connector in T of the type BNC. The 2 ends of the network are closed by a resistance of termination(stopper ) of 50 ohms. This termination is not obligatory, but the speed transmission is definitely reduced since this resistance eliminates
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the "reverberations on the cable": the transmitted signal returns on the cable and the stations believing in a true signal wait until the lineis free.

The connection is easy to start, nevertheless, as soon as one installs 3 PC or more, the speed transmission strongly decreases. This

solution is thus to used only in specific cases.

The maximum length of the network is 185 meters, with a maximum of 30 connected pieces of equipment. The minimal distance between 2 connections is 50 centimeters. This wiring is often used to connect "the small station in bottom of factory". This solution doesnot function badly but it is absolutely necessary to separate this part of the others with for example a HUB. The reason is not data-

processing but related to the electromagnetic disturbances, storms... If the cable takes these disturbances, all the network disturbed or is broken down.

4.4. Network Ethernet, IEEE 802.3 10 Base T

With the problems of wiring, AT&T imagined to re-use preexistent telephone wiring in the office buildings for the realization of thenetwork. That imposed two constraints: one of flow, the other of distance. The network thus carried out functioned with 1Mbps, thestations were connected on star concentrators via repeaters ( hub) and outdistances it between the hub and a station was limited to 250meters. This architecture (802.3 1 base 5 or Starlan) completely obsolete evolved to a version 10MBps (802.3 10 base T). The followingfigure presents network 10 bases T.
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Ethernet 10 bases T uses a wiring per telephone pair (8 pairs is 4 wire). Its maximum speed is 10 Mbps (mga bit a second). Wiring isof star type. The nodes consist of concentrators. This solution is currently most widespread, but if the standard evolved/moved of speed.

Wiring under RJ45 in 10BaseT requires 4 wires (for 8 accessible in the connector). The wire are sold done everything in thetrade, but one can easily manufacture cables RJ45. Generally, 8 wire are inserted but it is not obligatory, in particular if you wish to use acable for 2 stations (attention with the disturbances).


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Connector and taken board network Right cable RJ45 of them 10 Base T and 100 base T (not in fullduplex)

If one does not use a concentrator (connection of 2 stations) or to connect 2 concentrators between-them, the wire must be of type cablescross like below. You must respect the polarities and the pairs must be paired.

Why respect wiring per pairs.


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The signal at the beginning of the board network is sent on the T+ form and the form T (reversed signal). Let us suppose a parasite whichappears on the cable during the transmission of the signal. It is of the same direction on 2 wire. As a pair is twisted, the electricdisturbances related to induced currents will be generally different from one pair to another. For recall, the passage of an electricalcurrent in a son produces fields electromagnetic in its entourage and of this fact a current in close electric wire induces.

Let us reverse T(-). the signal and the parasite are reversed. While adding T(+) and T(-) reversed, the double signal but the parasite isremoved.

Material necessary for a cable RJ45:

Cable 4 twisted pairs category 5 Connectors RJ45 to crimp category 5 Sleeves rubber, to avoid dividing the cable. A grip to be crimped and if the grip does not include it: cutting pliers and a grip to be stripped.

Procedure to be followed:

To thread the sleeve on the cable. To strip the external sheath on approximately 15 mm. For the cord crossed, Trier wire according to the diagram below.


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Cable cross connection RJ45 (10 base T and 100 base T)

To maintain wire in place by respecting the pairs and to cut them well on line. There must remain approximately 13mm, the endshould not form an arc of circle.

To place wire in the connector while supporting on the whole of the wire so that the pairs return until the bottom of the connector. To crimp the connector. To plug in the sleeve.

Check, by transparency, the good state of your assembly, if the wire arrive well in end of connector.

4.5. Ethernet 100 Bases TX and 100 Base T4, Fast Ethernet

Since 1992, one uses the 100 base T. The theoretical flow is 100 Mbps. The fast Ethernet also obliges to use concentrators of thehub type or switch.

One finds 2 category of 100 Base T: 100 Base T4 and 100 Base TX . The 100 Base TX (most widespread) uses same the 2 pairsthat the 10 Base T On the other hand, the 100 T4 Base uses the 4 pairs. Nevertheless, the 100 T4 base (almost more used) simultaneouslyuses 3 pairs for the emission and the reception. This mode cannot thus use Full Duplex (simultaneous bidirectional communication). Itcan be used on cable of category 3, 4 or 5.
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In 100 base TX, wiring is the same one as in Ethernet bases 10, only the cable must be of better quality (category 5) and the 4 others wiremust be connected according to the colors below. Attention which each "cabler" often uses his own code of colors. The cross cables usethe two same crossings that into 10 base T.

Normal and cross cable RJ45 100 Base TX diagram Normal and cross cable RJ45 100 T4 Base diagram

4.6. Ethernet gigabit.

If at the beginning, the gigabit used an optical fibre connection, it is replaced by a connection of the type RJ45 of class 5e (with alimitation of distance limited to 100 meters). The gigabit uses the same format of screens of data that the 10 Base - T and the 100 BaseTX and the same anti-collision protocol, namely the CSMA-CD (Carrier Sense Multiple Access with Collision Avoidance). This


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standard makes it possible each computer to announce that it will transmit a message before transmitting the data on the network (whatavoids the collisions).

Network adapter INTEL PCI-X 64 bits - 133 MHz

1000 Base SX

(1 Gbit/s on multimode optical fibre (MMF): 500 m)

1000 Base LX(1 Gbit/s on monomode optical fibre (SMF): 3000 m)

1000 Base C(1 Gbit/s out of 4 pairs UTP5: 25 m)

1000 Base T - 1000 Base TX IEEE 802.3 ab ratified on June 26, 1999

1 Gbit/s on cable category 5, transmission out of 4 pairs (250 Mbits/paire) over a 100 meters length)

Nomenclature Speed Outdistance Media

10BaseT 10 Mbps 100m Copper


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100BASE-TX 100 Mbps 100m Copper

100BASE-FX 100 Mbps 412 m2 km

half Duplex Multimode Optical fibreMultimode Full Dumlex Optical fibre

1000BASE-LX 1000 Mbps1000 Mbps

5Km550m

Individual-mode Optical fibreMultimode Optical fibre

1000BASE-SX 1000 Mbps1000 Mbps

550m275m

Multimode Optical fibre (50u)Multimode Optical fibre (62.5 U)

1000BASE-CX(not supported by the industrialapplications standards)

1000 Mbps 25m Copper

1000BASE-T 1000 Mbps 100m Copper

1000 BASE LH 1000 Mbps 70 km Optical fibre

Wiring on twisted pairs of 1000 C and 1000 TX is identical to that of the 100 T4 Base, including for the Ethernet cables cross RJ45.

4.7. Network 10 Giga hertz

Currently in court of development, it should compete with on the lines at high speeds, connections ATM.

4.8. Ethernet Network adapter

One finds in the PC three types of boards networks: 10, 100 and Giga Ethernet. The first boards bases 10 of 3Com used only theconnectors coaxial and a specific connector. Currently, the network adapters 10 MB are connected into coaxial and RJ45. On the other hand, the boards does not base 100 do not use any more but the RJ45.

Consequently, the use of a network into coaxial obliges the use of a board bases 10. As the use of a cable RJ45 requires the use of a concentrator, this one and the boards connected must use the same parameters is of the 10 MBb/s. Concentrators 10 generally include(but not each time) a coaxial connector and the number specific to the concentrator of wiring RJ45. Concentrators 100 allow theconnections with 100 Mb, on some, they also detect boards 10 Mb.


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The networks boards are also characterized by the internal bus used: ISA and PCI. As a recall, there have sometimesincompatibilities between the boards PCI 3.3V and mother board in 5V (old Pentium). Like all boards PC, they are characterized by anaddress and an interruption for which are recognized by the PC. Certain adapter include a socket making it possible to insert Eprom tostart the PC via the network (without hard disk). This solution is used little.

Each Ethernet network adapter in RJ45 includes 2 LED. The first, generally green, announces that the lan is connected on aconcentrator via a cable. The second, orange or green, announce the transmission/reception of data.

The current network adapter make it possible to commutate on each Ethernet speed automatically (10 or 100).

With very rare exceptions (hub and switch the bottom-of-the-range one) , with a board in connected in RJ45 on a concentrator, it(them) LED must ignite on the board and the HUB, Switch, Routeur. As a technician hardware , that means that the accessnetwork is badly parameterized, it is spring of the administrators networks, except if the speed of connection is low.

4.9. Duplex Half and Duplex Full.A Ethernet network adapter can be of type Half Duplex and Full duplex. The boards Half Duplex (normal) cannot emit and

receive at the same time. By counter the boards Full Duplex (and the switch associated) can emit and receive at the same time onchannels (cables) different. This solution makes it possible to double the rate of transfer on the Ethernet network. For example, a board100 bases TX (100 T4 base does not authorize duplex Full) goes authorized a rate of transfer of 200 Mbps for 100 in the duplex casehalf.

It is necessary to slow down the network (to pass into 100 Half mode or even in the event of disturbances network to oblige the board 100 Base TX to work into 10 base T). The parameter setting is done in the parameters networks by using the properties of the

network adapter. Here for example the case of a Ethernet adapter at base of the circuit Realtec RTL8139D (10base T and 100 automatic base TX).


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4.10. Wiring RJ45 Ethernet, rules, problems of connections and tests equipments

Cables RJ45 can be bought done everything. Nevertheless, in professional wiring, they are integrated in chutes, pass throughwalls... The solution consists in buying a grip, the connectors (with protections), the cable and to respect strictly the colors of wiringRJ45 above.

To connect two structures between them by cables brings always various types of problems.

The first remains the maximum conditions of operating. It is trying to put a wire longer than that envisaged by the standard

between Hub (or a switch ) and computer (100 meters for one T bases 10 or 100). First error.

If the cable is bought done everything, connection is generally good. This is valid for the small internal networks but is seldomthe case for the industrial networks. As a tester of wiring network is worth easily the price of a small sporting car, better is worth to cablecorrectly in advance .

Each connection is limited by the number of HUBS in cascade. For a connection 10 bases T, the maximum number between 2stations east of 4. On the other hand, it is 2 into 100 base T
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In the last, cable RJ45 must be correctly posed. Among the encountered problems, one finds:

cable network cut or scratched or folded. more underhand: the cable passes to with dimensions from electric cables which disturb the signal, beside fluorescent tubes or

neon (minimum 50 cm). Proximity of electric motors of strong powers. The table below shows the distances minimum betweenthe cables networks and the electric cables according to the distance.

Spacing enters the cables current strong (electrical supply network, neon) and low current (Ethernet network)

Spacing incm

30 cm

20 cm

10 cm

5 cm

10 m 20 m 30 m 80 m Parallel advance in meters

For a cable RJ45 low length, one could put the electric cables and networks in the same chutes. This would be to forget theelectric safety requirements which prohibit to insert electric cables and telephone (low voltage) in the same chutes, even if it is commonin the suspended ceilings in industries.

One finds on the market various types of apparatuses of tests of the cables networks.

The first network tests equipment type functions like an ohmmeter on 8 lines. It is important that the apparatus can be dividedinto two part (a part of control and a case of termination) to allow the tests of cables posed. These equipments generally make it possibleto detect the right cables and the cross cables as well as other connectors (RJ11, RJ45, USB...). These apparatuses are reliable only up to


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one certain points. It check only if connection is correct, not if the connection is correct. If the apparatus detects an error of wiring, theson is to be started again. If it does not detect an error, that does not mean inevitably that the cable is good. A bad contact will be oftenregarded as good by the tester, but not of connection network.

Here, a test of cross cable. The left part takes again the module of order, the right part, the detachable termination. The 8 Ledabove indicates if the wire individually are correct. In the left part gives indications on connections. Shorts (cable cut or bad connectionon at least a son). CONNECTED which the cable is right. Non-Parrallel which the cable is cross. NO CONNECTION which the cable isnot inserted. The price varies from 100 to 150?.

The second type functions with the manner of a board network. These apparatuses test the line (and not only the wire theapparatus is connected at the end of a cable and tests the connection on a HUB or a switch. In this direction, they are more effective.They are a little more expensive.

The third type of tester network resembles a minicomputer. Does the price return easily to 10.000 and is thus not with therange of everyone. The method of test is identical to that of the first apparatuses. They offer the same possibilities that the apparatuses of the first group but allow moreover:

effective tests of the poor contacts or the cuts on each cable.


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cable length in the event of cut of a son (or of several), the distance to which it is cut. various disturbances which forward on the cable (electric disturbances).

4.11. MAC addressEach network adapter is characterized by a MAC address. This address is single for all the boards networks in the world. It consists of

6 bytes of the type XX.XX.XX.XX.XX.XX or each XX vary from 0 to 255. The address is often given in form hexadecimal. For example 4D.FF.56.D2.AF.26.

In Starts - > to carry out, type order WINIPCFG (present in the Windows repertory under Windows 98) or ipconfig/all in a windowDOS (Windows 2000 and XP) for given the following your board network.

The address Mac FF.FF.FF.FF.FF.FF is particular, the data are sent to the whole of the network. It is the address of Broadcast.

The Ethernet protocol uses this MAC address to make communicate equipment between them via network. When a machine wants tospeak with another, it sends a package on the network, containing the address MAC destination, the address MAC source, the length of the packet, the data and the CRC (Cyclic Redundancy Checking), a control of error...


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The MAC address has priority on address IP. When a communication network was established under Ethernet, order DOS arp - Amakes it possible to find the MAC address of the other PC of the network.

Structure network Exercise: structure of a corporatenetwork: choice of the servers,hub, switch, router, wirelessnetwork.

Web Positionnement

Internet Connection Parameter setting router withfirewall integrated and modemRJ45 in bridge mode

Network introductionIntroduction to local network

The continuation of the course Hardware 2 > Chapter 5: Hub, switch, router...

The Hardware 1 course: computers and peripherals , the Hardware 2 course: network, server and communication

The complete hardware training

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