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Practical TCP/IP and Ethernet Networking- P19

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Practical TCP/IP and Ethernet Networking- P19: The transmitter encodes the information into a suitable form to be transmitted over the communications channel. The communications channel moves this signal as electromagnetic energy from the source to one or more destination receivers. The channel may convert this energy from one form to another, such as electrical to optical signals, whilst maintaining the integrity of the information so the recipient can understand the message sent by the transmitter | 72 Practical TCP IP and Ethernet Networking spreads the laser light evenly over the core of the multimode fiber so the laser source looks more like a light emitting diode LED source. This spreads the light in a large number of rays across the fiber resulting in smoother spreading of the pulses so less interference. This conditioned launch is done in the 1000Base-SX transceivers. The following table gives the maximum distances for full-duplex 1000Base-X repeaters. Wavelength nm Cable Type Bandwidth MHz. km Attenuation dB km Maximum distance m 850 50 125 Multimode 400 3.25 500 850 50 125 Multimode 500 3.43 550 850 62.5 125 Multimode 160 160 220 850 62.5 125 Multimode 200 200 275 1300 50 125 Multimode 500 2.32 550 1300 62.5 125 Multimode 500 1.0 550 1300 9 125 Single mode Infinite 0.4 5000 Table 4.4 Maximum fiber distances for 1000Base-X full-duplex 4.5.2 Gigabit repeater rules The cable distance and the number of repeaters which can be used in a half-duplex 1000Base-T collision domain depend on the delay in the cable and the time delay in the repeaters and NIC delays. The maximum round-trip delay for 1000Base-T systems is the time to transmit 512 bytes or 4096 bits and equals 4.096 ps. A frame has to go from the transmitter to the most remote node then back to the transmitter for collision detection within this round trip time. Therefore the one-way time delay will be half this. The maximum sized collision domain can then be determined by the following calculation Repeater delays Cable delays NIC delays Safety factor 5 bits minimum 2.048 ps The following Table 4.5 gives typical maximum one-way delays for various components. Repeater and NIC delays for your specific components can be obtained from the manufacturer. System Maximum collision diameter point-to-point Half-duplex Maximum collision diameter One repeater segment 1000Base-CX 25 m 50m 1000Base-T 100 m 200m 1000Base-SX or LX 316 m 220 m Table 4.5 Maximum one-way gigabit Ethernet component delays These .