Network+

Скачать в pdf «Network+»


100BaseTX The implementation of 100BaseT that is simply a faster version of 10BaseT. It uses two UTP pairs (four wires) in a Category 5 UTP cable (or Type 1 STP).


100BaseT4 The implementation of 100BaseT that runs over four pairs


(eight wires) of Category 3, 4, or 5 UTP cable.

100BaseVG


This 100-Megabit Ethernet replacement came from HP, and in the popularity race, it lost. Even the name wasn’t settled upon, so you may find it referred to as VG LAN, VGAnyLAN, or AnyLAN. Although it used UTP cable, it didn’t follow the popular Ethernet standard. It attempted to improve on Ethernet by using collision avoidance as a method of controlling network traffic.


You will see details on Ethernet and several methods of handling traffic in chapters throughout this book. The point here is that the 100BaseVG standard was not compatible with 10BaseX and Ethernet. The combination of its incompatibility and its actually less than 100Mbps throughput (due to its media access method, which is discussed elsewhere in this book) ultimately spelled its demise. However, it was basically 100Mb, and it was out the door early in the game. Because some companies implemented this standard, you need to know about it.

Fiber-Optic Cable


Because fiber-optic cable transmits digital signals using light pulses rather than electricity, it is immune to EMI and RFI. You will find a complete discussion of these terms in Chapter 6, but you should know at this point that both could affect network performance. Anyone who has seen UTP cable for a network run down an elevator shaft would, without doubt, appreciate this feature of fiber. Light is carried on either a glass or a plastic core. Glass can carry the signal a greater distance, but plastic costs less. Regardless of which core is used, there is a shield wrapped around it, and it is surrounded by cladding, which is more glass that refracts the light back into the core. This is then wrapped in an armor coating, typically Kevlar, and then sheathed in PVC or Plenum.

Скачать в pdf «Network+»