n/ns (inches per nanosecond). Another method com- monly used to express the flow of electrons or photons is to calculate the number of nanoseconds that an electron or photon requires to traverse a meter. This is usually expressed as the inverse of the VoP (V-1), and for electrons in category 5 cable, this is approximately 5 ns/m. If we apply the preceding metric to a 100BASE-T LAN, we would obtain a value of approximately 127 m for the permissible network diameters, which is 27 percent above the 100 m specified by the stan- dard. The reason for the difference is that the prior computations did not examine other delay factors to include the repetition of a signal entering one port on a hub to the other ports on the hub and the time for an adapter to recognize a collision. Although the preceding compu- tations were not fully comprehensive, they illustrate that the speed of electrons through copper is a key governing factor for an achievable network diameter. FIBER-OPTIC MEDIA In a fiber-optic environment the speed of photons through the fiber is significantly higher. For example, for multimode fiber photon flow is approximately 3 ns/m. This is 40 percent beyond Fiber in the LAN the flow of electrons in a copper cable and expands the network diame- ter. Thus, you can use fiber-optic cable to connect stations on a LAN at a considerable distance beyond the 100 m allowed for 10BASE-T and 100BASE-T copper-based-medium LANs. One of the most popular devices that permits an extension of the diameter of a 10BASE-T or 100BASE-T Ethernet LAN is referred to as a LAN extender. The actual net- work diameter achievable depends on several factors. Those factors include the type of optical transmitter and detector used by a pair of extenders as well as the optical cable used to interconnect extenders. LAN Extenders There are several types of LAN extenders, each designed to convert an electrical signal to an optical signal for transmission over a specific type of fiber. For example, one popular extender converts 10BASE-T to multimod