or simply as 2ts in Objective-C

Create QR-Code in Objective-C or simply as 2ts

This means that the one-way slot time of 512 bits represents half the maximum delay before the network experiences late collisions Thus, the one-way delay must be doubled to 1024 bit times, which results in an engineering design constraint While an Ethernet or Fast Ethernet

Figure 58 The Ethernet and Fast Ethernet network diameter is a function of the propagation delay between the two stations farthest apart on the network

network will not collapse when this design constraint is exceeded, late collisions will increase Because collisions result in the execution of a random backoff algorithm, this adversely effects throughput and explains why you should observe network standards USING THE VELOCITY OF PROP AGATION We can use the velocity of propagation (VoP) to determine the effect of the slot time constraint on the network diameters of Ethernet and Fast Ethernet networks The velocity of propagation represents the speed of a signal traveling down a cable as a percentage of the speed of light in a vacuum The speed of light in a vacuum is 186,000 mi/s (miles per second) or approximately 300,000,000 m/s (meters per second) This is equivalent to 03 m/ns or 300 m/ s

COPPER MEDIA In a copper-medium environment the VoP represents 60 to 70 percent of the speed of light in a vacuum For category 5 cable, which is used primarily by Ethernet and Fast Ethernet, the VoP is 69 percent of the speed of light in a vacuum This means that an electrical signal travels along a category 5 cable at 03 m/ s 69 or approximately 021 m/ns For anyone accustomed to thinking in feet, this is equivalent to approximately 8 in/ns (inches per nanosecond) Another method commonly 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 standard 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 computations 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

the flow of electrons in a copper cable and expands the network diameter 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 network 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

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 multimode fiber, extending the transmission distance of the LAN to over 2 km Figure 59 illustrates the use of a pair of 10BASE-T multimode fiber extenders Note that in this example one extender is attached to the port of a hub and uses fiber to enable a remote LAN user to join the LAN even though it is outside the 100-m diameter of the network