Wireless Ethernet Vs FDDI PDF

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Wireless Ethernet Vs FDDI Summary...

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Compare and contrast the network configuration of Wireless Ethernet and FDDI. Network configuration is defined as a combination of access methodology, logical & physical topology as well as media used. Below is an outline and comparison of FDDI and Fast Ethernet in terms of network configuration Access methodology This is how a node gets access to the network and is entered by the network interface card. Wireless Ethernet uses use carrier sense multiple access with collision avoidance (CSMA/CA). With CSMA/CA, computers listen before they transmit and if no one else is transmitting they transmit. Wireless Ethernet attempts to avoid collisions to a greater extent than traditional Ethernet. CSMA/CA can use two approaches simultaneously to media; physical carrier sense method and virtual carrier sense method

FDDI uses an extension of token passing know as modified token passing. This has advantages over traditional token passing in that there can be several frames circulating on the ring at once. Permission (tokens) is still needed to access the network but unlike token passing the token is actually removed from the ring for a predetermined amount of time and the node transmits as many frames as possible for the length of time Logical Topology This refers to how the message is passed around the network, once access has been gained. Wireless Ethernet use a logical bus topology. In this type of logical topology the LAN delivers the signal generated by a transmitter to all attached devices. This is a true broadcast environment; no attached end device is required to regenerate a signal in order for other devices to receive it. In other words, the various nodes hear it and look to see if the data is for them. If so they keep the data if not- they ignore the data FDDI uses totally different logical topology. The type of logical topology that FDDI uses is called sequential. This means that messages are sent sequentially around the network in a clockwise manner unless otherwise changed by the admin. As the physical topology for FDDI is usually a dual counter rotating ring, the first primary ring is clockwise and the secondary is anti-clockwise by default Physical Topology This refers to the physical layout of the network. The three basic topologies used in computer networks are bus, star and ring. The physical topology used by Wireless Ethernet is the star topology. In a star topology separate cables connect each computer top a central switch or hub because each computer uses a separate cable, the failure of a network connection affects only the single machine involved. The other computers can continue to function normally. The only difference is that in a wireless Ethernet, a central wireless access point (AP) is a radio transmitter that plays the same role as a hub in traditional Ethernet. All devices in the WLAN use the same radio frequencies so the

WLAN use the same radio frequencies so the WLAN functions as a shared media LAN in the same manner as traditional Ethernet This is in contrast to FDDI, who use an entirely different physical topology. The physical topology for FDDI is usually a dual counter-rotating ring. In this type of topology, there us two rings, a primary outer ring and on inner secondary ring. If the primary ring fails, the secondary ring takes over in an anticlockwise motion. The use of a star topology here is known as a dual ring of trees Media Choice Media choice refers to type of wiring or cabling that acts as a network transmission medium that carries signals between computers. FDDI uses far more advanced fibre optic cables. In fibre-optic cable, optical fibres carry digital data signals in the form of modulated pulses of light. Fibre-optic cable is good for very high-speed, high-capacity data transmission because of the purity of the signal and lack of signal attenuation, with speeds of at least 100mbs This is in complete contrast to Wireless Ethernet where the computers on the WLAN have a network interface card inside the computer that is connected to an external transmitter that communicates with the access point. The external transmitter transmits radio signals to a receiver that acts like a network hub and enables wireless computers to communicate with each other and with traditional wired networks. Usually a set of access points are installed, so that there is complete wireless coverage in some area, enabling user to roam from access point to access point...