100BaseVG
100BaseVG is a 100 Mbit / s Ethernet standard specified to run more than four pairs of Category 3 UTP wires (known as voice grade, hence the “VG”). It is also called100VG-AnyLAN because it was defined to carry both Ethernet and token ring frame types.
100BaseVG was originally proposed by Hewlett-Packard, ratified by ISO in 1995 and was almost extinct in 1998.
100BaseVG began in the IEEE 802.3 committee as Fast Ethernet. Of this group, CSMA / CD wants to continue to keep the pure Ethernet, even though the collision domain problem limits the distances of up to one tenth of that 10BASE-T. Another faction wanted to change to a polling architecture of the hub (they called it “Demand Priority Protocol”) and to maintain the view to the 10BASE-T distances and also to make a deterministic protocol. The first faction argued that since it was IEEE 802.3 Ethernet committee, it was not the place to develop a different protocol. For example, the IEEE 802.12 committee was formed and standardized 100BaseVG.
100VG-AnyLAN vs. Fast Ethernet
Multiplexing
Instead of following the Fast Ethernet standard for twisted pair cabling with the aid of only two pairs of wires, 100VG-AnyLAN uses all four pairs in either category 3 or category 5 twisted pair cable. The design goals were to prevent radio frequency radiation on the higher frequencies by Fast Ethernet and the existing cabling systems of Category 3 cabling that most organizations had recently installed use up to 10 megabits twisted-pair Ethernet support. This had the added advantage that it is less sensitive to external RF interference, such as other network cables, fluorescent lamps, and high power lines. They multiplexed signal over all the 8 wires thereby to decrease the frequency and makes it more robust. This presented a problem with the early installations borrowed an unused twisted pair telephone traffic, but those plants were uncommon
Deterministic
With Ethernet Fast Ethernet was, continued to use the Carrier Sense Multiple Access with Collision Detection (CSMA / CD) mechanism to manage the traffic on the network. 100VG made to make use of the token passing concept ARCNET and Token Ring made popular in view of consistent performance, no matter how big has become the network. He removed passing the token of the responsibility of the wiring and the network nodes and placed it in the internal 100VG-AnyLAN hubs. These centers include the rotating token never left the hub itself. When sending a node wanted information, it would gain a bit on the hub port that indicates the hub that it was ready. If the token passed by a ready-made hub port, it would then open up traffic to that node. Because the token remained within the hub, it does not have to traverse long cables going to each node as in ARCNET, and Token Ring, therefore, faster and faster than that in other deterministic network standards, and are less prone to problems, network failures, and line interference cabling. Real-life load test showed 100VG-AnyLAN reaching 95% of the theoretical speed of the network instead of about 45% when used as a Fast Ethernet hubs. Fast Ethernet switches were not common primarily because of the high cost and limited availability so, initially, 100VG had a significant performance advantage.
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