Benefits of Switched Ethernet
It's a cost-effective technique for increasing the overall network throughput and reducing congestion on a 10-Mbps network. Other than the addition of the switching hub, the Ethernet network remains the same—the same network interface cards, the same client software, the same LAN cabling.

100BASE-T (IEEE 802.3u)
100BASE-T retains the familiar CSMA/CD media access technique used in 10-Mbps Ethernet networks. It also supports a broad range of cabling options: two standards for twisted pair, one for fiber. 100BASE-TX supports 2-pair Category 5 UTP or Type 1 STP cable. 100BASE-T4 uses 4-pair Category 3 or 4 cable. And 100BASE-FX supports fiber optic links via duplex multimode fiber cable.

Benefits of 100BASE-T
It retains CSMA/CD, so existing network management systems don't need to be rewritten. It can easily be integrated into existing 10-Mbps Ethernet LANs, so your previous investment is saved. It's also backed by hundreds of manufacturers in the high-speed networking industry.

100VG (IEEE 802.12)
100VG uses an encoding scheme called Quartet Signaling to transmit data simultaneously over all four pairs in the network cable, so it achieves a full tenfold increase in transmission speeds over 10BASE-T. It also replaces the CSMA/CD media access control protocol with Demand Priority to optimize network operation and eliminate the overhead of packet collisions and recovery. Demand Priority works like this: The hub directs all transmissions, acknowledging higher-priority packet requests before normal-priority requests. This effectively guarantees bandwidth to time-sensitive applications like voice, video, and multimedia applications.

Benefits of 100VG
It uses a transmission frequency very similar to traditional Ethernet, works on any conventional cabling system (Category 3, 4, or 5 UTP, Type 1 STP, and fiber optics), and uses the same connectors. In addition, 100VG may soon support Token Ring networks—a potential advantage over its rival standard 100BASE-T.

100-Mbps Ethernet Standards
		100BASE-T (IEEE 802.3u)				100VG (UEEE 802.12)
Variations of this Standard		100BASE-TX 100BASE-T4 100BASE-FX				IEEE 802.3 Ethernet Framing IEEE 802.5 Token Ring Framing (Pending)
Supported Cable Type		100BASE-TX		Category 5 (2-Pair)
		100BASE-T4		Category 3 or 4 (4-Pair)		Category 3, 4, or 5 (4-Pair)
		100BASE-FX		Duplex Multimode or Single-Mode Fiber		Duplex Multimode Fiber
Maximum Cable Segments (Hub-to-Node)		100BASE-T4		Category 3 or 4—100 m		Category 3, 4, or 5 (4-Pair)—100 m Multimode Fiber—2 km
		100BASE-TX		Category 5—100 m
		100BASE-FX		Multimode Fiber—2 km Single-Mode—10 km
Best Applications		Backbone using Ethernet switches to provide increased throughput. Small to medium workgroups using applications (i.e. CAD, CAM) that output huge data files.				Networks using extremely time-sensitive data such as videoconferencing or multimedia.

ATM
Asynchronous Transfer Mode (ATM) is a cell-based fast-packet communication technique that supports data-transfer rates ranging from sub-T1 speeds (less than 1.544 Mbps) up to 10 Gbps. Like other packet-switching services (Frame Relay, SMDS), ATM achieves its high speeds in part by transmitting data in fixed-size cells and dispensing with error-correction protocols. Instead, it relies on the inherent integrity of digital lines to ensure data integrity.