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High Speed Networking

What are my choices for high-speed networking?

Switched Ethernet
Switched Ethernet relies on centralized multiport switches to provide a physical link between multiple LAN segments. Inside each intelligent switch, high-speed circuitry supports wire-speed virtual connections between all the segments for maximum bandwidth allocation on demand. Adding new segments to a switch increases the aggregate network speed while reducing overall congestion, so Switched Ethernet provides superior configuration flexibility. It also gives you an excellent migration path from 10- to 100-Mbps Ethernet because both segments can often operate via the same switch.

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
  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
100BASE-FX   Duplex Multimode or Single-Mode Fiber Duplex Multimode Fiber
Maximum Cable Segments
  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.


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.

Benefits of ATM
Networks are extremely versatile. An ATM network can be treated as a single network, whether it connects points in a building or across the country. Its fixed-length cell-relay operation, the signaling technology of the future, offers more predictable performance than variable-length frames. And it can be integrated into an existing network as needed without having to upgrade the entire LAN.


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