HP 100Base-VG AnyLAN
Personal computers have undergone an amazing transformation over the past ten years. True to the high-technology tradition of "smaller, faster, cheaper," today's personal computers are 100 times more powerful and can store 100 times more information than the original IBM PC, yet they cost a fraction of the price and can be found in notebook-size -- even checkbook-size -- packages.
Over this same ten-year period of time, the use of local-area networks has exploded, with Ethernet networks accounting for the vast majority of installations. According to IDC, the number of computers connected by Ethernet alone is expected to reach nearly 20 million by the end of 1992, and more than double to over 40 million nodes by the end of 1995. In addition, the most-widely implemented Ethernet LAN infrastructure is 10Base-T over voice-grade, unshielded, twisted-pair (UTP) cabling.
Software applications, too, have grown in size and sophistication to match -- and sometimes push the limits of -- the increased capabilities of personal computers. Simple character-based command-line interfaces are being supplanted by true graphical interfaces. New, graphical applications are emerging as a result, including high-resolution, "true color" applications that are bringing photographic-quality images to the desktop.
However, while desktop processor performance and storage capacity, as well as the size of the data files generated by the more sophisticated applications, have increased more than a hundredfold, the information carrying capacity of Ethernet LANs has remained essentially constant at 10 megabits per second (Mbps). Although this may provide adequate performance for today's needs, the huge data volumes anticipated for graphical, image-based and multimedia applications threaten to grind these networks to a halt unless a way can be found to boost the LAN's information carrying capacity. Current proposals for high-speed Ethernet networks address only the raw transmission speed part of the problem. They fail to overcome the timing delays inherent in Ethernet's current media access scheme that can seriously affect the performance of the new generation of multimedia applications.
Economic Realities
One of the greatest obstacles facing any new LAN technology is the legacy of installed cabling. Companies today under economic pressure to contain costs, do more with less and extend their current infrastructure by leveraging their existing investment in cabling, backbones and wide-area connections. As a result, most are reluctant to re-cable to achieve higher network speeds, especially when most of their current applications perform adequately. The cost of installing new cabling can run as much as $500 per desktop for installation (plus cable costs), particularly in older buildings and in high-cost areas, not to mention the productivity loss while the changeover is being made.Although the technology for faster networks exists, until now these networks have been very costly to implement. A number of proposals for lower-cost 100-Mbps LAN technologies have emerged from several vendors and standards committees over the past year, but none of these proposals specifically states the support of the current standard 10Base-T wiring. Thus, what these proposals imply is that for most organizations, migrating to future higher performance LANs will require abandoning their significant investments in 10Base-T wiring and incurring costly reinstallations of more expensive cabling.
Benefits
Hewlett-Packard has been researching the characteristics of voice-grade UTP wiring for many years. HP Laboratories provided much of the initial technology behind the original 10Base-T standard for transmitting 10-Mbps Ethernet over voice-grade UTP wiring, and has continued its UTP research, investigating even higher speed approaches to use this medium.Now, HP and AT&T have developed core technologies that will deliver FDDI performance at Token Ring prices. Specifically designed for work group environments, the 100Base-VG AnyLAN approach is capable of providing 100-Mbps throughput over existing voice-grade 10Base-T Ethernet wiring. The 100Base-VG AnyLAN approach builds on the best features of first-generation Ethernet and 10Base-T, adding greatly improved performance under load, guaranteed bandwidth and increased security. 100Base-VG AnyLAN also provides a graceful migration from first-generation Ethernet LANs at significant cost savings compared to other high-speed LAN alternatives.
LAN TECHNOLOGY COST COMPARISON*
10Base-T (10 Mbps) $300 Token Ring (16 Mbps) $600-$800 100Base-VG AnyLAN (100 Mbps) $600-$800 CDDI (100 Mbps) $1500-$2000 FDDI (100 Mbps) $3000
*Estimates. Costs do not include cable installation, estimated at $500/node.At 100 Mbps, FDDI is ten times faster than Ethernet, but it is also ten times as expensive. It requires complete re-cabling with expensive optical fiber. The complex electro-optical network adapter cards for linking computers to the network are very costly, too. While 10Base-T networks typically run about $300 per node, a typical FDDI installation today may cost $3000 per node. The less costly copper-based derivative of FDDI -- CDDI -- may still run between $1500 and $2000 per node, and requires either data-grade UTP or shielded twisted-pair (STP) wiring.
Easy Upward Migration
Most LANs today are implemented using a star topology with intelligent hubs, or concentrators, managing individual connections to the desktop. A building- or campus-wide backbone system links these individual star clusters into an integrated network. HP and AT&T have carefully designed their 100Base-VG AnyLAN approach to fully support the existing 10Base-T wiring specifications, including full cable distances, cable bundles and connectors. No new cable needs to be installed. As a result, migrating an existing 10-Mbps 10Base-T Ethernet LAN installation to a 100-Mbps LAN becomes a simple two-step process.First, in the wiring closet, a new, high-speed LAN concentrator module is installed and connected to the existing backbone wiring. The existing 10Base-T cables are unplugged from the old concentrator and plugged into the new one as needed. Second, high-speed 100Base-VG AnyLAN LAN adapters and drivers replace the ones in each workstation being upgraded, reconnecting to the same 10Base-T cable.
100Base-VG AnyLAN networks can easily connect to existing first-generation Ethernet networks using a speed-matching bridge. They can also be connected to 100-Mbps FDDI backbones using either an encapsulating bridge or a router. Token Ring backbones or subnets can also be easily connected through a router. A broad range of backbone architectures are possible, including FDDI backbones and "collapsed" backbones implemented using routers. If necessary, 100Base-VG AnyLAN work group LANs can be connected into an organization's existing infrastructure of 10-Mbps Ethernet and 16-Mbps Token Ring backbones.
Migration can be easily phased in by individual workstation or entire work groups, facilitating a flexible, graceful and gradual changeover as performance demands and budgets require. LAN administrators and MIS directors will appreciate that their current investments in 10Base-T wiring are preserved. 100Base-VG AnyLAN is as an excellent foundation for the high-speed LANs of the years to come. At the same time, their migration to this future high-speed LAN is simplified, lowering the overall cost of increasing the performance to their end users.
Quartet Signalling
100Base-VG AnyLAN's breakthrough quartet signalling transmission technology will deliver 100-Mbps performance with the reliability, robustness and immunity from noise of today's 10Base-T Ethernet networks, yet it is elegantly simple and efficient. Unlike the original 10Base-T, which uses one twisted pair of wires for transmitting data and another for receiving, quartet signalling technology uses all four pairs of wires simultaneously to transmit or receive information.Quartet signalling technology dramatically reduces the signal frequencies needed to carry data at 100 Mbps. As a result, 100Base-VG AnyLAN networks avoid the radio frequency emission and interference problems that have hampered earlier approaches to transmitting high-speed data over UTP. In fact, when combined with TuboBase-T's advances in encoding techniques, the 100-Mbps 100Base-VG AnyLAN approach utilizes essentially the same frequency range (1-16 MHz) as today's 10-Mbps 10Base-T Ethernet (0-15 MHz).
Demand Priority Access
First-generation Ethernet required significant intelligence at each node to manage access to the shared media of a bus topology network. The star topology found in most of today's Ethernet installations, however, reduces the "shared media" of the network to the internal bandwidth of the hub. As a result, very little intelligence is actually needed to manage the simple node-to-hub links, and contention for the shared bandwidth of the hub can be managed internally within the hub itself.Demand priority access, the second major technology advance in 100Base-VG AnyLAN, takes advantage of the star topology's simple point-to-point links. Demand priority access leverages the centralized intelligence within the hub to shift the burden of managing network access from the nodes to the hub. It also dramatically reduces the complexity and cost of workstation LAN adapters.
With demand priority access, a computer transmitting data packets over the network first indicates its request to the intelligent hub. At the same time, the computer indicates the priority of its request as either normal or high priority. The hub, acting much like an intelligent packet switch, acknowledges requests from the attached nodes as they are received. The computer then transmits its packet to the hub, and the hub immediately directs the packet on-the-fly to the appropriate destination based on the address information contained in the packet.
If more than one request is received simultaneously, the hub recognizes the higher priority request first. In this way, packets are shuttled from source to destination with low latency and minimal delay. Any notion of packet collisions is avoided.
Guaranteed Bandwidth
Demand priority access enables the overall throughput of a 100Base-VG AnyLAN network to approach 100 percent of the full media bandwidth. First-generation Ethernet networks begin to show performance degradation at utilization levels as low as 35 percent of the theoretical bandwidth due to the statistical nature of their CSMA/CD access technique. The throughput of HP's 100Base-VG AnyLAN with demand priority access increases uniformly until the hub itself reaches saturation, when the hub is switching packets back-to-back continuously.With demand priority access, the hub can provide virtually guaranteed bandwidth to critical applications when it receives a high-priority transmission request. Regardless of other normal-priority traffic, the hub will acknowledge and pass high-priority packets as they are received. By controlling the number of nodes requesting high-priority access, high-bandwidth multimedia and interactive video applications, for example, are ensured a continual stream of information between source and destination regardless of other traffic or events on the network, up to the full bandwidth of the network.
Enhanced Security
Because demand priority access utilizes the hub as a packet switch rather than a repeater, conversations between an originating node, the hub and a destination node are not broadcast to any other nodes. As a result, demand priority access automatically provides a level of link privacy that prevents eavesdropping from any other device connected to another network port. This contrasts sharply with first-generation Ethernet and Token Ring networks, where transmissions are broadcast to multiple network nodes in addition to the intended destination.
Commitment to Standards
HP contributes to the development of national, multi-national and international standards by providing expertise, maintaining a leadership role and ensuring the continuity of networking and other industry standards activities worldwide. Since HP proposed the original 10Base-T standard to the IEEE five years ago, the technology has become the preferred choice for LANs, with more than 10 million nodes currently installed worldwide.More than 200 HP people in 83 divisions worldwide participate in standards development programs. More than 50 of these serve as officers in many of the 339 different standards organizations to which they belong.
HP serves a leadership role in the developemnt of national and international standards. The company works closely with the major standards organizations, including the American National Standards Institute (ANSI), the German National Standards Institute (DIN), the Institute of Electrical and Electronic Engineers (IEEE), the International Standards Organization (ISO) and the International Telegraph and Telephone Consultative Committee (CCITT), among others.
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