HIPPI technology delivers standard gigabit networking

HIPPI technology delivers standard gigabit networking

Available, affordable and interoperable, Serial HIPPI provides gigabit networking and can serve as a bridge to future infrastructures

bill boas

essential communications

Several network transmission technologies promise gigabit local area networking, but at present High-performance Parallel Interface (HIPPI) is the only one based on standard, proven fiber-optic and communications technologies that are available and affordable. Moreover, HIPPI provides interoperability with other existing technologies and can serve as a high-speed backbone for existing networks.

With the development and release of Serial HIPPI network interface cards (NICs), all the parts are available for creating end-to-end super-fast local area networks, or "super-LANs." These cards provide fiber-optics-based Serial HIPPI connectivity, delivering gigabit transmission rates for various bus architectures.

In addition, current HIPPI technology can function as a bridge to future technologies such as Fibre Channel, Asynchronous Transfer Mode (ATM), Super HIPPI (or HIPPI-6400) and gigabit versions of Ethernet.

Fibre Channel technology provides gigabit-per-second rates, but most Fibre Channel offerings today focus on peripheral connectivity. ATM products for local area networking currently operate at 155 megabits per second, and ATM products that provide 622 Mbits/sec might reach the marketplace this year (see "Status of ATM, Fibre Channel and HIPPI Technologies" below). Beyond these technologies, two versions of gigabit Ethernet-- Gigabit 100Base-T and Gigabit 100VG--are currently being defined by IEEE standards bodies.

HIPPI and fiber

HIPPI technology was conceived and developed in the late 1980s as a standard for supercomputer connectivity. The goal was to provide robust, high-speed communications between mainframes, workstations and peripheral data, video and audio devices. Over the years, as supercomputing power moved onto the desktop, HIPPI products and networks moved out of the laboratory and into the commercial marketplace. Today, several companies supply HIPPI switches, interface cards, network analyzers and signal extenders, and numerous workstation and computer vendors offer HIPPI interface options. At present, HIPPI furnishes reliable, high-speed local area networking at scientific and business sites worldwide.

A HIPPI link provides point-to-point simplex data transfers at 800 Mbits/sec; a single HIPPI connection consists of both an incoming and an outgoing link. Each connection can, therefore, provide dual-simplex or full-duplex operation at 1600 Mbits/sec. Originally, HIPPI cables contained 50 twisted-pair copper wires. These cables were about 0.5-inch in diameter, unwieldy, and limited to 25 meters in length.

The original framers of the HIPPI standards would have preferred to specify use of optical fiber, but in 1987, fiber-optic technology was judged to be immature for high speeds. Moreover, some components, such as serial encoder/decoder chips, were expensive or unavailable. However, the HIPPI standards committee recognized that fiber-optic technology would mature, increasing its applicability to networking in general and to HIPPI in particular. The standards committee, therefore, also defined a fiber-optics-based version of HIPPI, which is known as Serial HIPPI.

Serial HIPPI

HIPPI was proposed to the American National Standards Institute (ANSI) as a networking standard in 1987. The International Organization for Standardization (ISO) approved HIPPI for gigabit-per-second data transmission in the early 1990s. The emergence of Serial HIPPI in the early to mid-1990s was based on the advent of affordable and available fiber-optic technology. For example, the short-wavelength lasers used in compact-disc players represent easily obtainable and inexpensive optical sources for Serial HIPPI applications. Plus, the same lasers are specified for the emerging ATM and Fibre Channel standards, which is expected to translate into increased manufacturing volumes and result in declining costs and even more affordable gigabit LANs.

Serial HIPPI provides a signaling rate of 1.2 Gbits/sec (data payload is 800 Mbits/sec) over standard fiber-optic cable. An incoming and an outgoing fiber constitute a complete Serial HIPPI connection. Use of both singlemode (8- to 10-micron) and multimode (50- and 62.5-micron) fiber is defined.

With the use of short-wavelength (760- to 870-nm) lasers, network signaling distances are extended to 300 meters over 62.5-micron fiber, and to 500 meters over 50-micron fiber. With the use of long-wavelength lasers (centered at 1310 nm), the network signaling distance over 62.5-micron multimode fiber in increased to 1 kilometer, and to 10 km over singlemode fiber. (Note that the Serial HIPPI standard also provides for use of copper coaxial cables over short distances--such as intracabinet runs--although no such products are currently available.)

Other key capabilities of the HIPPI standard include the following:

Connect/set-up latency is less than 500 nanoseconds.

Transmission Control Protocol/Internet Protocol (TCP/IP) support provides interoperability with other network technologies.

Framing Protocol allows unlimited-size packets.

Size of IP packets is variable (to 64 kilobytes).

Intelligent Peripheral Interface-3 packets can be any size.

20B24B line-signal encoding allows loss-free transfers.

With out-of-band hardware flow control, the bit error rate is better than 10-12.

Physical-layer error reporting uses byte parity and parity-based checksums.

Building a super-LAN

All the parts needed to structure a gigabit super-LAN--switches, NICs and gateways or routers to other technologies--are available and affordable (see Fig. 1). The star topology is easily expandable. Network capacity can be added in stages by simply plugging in another media interconnect card (MIC). Each additional connection increases network bandwidth and improves network performance without increasing congestion, as would occur with ring or loop topologies.

The HIPPI standard specifies nonblocking crossbar switches. The switch connections are independent and capable of operating simultaneously. Available switches provide as many as 32 ports (for an aggregate bandwidth of 51 Gbits/sec). The nonblocking architecture always allows transmission between available devices, thus avoiding the buffering delays experienced with alternate approaches to switching.

Three types of MICs are available: parallel HIPPI, short-wavelength Serial HIPPI and long-wavelength Serial HIPPI. All the cards provide an incoming and an outgoing link. Card costs have dropped markedly over the past two years. For example, prices for parallel MICs are about $2000 per port, and for serial MICs range from $2900 (short wavelength) to $5800 (long wavelength). On a megabit-per-second basis, prices range from $2.50 to $7.25.

Workstation and server bus speeds are currently an order of magnitude greater than the signaling rate of both Fiber Distributed Data Interface (FDDI) and Fast Ethernet networks. For example, the peripheral component interconnect (PCI) bus rate is 1056 Mbits/sec, versus 100 Mbits/sec for FDDI and Fast Ethernet. By bringing gigabit data rates to the desktop, Serial HIPPI cards close the gap between network speed and that of current client/server equipment.

Serial HIPPI NICs are available for nearly all the major bus systems. Most of these cards use a single-slot, single-board design that integrates both source and destination ports. In advanced designs, a custom application-specific integrated circuit is incorporated on the card to manage data translation, buffering and host-to-network transfer (see Fig. 2).

The cost of a Serial HIPPI-PCI adapter card ranges from $2000 to $3000, which is comparable to the prices of many current low-speed NICs. However, in terms of price-per-megabit, the Serial HIPPI card is significantly less expensive than other fiber-optics-based NICs.

Gateway devices provide routing to FDDI, Fast Ethernet and ATM local area networks, as well as to Synchronous Optical Network wide area network connections. Gateways are being developed that will "tunnel" channel commands and data between the network and storage devices, such as tape-cartridge drives that use communications protocols such as Small Computer System Interface (SCSI-2).

HIPPI applications include entertainment production (film, video and broadcast), automotive and aeronautical design, seismic exploration, medical imaging, banking, and government and university communications research. Facilities with HIPPI network installations include Disney, Ford, Boeing, Schlumberger, TRW, NASA, the U.S. Navy, the University of Stuttgart and the Massachusetts Institute of Technology. Gigabit networking applications are expected to expand at an accelerating rate as gigabit technology becomes increasingly cost-effective for smaller organizations. u

Bill Boas is president and chief executive of Essential Communications in Albuquerque, NM.

Status of ATM, Fibre Channel and HIPPI Technologies

Three standards-based technologies--Asynchronous Transfer Mode (ATM), Fibre Channel and High-performance Parallel Interface (HIPPI)--are touted as being capable of serving as the next generation of gigabit local area networks while being compatible with existing networking infrastructures.

Asynchronous Transfer Mode

ATM technology currently provides 155-megabit-per-second transmission rates, placing it in essentially the same speed category as Fiber Distributed Data Interface (FDDI) and Fast Ethernet. Beyond that rate, the next ATM standard (OC-12 at 622 Mbits/sec) is still in development, so local area network products for this speed are not yet commercially available.

ATM was originally designed to simplify and standardize international telecommunications and has become an accepted standard for wide area networks (WANs). The ATM Forum standards group is currently working to adapt the technology to the requirements of local area networks. However, completion of this standards effort (and agreement between various vendors on interoperability issues) appears to be several years away. Furthermore, software and hardware upgrades will probably be necessary to take advantage of forthcoming ATM advances.

Fibre Channel

Although a gigabit-per-second technology providing a signaling rate of 1.062 Gbits/sec, Fibre Channel, too, is still considered in the development stage; that is, standards, architectures and connections for it are still being defined. In fact, differing sets of standards are being presented. Whereas storage device vendors have settled on a standard (for example, Arbitrated Loop), the networking community as yet has not. As a result, interoperable networks cannot be built with currently available products.

Basically, Arbitrated Loop defines a ring topology, which means adding users increases congestion and reduces the bandwidth available to each user. This approach tends to make the standard less acceptable in situations where consistent high-bandwidth networking is desired. At present, Fibre Channel is an appropriate technology for attaching storage devices to computers--the use for which it initially was intended.

HIPPI

HIPPI was originally developed in 1987 for supercomputer connectivity (and today`s workstations are nearly the equivalent of the supercomputers of a few years ago). It is now a proven, fully standard technology, with currently available switches representing the fifth generation. Serial HIPPI provides a signaling rate of 1.2 Gbits/sec over distances to 10 kilometers. HIPPI implements nonblocking switching and variable packet sizing. HIPPI switches, network interface cards, storage devices, and routers to other network technologies are commercially available.

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