High-performance parallel interface outraces technology counterparts

High-performance parallel interface outraces technology counterparts

Although not as well-known as other fiber optics technologies, the high-performance parallel interface--or Hippi standard--delivers networking capabilities that run three times faster than Fibre Channel and 10 times faster than fiber distributed data interface

Don Tolmie

Los Alamos National Laboratory

DON Flanagan

HIPpi Networking Forum

Essentially a data channel pipeline with switching capabilities, high-performance parallel interface technology is an American National Standards Institute computer channel standard that handles gigabit bandwidths. Although out-publicized by other fiber optics technologies, Hippi outclasses most of them in carrying very high-speed data rates and performs reliably and cost-effectively in concert with them.

Additional ANSI standards support the use of Hippi for networking, and an implementors` agreement delineates a serial physical standard for Hippi over fiber-optic cables. Delivering gigabit data rates and a connection-oriented physical layer allows Hippi to work efficiently with local-area network and wide-area network technologies such as Ethernet, synchronous optical networking, asynchronous transfer mode, Fibre Channel and fiber distributed data interface, as well as with the standard transmission control protocol/Internet protocol and intelligent peripheral interface protocol.

In general usage, Hippi serves in backbone data center networks, performs internetworking, accesses mass storage devices and clusters workstations and processors. It can be used to construct a complete network fabric of switches, network interface cards, serial extenders, routers, bridges, analyzers and test equipment. Moreover, it can connect supercomputers, workstations, parallel processors, mass storage devices and frame buffers.

Specific applications abound for Hippi technology. Current uses include animation and special movie effects, medical imaging, seismic energy analyses, pharmaceutical molecular modeling, aerospace fluid dynamics, structural automotive analysis and electronic component design.

In the past, Hippi networks were expensive and therefore confined primarily to supercomputer environments and their associated storage and display devices. But recent products have dramatically decreased the cost per switch port from $15,000 to $2000. Moreover, affordably priced fiber-optic interfaces for switches and network interface cards are available. As a result, the gigabit stream power of Hippi technology is being focused on internetworking and client/server applications.

Mature technology

Hippi is a mature, stable technology supported by demonstrated interoperability and a variety of products. It provides a simple, elegant network solution characterized by strong flow control and high throughput. Hippi is expected to be interconnected with other lightwave networking technologies, such as ATM, Fibre Channel and Sonet, to meet the increasing need for high-bandwidth local- and wide-area networking solutions.

When Hippi was initially proposed, the associated X3T9.3 ANSI committee planned for a wideband data channel, few or no options, no new technology developments and no new silicon components. Because of this simplified design approach and the economies of using existing components, products incorporating Hippi interfaces were quickly developed, marketed and installed during the late 1980s. These products and their second-generation successors in the 1990s are available from about 65 vendors for use with computers, peripherals and networking equipment.

The salient features of Hippi suit many applications that cannot currently be handled by other standard networking technologies.

Very high-speed data transfer rates--0.8 or 1.6 gigabits per second. The network runs faster than the attached hosts, thereby eliminating bandwidth bottlenecks

Point-to-point simplex connections, with two connections used for duplex communications

Physical layer flow control enables the direct attachment of storage devices and ensures reliable data flow between fast and slow computers

Straightforward signaling sequences

Support for both serial and parallel media

Use of twisted-pair copper wire for short distances (25 meters), fiber-optic cable for campus or metropolitan environments and Sonet or ATM technology for longer geographical distances

Use of standard TCP/IP and IPI-3 upper-layer protocol

Known as X3T11, Hippi-Serial--an addition to the original standards under review by the ANSI committee--is slated to function as a transparent extension cord for Hippi or as a native interface without an intervening Hippi-Physical Layer. It is based on the Hewlett-Packard G-Link integrated circuit. Its serial rate is 1.2 gigabaud, and it provides either a data rate of 800 megabits per second or 1600 Mbits/sec with two serial links.

The draft standard specifies support for distances to 10 kilometers on singlemode fiber using a 1310-nanometer laser. Network demonstrations have been run successfully over distances to 43 km. Specifications are being added for short-wavelength lasers and multimode fiber to extend operations to distances exceeding 300 meters.

The Hippi-Physical standard defines a connection-based protocol and addressing scheme for networking. With the development of crosspoint switches allowing non-blocking connections among several sources and destinations, hundreds of nodes could be connected through a series of cascaded switches.

Like switches used in Fibre Channel, ATM and a telephone central office, the Hippi switch is circuit-based. Multiple concurrent conversations are possible with any combination of input and output ports. Hippi switches come in varying port sizes, from 4 ports to 32 ports and more.

In addition to crosspoint switches, the suite of available Hippi products encompasses the following:

Network interface cards for workstations and personal computers using PCI, Eisa, Sbus, VME and Micro Channel interface standards

Storage devices--high-performance redundant array of independent disks, tape, and solid-state direct access storage device

Mainframe and supercomputer channels

Routers, allowing communications with other LAN and WAN media

Hippi-Serial fiber extenders that stretch the effective distance of a Hippi LAN to 10 km and beyond

Hippi-Sonet bridges and Hippi-ATM gateways, providing wide-area connectivity at speeds of optical carrier, level 3c and OC-12c

Network testers

Frame buffers, for capturing and displaying flicker-free, high-resolution color video

Embedded system interconnections

Devices for data acquisition and telemetry.

Functional applications

From a networking perspective, Hippi has proved to be the backbone of choice in high-performance data centers, connecting workstations, supercomputers, Raid storage devices and random access memory disks, as well as providing interconnections to legacy LANs such as FDDI, Ethernet and wide-area links.

For example, Hippi was installed as the backbone technology at the Supercomputing `94 conference in Washington. The network consisted of 18 miles of multimode fiber interconnecting 16 exhibitors. It demonstrated an aggregate bandwidth of 92 Gbits/sec, making it the world`s first all-fiber-optic multigigabit computer network. Connections were also made to an FDDI LAN, and external connections provide service to the Internet. In operation, the Hippi network transferred high-resolution color images from a supercomputer running through a frame buffer to a display monitor. Each image represented 12 to 16 megabytes of data, which were continuously displayed at a rate of 2 to 3 per second, making for a throughput of at least 24 megabytes per second.

As other high-speed LAN and WAN technologies emerge and stabilize, Hippi is expected to play a major internetwork role, such as with Fibre Channel, ATM and Sonet. The objective is improved interoperability through the provision of a rich set of internetworking capabilities.

Fibre Channel is under the direction of the same ANSI committee--now known as X3T11--that oversees Hippi. Fibre Channel was conceived as more scalable, feature- and option-rich than Hippi, and it was to be exclusively serial and primarily fiber-based. In sharp contrast to Hippi`s simplicity, the Fibre Channel standard is marked by complexity.

Fibre Channel works with four data rates, three kinds of media, four transmitter types, three distance categories, three classes of service and three fabrics. Its complexity has contributed to delays in product development. Moreover, available products generally run at a data rate of 200 Mbits/sec (266-Mbit/sec signaling rate)--a quarter of the standard`s highest rated speed. Like Hippi switches (and ATM), but unlike shared-media technologies like Ethernet and FDDI, Fibre Channel switches are circuit-based and non-blocking. Its bandwidth equals the number of ports times the port speed.

Hippi and ATM

Switched Hippi connections differ markedly from the multiplexed 53-octet ATM cells over several media and bus-based switches. ATM has found the most interest in networks running at 25, 155 and 622 Mbits/sec. Although these networks meet the needs of many users, they do not satisfy the need for gigabit transfers of data and images. Typical ATM switches have an aggregate bandwidth to 3.2 Gbits/sec, whereas current Hippi switches have an aggregate bandwidth ranging from 12.8 to 25.6 Gbits/sec.

Some industry analysts are predicting that ATM will displace Hippi. However, Hippi`s parallel interface with ready-resume flow control suits the attachment of storage devices to the network. Presently, there are no proposed standards for direct peripheral attachments to ATM networks. Without high-performance host and storage attachment, ATM cannot provide very high-speed access to computer and storage access. Realistically, therefore, Hippi stands as the best available choice for gigabit networking for the next few years. In addition, there is no provision in the ATM standard for the direct attachment of storage peripherals to a network. It seems likely, therefore, that Hippi will continue as the current backbone technology, with ATM and Sonet used in WANs.

Hippi`s strengths--performance, flow control and direct storage attachment--outweigh its limitations--reduced scalability and high cost per connection. A gateway to ATM from a Hippi cluster can implement a client access network. In this network, multimedia data can fan out from Hippi-attached servers to multiple ATM destinations for desktop applications.

Hippi and Sonet

Sonet is a point-to-point physical layer connection, analogous to a T1 leased line. ATM has a cell structure that provides a switched service on top of Sonet. Gateways between Hippi and Sonet are being developed to provide wide-area service between Hippi LANs.

For example, Los Alamos National Laboratory has been a participant in the CASA Gigabit Testbed network, along with Jet Propulsion Laboratory, California Institute of Technology and San Diego Supercomputer Center. Hippi-Sonet gateways developed at Los Alamos are used to connect Hippi LANs at each location. The combination has proved effective in several ways. For one, Hippi and Sonet specifications are both stable, so there are few interoperability problems. For another, a forward error control scheme proves beneficial in solving failure modes. And the sustained performance of 784 Mbits/sec over 2000 km has been reliable. u

The Los Alamos National Laboratory is operated by the University of California for the United States Department of Energy under Contract W-7405-ENG-36. Don Tolmie`s work was performed under the auspices of the U.S. Department of Energy.

Don Tolmie is a technical coordinator at Los Alamos National Laboratory, Los Alamos, NM, and chairs the Hippi working group of ANSI Technical Committee X3T11.

Don Flanagan is the administrator of the Hippi Networking Forum (HNF), based in Melbourne, FL. HNF is a consortium of vendors and users interested in high-bandwidth networking with Hippi.

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