HiPPI-based communications can be used for a wide range of applications ranging from
HiPPI-based networks were the surprise of the trade-show, especially serial HiPPI connections. HiPPI has the potential bandwidth of 800 megabits-per-second, while Dual-HiPPI can provide 1.6 gigabits-per-second. Serial HiPPI protocols have freed standard HiPPI from a 25 meter maximum cable-length limitation, so HiPPI links can now be placed over dual-mode fiber optic cable with significantly greater cable run lengths. HiPPI networks were prolific on the trade show floor, with a subset of SCinet '94 being the first all fiber-optic multi-gigabit-per-second computer network that included:
HiPPI appears to be a networking technology that primarily has a home in the supercomputing community. There are no other networking area that actually has applications that can utilize 800 to 1600 megabits-per-second throughput at the present time. In many cases, these speeds are not fully obtained because of the capacity of end-user systems, such as workstations and frame-buffers. At Interop+Networld this September in Atlanta, I saw no HiPPI networking, which possibly was strongly influenced by the fact that switched serial HiPPI is such a new technology. Conventional HiPPI has 25 meter maximum cable lengths, limiting wire-based HiPPI to the machine room, and consequently limiting conventional HiPPI as a general-purpose networking technology. Meanwhile, serial HiPPI has the potential for more realistic cable-run lengths, but switched serial HiPPI was demonstrated only for the first time at this show. Technologies generally do not show up at Interop or Networld until there is some degree of stability in the technology and some degree of interoperability between vendor's equipment has been established. Moreover, HiPPI may never become a mainstream networking technology, because of the limited number of applications that require the extensive bandwidth. Moreover, SuperComputing conferences tend to highlight the state-of-the-art in computing and networking technologies, with Interop+Networld conferences tending to highlight interoperability.
HiPPI is a networking technology that is in competition with some networking technologies, while complementing other technologies. HiPPI is in direct competition with Fibre Channel technology. As illustrated in figure 3, these two technologies are attempting to operate in the same environments. Meanwhile, networking technologies, like ATM compliment HiPPI, because ATM offers protocols designed for metropolitan and wide area networks. HiPPI can provide gigabit-per-second throughput for peripherals or workstations in switched LAN configurations, however, the protocol is not suited for wide-area data transfers. ATM will eventually be able to provide gigabit-per-second bandwidths available today with HiPPI, but at greater distances, even over WANs. Fibre Channel and ATM technologies will be discussed below in subsequent parts of this section of the paper.
There are several technology problems that illustrate the downside of HiPPI technology. Maximum throughput for interfaces and switches often can only be reached with large sized data packets. Multiplexing of HiPPI signals between switches appears to be a problem, because no data stream buffering is possible at the high HiPPI data rates. Network management for HiPPI switches must be performed manually, with no automated network interface capabilities. Lastly, present workstations can handle the communications throughput of a HiPPI interface but there is little workstation left over to do other work.
The cost of HiPPI is comparable to Fibre Channel, for those applications that require the bandwidth available with this technology. Conventional HiPPI uses heavy multi-wire shielded twisted pair cables with 25 meter length limitations, while serial HiPPI uses fiber optic transceivers, incurring similar costs to FDDI or ATM over glass. Nevertheless, HiPPI will never be a cost-effective LAN technology. HiPPI interfaces and switches are often more expensive than other shared media and switched media LAN technologies, due to the economy of scale available in the manufacture of more mainstream networking technologies. Also the raw speeds of HiPPI links require high-speed components, often requiring components manufactured from GaAs --- which significantly increases the cost of HiPPI technology.
HiPPI has matured significantly as a networking technology and is no longer a high-speed point-to-point protocol, once referred to at a roundtable as RS232 on steroids. Rather, at SuperComputing '94, HiPPI was demonstrated to have the capabilities to connect networked peripherals and networked workstations with supercomputers. HiPPI has direct competition with Fibre Channel technology, although other networking technologies complement the capabilities of HiPPI.